Genetic Variation for Biomass Production and Kernel Number Determination In a Maize Population of RILs.

The development of maize germplasm with good performance under nitrogen (N) stress implies a detailed knowledge of the physiological aspects involved, and of the interaction among the promising traits and the target environment. We phenotyped some of these traits for a collection of 180 recombinant inbred lines (RILs) derived from two contrasting parental inbreds (B100: American semident; LP2: Argentine flint). The collection, both parentals and a tester line (LP612) were grown under irrigation during 2009-2010 in a low-N soil condition. The experimental layout was a completely randomized block design with two replicates, without N application. Five plants were tagged in each plot at V₁₀, and measurements of time to anthesis and silking, anthesis - silking interval (ASI), and maximum leaf area index (LAI_MAX) were performed on these plants at flowering. At harvest, all tagged plants were collected separately, and plant biomass, harvest index (HI), plant grain yield (PGY), prolificacy (P), kernel number per plant (KNP) and kernel weight (KW) were determined. Significant genotypic variation (P<0.01) was detected for all measured traits. PGY of RILs and parental inbreds was highly correlated (p<0.001) with KNP (r=0.84), plant biomass (r=0.76), HI (r=0.69), P (r=0.43) and ASI (r=-0.41). Also, plant biomass was associated with LAI_MAX (r=0.68, p<0.001). Time to anthesis, LAI_MAX, KNP and KW showed a normal distribution (p>0.5). Contrarily, a significant (p<0.001) (i) positive skew was detected for ASI, P and plant biomass, and (ii) negative skew for HI. Plant biomass, PGY and P had a positive kurtosis (k>1.5). Inbreds in the uppermost quartile for PGY (>80 g pl^-1) were those within the uppermost quartile for plant biomass, LAI_MAX, HI and KNP. These results demonstrate the importance of enhanced light capture at low N offer, achieved through a high LAI, in determining plant biomass at maturity and, therefore, PGY.