PLANT DENSITY TOLERANCE OF 28 EGYPTIAN COMMERCIAL MAIZE (Zea mays L.) HYBRIDS AND ITS CORRELATED TRAITS

Growing maize (Zea mays L.) at high-plant density using proper genotypes that withstand high density stress is a new approach to maximize its grain productivity. The objectives of the present investigation were to identify the density tolerant and high yielding Egyptian maize hybrids, to estimate the superiority of tolerant (T) to sensitive (S) hybrids and to identify the trait(s) related with the density tolerance capacity. Twenty-eight Egyptian modern commercial maize hybrids were evaluated in Giza, Egypt under four levels of plant density, namely 47,600 plants/ha (D1), 71,400 plants/ha (D2), 95,200 plants/ha (D3) and 119,000 plants/ha (D4) using a split plot design with three replications in two years. The highest density stress tolerance index (STI) under D2, D3 and D4 was exhibited by the hybrids P3444, SC 131, P3433, SC 235 and SC 10. Grain yield/ha (GYPH) of density tolerant (T) hybrids was greater than the sensitive (S) hybrids by 62.37, 74.15, 57.98 and 56.02 %, under plant density conditions of D1, D2, D3 and D4, respectively. Superiority of T in GYPH was associated with superiority in grain yield/plant (GYPP), kernels/plant (KPP), rows/ear, ears/plant, ear leaf area, leaf area index and reduction in leaf angle, leaf area to produce 1g grain (LA/1gG), ear height, thickness of lower and upper stem diameter as compared to S hybrids. The correlation analysis suggested that the secondary traits for high density tolerance in the stressed environments D2, D3 and D4 are high GYPP, high GYPH, high KPP and low LA/1gG and low anthesis-silking interval.