The concept of hybrids: I. Comparative performance of pure line, hybrid and vybrid varieties in sorghum

Three pure line cultivars, two F1 hybrids and 44 vybrids (F4 plants from crosses between sexual and facultative apomictic lines and among facultative apomicts) were evaluated in the field for six yield components. In general, hybrid plots were the most uniform in appearance, followed by pure line cultivars and then vybrids. Two plant types were distinguished in vybrid plots: (1) highly vigorous plants which resembled each other, presumed to have arisen through apomixis; and (2) less vigorous and morphologically variable plants, produced sexually. Vybrids were generally intermediate between cultivars and hybrids, except in earliness and 100-grain weight. Hybrids had the highest economic yields and harvest indices, while pure line cultivars gave the most total dry matter and took the longest to reach 50% flowering. The three groups differed significantly for all traits, except harvest index, while differences within groups were mostly not significant