Mutagenesis Of Cowpea for Early Maturity and Higher Yield

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2020-10

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University of Ghana

Abstract

ABSTRACT Cowpea [Vigna unguiculata (L.) Walp.] is an important grain legume that is widely grown in sub-Saharan Africa (SSA) for food and feed. Its grain is composed of high levels of protein, carbohydrate, micro-nutrients and macro-nutrients which are essential for human nutrition. In Ghana, cowpea productivity is considerably low due to frequent terminal drought as a result of climatic changes. Therefore, breeding improved varieties by incorporating “farmer-preferred” traits remains an overriding consideration to boost the productivity of cowpea in Ghana. The main objective of this study was to develop early maturing and high seed yielding cowpea varieties through mutation induction using gamma irradiation. Before the commencement of the mutagenesis, it is important to determine the right dose of gamma radiation for causing genetic variability in the desired agro-economic trait. Therefore, seeds of a farmer-preferred cowpea variety ‘Videza’ (obtained from a farmer in Akatsi, Volta region of Ghana) were gamma irradiated using twelve irradiation doses (0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 and1100 Gy) at GAEC. Using a linear regression model, the LD50 value of the cowpea variety ‘Videza’ was calculated as 240.51Gy. A dose-dependent reduction was observed in seed germinastion, seedling survival and plant height. For mutation induction, 2000 seeds of cowpea variety ‘Videza’ were acutely irradiated at 230 Gy, at the Radiation Technology Centre (RTC) of Ghana Atomic Energy Commission (GAEC), Accra, Ghana, using a Cobalt 60 source, delivering at a dose rate of 300 Gy/hr. Normal looking M1 plants with the desired traits (early maturity and high seed yield) were advanced to M2 generation and further advanced to M3 generation. The planting was linear and serpentine at a seeding rate of one seed per hill using 75cm x 40 cm. Control seeds were sown in three rows after every ten rows of the irradiated seeds separated by a spacing of 1.50m. Compared to the Control (Videza), genetic variability was recorded among plants in both M2 and M3 generation. The extent of genetic variability for the number of days to 50% flowering, number of days to 90% maturity, number of pod-bearing branches per plant, number of pods per plant, number of seeds per pod, 100-seed weight (g) and seed yield per plant (g) were evaluated in M2 and M3 generations. The number of days to 50% flowering and 90% maturity reduced in putative mutants in both M2 and M3 generations compared to the parental line (Control). The number of days to 50% flowering and days to 90% maturity, reduced further in the M3 generation as compared to M2. Increments in 100-seed weight per plant (g) and seed yield per plant (g) were observed among the putative mutants in M3 generation compared to the parental line (Control). The following twelve putative mutant lines P1N06#20, P1N06#9, P1N08#13, P1N08#17, P2N09#12, P4N03#2, P4N14#7, P5N05#10, P5N07#14 and P6N10#19 were outstanding in the M3 generation, exhibiting both early maturity as well as high seed yield. The twelve putative mutant lines are recommended for yield trials (preliminary and advanced), alongside the parental line (Videza) as well as a local check (as Controls), in farmer-participatory multilocational trials (including the Akatsi District of the Volta Region of Ghana) towards identifying superior lines for release as new variety or varieties.

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MPhil Nuclear agriculture

Keywords

Mutagenesis, Cowpea, Ghana, Nuclear Agriculture

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