Uneven ploidy levels and a reproductive mutant required for interspecific hybridization of Medicago sativa L. × Medicago dzhawakhetica Bordz.

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Abstract
Crossing diploid (2n = 2x = 16) M. sativa L. (homozygous for the gene, jp, that causes failure of the postmeiotic cytokinesis) and tetraploid (2n = 4x = 32) M. dzhawakhetica Bordz. resulted in efficient recovery of interspecific hybrids. Interspecific hybrids were produced in large numbers (1.15-5.60 hybrids/pollination), comparable to intraspecific same-ploidy level crosses within M. sativa. All 237 interspecific hybrids were triploid (2n = 3x = 24) or near triploid. Morphologically, the F1 hybrids were also resistant to P. medicaginis. Chromosome pairing in the hybrids showed plant-to-plant variation; trivalent frequencies in some F1 hybrids were comparable to that observed in M. sativa triploids, indicating potential for recombination between M. sativa and M. dzhawakhetica genomes. Although the triploid hybrids were male sterile, and nealy female sterile, it was possible to produce backcross progeny. The first backcross was male and female fertile.