Studies on the pre-harvest sprouting resistance of Kenyan commmercial varieties of wheat (Triticum aes tivum L.)

Abstract

In searching for pre-harvest sprouting resistant wheats (Triticum aestivum L.) for breeding purposes in many countries, one of the major hindrance has been the identification of varietal factors governing the resistance and how each factor correlates to sprouting. This study was undertaken to determine those factors that contribute to sprouting resistance in 25 Kenyan wheat cultivars. The major factors which were found to confer resistance to sprouting in this study are high seed dormancy, high germination inhibition by the chaff, slow rate of water uptake by germinating seeds and low alpha-amylase content in seeds exposed to high humidity and rain prior to harvest wide varietal differences were observed in every factor studied and these were significantly correlated with sprouting in the field or in la~oratory, however dormancy and aloha-amylase content had stronger correlations with s~routing than the o~her two factors. Cultivars that showed sprouting resistance had two or more of these factors suggesting that adequate resistance would only be achieved when several factors are incorporated in a variety. Varieties having desirable attributes were identified and could form the basis of breeding against sprouting in Kenyan wheats. Cultivars ranking for a particular factor varied with seasons. 7here was ranking consistency in some cultivars for a particular factor studied in various seasons but some deviated. Two or more seasons data would provide a better varietal ·picture in the factors governing sprouting resistance than one season's data. This study was also undertaken to determine the number of genes controlling red seed coat colour in four wheat cultivars. The study also included inheritance of dormancy in Kenya Kongoni/ PAA cross and its relation to seed coat colour. Red seed coat colour was observed to be controlled by one gene in Kenya Fahari (K2H), Kenya Tembo (KTS) and Bounty (STY) and by two genes in Kenya Kongoni (KKN). Seed dormancy was observed to be low in STY and KFH, intermediate in KT6 and high in KKN. This suggested that increase in genes controlling red seed coat colour would increase dormancy. It was further observed that dormancy in KKN was controlled by two recessive genes with a heritability of 0.79. This implied that it is possible to select for dormancy in early generations When Large populations are created.