DETECTION OF GENOTYPIC DIFFERENCES IN EARLY GROWTH-RESPONSE TO WATER-STRESS IN WHEAT USING THE SNOW AND TINGEY SYSTEM

Early detection of genotypic differences in response to water stress w ould help in increasing selection intensity in breeding drought tolera nt wheat (Triticum aestivum L.). However, detection of small differenc es requires adequate control of the stress level. A system was used to determine if differences among genotypes in growth response to water stress could be detected. Haun stage and shoot dry weight were determi ned after 20 d in 25 cultivars grown with adequate water supply or wit h a water deficit imposed by lowering the water table by 8 cm and by i nterposing a porous ceramic disk, with an air exclusion value of 0.5 M Pa, in the conducting medium between the water table and the roots. Si gnificant differences were found among cultivars in the response to th e imposed water deficit. Haun stage reduction varied between 13% in th e spring wheat' Klasic' and 36% in 'Apollo', while shoot dry weight re duction was between 21% in Klasic and 67% in the club wheat 'Moro'. Th e coefficient of correlation between the Haun stage and shoot dry weig ht response to water stress was highly significant (r = 0.78). Althoug h no direct comparison could be made between response of early growth to water deficits and yield response in the field under drought stress , the results of the seedling growth test corresponded well with previ ous knowledge about the performance of the tested cultivars under wate r stress. Our results verified that the system could be useful for rap id evaluation of drought response in wheat breeding.