Resistance to bacterial wilt in tomato: gene dosage effects

Resistance to bacterial wilt in tomato: gene dosage effects

Hartman, G.L. Book author
Hayward, A.C. Book author

Canberra ACIAR Australia

1993

p.142-148

SB741.B33H3

Sixteen breeding lines and exotic introductions of tomato were identified as having resistance to Pseudomonas solanacearum. Two experiments were designed to elicit information on (i) behaviour of F1s for disease resistance using lines differing in levels of resistance, (ii) genetic makeup of resistantlines, and (iii) possibilities of exploiting heterosis for yield with these lines. In the first experiment, several parents differing in survival rates were used in a diallel cross. F1s showed dominance for resistance in two parents and recessive in one. F1 from a cross of two moderately resistant parents had higher levels of resistance, indicating additive gene action. High level of resistance was reflected by high survival rates, reduced browning of vascular tissue and absence of ooze. In the second experiment, seven resistant (R) lines, including two from the previous set, were crossed with a susceptivle (S) line and among each other. Twenty F1s among R x R parents and nine F1s of R x S and F2s of R x R and R x S were studied. Although all the R parents had 100% survival, F1s of R x S had variable survival percentages, indicating differences in levels of dominance among the resistant parents. Vascular browning, indicative of bacterial invasion, was used as a selection criterion for resistance. F1s of R x R crosses with parents differing in genetic systems for resistance had higher levels of resistance than R x S crosses, suggesting complementation of resistance genes. Segregation ratios of R x R clearly indicated the nonallelic nature of resistance genes in four of the parents. significant heterosis for yield in both experiments indicated greater genetic diversity for yield and its components. This was also evident among the parents. In the hybrids, it is essential that both parents carry resistance genes at different loci, so as to utilise the gene dosage effects for enhanced resistance in an appropriate genetic background. [AS]

Bacterial wilt; Proceedings of

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