“Allele”. An allele is any of one or more alternative forms of a gene, all of which relate to a trait or characteristic. In a diploid cell or organism, the two alleles of a given gene occupy corresponding loci on a pair of homologous chromosomes.

“Backcrossing”. Backcrossing is a process in which a breeder repeatedly crosses hybrid progeny back to one of the parents, for example, a first generation hybrid F₁with one of the parental genotype of the F₁hybrid.

“Big Vein virus”. Big vein is a disease of lettuce caused by Lettuce Mirafiori Big Vein Virus which is transmitted by the fungus Olpidium virulentus, with vein clearing and leaf shrinkage resulting in plants of poor quality and reduced marketable value.

“Bolting”. The premature development of a flowering stalk, and subsequent seed, before a plant produces a food crop. Bolting is typically caused by late planting when temperatures are low enough to cause vernalization of the plants.

“Bremia lactucae”. An Oomycete that causes downy mildew in lettuce in cooler growing regions.

“Core length”. Length of the internal lettuce stem measured from the base of the cut and trimmed head to the tip of the stem.

“Corky root”. A disease caused by the bacterium Sphingomonas suberifaciens, which causes the entire taproot to become brown, severely cracked, and non-functional.

“Cotyledon”. One of the first leaves of the embryo of a seed plant; typically one or more in monocotyledons, two in dicotyledons, and two or more in gymnosperms.

“Double haploid line”. A stable inbred line achieved by doubling the chromosomes of a haploid line, e.g., from anther culture. For example, some pollen grains (haploid) cultivated under specific conditions develop plantlets containing 1n chromosomes. The chromosomes in these plantlets are then induced to “double” (e.g., using chemical means) resulting in cells containing 2n chromosomes. The progeny of these plantlets are termed “double haploid” and are essentially not segregating any more (e.g., are stable). The term “double haploid” is used interchangeably herein with “dihaploid.”

“Essentially all of the physiological and morphological characteristics”. A plant having “essentially all of the physiological and morphological characteristics” (and similar phrases) means a plant having all of the physiological and morphological characteristics of lettuce cultivar Thunderstruck, except for the characteristic(s) derived from a converted locus/loci (e.g., a single converted locus), for example, introduced via backcrossing to variety Thunderstruck, a modified gene(s) resulting from genome editing techniques, an introduced transgene (i.e., introduced via genetic transformation techniques) or mutation, when both plants are grown under the same environmental conditions. In embodiments, a plant having “essentially all of the physiological and morphological characteristics” means a plant having all of the characteristics of the reference plant with the exception of five or fewer traits, 4 or fewer traits, 3 or fewer traits, 2 or fewer traits, or one trait. In embodiments, a plant having “essentially all of the physiological and morphological characteristics” (and similar phrases) optionally has all of the physiological and morphological characteristics described in Tables 1-15.

“First water date”. The date the seed first receives adequate moisture to germinate. This can and often does equal the planting date.

“Gene”. As used herein, “gene” refers to a segment of nucleic acid comprising an open reading frame. A gene can be introduced into a genome of a species, whether from a different species or from the same species, using transformation or various breeding methods.

“Head diameter”. Diameter of the cut and trimmed head, sliced vertically, and measured at the widest point perpendicular to the stem.

“Head height”. Height of the cut and trimmed head, sliced vertically, and measured from the base of the cut stem to the cap leaf.

“Head weight”. Weight of saleable lettuce head, cut and trimmed to market specifications.

“Inbred line”: As used herein, the phrase “inbred line” refers to a genetically homozygous or nearly homozygous population. An inbred line, for example, can be derived through several cycles of sib crossing and/or selfing and/or via double haploid production. In some embodiments, inbred lines breed true for one or more traits of interest. An “inbred plant” or “inbred progeny” is an individual sampled from an inbred line.

“Lettuce Mosaic virus”. A disease that can cause a stunted, deformed, or mottled pattern in young lettuce and yellow, twisted, and deformed leaves in older lettuce.

“Maturity date”. Maturity refers to the stage when the plants are of full size and/or optimum weight and/or in marketable form to be of commercial or economic value.

“Nasonovia ribisnigri”. A lettuce aphid that colonizes the innermost leaves of the lettuce plant, contaminating areas that cannot be treated easily with insecticides.

“Plant.” As used herein, the term “plant” includes plant cells, plant protoplasts, plant cell tissue cultures from which plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as leaves, pollen, embryos, cotyledons, hypocotyl, roots, root tips, anthers, pistils, flowers, ovules, fruit, stems, and the like.

“Plant material”. The terms “plant material” and “material obtainable from a plant” are used interchangeably herein and refer to any plant material obtainable from a plant including without limitation, leaves, stems, roots, flowers or flower parts, fruits, pollen, ovules, zygotes, seeds, cuttings, cell or tissue cultures, or any other part or product of the plant.

“Plant part”. As used herein, a “plant part” includes any part, organ, tissue or cell of a plant including without limitation an embryo, meristem, head, leaf, pollen, cotyledon, hypocotyl, root, root tip, anther, flower, flower bud, pistil, ovule, shoot, stem, stalk, petiole, pith, capsule, a scion, a rootstock and/or a fruit including callus and protoplasts derived from any of the foregoing. In representative embodiments, the plant part is a non-propagating plant part, for example, is not a seed.

“Quantitative Trait Loci”. Quantitative Trait Loci (QTL) refers to genetic loci that control to some degree, numerically representable traits that are usually continuously distributed.

“Ratio of head height/diameter”. Head height divided by the head diameter is an indication of the head shape; <1 is flattened, 1=round, and >1 is pointed.

“Regeneration”. Regeneration refers to the development of a plant from tissue culture.

“Resistance”. As used herein the terms “resistance” and “tolerance” (and grammatical variations thereof) are used interchangeably to describe plants that show reduced or essentially no symptoms to a specific biotic (e.g., a pest, pathogen or disease) or abiotic (e.g., exogenous or environmental, including herbicides) factor or stressor. In some embodiments, “resistant” or “tolerant” plants show some symptoms but are still able to produce marketable product with an acceptable yield, e.g., the yield may still be reduced and/or the plants may be stunted as compared with the yield or growth in the absence of the biotic and/or abiotic factor or stressor. Those skilled in the art will appreciate that the degree of resistance or tolerance may be assessed with respect to a plurality or even an entire field of plants. A lettuce plant may be considered “resistant” or “tolerant” if resistance/tolerance is observed over a plurality of plants (e.g., an average), even if particular individual plants may be susceptible to the biotic or abiotic factor or stressor.

“RHS”. RHS refers to the Royal Horticultural Society of England which publishes an official botanical color chart quantitatively identifying colors according to a defined numbering system. The chart may be purchased from Royal Horticulture Society Enterprise Ltd., RHS Garden; Wisley, Woking; Surrey GU236QB, UK.

“Single locus converted”. A single locus converted or conversion plant refers to a plant that is developed by plant breeding techniques (e.g., backcrossing), genome editing techniques, genetic transformation techniques and/or mutation techniques wherein essentially all of the desired morphological and physiological characteristics of a line are recovered in addition to the single locus introduced into the line via the plant breeding, genome editing, genetic transformation, or mutation techniques.

“Substantially equivalent characteristic”. A characteristic that, when compared, does not show a statistically significant difference (e.g., p=0.05) from the mean.

“Tip burn”. Means a browning of the edges or tips of lettuce leaves that is a physiological response to a lack of calcium.

“Tomato Bushy Stunt”. Also called “lettuce necrotic stunt”. A disease that causes stunting of growth and leaf mottling.

“Transgene”. A nucleic acid of interest that can be introduced into the genome of a plant by genetic engineering techniques (e.g., transformation) or breeding. The transgene can be from the same or a different species. If from the same species, the transgene can be an additional copy of a native coding sequence or can present the native sequence in a form or context (e.g., different genomic location and/or in operable association with exogenous regulatory elements such as a promoter) than is found in the native state. The transgene can comprise an open reading frame encoding a polypeptide or can encode a functional non-translated RNA (e.g., RNAi).

Botanical Description of the Lettuce Cultivar Thunderstruck.

Characteristics. Lettuce cultivar Thunderstruck is a dark green Greenleaf (also known as Batavia) lettuce variety suitable for conventional lettuce production settings. Thunderstruck performs well in all lettuce growing production slots and areas of the Coastal California and Desert Southwest of California and Arizona regions. Greenleaf lettuce variety Thunderstruck is the result of a cross between Greenleaf lettuce non-commercial experimental elite advanced line 14BS-0014.1—used as a female in a cross with a non-commercial elite individual plant selected from an F4 family designated as 14BS-0037.3-used as male parent to create F1 seeds. Thunderstruck was developed with numerous subsequent generations of individual plant selections chosen for horticultural traits such as refined Greenleaf, short core, color, straight midribs, good internal fill, density, and pliability. Thunderstruck possesses strong resistances for Tomato Bushy Stunt Virus and all Downy mildew races presently designated in the United States.

Lettuce variety Thunderstruck has shown uniformity and stability for all the traits within the limits of environmental influence on the characteristics. The variety has been increased with continued observation for uniformity. No variant traits have been observed or are expected in lettuce variety Thunderstruck.

Table 1: Variety Description Information

Note that lettuce cultivar Thunderstruck is an open leafy/non-heading lettuce variety. Where values are provided for “head” characteristics herein, the best approximation was made. For example, the size of the “head” is measured from the base of the plant to the tip of the longest leaf.

Plant Type: Greenleaf/Batavia

Seed

- Seed color: Black
- Light dormancy: Light not required
- Heat dormancy: Susceptible
  
  Cotyledon to Fourth Leaf Stage
- Shape of cotyledons: Broad
- Undulation: Flat
- Anthocyanin distribution: Absent
- Rolling: Absent
- Cupping: Uncupped
- Reflexing: None
  
  Mature Leaves
- Margin incision depth: Moderate
- Margin indentation: Entire
- Margin undulation of the apical margin: Moderate
- Green color: Light green
- Anthocyanin distribution: Absent
- Glossiness: Dull
- Leaf blistering: Absent
- Trichomes: Absent
- Leaf thickness: Thick
  
  Plant at Market Stage
- Head shape: Non-heading
- Head size class: Not applicable
- Head weight (g): 914.6
- Head firmness: Not applicable
  
  Core
- Diameter at base of head (mm): 38
- Core height from base of head to apex (mm): 92
  
  Maturity (days)
- Summer: 60 days
- Winter: 90 days
  
  Adaptation
- Primary U.S. Regions of Adaptation (tested and proven adapted)
- Southwest: Yes
- West Coast: Yes
- Southeast: Not tested
- Northeast: Not tested
- Spring area: Salinas, Santa Maria and San Benito (CA); and Yuma (AZ)
- Summer area: Salinas (CA)
- Fall area: Salinas (CA)
- Winter area: Salinas (CA)
- Greenhouse: Year-round
- Soil type: Both of mineral and organic
  
  Disease and Stress Reactions
  
  Virus
- Tomato Bushy Stunt virus (TBSV): Highly resistant
- Big vein: Not tested
- Cucumber Mosaic virus: Not tested
- Broad Bean Wilt: Not tested
- Turnip Mosaic virus: Not tested
- Best Western Yellows: Not tested
- Lettuce Infectious Yellows: Not tested
- Lettuce mosaic virus (LMV): Not tested
  
  Fungal/Bacterial
- Corky Root Rot (Pythium Root Rot): Not tested
- Bremia lactucae (Downy Mildew): Highly resistant to BI: 16-28, 30-32EU and 5-9US
- Powdery Mildew: Not tested
- Sclerotinia Rot: Not tested
- Bacterial Soft Rot (Pseudomonas spp. & others): Not tested
- Botrytis (Gray Mold): Not tested
  
  Insects
- Nasonovia ribisnigri biotype 0 (Nr: 0): Susceptible
- Cabbage Loopers: Not tested
- Root Aphids: Not tested
- Green Peach Aphid: Not tested
  
  Physiological/Stress
- Tip burn: Not tested
- Heat: Intermediate
- Drought: Not tested
- Cold: Tolerant
- Salt: Not tested
- Brown Rib: Resistant
  
  Post-Harvest
- Pink Rib: Not tested
- Russett Spotting: Not tested
- Rusty Brown Discoloration: Resistant
- Internal Rib Necrosis (Blackheart, Gray Rib, Gray Streak): Resistant
- Brown Stain: Not tested

TABLE 2

Fourth Leaf Length (mm) at 20 Days Under Greenhouse Conditions

Thunderstruck
Bergams Green

71
51

92
33

101
24

98
46

79
47

106
47

91
27

71
36

83
28

84
34

91
33

103
37

78
47

96
55

85
36

92
31

86
33

87
25

92
41

99
50

AOV Table

Df
SS
MS
F
P-Value

Variety
1
26214.4
26214.400
284.232
0

Residuals
38
3504.7
92.229
NA
NA

ANOVA shows a significant difference (p < 0.05) in Fourth Leaf Length (mm).

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
89.25
A

Bergams Green
38.05
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
38.05
9.33
20
2.15
24
55
32.50
36
47.0

Thunderstruck
89.25
9.87
20
2.15
71
106
83.75
91
96.5

TABLE 3

Fourth Leaf Width (mm) at 20 Days Under Greenhouse Conditions

Thunderstruck
Bergams Green

20
20

28
12

30
8

27
16

24
14

32
17

27
8

18
12

25
9

28
12

28
12

31
14

26
18

30
22

31
9

31
9

31
12

35
8

28
12

36
17

AOV Table

df
SS
MS
F
P-Value

Variety
1
2325.625
2325.625
127.496
0

Residuals
38
693.150
18.241
NA
NA

ANOVA shows a significant difference (p < 0.05) in Fourth Leaf Width (mm).

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
28.30
A

Bergams Green
13.05
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
13.05
4.15
20
0.96
8
22
9.00
12
16.25

Thunderstruck
28.30
4.39
20
0.96
18
36
26.75
28
31.00

TABLE 4

Cotyledon Length (mm) at 20 Days Under Greenhouse Conditions

Thunderstruck
Bergams Green

22
21

20
23

21
22

22
25

20
23

20
26

23
22

21
24

22
23

23
22

21
21

22
22

24
23

24
21

19
24

21
21

22
21

21
22

22
21

20
21

AOV Table

Df
SS
MS
F
P-Value

Variety
1
8.1
8.100
4.061
0.051

Residuals
38
75.8
1.995
NA
NA

ANOVA shows no significant difference (p = 0.051) in Cotyledon Length (mm).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
22.4
A

Thunderstruck
21.5
A

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
22.4
1.47
20
0.32
21
26
21.00
22.0
23

Thunderstruck
21.5
1.36
20
0.32
19
24
20.75
21.5
22

TABLE 5

Cotyledon Width (mm) at 20 Days Under Greenhouse Conditions

Thunderstruck
Bergams Green

11
11

10
11

9
12

10
12

10
11

10
13

11
13

12
12

10
11

11
10

12
12

11
11

11
12

10
11

11
12

11
11

11
10

11
11

12
10

11
11

AOV Table

df
SS
MS
F
P-Value

Variety
1
3.6
3.600
5.202
0.028

Residuals
38
26.3
0.692
NA
NA

ANOVA shows a significant difference (p < 0.05) in Cotyledon Width (mm).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
11.35
A

Thunderstruck
10.75
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
11.35
0.88
20
0.19
10
13
11
11
12

Thunderstruck
10.75
0.79
20
0.19
9
12
10
11
11

TABLE 6

Fourth Leaf Length to Width (L:W) Index

at 20 Days Under Greenhouse Conditions.

Thunderstruck
Bergams Green

3.55
2.55

3.29
2.75

3.37
3.00

3.63
2.88

3.29
3.36

3.31
2.76

3.37
3.38

3.94
3.00

3.32
3.11

3.00
2.83

3.25
2.75

3.32
2.64

3.00
2.61

3.20
2.50

2.74
4.00

2.97
3.44

2.77
2.75

2.49
3.13

3.29
3.42

2.75
2.94

AOV Table

df
SS
MS
F
P-Value

Variety
1
0.410
0.410
3.172
0.083

Residuals
38
4.913
0.129
NA
NA

ANOVA shows no significant difference (p > 0.05) in Fourth Leaf L:W Index.

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
3.19
A

Bergams Green
2.99
A

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
2.99
0.38
20
0.08
2.50
4.00
2.75
2.91
3.19

Thunderstruck
3.19
0.34
20
0.08
2.49
3.94
2.99
3.29
3.33

TABLE 7

Cotyledon Length to Width (L:W) Index at 20 Days under Greenhouse Conditions

Thunderstruck
Bergams Green

2.00
1.91

2.00
2.09

2.33
1.83

2.20
2.08

2.00
2.09

2.00
2.00

2.09
1.69

1.75
2.00

2.20
2.09

2.09
2.20

1.75
1.75

2.00
2.00

2.18
1.92

2.40
1.91

1.73
2.00

1.91
1.91

2.00
2.10

1.91
2.00

1.83
2.10

1.82
1.91

AOV Table

df
SS
MS
F
P-Value

Variety
1
0.009
0.009
0.361
0.552

Residuals
38
0.979
0.026
NA
NA

ANOVA shows no significant difference (p > 0.05) in Cotyledon L:W Index.

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
2.01
A

Bergams Green
1.98
A

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
1.98
0.13
20
0.04
1.69
2.2
1.91
2
2.09

Thunderstruck
2.01
0.19
20
0.04
1.73
2.4
1.89
2
2.11

TABLE 8

Head Weight (g) at Harvest Maturity

Thunderstruck
Bergams Green

468
1034

960
852

754
1177

747
1352

1249
1469

909
1277

480
1223

564
793

781
1161

811
1199

844
1089

1194
862

638
1130

1511
1073

1084
1155

887
1240

1227
1048

948
986

921
810

1316
1344

AOV Table

df
SS
MS
F
P-Value

Variety
1
396209
396209.03
6.924
0.012

Residuals
38
2174493
57223.49
NA
NA

ANOVA shows a significant difference (p < 0.05) in Head Weight (g).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
1113.70
A

Thunderstruck
914.65
B

Mean
Std
r
Se
Min
Max
Q25
Q50
Q75

Bergams Green
1113.70
186.70
20
53.49
793
1469
1022.00
1142.5
1227.25

Thunderstruck
914.65
282.12
20
53.49
468
1511
752.25
898.0
1111.50

TABLE 9

Head Circumference (g) at Harvest Maturity

Thunderstruck
Bergams Green

31
34

35
32

31
33

32
34

32
32

34
33

30
34

31
30

30
32

30
33

31
32

32
32

27
31

31
32

34
34

33
34

32
34

34
32

31
32

35
34

AOV Table

df
SS
MS
F
P-Value

Variety
1
8.1
8.100
3.097
0.087

Residuals
38
99.4
2.616
NA
NA

ANOVA shows no significant difference (p > 0.05) in Head Circumference (g).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
32.7
A

Thunderstruck
31.8
A

Mean
std
r
Se
Min
Max
Q25
Q50
Q75

Bergams Green
32.7
1.17
20
0.36
30
34
32
32.5
34.00

Thunderstruck
31.8
1.96
20
0.36
27
35
31
31.5
33.25

TABLE 10

Core Length (mm) at Harvest Maturity

Thunderstruck
Bergams Green

82
109

110
113

68
87

100
95

83
88

84
90

60
99

77
72

75
102

66
90

94
88

120
92

67
100

98
110

116
105

94
86

98
105

126
91

113
88

111
108

AOV Table

df
SS
MS
F
P-Value

Variety
1
144.4
144.400
0.576
0.453

Residuals
38
9529.6
250.779
NA
NA

ANOVA shows no significant difference (p > 0.05) in Core Length (mm).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
95.9
A

Thunderstruck
92.1
A

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
95.9
10.47
20
3.54
72
113
88.0
93.5
105.00

Thunderstruck
92.1
19.80
20
3.54
60
126
76.5
94.0
110.25

TABLE 11

Core Width (mm) at Harvest Maturity

Thunderstruck
Bergams Green

27
40

40
41

40
48

40
45

41
55

38
48

33
46

32
42

33
48

35
51

38
45

40
44

36
50

45
42

42
45

38
45

41
43

44
46

40
41

40
45

AOV Table

df
SS
MS
F
P-Value

Variety
1
540.225
540.225
32.712
0

Residuals
38
627.550
16.514
NA
NA

ANOVA shows a significant difference (p < 0.05) in Core Width (mm).

Duncan Grouping

Mean
Duncan Grouping

Bergams Green
45.50
A

Thunderstruck
38.15
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
45.50
3.73
20
0.91
40
55
42.75
45
48.00

Thunderstruck
38.15
4.37
20
0.91
27
45
35.75
40
40.25

TABLE 12

Frame Leaf Length (cm) at Harvest Maturity

Thunderstruck
Bergams Green

34
29

33
30

32
26

34
31

36
29

32
33

34
32

33
28

34
30

31
27

33
29

34
29

35
29

35
30

33
34

35
29

35
30

33
30

32
30

33
29

AOV Table

df
SS
MS
F
P-Value

Variety
1
148.225
148.225
59.197
0

Residuals
38
95.150
2.504
NA
NA

ANOVA shows a significant difference (p < 0.05) in Frame Leaf Length (cm).

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
33.55
A

Bergams Green
29.70
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
29.70
1.84
20
0.35
26
34
29
29.5
30.00

Thunderstruck
33.55
1.28
20
0.35
31
36
33
33.5
34.25

TABLE 13

Frame Leaf Width (cm) at Harvest Maturity

Thunderstruck
Bergams Green

18
15

19
17

17
15

20
18

17
16

20
20

17
17

19
20

18
17

20
18

19
17

17
16

18
17

18
17

17
16

17
15

16
18

16
17

19
17

17
17

AOV Table

df
SS
MS
F
P-Value

Variety
1
9.025
9.025
5.122
0.029

Residuals
38
66.950
1.762
NA
NA

ANOVA shows a significant difference (p < 0.05) in Frame Leaf Width (cm).

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
17.95
a

Bergams Green
17.00
b

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
17.00
1.38
20
0.3
15
20
16
17
17.25

Thunderstruck
17.95
1.28
20
0.3
16
20
17
18
19.00

TABLE 14

Core Index (length to width) at Harvest Maturity

Thunderstruck
Bergams Green

3.04
2.73

2.75
2.76

1.70
1.81

2.50
2.11

2.02
1.60

2.21
1.88

1.82
2.15

2.41
1.71

2.27
2.13

1.89
1.76

2.47
1.96

3.00
2.09

1.86
2.00

2.18
2.62

2.76
2.33

2.47
1.91

2.39
2.44

2.86
1.98

2.83
2.15

2.78
2.40

AOV Table

df
SS
MS
F
P-Value

Variety
1
0.809
0.809
5.816
0.021

Residuals
38
5.289
0.139
NA
NA

ANOVA shows a significant difference (p < 0.05) in Core Index.

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
2.41
A

Bergams Green
2.13
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
2.13
0.33
20
0.08
1.6
2.76
1.90
2.10
2.35

Thunderstruck
2.41
0.41
20
0.08
1.7
3.04
2.14
2.44
2.76

TABLE 15

Frame Leaf Index (length to width) at Harvest Maturity

Thunderstruck
Bergams Green

1.89
1.93

1.74
1.76

1.88
1.73

1.70
1.72

2.12
1.81

1.60
1.65

2.00
1.88

1.74
1.40

1.89
1.76

1.55
1.50

1.74
1.71

2.00
1.81

1.94
1.71

1.94
1.76

1.94
2.13

2.06
1.93

2.19
1.67

2.06
1.76

1.68
1.76

1.94
1.71

AOV Table

df
SS
MS
F
P-Value

Variety
1
0.158
0.158
5.86
0.02

Residuals
38
1.021
0.027
NA
NA

ANOVA shows a significant difference (p < 0.05) in Frame Leaf Index.

Duncan Grouping

Mean
Duncan Grouping

Thunderstruck
1.88
A

Bergams Green
1.75
B

Mean
std
r
se
Min
Max
Q25
Q50
Q75

Bergams Green
1.75
0.15
20
0.04
1.40
2.13
1.71
1.76
1.81

Thunderstruck
1.88
0.17
20
0.04
1.55
2.19
1.74
1.92
2.00

Tissue Culture.

Further reproduction of lettuce plants of the variety can occur by tissue culture and regeneration. Tissue culture of various tissues of lettuce and regeneration of plants therefrom is well known and widely published. For example, reference may be had to Teng, et al., HortScience, 27:9, 1030-1032 (1992); Teng, et al., HortScience, 28:6, 669-1671 (1993); Zhang, et al., Journal of Genetics and Breeding, 46:3, 287-290 (1992); Webb, et al., Plant Cell Tissue and Organ Culture, 38:1, 77-79 (1994); Curtis, et al., Journal of Experimental Botany, 45:279, 1441-1449 (1994); Nagata, et al., Journal for the American Society for Horticultural Science, 125:6, 669-672 (2000); and Ibrahim, et al., Plant Cell Tissue and Organ Culture, 28 (2), 139-145 (1992). It is clear from the literature that the state of the art is such that these methods of obtaining plants are routinely used and have a very high rate of success. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce lettuce plants having desired characteristics of lettuce cultivar Thunderstruck. Optionally, lettuce plants can be regenerated from the tissue culture of the invention comprising all or essentially all of the physiological and morphological characteristics of lettuce cultivar Thunderstruck.

As used herein, the term “tissue culture” indicates a composition comprising isolated cells of the same or a different type or a collection of such cells organized into parts of a plant. Exemplary types of tissue cultures are protoplasts, calli, meristematic cells, and plant cells that can generate tissue culture that are intact in plants or parts of plants, such as leaves, pollen, embryos, roots, root tips, anthers, pistils, flowers, petioles, suckers, and the like. Means for preparing and maintaining plant tissue culture are well known in the art. By way of example, a tissue culture comprising organs has been used to produce regenerated plants. U.S. Pat. Nos. 5,959,185, 5,973,234, and 5,977,445 describe certain techniques.

Additional Breeding Methods.

This invention is also directed to methods for producing a lettuce plant by crossing a first parent lettuce plant with a second parent lettuce plant wherein the first or second parent lettuce plant is a plant of lettuce cultivar Thunderstruck. Further, both first and second parent lettuce can come from lettuce cultivar Thunderstruck. Thus, any of the following exemplary methods using lettuce cultivar Thunderstruck are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, double haploid production, and the like. All plants produced using lettuce cultivar Thunderstruck as at least one parent are within the scope of this invention, including those developed from lettuce plants derived from lettuce cultivar Thunderstruck. Advantageously, lettuce cultivar Thunderstruck can be used in crosses with other, different, lettuce plants to produce the first generation (F₁) lettuce hybrid seeds and plants with desirable characteristics. The lettuce plants of the invention can also be used for transformation where exogenous transgenes are introduced and expressed by the plants of the invention. Genetic variants created either through traditional breeding methods or through transformation of the cultivars of the invention by any of a number of protocols known to those of skill in the art are intended to be within the scope of this invention.

The following describes exemplary breeding methods that may be used with lettuce cultivar Thunderstruck in the development of further lettuce plants. One such embodiment is a method for developing lettuce cultivar Thunderstruck progeny lettuce plants in a lettuce plant breeding program comprising: obtaining a plant, or a part thereof, of lettuce cultivar Thunderstruck, utilizing said plant or plant part as a source of breeding material, and selecting a lettuce cultivar Thunderstruck progeny plant with molecular markers in common with lettuce cultivar Thunderstruck and/or with some, all or essentially all of the morphological and/or physiological characteristics of lettuce cultivar Thunderstruck (see, e.g., one or more of Tables 1-15). In representative embodiments, the progeny plant has at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more of the morphological and physiological characteristics of lettuce cultivar Thunderstruck (e.g., as described in one or more of Tables 1-15) or even all of the morphological and physiological characteristics of lettuce cultivar Thunderstruck so that said progeny lettuce plant is not significantly different for said traits than lettuce cultivar Thunderstruck, as determined at the 5% significance level when grown in the same environmental conditions; optionally, with the presence of one or more desired additional traits (e.g., male sterility, disease resistance, pest or insect resistance, herbicide resistance, and the like). Breeding steps that may be used in the breeding program include pedigree breeding, backcrossing, mutation breeding and/or recurrent selection. In conjunction with these steps, techniques such as RFLP-enhanced selection, genetic marker enhanced selection (for example, SSR markers) and/or and the making of double haploids may be utilized.

Another representative method involves producing a population of lettuce cultivar Thunderstruck progeny plants, comprising crossing lettuce cultivar Thunderstruck with another lettuce plant, thereby producing a population of lettuce plants that, on average, derives 50% of its alleles (i.e., TAC) from lettuce cultivar Thunderstruck. A plant of this population may be selected and repeatedly selfed or sibbed with a lettuce plant resulting from these successive filial generations or backcrossed to lettuce cultivar Thunderstruck. Another approach is to make double haploid plants to achieve homozygosity. One embodiment of this invention is a lettuce plant produced by these methods and that has obtained at least 50% of its alleles from lettuce cultivar Thunderstruck. In embodiments, the methods of the invention produce a population of lettuce plants that, on average, derives at least 6.25%, 12.5%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% of its alleles (i.e., TAC) from lettuce cultivar Thunderstruck, e.g., at least about 6.25%, 12.5%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% of the genetic complement of lettuce cultivar Thunderstruck. One representative embodiment of this invention is the lettuce plant produced by the methods of the invention and that has obtained at least 6.25%, 12.5%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% of its alleles (i.e., TAC) from lettuce cultivar Thunderstruck, and optionally is the result of a breeding process comprising one or two breeding crosses and one or more of selfing, sibbing, backcrossing and/or double haploid techniques in any combination and any order. In embodiments, the breeding process does not include a breeding cross, and comprises selfing, sibbing, backcrossing and or double haploid technology.

One of ordinary skill in the art of plant breeding would know how to evaluate the traits of two plant varieties to determine if there is no significant difference between the two traits expressed by those varieties. For example, see Fehr and Walt, Principles of Cultivar Development, pp. 261-286 (1987). In embodiments, the invention encompasses Thunderstruck progeny plants having a combination of at least 2, 3, 4, 5, 6, 7, 8, 9, 10 or more of the characteristics as described herein for lettuce cultivar Thunderstruck, so that said progeny lettuce plant is not significantly different for said traits than lettuce cultivar Thunderstruck, as determined at the 5% significance level when grown in the same environmental conditions. Using techniques described herein and those known in the art, molecular markers may be used to identify said progeny plant as progeny of lettuce cultivar Thunderstruck. Mean trait values may be used to determine whether trait differences are significant, and optionally the traits are measured on plants grown under the same environmental conditions.

Progeny of lettuce cultivar Thunderstruck may also be characterized through their filial relationship with lettuce cultivar Thunderstruck, as for example, being within a certain number of breeding crosses of lettuce cultivar Thunderstruck. A breeding cross is a cross made to introduce new genetics into the progeny, and is distinguished from a cross, such as a self or a sib cross or a backcross to Thunderstruck as a recurrent parent, made to select among existing genetic alleles. The lower the number of breeding crosses in the pedigree, the closer the relationship between lettuce cultivar Thunderstruck and its progeny. For example, progeny produced by the methods described herein may be within 1, 2, 3, 4, 5 or more breeding crosses of lettuce cultivar Thunderstruck.

In representative embodiments, a lettuce plant derived from lettuce cultivar Thunderstruck comprises cells comprising at least one set of chromosomes derived from lettuce cultivar Thunderstruck. In embodiments, the lettuce plant or population of lettuce plants derived from lettuce cultivar Thunderstruck comprises, on average, at least 6.25%, 12.5%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% of its alleles (i.e., TAC) from lettuce cultivar Thunderstruck, e.g., at least about 6.25%, 12.5%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% of the genetic complement of lettuce cultivar Thunderstruck, and optionally is the result of a breeding process comprising one or two breeding crosses and one or more of selfing, sibbing, backcrossing and/or double haploid techniques in any combination and any order. In embodiments, the breeding process does not include a breeding cross, and comprises selfing, sibbing, backcrossing and or double haploid technology. In embodiments, the lettuce plant derived from lettuce cultivar Thunderstruck is one, two, three, four, five or more breeding crosses removed from lettuce cultivar Thunderstruck.

In representative embodiments, a plant derived from lettuce cultivar Thunderstruck is a double haploid plant, a hybrid plant or an inbred plant.

In embodiments, a hybrid or derived plant from lettuce cultivar Thunderstruck comprises a desired added trait. In representative embodiments, a lettuce plant derived from lettuce cultivar Thunderstruck comprises all of the morphological and physiological characteristics of lettuce cultivar Thunderstruck (e.g., as described in one or more of Tables 1-15). In embodiments, the lettuce plant derived from lettuce cultivar Thunderstruck comprises essentially all of the morphological and physiological characteristics of lettuce cultivar Thunderstruck (e.g., as described in one or more of Tables 1-15) in any combination, with the addition of a desired added trait.

Those skilled in the art will appreciate that any of the traits described above with respect to plant transformation methods can be introduced into a plant of the invention (e.g., lettuce cultivar Thunderstruck and hybrid lettuce plants and other lettuce plants derived therefrom) using breeding techniques.

Genetic Transformation.

With the advent of molecular biological techniques that have allowed the isolation and characterization of genes that encode specific protein products, scientists in the field of plant biology developed a strong interest in engineering the genome of plants to contain and express foreign nucleic acids including additional or modified versions of native (endogenous) nucleic acids (optionally driven by a non-native promoter) in order to alter the traits of a plant in a specific manner. Any nucleic acid sequences, whether from a different species, the same species or an artificial sequence, which are introduced into the genome using transformation or various breeding methods, are referred to herein collectively as “transgenes.” Over the last fifteen to twenty years, several methods for producing transgenic plants have been developed, and in particular embodiments the present invention also relates to transformed versions of the plants disclosed herein.

Genetic engineering techniques can be used (alone or in combination with breeding methods) to introduce one or more desired added traits into plant, for example, lettuce cultivar Thunderstruck or progeny or lettuce plants derived thereof. Once a transgene has been introduction into a plant by genetic transformation, it can be transferred to other plants via conventional breeding.

Plant transformation generally involves the construction of an expression vector that will function in plant cells. Optionally, such a vector comprises one or more nucleic acids comprising a coding sequence for a polypeptide or an untranslated functional RNA under control of, or operatively linked to, a regulatory element (for example, a promoter). In representative embodiments, the vector(s) may be in the form of a plasmid, and can be used alone or in combination with other plasmids, to provide transformed lettuce plants using transformation methods as described herein to incorporate transgenes into the genetic material of the lettuce plant.

Additional methods include, but are not limited to, expression vectors introduced into plant tissues using a direct nucleic acid transfer method, such as microprojectile-mediated delivery (e.g., with a biolistic device), DNA injection, Agrobacterium-mediated transformation, electroporation, and the like. Transformed plants obtained from the plants (and parts and tissue culture thereof) of the invention are intended to be within the scope of this invention.

Expression Vectors for Plant Transformation-Selectable markers.

Expression vectors typically include at least one nucleic acid comprising or encoding a selectable marker, operably linked to a regulatory element (for example, a promoter) that allows transformed cells containing the marker to be either recovered by negative selection, e.g., inhibiting growth of cells that do not contain the selectable marker, or by positive selection, e.g., screening for the product encoded by the selectable marker. Many commonly used selectable markers for plant transformation are well known in the transformation art, and include, for example, nucleic acids that code for enzymes that metabolically detoxify a selective chemical agent which may be an antibiotic or an herbicide, or nucleic acids that encode an altered target which is insensitive to the inhibitor. Positive selection methods are also known in the art.

Commonly used selectable markers in plants include, but are not limited to: neomycin phosphotransferase II (nptII) conferring resistance to kanamycin, hygromycin phosphotransferase conferring resistance to the antibiotic hygromycin, bacterial selectable markers that confer resistance to antibiotics (e.g., gentamycin acetyl transferase, streptomycin phosphotransferase, and aminoglycoside-3′-adenyl transferase, selectable markers conferring resistance to herbicides (e.g., glyphosate, glufosinate, or bromoxynil). Selection of transformed plant cells can also be based on screening presumptively transformed plant cells rather than direct genetic selection of transformed cells for resistance to a toxic substance such as an antibiotic; such markers include without limitation alpha-glucuronidase (GUS), alpha-galactosidase, luciferase, and Green Fluorescent Protein (GFP) and mutant GFPs.

Expression Vectors for Plant Transformation-Promoters.

Transgenes included in expression vectors are generally driven by a nucleotide sequence comprising a regulatory element (for example, a promoter). Numerous types of promoters are well known in the transformation arts, as are other regulatory elements that can be used alone or in combination with promoters.

As used herein, “promoter” includes reference to a region of DNA upstream from the start of transcription and involved in recognition and binding of RNA polymerase and other proteins to initiate transcription. A “plant promoter” is a promoter capable of initiating transcription in plant cells.

Examples of promoters under developmental control include promoters that preferentially initiate transcription in certain tissues, such as leaves, roots, seeds, fibers, xylem vessels, tracheids, or sclerenchyma. Such promoters are referred to as “tissue-preferred.” Promoters that initiate transcription only in certain tissue are referred to as “tissue-specific.” A “cell type” specific promoter preferentially drives expression in certain cell types in one or more organs, for example, vascular cells in roots or leaves. An “inducible” promoter is a promoter that is under environmental control. Examples of environmental conditions that may affect transcription by inducible promoters include anaerobic conditions or the presence of light. Tissue-specific, tissue-preferred, cell type specific, and inducible promoters constitute the class of “non-constitutive” promoters. A “constitutive” promoter is a promoter that is active under most environmental conditions.

Many suitable promoters are known in the art and can be selected and used to achieve the desired outcome.

Signal Sequences for Targeting Proteins to Subcellular Compartments.

Transport of polypeptides produced by transgenes to a subcellular compartment such as the chloroplast, vacuole, peroxisome, glyoxysome, cell wall, or mitochondrion, or for secretion into the apoplast, is generally accomplished by means of operably linking a nucleotide sequence encoding a signal sequence to the 5′ and/or 3′ region of a nucleic acid encoding the polypeptide of interest. Signal sequences at the 5′ and/or 3′ end of the coding sequence target the polypeptide to particular subcellular compartments.

The presence of a signal sequence can direct a polypeptide to either an intracellular organelle or subcellular compartment or for secretion to the apoplast. Many signal sequences are known in the art. See, for example, Becker, et al., Plant Mol. Biol., 20:49 (1992); Close, P. S., Master's Thesis, Iowa State University (1993); Knox, C., et al., “Structure and Organization of Two Divergent Alpha-Amylase Genes from Barley,” Plant Mol. Biol., 9:3-17 (1987); Lerner, et al., Plant Physiol., 91:124-129 (1989); Fontes, et al., Plant Cell, 3:483-496 (1991); Matsuoka, et al., PNAS, 88:834 (1991); Gould, et al., J. Cell. Biol., 108:1657 (1989); Creissen, et al., Plant J, 2:129 (1991); Kalderon, et al., A short amino acid sequence able to specify nuclear location, Cell, 39:499-509 (1984); and Steifel, et al., Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation, Plant Cell, 2:785-793 (1990).