EFFECTS OF RECURRENT SELECTION FOR RESISTANCE TO SCAB (GIBBERELLA-ZEAE) IN WHEAT

Scab caused by Gibberella zeae Petch., in common wheat, is one of the most severe diseases in China. A source population CO, bred for scab r esistance, was developed through three cycles of multiple-parent cross ing and intercrossing by means of the dominant male-sterile gene Tal ( Ms2), according to Wu's scheme. Phenotypic recurrent selection methods for increasing the resistance to scab-infection of spikelets and seed s with the male-sterile plants were carried out simultaneously in Nanj ing and Shanghai and at Jianyang, Fujian Province, for three cycles. T he generations from C0 to C3 and two check cultivars were evaluated, u sing a randomized block design, under conditions of an artificially in duced epidemic of scab during 1988-1990. The results indicate that the re were significant differences in the resistance to scab between thes e generations. On average, the percentages of diseased spikelets and s eeds of the male-fertile plants were reduced by 9% and 10%, respective ly. The frequency of resistant plants was distinctly enhanced by recur rent selection. Analysis of variance showed that no significant differ ences existed between cycles of recurrent selection in agronomic chara cters such as plant height, spikes per plant, spike length, numbers of spikelets and seeds per spike, weight of seeds per spike and 100-kern el weight, days to heading and to maturity. Except for plant height, m ost of these traits tended to be slightly improved with improvement of resistance in the gene pool. The variance for resistance in the gener ations was decreased under selection. Recurrent selection for scab res istance using the dominant male-sterile gene Tal (Ms2) was both an eff ective and feasible breeding method for producing this character in wh eat.