COWPEA SEEDS RESPONSE TO X-RAY & ENVIRONMENT

COWPEA SEEDS RESPONSE TO X-RAY & ENVIRONMENT

ABSTRACT

Cowpea falls among the most valued food legumes in the majority of African countries and it is a valuable source of dietary protein for Kingdom Animalia. When cowpea seeds are exposed to X-rays, cowpeas can change genetically through mutagenesis. Mutagenesis is used to create new genetic variability while improving cultivars. This study was carried out with cowpea seeds from the Abakpa market in Ebonyi State. The seeds were exposed to different levels of X-rays: 0 mAs, 5 mAs, 10 mAs, 15 mAs, 20 mAs, 25 mAs, and 30 mAs; before they were taken to Ebonyi State University farm for planting. Two environments were used: a field and a greenhouse. The field had ridges and the greenhouses had polythene pots filled with a mix of sand and manure. The pots were filled with a mixture of sand and manure at a ratio of 3:1. Each treatment was planted in five replicates, and data was collected on parameters like leaf number, shoot length, leaf length, leaf width, and viability. In the field, 15 mAs and 20 mAs treatments had better germination, while in the greenhouse, 5 mAs and 10 mAs did better. For growth, 5 mAs and 20 mAs did well in the field, and 10 mAs and 25 mAs did well in the greenhouse. The differences weren’t significant, possibly because the variation caused by X-ray was not high enough to have given wide phenotypic differences.

INTRODUCTION

In the plant life cycle, germination and seedling establishment are crucial phases. Plant density, homogeneity, and management options are determined by the stand establishment in agricultural production (Cheng and Bradford, 1999). It is the most critical stage in seedling establishment, determining successful crop production (Almansouri et al., 2001; Bhattacharjee, 2008). The germination of cowpea seed is a complex process depending on the genetic and environmental factors, such as temperature, light, and salinity (Mahmoud, 1985; Barbour, 1988).

Environmental factors such as temperature, light, pH, and soil moisture are known to affect seed germination (Rizzardi et al., 2009).  Each factor separately or jointly, affects the germination percentage and germination rate. The frequency of extreme stress events on plant growth, development, and yield differ among varieties of plant species, depending on the prevailing optimal environments as well as the susceptibility capacity of individual species to a particular stress type.

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Cowpea is considered more tolerant to drought than soybean or mung bean because it tends to form a deep taproot (Turk et al., 1980; Ziska and Hall, 1983; Petrie and Hall, 1992; Hall, 2004). Cowpea seeds should not be cultivated on poorly drained soils because it has a competitive niche in sandy soils and cannot withstand extremely wet circumstances. The fact that cowpea grows well in arid climates is among its most amazing characteristics.

Cowpea has an estimated global production area of over 14.5 million hectares  (FAO 2003)and its annual grain production increased to over 6.3 million metric tons in 2008 (Singh, 2012) due to concerted research efforts that have led to the release of improved cowpea seeds of different varieties to farmers in producing countries. Nigeria is the number one world producer of cowpeas with an annual production of 2,950,000 MT in 2013 (FAO 2003). Kaduna, Katsina, Zamfara, Bauchi, Sokoto, Kebbi, Plateau, Adamawa, Taraba, Gombe, Borno, Yobe, Jigawa, Niger, Benue, Nasarawa, and Kano are the principal states in Nigeria that produce cowpeas. In these regions, the crop is historically produced and intercropped with cereals like maize and sorghum (Timkoet al., 2007).

However, cowpea productivity and production in Nigeria have major constraints. These include harmful illnesses and insect pests, a limited genetic pool for breeding, subpar cultural norms, and subpar products (Rachie, 1985). Abiotic stresses such as low pH, low fertility, excessively high temperatures, drought, and inadequate crop protection practices also limit production. These stimulate the interest of plant breeders and researchers. Plant breeders’ main goal is to create crops that outperform current cultivars in terms of germination, growth production, and quality. This goal depends on genetic variation being available, ideally in the main gene pool.

There are now several reports showing experimental evidence for reproducible gene transfer to cowpea, including genes for pod borer (Higgins et al., 2012), cowpea weevil (Solleti et al., 2008), and for weed control (Citadin, et al., 2013) as well as a range of model genes to assess the technology (Citadin, et al., 2013; Behura et al., 2014). Where genetic variability is not enough, new material needs to be examined or new variation formulated through induced mutation. Mutation induction has become an established tool in plant breeding to supplement existing germplasm and to improve cultivars in certain specific traits.

The effect of irradiation on the germination process of seeds has been widely studied and different effects were reported according to the plant species, the state of water in the seed, and the dose of irradiation. The rate, the speed, and the percent of germination were found to be markedly reduced in response to irradiation (Corovic and Canak, 1958; Cardona, et al., 1960; Campell, 1967; Van HysteeandCherry1967). Higher exposures to gamma rays may result to injury in seeds and usually show inhibitory effects on seeds of angiosperms and gymnosperms (Akhaury and Singh 1993; Thapa, 1999). Mutagenesis in cowpea seeds can be achieved by using physical agents (ionizing and non-ionizing radiations) or chemical mutagens.

However, several practical problems with chemical mutagens have been identified, which include soaking of seeds, penetration of the relevant target cells, and safety of handling and disposal among many others (Micke et al., 1990). Among the radiation-based methods, gamma-ray and fast neutron bombardment now supersede X-ray in most applications.

AIM OF THE STUDY

To determine the influence of X-ray and Environment on germination and growth of cowpeas.

OBJECTIVES OF THE STUDY

The main objectives of this study were to:

1. To evaluate the X-ray effect on the germination and growth of cowpea
2. To determine the environmental  effect X-ray effect on the germination and growth of cowpea
3. To compare X-ray and environmental effects on germination and growth of cowpea

CONCLUSION

Increasing the dose of X-ray did not have a significant effect on cowpea seeds’ germination and growth characteristics of cowpeas. The environment in which the cowpeas were sowed contributed to the variations that were found for those parameters that were considered.