Cytogenetics of a reciprocal translocation integrating distichous pedicel and tendril-less leaf mutations in Lathyrus sativus L.

Grass pea (Lathyrus sativus L.) is a crop with 2n = 2x = 14 chromosomes. Two variants were isolated from 250 Gy gamma ray treated M2 progenies of variety BioL-203: (i) two pedicels per peduncle (distichous pedicel); and (ii) complete absence of tendril in leaf (tendril-less). Occurrence of quadrivalents at meiosis I and partial pollen sterility (48.50%) indicated that the plants were heterozygous for a reciprocal translocation (RT), and were tentatively designated as RT-7. It transmitted at an average of 44% in the progeny, and along with normal fertile plants (N/N), produced trisomic plants (5.76%) with association of five chromosomes in selfed and intercrossed progenies. Test of independence of this newly found translocation was performed by analyzing the pattern of chromosomal ring formation at meiosis I in the F1 progeny of crosses between RT-7 and six previously detected RT lines. Presence of a ring of six chromosomes in F1 plants indicates that the two translocations have one chromosome in common in crosses between RT-7 and RT-2, RT-3, RT-5 and RT-6, but possessed two different chromosomes in RT-7 × RT-1 and in RT-7 × RT-4. The two mutant traits assorted independently in F2 and back cross progenies of N/N plants. However, a strong deviation of segregation of four phenotypes derived from N/N × RT-7 from normal F2 and back cross ratios revealed tight linkages among translocation breakpoint, distichous pedicel and tendril-less leaf. The results suggested that the two mutations, distichous pedicel and tendril-less leaf, which assorted independently in N/N plants, were integrated on a single chromosome by a reciprocal translocation in RT-7 line.