A DIALLEL CROSS ANALYSIS OF SPREADING RESISTANCE TO SCAB (Gibberella zeae(Schw) Petch) WITH 8 VARIETIES OF WHEAT ( Triticum aestivum L.)

D Aiallel cress with 8 varieties of wheat (T.aestivum L.)which had different resistance to scab (Gibberella zeae (Schw.) Petch) was tested.Combining ability of diseased spikelets,eritability,correlations of characters and spreading rate of disease were analysed.There-cults showed that varietal resistance to scab was determined by additive effect of genes was.not very important.Heritability for scab resistant was rather low and affected by environ mental factors.It was also demonstrated that in number of diseased spikelets to effective spikelets and to spikelet density there existed positive correlation between phenotypeand genotype.There was weak negative correlation of phenotype and genotype between diseasedpikelet number and plant height,panicle lenght,noneffective spikelet number and grain number.There was significant correlation between the characters mentioned above and varie-tal resistance to scab.The incubation periods of the highly susceptible variety-Fulon Shen and highly resistant variety-Wan Shube were the longest and the shortest,respectively.The incubation periods of the other varieties were between 6.2 to 6.9 days.The sprading rates.of highly resistant varieties and highly susceptible varieties for scab were slower and faster respectively