Effect of post anthesis water deficit on yield potentional and effective traits in promising winter and facultative bread wheat genotypes

Wheat cultivars that are more tolerant to terminal drought are more suitable to Mediterranean conditions. To increase water use efficiency, the target environment shound be taken in to account, because one trait might be effective in an environment but ineffective in another environment. Phenological adjustment with pathern of seasenal precipetation adaptation, improve water use efficiency in drought conditions. Suitable flowering time is the most important trait that is correlated with increasing water use efficiency in drought conditions. Seed size is also important in moisture stress prone environment. Larger grains facilitate germination and emergence, good early ground cover and biomass, because at seedling stage when plant is more dependent on seed storages (heterotrophic stage), it provides adequate reserves for seedling growth. Spike growth period is a crucial stage and significantly affects grain yield determination. During this stage demand for assimilate increases due mainly to enhanced growth and competition between growing structures and organs, particularly, growing spike and elongating stem. This study was carried out to investigate the effect of moisture deficit yield on potentional and effective traits inpromising winter and facultative bread wheat genotypes.
In order to evaluate yield potentional and effective traits inpromising winter and facultative bread wheat genotypes, the present investigation, was carried out in 2008-09 and 2009-10 growing seasons in Torogh Agricultural Research Field Station, Mashhad in the North East of Iran in 36º 13´ N, 59º 40´ E and 985 m above see level, in split plot arrangements using randomized complete block design with three replications. Main plots were water limited conditions with three levels (L1: Optimum condition, L2: water deficit using rainshelter from milky grain stage to maturity; L3: water deficit using rainshelter from anthesis stage to maturity). Ten bread wheat genotypes, suitable for cold and dry regions (V1: (Toos), V2: (C-81-10),V3: (pishgam),V4: (C-84-4), V5: (Mihan), V6: (C-D-85-15),V7: (C-D-85-9),V8: (C-D-84-5502),V9: (C-D-85-5502), V10: (C-85-6)) were assigned to subplots. Grain yield and biological yield were measured by harvesting of whole plot, weighing and then thrashing. Harvest index was calculated using following equation: HI= Grain yield / Biological yield *100. Number of kernel per spike (NK/S), Kernels weight per spike (KW/S) were obtained by using at least 20 spikes. Number of fertile spikes per square meter, 1000 kernel weight (1000KW) also were measured. Anthesis and physiological maturity were determined by observing of anters in %50 spikes and changing color of %50 pedancles to yellow, respectively.
The results showed that water stress (L2 and L3 treatments)decreased grain yield (18.6% and 45.6%, respectively) due to reduction in thousands kernel weight (TKW) and kernels per spike in compairin with optimum conditions. The results showed that genotypes V5 and V4 had higher grain yield (7593 and 7170 Kg/ha, respectively) due to optimum amount of yield component, such as fertile spike per square meter (806 and 765 spike), thousands kernel weight (37.87 and 38.33 gr), kernels per spike(36.2 and 36.0 kernels) and grain weight per spike(1.17 and 1.23 gr) respectively. The results showed that the highest harvest index(HI) is happended in optimum condition (40.95%). The lowest harvest index(HI) was belong to (L3)water limited conditions from anthesis to maturity(36.37%), due to reduction in water use in post anthesis staegs in compairin with optimum condition. genotypes V5 (Mihan) and V4 were the best in both optimum and stress conditions, so could be recomanded to cultivation for similar conditions of this study.
Results indicated that genotypes, V5: (C-84-8, recently released and named Mihan) and V4: (C-84-4) had the best performace amoung other genotypes, respectively. These cultivars had higher grain yield in both optimum and stress conitioms other genotypes, wich is the most important charachter for slow stressing. So these cultivars could be recomanded to cultivation for similar conditions of this study.