Useful Heterosis and Combining Ability in Maize (Zea mays L.) Agronomic and Yield Characters under Well Watering and Water Stress at Flowering

Selecting superior parents for hybrid combinations and studying the nature of genetic variation are prerequisites for starting a successful breeding program. The main objective of the present study was to assess performance, useful heterosis and combining ability among maize inbreds under optimum and drought conditions. Six inbreds and their diallel F1's were evaluated in 2013 and 2014 seasons in two experiments, one under well watering (WW) and one under water stress (WS) at flowering. Data combined across seasons revealed that the inbreds L53, L20 and Sk5 and the crosses L20 × L53, L53 x Sk5 and L53 × Sd7 under WW and WS had the highest grain yield/plant (GYPP) and its components. The largest average heterobeltiosis (236.58%) was shown under WS by GYPP. Maximum GYPP heterobeltiosis reached 736.0% by the cross L28 x Sd7 under WS. (non-additive) mean squares for leaf angle (LANG), ears/plant (EPP), rows/ear (RPE), 100-kernels weight (100 KW), kernels/plant (KPP) and barren stalks (BS) under WW and WS, days to anthesis (DTA) under WW and anthesis silking interval (ASI) under WS. On the contrary, the magnitude of SCA was higher than GCA mean squares for ear height (EH), kernels/row (KPR) and GYPP, under WW and WS, DTA under WS and ASI under WW. The best inbreds in GCA effects for GYPP and all yield components were L53 followed by L20 and Sk5. The best crosses in SCA effects for the same traits were Sk5 × L18 followed by L20 × L53 and L28 × Sd7 under WW and WS. Mean performance of inbreds and crosses was significantly correlated with GCA and SCA effects, respectively for most studied traits under WW and WS.