Partial leaf rust resistance in wheat
1990
Broers, L. (CIMMYT, Mexico, DF (Mexico). Wheat Program)
Partial resistances (PR) acted in two steps. Step 1 led to a reduction of the infection frequency due to the presence of cell wall appositions. Step 2 led to the prolongation of latency period (LP) and reduction of pustule size (PS). The mechanism of step two is not yet known. Longer LP was inherited in a recessive way. PR-genotypes studied contained two or three genes for longer LP. These genes were at least partly different as transgressive segregation was observed. PR measured as LP was best expressed in adult plant stage and at low temperatures. Disease severity and the area under the disease progress curve were reliable estimators for PR in the field. Both showed high correlations with components of PR measured in the greenhouse. The logistic growth rate appeared to be unsuitable as an estimator of PR. Irrespective of the temperature sensitivity of the expression of LP, PR was expressed in a wide range of environments indicating that PR is a stable trait. Differences in the level of PR were observed among years and locations indicating that the levels of PR in the genotypes studied might not always be sufficient under conditions highly conducive to wheat leaf rust
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