Abstract:

Plant height is a crucial agronomic trait for grain yield in wheat (Triticum aestivum L.). To detect changes of drought resistance in wheat development, drought stress coefficient (DS|WW) was calculated in five environments (year &#61620; experimental site) based on plant heights of 150 doubled haploid (DH) lines derived from Hanxuan 10× Lumai 14 at five measuring stages using conditional analysis method. The plant heights were measured every 7 d from jointing to flowering (S1–S5) in both rain-fed (drought stress, DS) and well-watered (WW) conditions in five environments including Fenyang, Shanxi in 2001 (F01), Haidian, Beijing in 2005 (H05) and 2006 (H06), Changping, Beijing in 2005 (Ch05) and 2006 (Ch06). DS|WW is the special responding of plant height to DS condition relative to WW condition. Unconditional drought stress coefficient (UDS|UWW) represents drought resistance before time t, and conditional drought stress coefficient (CDS|CWW) represents drought resistance within the period from time(t-1) to t. In all five environments, the plant heights were significantly lower under DS than under WW at all five stages (P<0.005). The largest plant height difference between under DS and under WW appeared in F01. The differences among environments for both UDS|UWW and CDS|CWW at each developmental stage were significant at P<0.0001. However, the result from multiple comparison analysis showed that part differences between environments in the same experimental site or year after S2 were insignificant, such as UDS3|UWW3 between H06 and Ch06, UDS5|UWW5 between H05 and H06. The significant positive correlations were detected for UDS|UWW between stages except five of ten correlation coefficients in Ch05. Poor correlations were observed for CDS|CWW between stages, however, the correlations between the adjacent stages appeared closer. In all environments, the significant positive correlations were always detected between UDS|UWW at time t and CDS|CWW before time t in one or more periods, indicating that the drought resistance at time t might partially attribute to that before time t. Path analysis suggested that drought resistance before jointing stage (CDS1|CWW1) and from heading to flowering (CDS5|CWW5) might play important roles for plant height at maturity, so, an ample supply of water at these periods are helpful for gaining higher yield.

Key words: Wheat, Plant height, Drought resistance, Development, Environment