Yield components, harvest index and plant type in relation to yield differences in field pea genotypes

The effectiveness of yield components, harvest index and morphological characteristics as selection criteria among four field pea (Pisum sativum L.) genotypes was examined. Genotypes were grown at a wide range of plant populations (9 to 400 plants m(-2)) to maximise environmental diversity. Both biological and seed yields approximately doubled from 9 to 100 plants m(-2). This response flattened from 100 to 400 plants m(-2). Differences among the genotypes were found only at 225 and 400 plants m(-2). Analysis of the yield components highlighted the plasticity and large genotype by environment interactions of field peas. The numbers of pods per plant and peas per pod were maximised when each genotype was grown as spaced plants, but the low plant numbers meant seed yields per unit area were at their lowest. Genotypic differences for plant harvest index (PHI) were also only found at 225 and 400 plants m(-2). Broad sense heritability estimates indicated that direct selection for PHI was not feasible. The inference from the yield component and pill results was that alternative selection criteria such as physiological or morphological characteristics may be necessary for improved yield potential. Classification of each genotype indicated that low seedling vigour may be a positive attribute for crop plants of semi-leafless and conventionally leafed field peas. Selection based on any single plant attribute is unlikely to lead to dramatic improvements in the yield potential of field peas. Selection should be based on plant characteristics rather than on differences in yield components.