Recovery of induced mutations in M2 generation of gamma irradiated cowpea (Vigna unguiculata L. Walp)

Abstract

A study was carried out on the recovery of induced mutations in the M₂ generation of gamma irradiated cowpea.  About 350g of dry cowpea seeds ‘IT84S-2246’ were equlibrated to 12% moisture content in a dessicator over 65% glycerol for seven days.  The sample were irradiated with gamma rays from Cobalt 60 source to a dosage level of 245Gy at the rate of 24.0 Gy/minute.  The treated seeds were planted at a spacing of 30 x 30 cm to raise the M₁ generation. At maturity, 150 M₁ plants were harvested according to the branching pattern of cowpea and peduncle by peduncle.  Progenies so obtained from M₁  plants were sown peduncle to row at a spacing of 15 x 15cm to produce M₂ plants.  Chlorophyll mutations were evaluated at the seedling stage.  The frequencies of chlorophyll mutations were computed.  Results obtained were analysed by chi-square test.  A wide spectrum of chlorophyll mutations ranging from Albina, Maculata, Viridis, Zonata and Marginata were observed.  The highest frequency of chlorophyll mutations (0.33) was obtained for M₂  plants that originated from peduncle three(3) of the main branch (1) while the least (0.05) was obtained for M₂ plants that originated from peduncle  three (3) of secondary branch five (V).  The occurrence of mutation was not significantly different from peduncle to peduncle.  This implies that selection of pods for the perpetuation of mutations in subsequent generation could be done from any part of the plant, though the four peduncles originating from the main branch (1) have higher mutation frequencies than secondary branches, and this may confer selection advantage on the former