A model analysis of yield differences among recombinant inbred lines in barley

Crop models ran support plant breeding if they can predict differences in p erformance of different genotypes. In this study, the ability of a crop mod el to explain yield differences among genotypes in a recombinant inbred lin e (RIL) population of two-row barley (Hordeum vulgare L.) was explored. Yie ld and model-input traits of 94 RILs and their parents, 'Prisma' and 'Apex' , were measured in field experiments conducted in Wageningen, Netherlands, in 1996 at low and in 1997 at high N levels. The major gene, dense, with th e dwarfing allele from Prisma, was segregating in this population. Short de nse RILs outyielded tall types in both years, and this yield advantage was stronger in 1997, largely because the tall genotypes lodged. A crop model b ased on existing routines for biomass production explained only 26 to 38% o f the yield variation among genotypes. The model, using input traits measur ed from the 1997 data, did not accurately predict growth of genotypes in 19 96 because some traits varied with plant N status, which the model did not account for. Model analysis in the high-N environment showed that of the se ven model-input traits examined, only lodging store, preflowering duration, and fraction of biomass partitioned to spikes had a significant effect on yield. When these three traits were used while fixing others at their acros s-genotype means, the model explained 6-5% of yield variation. To allow eff ective use of crop modeling in breeding, the ability of crop models to expl ain yield differences among genotypes has to be improved.