A Method for the Identification and Evaluation of Stay-Green Wheat Variety

Leaf senescence is synchronized with grain-filling in wheat. Delayed leaf senescence, or stay-green, can im-prove wheat yield. In this study, a method has been proposed to identify and evaluate the stay-green wheat. First, chlorophyll content of flag leaf was measured by SPAD-502 meter at three-day intervals from seven days after anthesis to physiological matur-ity. Meanwhile, green leaf area duration was visually recorded using 0–9 scale. Secondly, a mathematical model was simulated according to the above pheno-typic dates. Thirdly, the senescence characteristic parameters were calculated, including the time from anthesis to (i) senescence start (T_s ), (ii) complete senescence (T_o), and (iii) maximum rate of senescence (T_MRS), as well as the maximum rate of senescence. Finally, wheat varieties were divided into three stay-green types by hierarchical cluster analysis, including stay-green, early senescence and intermediate type. Based on this approach, a functional stay-green variety, Tainong 18 was screened. Tainong 18 with a delayed T_s and normal rate of senescence (RS) was similar to dSnR of type A under normal irrigation. However, it had earlier T_s and very small RS, and was similar to type B under drought stress. It can be used as a par-ent of crossing combinations in future wheat breeding, due to a longer photosynthetic activity and high yield potential.