Seed vigor of maize (Zea mays) cultivars affected by position on ear and water stress

A field experiment was conducted in 2014 to investigate the effects of different irrigation treatments (I1, I2, I3 and I4: irrigation after 60, 80, 100 and 120 mm evaporation from class A pan, respectively), cultivars (SC704, NS640 and DC303: late, mid and early maturing, respectively) and positions on ear (upper, lower and middle) on seed vigor of maize. The experiment was arranged as split-split plot based on RCB design with three replications. Irrigation treatments, cultivars and seed positions were considered as main, sub and sub-sub plots, respectively. Although, water limitation had no significant effect on seed weight, seeds produced under limited irrigation conditions showed low vigor as measured by electrical conductivity of seed leachates, germination rate and seedling dry weight. Seeds of SC704 germinated earlier and consequently produced larger seedlings in comparison with other cultivars. The higher seedling dry weight of the lower position seeds of ear was mainly the result of larger reserve accumulation and rapid germination. The advantage of the lower position seeds was more evident under severe water deficit. Thus, selection of the large and uniform seeds could be a simple way for improving seed and seedling vigor in maize cultivars.