Biomass accumulation and main stem elongation of durum wheat grown under Mediterranean conditions

Detecting and exploiting genetic variation in biomass accumulation is of gr eat importance for increasing wheat yield when the harvest index is close t o its upper limit. This study was undertaken to analyse the pattern of biom ass accumulation and main stem elongation in 25 durum wheat (Triticum turgi dum L. 'Durum') genotypes. Field experiments were conducted over 2 years in two environments contrasting in the amount of available water, in northeas tern Spain. Plants were sampled at the main stages of Zadoks' scale, and dr y weight per plant, crop dry weight (CDW) and main stem length were measure d at each stage. Measurements for growth traits and thermal time from sowin g fitted better to an asymmetric logistic peak curve than to the Richards l ogistic model. Four biological variables were computed from the curve. Diff erences among curves describing changes in biomass were found to be greater between irrigated and rainfed sites than between years. Drought stress had less effect on main stem elongation than on biomass accumulation. Average dry weight per plant and CDW were reduced by drought by 42 and 38%, respect ively, due mainly to similar reductions in the mean rate of growth of the t wo variables. In contrast, cycle length from sowing to the maximum values o f dry weight per plant and CDW was only slightly modified by drought. (C) 2 001 Annals of Botany Company.