پاسخ عملکرد دانه هیبریدهای ذرت به تنش خشکی در مراحل مختلف رشد

Drought stress is the most important limiting factor in crop plants including maize (Zea mays L.), which is the third important world crop after wheat and rice. Water deficiency at different growth stages affects maize yield differently. To examine the response of four maize hybrids to drought stress at different growth stages, a field experiment was carried out as a split plot based on completely randomized block design at Research Farm of College of Agriculture, Shiraz University, during 2009 and 2010 growing seasons. The main plots composed of four drought stress levels including optimum irrigation, withholding irrigation at vegetative growth stage (8-leaf to flowering), flowering and kernel filling. Four maize hybrids including Zola, BC666, Maxima and SC704 were allocated into sub-plots. Data analysis showed that the effect of year was not significant on measured characters thus, the data of both years were combined. Drought stress affected all measured characters except number of kernels per ear. The most significant effect of drought stress at vegetative growth phase was on reduction of plant height (10.2%). Drought stress at flowering reduced ear length (12.6%), kernel per ear (17.8%), yield (29.1%) and harvest index (20.4%). The 1000-kernel weight was significantly reduced (10.3%) when drought stress occurred at kernel filling stage. SC704 hybrid had the highest height (281.07 cm), kernel per ear (710.62), ear length (19.45 cm), 1000-kernel weight (316.49 gr), biological yield (25368 kg/ha) and kernel weight (11291 kg/ha). The highest harvest index (46.99%) was achieved in Maxima hybrid. It appears that flowering stage was the most sensitive stage to drought. Although drought stress at all growth stages reduced maize yield, but in dry areas, it might be possible to accept a small reduction in maize yield and save an irrigation in favor of other crops, simultaneously grown with maize. According to the results of this 2-year experiment, Maxima hybrid appeared to be suitable for drought-prone areas, while SC704 is better for normal conditions.