Effect of cultivar and environment on seed yield in alfalfa
Huyghe C., Julier B., Bolaños-Aguilar E.D., Ecalle C.
Unité de Génétique et d’Amélioration des Plantes Fourragères, INRA, 86600 Lusignan, France.
The seed yield improvement is critical for the commercial development of varieties. The seed yield of 12 varieties was analyzed in 12 environments obtained through the combination of four locations and three years of harvest in a three-replicates design.
At harvest, the seeds were collected as well as the whole aerial biomass. The harvest index was calculated as the ratio between seed yield and the aerial biomass. Seed yield, above ground biomass, harvest index, seed weight per inflorescence and lodging susceptibility were measured.The main source of variation in seed yield among environments was the biomass. The genetic variance for seed yield was large and the genotype x environment variance was small. Thus, its broad-sense heritability was high (0.55). The genetic correlation between seed yield and lodging was also high with the lodging-tolerant varieties showing a higher seed yield. Seed yield was genetically correlated with harvest index (rg=0.99, figure 1). A higher harvest index was achieved through a genetic increase in seed weight per inflorescence (rg=0.91). There was no genetic correlation between seed yield and the vegetative biomass suggesting that breeding for a higher seed yield should not be deleterious to the vegetative growth and forage production potential.
Seed weight per inflorescence could be a valuable selection criterion to be used under a spaced plant design.
Figure 1 : Relationship between harvest index and seed yield among 12 varieties in 12 environments