| Inheritance of leaf rust resistance in wheat GEETA TONDON and VEENA CHAWLA Haryana Agricultural University, Hisar - 125004, India Coevolution of host pathogen relationship (VAN DER PLANK 1968) and clossal losses which diseases like rusts can cause under epiphytotic conditions (JOSHI 1978) warrants for the identification of diverse sources of resistance. Moreover genotypes with diversified resistance be incorporated in breeding programme to avoid chances of narrow genetic base of resistant wheat cultivars. In that context it would be imperative to know the nature and number of genes controlling the rust resistance in wheat. Present study deals with such an attempt. Materials and Methods Nine wheat genetic stocks were screened against three single spore cultures (IL004-162A, IL007-108 and IL009-11) of leaf rust (Puccinia recondita Rob. ex. Desm. f. sp. tritici Eriks) with known avirulence/virulence formulae (Table 1) at seedling stage and resistants were crossed with Agra local (a genotype devoid of any resistance gene). The F1's and F2's of these crosses were also screened against the same three cultures. Twenty five plants of each parent and F1 and about hundred plants of each F2 were raised in earthen pots in a growth chamber maintained at a constant temperature of 20 + or - 2C and 80-100% humidity. Normal procedures of seedling inoculations and green house maintainance were followed. Observations regarding reaction type (resistant or susceptible) as suggested by STAKMAN et al. (1962) were noted after 14 days of inoculations. Results and Discussion Among the nine genotypes screened against three cultures, only two (WC 313 and Fortylaya) were resistant to all the three cultures. On the contary Agra local was susceptible to these cultures. Remaining six genotypes were resistant to two cultures, IL004-162 A and IL007-108. (Table 1a). In order to have an idea about nature and number of resistance genes the F1 and F2 populations of crosses of resistant parents with Agra local were analysed. The F1 data (Table 1b) indicated that resistance was dominant in all the cases. The reaction of F2 population against the three cultures indicated monogenic or digenic ratios of resistant/susceptible plants. (Table 2). This showed that either one or two genes are controlling the resistance against these cultures. In many cases two ratios (both monogenic or digenic) showed goodness of fit by X2 test. This ambiguity for monogenic or digenic control for rust resistance in present cace could be attributed to one of the following reasons: |
| --> Next |