Effect of temperature on intra- and interspecific crosses of diploid and tetraploid red clover, Trifolium pratense L.

Reciprocal intraspecific crosses of diploid and tetraploid Trifolium pratense L. and reciprocal interspecific crosses of 4N T. pratense and T. medium were attempted in conjunction with a 40 °C temperature treatment on the female parent. The temperature treatment was found to be of little benefit in interspecific and intraspecific hybridization attempts. No cytologically verified interspecific hybrids were found from either heat-treated or non-heat-treated crosses. Intraspecific crosses produced no viable triploid offspring. One seedling was found to possess 17 chromosomes but died before positive verifications could be made. However, several seedlings from male-sterile diploid × tetraploid crosses were found to possess 28 chromosomes. These resulting tetraploids were cross compatible with other tetraploids.