Seven Different Primary Trisomics In Grass Pea (Lathyrus sativus L.). II. Pattern of Transmission

The seven different primary trisomics, isolated by the present authors in grass pea (Lathyrus sativus L.) transmitted at reduced rate than the expected 50% in the progeny of selfed trisomics and in the intercrossed progeny of trisomics and diploid plants (2n=14). Among the trisomics, type-IV (ternate-verticillate leaflet) exhibited the highest transmission rate (29.3%) while it was minimum (16.0%) in case of type V (alternate leaflet) in selfed progeny. When trisomic plant was used as seed parent during intercrossing with normal diploids, rate of transmission of trisomy was found to be higher than when it was used as pollen parent. Several factors like seed size, rate of germination and survival of seedlings, trivalent/univalent frequency and pollen sterility might affect the transmission of trisomics in grass pea. Small, light-weight seeds germinated poorly and survival of its seedlings was not good at all but higher number of trisomic plants appeared from small sized seeds than from large, heavy weight seeds although it germinated and survived at better rate than small seeds. Higher frequency of trivalent during metaphase-I as well as transmission rate of extra chromosome were encountered in trisomics I, II, IV and VI than types III and V where univalents appeared more frequently than trivalents at microsporocytes. Among the trivalents, frying pan configuration was the lowest in type IV showing highest rate of transmission, while this configuration was maximum in PMCs of type V exhibiting lowest rate of transmission. Increased frequency of trivalent led to high incidence of pollen sterility and influenced rate of transmission of the extra chromosome in trisomic plants through anaphasic disturbances.