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Pod and Seed Growth in Five Cowpea Genotypes

M. S. A. Fakir
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M.J. Hossain
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

A field experiment was conducted to determine physiological maturity (PM) of seed, appropriate time of harvest of vegetable pod and protein content of pericarp and seed in five cowpea genotypes in Mymensingh (24.75⁰ N, 90.50⁰E). Results revealed that maximum dry weight of seed or physiological maturity (PM) obtained around 15 days after anthesis (DAA). The results further showed that the higher fresh weight of pod was achieved between 10 and 15 DAA. Genetic variations for protein content of pericarp and seed exist. Results conclude that vegetable pods of these cowpea varieties may be harvested at PM around 15 DAA with good protein content.

Keywords: Morphology, Physiological maturity, Growth rate, Nutrient content, Vigna unguiculata.

Location: Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date:

End Date:

Program Area: Seed Technology

Commodity: Cowpea

Objectives:

To study some morphological and growth characters of pod at different stages, and
To investigate time of physiological maturity of seed and to determine appropriate time of harvest of vegetable pod in five cowpea genotypes.

Methodology:

Five, three local and two exotic, genotypes of cowpea (Vigna unguiculata (L.) Walp.) were used. The two local varieties (Fallon-1 and Fallon-2) were collected from Bangladesh Agricultural Research Institute (BARI), Joydebpur. The third local variety (abbreviated as Local) was collected from local market of Mymensingh. The two exotic genotypes were collected from Republic of Trinidad and Tobago, West Indies and were designated as VRB-2 and VRB-5, respectively. The cultivars Fallon-1, Fallon-2, VRB-2 (virus resistant ‘bodi’-2) and VRB-5 (virus resistant ‘bodi’-5) are dwarf types and the local one is viney type. All of them appear to be relatively photoperiod insensitive. The experiment was conducted at the Crop Botany Field laboratory, BAU, Mymensingh. The experiment was laid out in a randomized complete block design with three replications. The experimental plots were divided into three blocks each representing a replication. Each block was divided into five unit plots, where five treatments (5 genotypes) were allotted at random. Thus, there were 15 unit plots in the experiment. The experimental land was first ploughed on the 16th June 1999 with a power tiller. The land was further ploughed and cross-ploughed several times followed by laddering until a good tilth was achieved. After ploughing and laddering, weeds and stubble were removed during final land preparation. Three seeds of each of the genotypes of cowpea were sown by hand at 5 cm depth using a spacing of 50 cm × 50 cm. Emergence of seedlings was completed between 3 and 5 days after sowing (DAS). Seedlings were thinned to one hill-1 at 10 DAS. Other recommended cultural and management practices such as weeding, use of pesticides and staking were performed as and when needed. Data on different parameters were collected from sampled plants. For pod growth analysis, samples from selected plants were collected beginning from the flowering until maturity. Flowers in the main stem and branches were tagged with coloured woolen threads at the beginning of the anthesis. Flowers were tagged at different dates so that data on different ages of pods i.e. 0, 3, 7, 10, 15 and 20 days after anthesis (DAA) were obtained. At each stage, at least 10 pods were randomly picked up from each replication and were enclosed in polythene bag to avoid loss of water. The collected pods were labelled and brought carefully to the laboratory. The samples were used to record different characters such as pod length (measured from the base to the tip, excluding the pedicel and stigma) and pod diameter (average of base, mid and top portion). Approximate whole pod area was calculated using the formula 2πr(r+h) assuming the shape of pod to be a cylinder, where π =3.14, r = radius of pod (cm) and h = length of pod (cm). Freshly harvested pods were shelled, and green seeds and pericarps were recorded at each age. The samples were oven dried at 800C±2 for 48 h and their corresponding dry weights of pericarp and seed, total dry pod (pericarp plus seed) were recorded at each stage. Moisture content of pod was determined on fresh weight basis. Absolute growth rate (AGR) and relative growth rate (RGR) of pod was computed. Nitrogen content of pericarp and seed at only 7 and 15 DAA was determined by MicroKjeldahl. Protein content of pericarp and seed was obtained by multiplying nitrogen content by 6.25. The collected data on various characteristics under study were compiled and analysed statistically to find out the significance of the results. The means for different characters were calculated and the analyses of variance were performed. The mean differences were evaluated by least significant difference (LSD) test.

Source of Information: Bangladesh J. Seed Sci. & Tech. 14 (1 &2): 237-243 (2010), ISSN 1029 - 8800

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

This result indicates that pod area became highest by 15 DAA. Maximum fresh weight was achieved 10 DAA in pericarp but 15 DAA in seed. Total (pericarp plus seed) fresh weight became highest by 15 DAA indicating that the appropriate time of harvesting the green pod. In harvesting time is due to different species used. Although protein content of pericarp decreased from 7 DAA to 15 DAA but it remained fairly good in the seed at 15 DAA indicating good quality of pod around 15 DAA. Results revealed that moisture content of pod may not be a good index of PM since it varies with varieties. However, particular age of pod i.e. certain time after anthesis (15 DAA) may be a reliable indicator of PM or maximum DM accumulation since all the genotypes required the same time (15 days after anthesis) to get the highest DM. Appropriate harvesting time for vegetable cowpea seemed to be after 10 DAA but before 15 DAA. Results concluded that a period of 15 days after anthesis (DAA) may be used as physiological maturity and vegetable cowpea pod may be harvested between 10 and 15 DAA in the five cowpea genotypes.

Knowledge Management: Journal