Kernel Weight and Kernel Composition in Maize: Heritability and Genetic Control of Its Physiological Determinants in a Dent x Flint-Caribbean RILs Family.

The aim of this work was to expand current knowledge of the genetic control of maize (Zea mays L.) kernel weight (KW) and its physiological determinants (KGR: kernel growth rate; KFD: kernel filling duration) to (i) a RILs family of broad genetic background (dent × flint-Caribbean), and (ii) grain composition (protein, starch and oil, in %). A population of 193 RILs and its parental inbreds (B100 and LP2) were grown in the field during two seasons (Exp1: 2009-2010; Exp2: 2011-2012) in a completely randomized block design with two replicates. A total of 13 plants were tagged in each plot, and the date of silking was registered on all these plants. The apical ears of eight tagged plants were collected each 4 days from 18 days after silking onwards, and 15 grains per ear were sampled from the 10th (bottommost) spikelet position. Kernels were oven dried and weighed for the determination of potential KW (KWp), KGR and KFD. Mean KW (KWm) and grain composition were measured at maturity on all kernels set per plant in the remaining five ears. Significant genotypic, year and genotype × year interaction effects (P<0.01) were detected for all measured traits, except for KFD (no year effect). All traits had a normal distribution (P>0.5), except for KFD in Exp1 and starch in Exp2. Heritability was high for KWp and KWm (h²=0.74), and intermediate for the other traits (0.61 for protein and oil, 0.55 for starch and KGR, and 0.42 for KFD). Ten joint QTL were detected on seven chromosomes, but many with inconsistent effects across years. Two QTL (chromosomes 5 and 7) had a large and consistent effect for KFD, KWp, and KWm across years, the one in chromosome 5 also for KGR.