Cytogenetic studies in trifolium spp. related to berseem : II. Relationships within the echinata group.

In order to clarify the interspecific relationships between T. carmeli Boiss., T. echinatum M.B. and T. latinum Seb., numerous F1, F2 and BC1 hybrids of these species were raised, and their growth, pollen fertility, cytology and seedset were determined. T. carmeli was found to differ from both T. echinatum and T. latinum by at least three translocations, and their hybrids were semisterile as to pollen and seedset. T. latinum was more or less interfertile with T. echinatum and hybrids had normal meiosis, except for T. echinatum NYT 1401, whose hybrids with T. latinum were semisterile and evinced major chromosomal changes. Some implications of sterility and chromosomal heterogeneity are discussed. Backcrosses of T. echinatum × T. latinum F1s to either parent resulted in partial breakdown of the self-incompatibility system found in both parental species and their F1 hybrids.