Genetic Progress in Grain Yield and Physiological Traits in Chinese Wheat Cultivars of Southern Yellow and Huai Valley since 1950.

Understanding the key characteristics associated with genetic gains achieved through breeding is essential for improving yield-limiting factors and designing future breeding strategies in bread wheat (Triticum aestivum L.) cultivars. The objective of the present study was to investigate the genetic progress in yield-related and physiological traits in cultivars released from 1950 to 2012 for irrigated conditions in the southern Yellow and Huai Valleys Winter Wheat Zone. Field trials including 26 leading cultivars from 1950 to the present time were conducted at Zhengzhou and Zhoukou in Henan Province, during the 2013-2014 and 2014-2015 cropping seasons, providing data from four environments. Grain yield (GY) was significantly increased by the linear rate of 57.5 kg ha-1 yr-1 or 0.70% (R2 = 0.66, P < 0.01) and significantly correlated with increased thousandkernel weight (TKW) (r = 0.48, P < 0.05), spike number m-2 (r = 0.44, P < 0.05), kernels m-2 (r = 0.56, P < 0.01), aboveground biomass (AGBM) (r = 0.80, P < 0.01), harvest index (HI) (r = 0.84, P < 0.01), watersoluble carbohydrate at 10 d postanthesis (WSC-10) (r = 0.80, P < 0.01), and reduced plant height (PH) (r = -0.85, P < 0.01). There was no significant change in kernel number per spike, heading date, normalized difference in vegetation index at anthesis and at 10 d postanthesis, leaf area index at anthesis and at 10 d postanthesis, and canopy temperature depression at anthesis during the past 60 yr. Soil plant analysis development (SPAD) estimates of chlorophyll content at 10 d postanthesis (Chl-10) increased with year of release and were significantly correlated with GY (r = 0.69, P < 0.01), PH (r = -0.76, P < 0.01), AGBM (r = 0.52, P < 0.01), HI (r = 0.71, P < 0.01), and WSC-10 (r = 0.73, P < 0.01). Cultivars conferring Rht-D1b and Rht- D1b + Rht8c showed increased GY, TKW, AGBM, HI, WSC-10, and Chl-10. Stem water solubility content can be used as a selection criterion for further improving yield potential. [ABSTRACT FROM AUTHOR]