Cytogenetic studies in Trifolium sp. related to berseem : III. The Relationships between the T. scutatum, T. plebeium and the echinata group.

In a cytogenetic study of five annual Trifolium spp. the genetical relationships between (1) T. scutatum Boiss. and (2) T. plebeium Boiss., and between them and (3) T. carmeli Boiss., (4) T. echinatum M. B. and (5) T. latinum Seb., were studied in intra- and interspecific F1 and F2 hybrids. Germination, seedlings development, pollen fertility and chromosome configurations during meiosis and seedset were recorded. All the T. scutatum x T. plebeium F1 were green, but the hybrids between either T. plebeium or T. scutatum and T. carmeli, T. echinatum or T. latinum were mainly albinos. Those that were green had a very high rate of mortality and the survivors produced many albino seedlings. Pollen fertility was about 60% in scutatum x plebeium F1s, and one of their eight bivalents was heteromorphic. Hybrids between either of these and T. carmeli, T. echinatum or T. latinum had 30-50% stainable pollen and had several multivalents, suggesting the existence of a system of chromosomal translocations in these species. Seed set was roughly correlated with pollen stainability. The nature of the isolation mechanisms operating between these species is discussed.