Evaluation of defoliation on leaf water relations, chlorophyll content, and grain yield of triticale (x triticosecale wittmack) genotypes under water stress

ABSTRACT Optimizing the source size and its utilization by the sink is one of the main factors enhancing the yield potential and decreasing water demand in crops when exposed to drought. To investigate the effect of defoliation on leaf water relations, chlorophyll content and yield components of five triticale genotypes including Sanabad, Juanillo, ET833, ET845 and ET848 under wellwatered (100% FC) and water stress (50% FC) conditions, a controlled experiment was carried out at Shiraz University in 2013. The results showed that ET848 and Sanabad genotypes had higher chlorophyll content (ranged from 49.1 to 54.6 SPAD unit) under water stress. Among the triticale cultivars, water stress caused 21 to 42% decline in rate of water loss (RWL) In all genotypes except ET833 and Juanillo, the excised leaf water retention (ELWR) was slowly decreased under water stress conditions. In all triticale genotypes except ET848, water stress declined main shoot yield 2122%, while in ET848 was only 9%. Interestingly, in ET848, grain number per spike was not affected by moisture regimes. Sanabad cultivar, with 2.57 g/g had the highest initial water content (IWC) at defoliation of all leaves except the flag leaf and penultimate leaf treatment under water stress. Under defoliation and water stress, ET848 and Sanabad genotypes showed a greater 100grain weight ranged from 3.60 to 3.74 g. It was concluded that triticale cultivars were more sinklimited especially under water stress, and source restriction by defoliation which had less effects on main shoot yield could be used as a useful tool for lowering water consumption during grain filling.