Drought tolerance studies in spring wheat cultivars produced in South Africa

[摘要] ENGLISH SUMMARY: Drought is considered, worldwide, to be the most important factor limitingcrop yields. Spring wheat produced in the Western Cape region of South Africa isalso affected by water stress. The onset of global warming may cause periods ofwater stress in the winter rainfall regions of South Africa more frequently, whichmakes it important to identify spring wheat cultivars that can withstand theseconditions. The aim of this study was to determine whether cultivar differences indrought tolerance could be detected through the use of a series of physiologicaltests on spring wheat plants subjected to water stress at different growth stages.Furthermore to determine whether differences in physiological responses wouldbe of any commercial value. To evaluate this, plants were analyzed to comparebiomass production, yield and quality of stressed and control (unstressed) plants.A preliminary trial showed that the withholding of water might be moreappropriate in the induction of water stress than the use of polyethylene glycol.The trial also showed that the reduction of 2,3,5-triphenyltetrazoliumchloride(modified method) was not sensitive enough to detect water stress in springwheat.The evaluation of the physiological parameters showed that differences indrought tolerance do exist in spring wheat cultivars produced in the WesternCape region. The accumulation of proline and the water content of leaves provedto be the most sensitive parameters tested. A combination of these parametersmay provide valuable information in newly bred spring wheat cultivars. In a study on biomass production it was shown that the above groundbiomass was reduced by applied water stress. No clear distinctions in droughttolerance could, however, be made between cultivars. The use of leaf area (rateof leaf abscission) shows promise as a method to distinguish between droughttolerant cultivars.Yield and the yield components of all cultivars tested were severelyreduced by water stress at both the flag leaf-, milky kernel growth stage.Although reductions in yield and yield components was shown, no single cultivarproved more tolerant than the other.The application of water stress resulted in a general increase in kernelprotein content. Flour yield was lower, due to a relatively smaller production ofnon-protein components in the kernel. Although protein content increased withincreased water stress, no significant differences were noted in micro-loafvolumes. The results of the mixograph parameters tested were also similar.

[发布机构] Stellenbosch University