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Knowledge of the genetic control of disease tolerance is necessary for effective transfer of desirable genes in resultant progenies leading to development of disease tolerant cultivars and hybrids. Bacterial wilt (BW) disease-resistant varieties of tomato (Solanum lycopersicum L.) express differential reactions to bacterial biovars distributed in specific regions. Genetic control of host tolerance to BW disease was studied using the generations P1, P2, F1, F2, BC1, BC2 of three tolerant × susceptible crosses ("Utkal Kumari × CLN- 2460E;" "Utkal Kumari × CLN-2764A;" "Utkal Deepti × CLN-2460E") involving two tolerant ("Utkal Kumari," "Utkal Deepti"), and two susceptible ("CLN-2460E" and "CLN-2764A") genotypes exposed to the virulent bacterial biovars III and VI. The inheritance pattern indicated tolerance to BW disease was conditioned by a single dominant gene in three crosses when exposed to both biovars. Genetic control of bacterial wilt resistance did not depend on the interaction between genotype and bacterial biovars tested. Predominance of non-additive gene action and duplicate epistasis for conditioning of first appearance and incidence of BW disease in crosses indicated hindrance in progress through conventional selection. Selection for improvement of BW disease-related traits should be delayed to later segregating generations. The modified bulk method of selection appeared to be best for improving BW disease-related traits of tomato. Tomato hybrids tolerant to BW disease could be developed with the involvement of one parent tolerant to this disease. [ABSTRACT FROM AUTHOR]

Three experiments were conducted to assess the effect of different doses of gamma radiation on various seedling traits; determine the optimum doses of gamma radiation for different faba bean genotypes; find out the variation in optimum doses with respect to the different times of sowings after irradiation and methods of irradiation. Five faba bean genotypes viz., L-2013-060, L-2013-092, Anandnagar Local, Gazipur Local and Bangla Gangachar were used in these experiments. In Experiment I, seeds of five experimental genotypes were exposed to different doses (100 Gy 200 Gy, 300 Gy, 400 Gy, 500 Gy, 600 Gy, 700 Gy and 800 Gy) of gamma radiation and were sown immediately after irradiation. In Experiment II, seeds of Bangla Gangachar and L-2013-060 were exposed to varying doses (100–800 Gy) of gamma radiation and were sown at seven sowings starting from 0 h to 24 h at 4-h intervals after irradiation. In Experiment III, L-2013-092 genotypes was exposed to different doses (100 –800 Gy) of gamma radiation with two different methods of irradiation. In Experiment I, the lethal dose 50 (LD50) values have arrived at 140 Gy, 669 Gy, 575 Gy, 386 Gy and 158 Gy for L-2013-060, L-2013-092, Anandnagar Local, Gazipur Local and Bangla Gangachar, respectively. The growth reduction 50 (GR50) doses for different seedling traits ranged from 130 Gy to 320 Gy for L-2013-060, 250 Gy to 480 Gy for L-2013-092, 130 Gy to 370 Gy for Anandnagar Local, 200 Gy to 350 Gy for Gazipur Local and 250 Gy to 400 Gy for Bangla Gangachar. In Experiment II, the values for LD50 of the genotypes Bangla Gangachar and L-2013-060 were significantly singular for different time intervals of sowing. The values of GR50 for most of the seedling traits were found to increase with the delay in sowing after irradiation from 4 to 24 h when compared with the immediately sown seed lots. In Experiment III, LD50 for L-2013-092 was 337 Gy with Method 1 and 669 Gy with Method 2. In Method 1, most of the growth parameters attained GR50 doses lower than Method 2. The first method was found to increase the radiosensitivity of L-2013-092. Every experimental genotype used in these three experiments showed dose-dependent retardation of different seedling traits. These optimized doses may be employed to establish mutant populations for exploiting the novel traits of faba bean. The time of sowing after irradiation and method of irradiation was found to be essential for confirming optimum doses. [ABSTRACT FROM AUTHOR]

Recombination of commercially available hybrids could produce desirable segregants that act as sources of new alleles for tomato breeding. Seven commercial single cross (SC) hybrids of tomato (Solanum lycopersicum L.) were crossed in a half diallel fashion to obtain 21 double cross hybrids (DC) to estimate combining ability, mode of gene action and extent of heterobeltiosis for fruit yield, processing qualities and tomato leaf curl virus (ToLCV) disease severity traits. Predominance of non-additive gene action occurred in the control for all characters except for total soluble solids (TSS) content in fruit that was conditioned by both additive and non-additive gene action. Improvement of most traits in DC hybrids over SC hybrids occurred. Maximum heterotic effect in DC hybrids was for vitamin C content followed by lycopene content, fruit yield per plant, titratable acidity content, number of fruit per plant and percent disease index of ToLCV. Two good combiners, 'PAN-1286' and 'Devi' among SC hybrids were identified based on general combining ability effects and average performance. Commercial exploitation of DC hybrids, 'TO-1458 × L-37' and 'NS-501 × TO-1458' following multilocational testing in the tropics and subtropics might be useful. High yielding, ToLCV disease tolerant DC hybrids could be exploited in segregating generations to identify elite multi-parent advanced generation inter-cross (MAGIC) populations. [ABSTRACT FROM AUTHOR]