Dark induced senescence as a tool in breeding wheat for optimum senescencepattern

Senescence can influence: (1) leaf area duration, (2) area of transpiring t issue and (3) translocation of nutrients - mainly nitrogen to grain. Theref ore, selection for optimum senescence pattern might be efficient for improv ing performance of wheat in a given environment. This study was conducted t o investigate the feasibility of a seedling test for estimating genotypic d ifferences in senescence rate of wheat. We studied the response of several wheat genotypes to dark exposure of seedlings, by measuring the rate of chl orophyll loss in the first leaf. The rate of chlorophyll loss varied signif icantly among genotypes, the highest rate being more than double of the low est. Linear regression accounted for most of the chlorophyll content variat ion during dark treatment in all cultivars. Significant correlation was fou nd between the rate of chlorophyll loss following exposure to darkness and chlorophyll loss during aging in an environment relatively free of diseases and stresses. A good correlation was also found between the response of se veral genotypes to dark exposure and chlorophyll loss of seedlings followin g starvation. We conclude that a seedling test for dark induced senescence might allow an easy characterization of senescence pattern, allowing increa sed genetic progress in its optimization.