Genetic Variation for the Physiological Determinants of Maize Kernel Weight In a Population of RILs.

In maize, kernel weight (KW) is determined by the rate and the duration of grain filling. Currently, the genetic differences that handle the changes observed in these two physiological determinants are unknown. The aim of this work was to study the genotypic variation of KW, the growth rate during active grain-filling period and the duration of this period. A population of 180 recombinant inbred lines (RILs), the two parental inbred lines (B100 and LP2) and a tester line (LP612) were grown in the field during 2009-2010 in a completely randomized design with two replicates. At the start of silking a total of eight plants were tag in each plot and the date of silking registered for each plant. Apical ears of tagged plants were collected on 18, 23, 28, 33, 38, 43, 48 and 53 days after silking and 15 grains from each ear at the position 10 from the bottommost spikelet were sampled, oven dried and weighed for the determination of kernel dry weight. The rate of grain growth during the active filling period and its duration were estimated. Significant genotypic variation (P<0.01) was detected for all measured traits. Parental inbreds showed similar KW (187 and 186 mg for B100 and LP2, respectively) achieved through different mechanisms, they differed in rate (7.8 and 10.1 mg/day for B100 and LP2, respectively) and duration of filling (44 and 36 days for B100 and LP2, respectively). Kernel weight of all dataset was more associated with the duration (r²=0.27, p<0.01) than the rate of filling (r²=0.15, p<0.01). The rate and KW showed a normal distribution (p>0.5). Contrarily, a significant (p≤0.001) negative skew was detected for the duration. Inbreds with high rates and duration (i.e., located in the uppermost quartile) were identified and were those within the uppermost quartile for KW (>280 mg).