In our previous work it was shown that resistance of the tomato variety Gumbert to blossom-end rot (BER) was caused by 2-4 independent incompletely-dominant genes with additive effect (TGC Report, 1978, N 28, p.4). We selected another BER-resistant line, RB-1-1979, which was not affected by BER in five years of experiments. Line RB-1-1979 was crossed with the susceptible variety Rich-82-P and hybrids and parents were grown on a special plot of the field conducive for BER, using special agrotechnics. In F1 progeny, as well as in F2 and B1, resistance to BER or a low intensity of the disease predominated (table 1). In the 1989 experiment the segregation ratios for (P2+F1):P1 was 23:10 in the F2 and for F1:P1 it was 6:6 in backcrosses; these data conform to a monogene hypothesis. In 1990 the range of F1 progeny distributions of plants with affected fruits was wider than in 1989. Accepting the monogene hypothesis of segregation we examined the extent to which genotype ratios in F2 and B1 would correspond to expected ones. In F2(P1xP2) combination the ratio of (P2+F1):P1 was 36:17 (P2+F1=29+26.5% from 26,5 F1-plants), and in F2(P2xP1)-26:9 (P2+F1=21+26.5% from 17.5 F1). In the 1990 backcross a segregation of F1:P1 was 9:11 (table 2). The data on five F2-B1 segregations and high P-value confirm the monogene hypothesis of inheritance of the resistance to blossom-end rot in line RB-1-79. The resistance is caused by one pair of high effective dominant genes which may be designated as Ber (Ber-1).
Table 1. Distribution of plants into 8 classes according to the degree of expression of BER in hybrid combination (Line RB-1-79 x Rich-82-P)
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% of Average
Varieties Total plants intensity
& hybrids plants % of fruits affected by BER affected of BER,%
____________________________________________ by BER
0 0.01- 6.9- 13.8- 20.7- 27.6- 34.5- >41.3
6.8 13.7 20.6 27.5 34.4 41.3
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1989
P1=Rich-
82-P 20 1 6 5 4 2 2 100 25.67
P2=RB-1-79 20 20 0 0
(P1xP2) F1 9 6 3 66.7 0.95
(P1xP2) F2 33 21 2 3 3 1 3 36.4 6.36
F1 x P1 12 4 2 3 1 2 66.7 8.20
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0 0.01- 6.2- 12.3- 18.4- 24.5- 30.6- >36
6.1 12.2 18.3 24.4 30.5 36.6
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1990
P1=Rich-
82-P 28 1 7 12 3 3 1 1 100 15.88
P2=RB-1-79 32 32 0 0
(P1xP2) F1 34 25 3 4 2 26.5 2.62
(P1xP2) F2 53 29 1 16 4 2 1 45.2 5.53
(P2xP1) F2 35 21 2 7 3 1 1 40 4.91
F1(P1xP2)xP1 20 6 4 5 3 2 65 7.80
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Table 2. Segregation of the plant population in the F2 and backcrosses of the
hybrid combination (Line RB-1-79x^2^Rich-82-P)
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Year Hybrids Total Genotype Segregation
exp. plants ratio Observ. expect. X^2 P-value
(correc.) F2(3:1)
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1989 F2(P1xP2) 33 (P2+F1):P1 23:10 24,8:8,2 0,439 0,50-0,75
1990 F2(P1xP2) 53 (P2+F1):P1 36:17* 39,8:13,2 1,45 0,10-0,25
1990 F2(P2xP1) 35 (P2+F1):P1 26:9* 26,2:8,8 0,01 0,75-0,95
1989 F1xP1 12 F1:P1 6:6 6:6 0,00 >0,99
1990 F1xP1 20 F1:P1 9:11* 10:10 0,20 0,50-0,75
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*approximate numbersWhen PO,5, X^2 = 3,84