Chromosome Interchanges in Lentil (Lens culinaris Med.)

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A number of interchanges (>100) were induced with the help of gamma rays in a lentil cultivar (PL 639). Trisomics were also available in the progeny of one interchange heterozygote (T₃₅); these were found to be trisomic for one of the two chromosomes involved in the interchange. For the identification and isolation of interchange homozygotes from the progeny of each interchange heterozygote, several progeny plants exhibiting 7 bivalents were crossed to normal plants. The resulting hybrids showing an association of 4 chromosomes were marked and their parental lines (that were progeny of interchange heterozygotes) were identified as interchange homozygotes. By using this approach, 15 interchange homozygotes were isolated. For the purpose of assembly of an interchange tester set, chromosomes involved in each of a number of interchanges were identified through intercrossing and karyotype analysis. 7 of the above 15 interchange homozygotes were subjected to intercrossing followed by meiotic analysis of hybrids. These 7 interchange stocks could be arranged in following three groups : (i) A set of 3 interchanges (T₁, T₁₁, T₂₉) designated as T_a-b. (ii) Another set of 3 interchanges (T₂, T₃, T₁₇) designated as T_c-d. (iii) A solitary interchange (T₅) designated as T_e-f. Further, for the identification of interchanged chromosomes in each of the interchange of the above tester set and in 7 other interchanges, their corresponding interchange homozygotes were subjected to simple karyotype analysis. In 4 of the 7 interchange homozygotes of the tester set, the interchanged chromosomes could be identified through altered chromosome morphology due to exchange of unequal chromosome segments. The results of intercrossing and karyotype analysis for chromosome identification were comparable and no discrepancy was observed. The altered chromosome morphology was also observed in the following 5 interchange homozygotes (not included in the tester set) : T₉, T₁₄, T₁₅, T₂₅, T₄₄.