Direct vs Indirect Selection for Maize (Zea mays L.) Tolerance to High Plant Density Combined with Water Stress at Flowering

Aim: The objectives of this investigation were to identify secondary trait(s) for selection of high maize grain yield under high plant density combined with drought stress at flowering and to identify whether the best selection environment is the optimum or stressed one.

Study Design: Randomized complete blocks design (RCBD) in 3 replications.

Place and Duration of Study: This study was carried out at the Agricultural Experiment and Research Station of the Faculty of Agriculture, Cairo University, Giza, Egypt in 2012, 2013 and 2014 seasons.

Methodology: Six maize inbred lines differing in tolerance to high density and drought at flowering [three tolerant (T); L-20, L-53, Sk-5, and three sensitive (S); L-18 , L-28, Sd-7] were chosen for diallel crosses. Parents and hybrids were evaluated in the field in two seasons under two contrasting environments; well watered and low density of 47,600 plants ha-1 (WW-LD) and water stress and high density of 95,200 plants ha-1 (WS-HD).

Results: Strong favorable and significant genetic correlations were detected between grain yield/plant (GYPP) or stress tolerance index and all yield components for inbreds and hybrids and days to anthesis (DTA), plant height (PH), ear height (EH), barren stalks (BS) and leaf angle (LANG) for hybrids. The traits DTA, EH, LANG, ears/plant (EPP), rows/ear (RPE), kernels/row (KPR), kernels/plant (KPP) and 100- kernel weight (100 KW) under both WW-LD and WS-HD environments had high narrow sense heritability (h2n).

Conclusion: Low DTA, EH and LANG and high rows/ear (RPE), EPP, 100KW, KPR and KPP could be considered secondary traits to drought and high density tolerance. The optimum selection environment for GYPP is the WS-HD environment for hybrids and WW-LD environment for inbreds.