Interpopulational and intervarietal F₁ hybrids in Lolium perenne: heterosis under simulated-sward conditions

SUMMARY The performance of a series of intervarietal F 1 hybrid populations was determined in simulated swards in a range of environmental conditions. On average the hybrids were more stable in performance than their parental varieties, but they showed no general yield advantage. Several hybrids were markedly heterotic at the higher-parental level, however. More heterosis was exhibited in high productivity conditions than in less favourable environments. A generally poor correlation between parental and F 1 hybrid performance under competitive simulated-sward conditions and performance in noncompetitive spaced-plant conditions was found.