Summary Three distinct variants differing for their phenotypic appearance and floral characters were identified and isolated in M 1 generation of 200 Gy gamma irradiated set in Lathyrus sativus. They were subjected to meiotic analysis to understand their genotypic sensitivity to induced cytological changes. One interesting abnormality encountered during the present study was nucleolar dysfunctioning in the treated plants. Despite of chromosomal abnormalities like laggards, stickiness, micronuclei, etc. chiasma frequency was found to increase in the 3 plants isolated at 200 Gy dose of gamma rays. Pollen fertility was also moderately affected.

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Summary During the meiotic analysis of gamma ray treated sets, two induced translocation heterozygotes (P-1 and P-8) were cytologically isolated at 200 Gy and 400 Gy doses in Lathyrus sativus L. var. Pusa-24. However, both translocation heterozygotes (P-1 and P-8) exhibited the formation of a ring and chain of multivalents in majority of PMCs at diakinesis and metaphase-I. At anaphase-I, both the translocation heterozygotes displayed various abnormalities as well, although some PMCs showed normal 7 : 7 separations but the most common and frequent separation to be encountered in these two variants was 6 : 8 separation. Pollen fertility was found to decline to 41.32% in P-1 and 39.46% in P-8 against 98.92% in the control sets.

Gamma irradiation is one of the most important physical mutagen used for inducing beneficial as well as harmful cytogenetic effects in many crop plants. The cytogenetic changes occurring due to the storage of Lathyrus sativus L. seeds after gamma irradiation were examined during the present study. Mitotic index showed a dose dependant decrease while the dose and duration of treatments increased. The effect of ageing accompanied with gamma irradiation was found to be more deleterious as compared to that of individual treatments of the two. Various chromosomal abnormalities viz. fragmentation, scattering, bridges, laggards, stickiness, etc. were found at all the three treatment sets. A significant reduction in moisture content, germination percentage and increase in the percentage of chromosomal anomalies was recorded maximum in the stored gamma irradiated seeds which ultimately ensures the fact that immediate sowing of the irradiated seeds is of prime importance and it may adversely affect the survivability of the seeds as well as plant when sowing is delayed.