Plant Density Tolerance of 23 Inbred Lines of Maize (Zea mays L.) and Their 69 Testcrosses

Maximum yield per unit area may be obtained by growing maize hybrids that can withstand high plant density. Maize genotypes differ in plant density tolerance (PDT). The objectives of the present investigation were to identify the density tolerant genotypes, to estimate the superiority of tolerant (T) over sensitive (S) inbreds and testcrosses and to identify the trait(s) of strongest association with PDT. Ninety-six testcrosses were produced between 23 inbreds and three testers. All genotypes were evaluated under low (LD), medium (MD) and high (HD) density (47,600, 71,400 and 95,200 plants/ha, respectively). The highest stress tolerance index (STI) under HD and MD was exhibited by the inbred lines L21, IL15, IL53, Inb176, IL80, L28, IL151 and L14 and the testcrosses IL51 × Giza2 , IL51 × SC10, L14 × SC10, L28 × Sd7, IL53 × SC10 and L28 × SC10, in descending order. Grain yield/ha (GYPH) of density tolerant (T) was greater than the sensitive (S) inbreds and testcrosses by 100.6 and 89.3%, respectively under HD. Superiority in GYPH was associated with superiority in all yield components, earliness in anthesis, shortening of anthesis-silking interval and plant height, thickness of lower and upper stem diameter, decrease in leaf angle and leaf area to produce 1g grain, increase in penetrated light to ear and in chlorophyll concentration index than the sensitive ones. The study concluded that to have a density tolerant cross, both parents should be tolerant.