Study of reproductive compatibility and morphological characterization of interspecific hybrids in Sesamum sp.

In the present study, three wild species of sesame, Sesamum alatum, Sesamum malabaricum and Sesamum radiatum and one wild variety of Sesamum indicum, that is, S. indicum var. yanamalaiensis were crossed with eight cultivated varieties of S. indicum L. in both direct and reciprocal forms. All the wild species exhibited different degrees of cross compatibility with cultivated S. indicum. There was no crossed seed set in the direct and reciprocal crosses involving cultivars of S. indicum (2n = 26) with S. radiatum (2n = 64) and with S. alatum (2n = 26). The crosses involving S. malabaricum and S. indicum var. yanamalaiensis having the same chromosome number (2n = 26) as in the cultivated sesame genotypes were fairly successful in producing high percentage of crossed capsules with well filled seeds. The morphology of four wild species along with the cultivated species of sesame and the interspecific hybrids derived were compared. The wild species utilized in the present study differed significantly from the cultivated in branching pattern, leaf pubescence, flower size, color of corolla and anther, size, shape and color of extra floral nectary, capsule size, and shape, texture and size of the seed. All the successful interspecific hybrids showed predominance of wild characters than cultivated S. indicum.   Key words: Sesame, wild species, cross compatibility, morphological characterization.