| II. Leaf rust Inheritance of mature plant reaction to leaf rust of wheat was studied in six crosses constituting a complete dial between the three susceptible vulgare wheat cultivars; Tosson, (H. 62 x H. 722) and Kenya Farmer, and the resistant cultivar FKN (Fn-K58-N11-50-18. These studies included F1, F2, backcrosses and F3 families, which were tested during the two successive seasons 1967-68 and 1968-69. Parents were included in the two seasons under natural leaf rust epiphytotic, which was fortunately severe during both seasos, and susceptible plants were severely infected. Crosses studied were grouped into two groups: (1) Resistant x susceptible crosses: This group was represented by three crosses including the cultivar FKN as a resistant parent crossed with each of the three susceptible cultivars Tosson, (H. 62 x H. 722) and Kenya Farmer. All F1 plants in the three crosses were completely resistant as in the resistant parent FKN, indicating complete dominance of resistance to leaf rust. Results showed that leaf rust resistance was simply inherited in these crosses. The resistant cultivar FKN might possess one dominant gene for leaf rust resistance designated as (Lr), while the susceptible cultivars Tosson, (H. 62 x H. 722) and Kenya Farmer carried the recessive allele (lr) for leaf rust susceptibility. II. Susceptible x susceptible crosses: This group was represented by three crosses; Tosson x (H. 62 x H. 722), Tosson x Kenya Farmer and (H. 62 x H. 722) x Kenya Farmer. The F1 plants were as susceptible as the parents. Results showed clearly that all these susceptible parents possessed the same genetic constitution or similar genes for susceptibility. Nevertheless, it was previously proposed the presence of the recessive allele (lr) for leaf rust susceptibility, which also confirmed the present finding in this group of crosses. From these results, it could be suggested that the genetic constitution of the parental cultivars would be :- Resistant : FKN LrLr Susceptible : Tosson, (H. 62 x H. 722) and Kenya Farmer lrlr III. Stem rust Inheritance of mature plant reaction to stem rust of wheat was studied in six crosses forming a complete dial between the four common wheat cultivars; Tosson, (Hindi 62 x Hindi 722), Kenya Farmer and FKN (Fn-K58-N 11-50-18). The parents, F1, F2 populations and backcrosses were grown in season 1967-68 while parents, F1 and F3 families were grown innseason 1968-69. Artificial epidemics were created, including the prevalent stem rust races, during the two successive seasons and caused severe infections to the susceptible plants. According to mature plant reactions to stem rust, the cultivars were classified into three classes :- Resistant : FKN Moderately resistant : Kenya Farmer Susceptible : Tosson and (H. 62 x H. 722) Crosses studied were grouped into four groups: (1) Moderately resistant x Susceptible group, represented by the two crosses; Kenya Farmer crossed with each of the susceptible cultivars Tosson and (H. 62 x H. 722). F1 plants showed susceptibility to stem rust as in the susceptible parent indicating complete dominance of susceptibility. Data in F2 and F3 indicated the presence of two pairs of gene difference between parents. It could be assumed that each of the susceptible cultivars Tosson and (H. 62 x H. 722) carried the dominant gene (S) for stem rust susceptibility while the moderately resistant cultivar Kenya Farmer might carry the dominant gene (R1) for moderate resistance. The gene (S) for susceptibility was epistatic over the gene (R1) for moderate resistance. |
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