Phenotypic Characterization of Common bean (Phaseolus vulgaris L.) Accessions Conserved at the Genetic Resources and Biotechnology Institute: Experimental Investigation

Abstract

The purpose of this study was to access variability in qualitative and quantitative traits among ten accessions that were obtained from Genetic Resources and Biotechnology Institute (GRBI) in Zimbabwe. The accessions were planted in a Randomized Complete Block Design, with three replicates. The qualitative and quantitative characteristics were recorded using the International Board for Plant Genetic Resources (IBPGR) common bean descriptor list. The quantitative data for the number of days to fifty percent flowering, plant height, days to maturity, seed size, grain yield and number of seeds per pod were analysed using hierarchical cluster analysis Minitab Release 12.22 version and GenStat Discovery versions 14 software. Cluster analysis divided genotypes in two main groups when the dendrogram was partitioned at the 26:22 % similarity levels. Cluster A comprised of 2 bean genotypes and cluster B comprised of 8 genotypes distributed in 2 sub-groups. Genetic similarity among the accessions varied significantly depending on the genotype pairs, groups and sub-groups. The genetic similarity was lower between accessions of different clusters (A and B) and higher between accessions within each cluster. Significant differences (P<0.01) were observed among the accessions for the number of pods per/plant, number of seeds per pod, length and seed size. Based on different morphological characters exhibited by different accessions, it could be concluded that morphological diversity exists among the ten accessions of common beans. It can also be concluded that there are no duplicate accession among the ten common bean accessions. *Corresponding Author: Rudo Musango  musangor@yahoo.co.uk Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 8, No. 6, p. 26-36, 2016 http://www.innspub.net J. Bio. Env. Sci. 2016 27 | Musango et al. Introduction The common bean (Phaseolus vulgaris L.) is among the five leguminous food crops grown worldwide (Kaplan and Lynch, 1999). It is the second most significant origin of human dietary protein and the third most important source of calories of all agricultural crops in eastern and Southern Africa (Spence, 2006). The Phaseolus vulgaris L. has two eco-geographical gene pools, Mesoamerica and Andes with multiple domestications (Kwak and Gepts, 2009). A lot of the genetic variability of this species is kept as ex-situ, outside the canters of origin, in genebanks (Borda 2011). In Zimbabwe, the collected germplasm that is maintained at the GRBI plays an important role in generating new crop varieties with high yield potential and resistance to biotic and abiotic stresses. The knowledge about the extent of genetic diversity, identification, differentiation and characterisation of genotype, provides an information tool for the detection of duplicates in the collection, hence an establishment of Gene bank core collections. This is also done in order to identify accessions with particular interest for plant breeders and researchers. Characterization of germplasm is an important first step in breeding efforts and it benefits plant breeders in selecting proper parental materials (Cilliers et al., 2000; Sarutayophat et al., 2007). In Zimbabwe the utilization of common bean accessions by plant breeders in their breeding programs is restricted due to lack of information about these genetic resources, (Valls, 2007). There are a considerable number of common beans conserved at the GRBI in Zimbabwe. This study focuses on characterising the common bean accessions using phenotypic characters to determine desirable agricultural traits. This allows the breeder to identify valuable traits or potentially valuable genotypes quickly. Data generated from characterization is as well employed in collection management and this encompasses verifying that an accession has not been mislabelled during harvesting, collection, monitoring of contamination through source and determining future handling procedures. The aim of the study is to measure variability in qualitative and quantitative characteristics among ten local landraces of common bean conserved at the GRBI. Materials and methods Study site Morphological characterization of the common bean accessions was conducted at the Crop Breeding Institute’s (CBI) Harare Research Farm. CBI is situated at the Department of Research and Specialist Services (Latitude 18o 11” South, longitude 31o 28” East), Mean annual rainfall ranges from 700 mm to 959 mm and average summer temperatures are between 24oC to 26oC. The soils are well-drained red clay loam. Experimental Design trial establishment and measurements The ten common bean accessions were planted in a Randomized Complete Block Design with three replications. Each accession was sown in a four rows, two meter long. Inter-plant spacing of 0.15m and inter-row, row spacing of 0.45m was used. The central two rows were used for data collection and analysis. The crop was rain fed. Plant characters and data recording The phenotypic characterization was done using the International Plant Genetic Resources Institute (IPGRI) descriptor list for common bean as the resource guide. Data for qualitative and quantitative characteristics was recorded on an individual plant basis using ten randomly selected plants per plot. The ten plants were selected from the two inner rows using the systematic random sampling method per plot, tagged and scored consistently over all characters. The phenotypic characters that were recorded in this study were cotyledon colour, hypocotyls colour, germination period, growth habit, terminal leaflet shape, days to 50% flowering, colour of flowers standard, days to 95% pod maturity, immature pod pigmentation, pod length, number of pods per plants, number of seeds per pod, seed size, seed shape, 100 J. Bio. Env. Sci. 2016 28 | Musango et al. seed weight, seed texture, seed colour and seed pattern as described in the IPGRI descriptor (1995.) Statistical analysis Data was analyzed using the GenStat Discovery Version 3.0 for quantitative characteristic. Duncan’s multiple-range test (P>0.05) was used for mean separation. Variation in both qualitative and quantitative characteristics was analyzed using hierarchical cluster analysis Minitab Release 12.22 versions (Minitab, 1998). Results Variations in morphological characteristics The dendrogram revealed the results of the hierarchical clustering of common bean accessions using their phenotypic characteristics (Fig. 1). A dendrogram is a binary tree over the common bean accessions being clustered, with each branch indicating the distance between the two accessions. The nodes of the hierarchy tree (dendrogram) indicated the levels of similarities that had occurred. The results displayed by the dendrogram showed that the ten common bean accessions were grouped into two (major) groups. Table 1. Source of germplasm. Collector's number Accession number Local name Place of collection Altitude MS11 3810 Sugar bean ZiwaNyanga 18 о 09. 624 South MS 13 3812 Chidhlau ZiwaNyanga 18 о 09. 624 South MS15 3814 Katonga small ZiwaNyanga 18 о 09. 624 South MS16 3815 Unknown ZiwaNyanga 18 о 09. 624 South MS20 3817 Pfumai Mukoyi-Honde Valley 18 о 30.141 South MS22 3819 Red bean MukoyiHonde Valley 18 о 30.141 South MS28 3824 Sugar bean 4 MukoyiHonde Valley 18 о 30.141 South MS30 3826 Pfumisai Hauna-Honde Valley 18 о 23.945 South MS32 3828 Sugar bean 2 Hauna-Honde Valley 18 о 23.945 South MS36 3831 Purple mottled CBI 18о 11 South These two main groups A and B were partitioned at the 26.22% similarity level, grouping influenced by the number of days by 50% flowering, growth habit, number of days to 50% germination, number of pods per plants and numbers of seeds per pod. The dissimilarity distance level between the two major groups was 68.324 (Table 2.). Accessions MS16 and MS36 were in group A. These accessions flowered and matured late (36 to 41 days to flowering) and with a range of 83 to 84 days to maturity. MS16 and MS36 had a range of seven to eight days to 50% germination and were also susceptible to lodging (11 to 12%) respectively. Both accessions had the same growth habit with moderate vigour, formed pods throughout the plant and had terminal leaf shapes, (sub-globose). Accessions MS28, MS15, MS11, MS22, MS32, MS30, MS20 andMS13 were in group B. Similarities in this group were in the number of days to 50% germination, cotyledon colour, terminal leaf shape, colour of standard flower, number of days to flowering, seed size, seed shape and seed texture. When the dendrogram was divided at the 39.03% similarity and 56.469 distance levels, two sub-groups were obtained as shown in Fig.1. These were designated I and II. It was noted that there was an apparent decrease in similarity or apparent increase in dissimilar from the first sub-group I to II subgroup. Starting from the smaller sub-groups upwards accessions MS30 and MS32, in sub-group I were the most similar, hence were the first to be joined (Fig. 1). They were 78.70 % similar and were separated by a distance level of 19.720. J. Bio. Env. Sci. 2016 29 | Musango et al. Table 2. Clustering of common bean accessions into major and sub-groups based on different levels of dissimilarity coefficient. Group Level of split Characteristics Accession numbers Major group A 26.66% This group consist of large seeds which belong to Andean South American genotype based on the seed size and 100 seed weight. Cotyledon colour (all green), number of days to 50 % to flowering (41 to 36 days ) and number of days to 95 % maturity (range of 83 to 84 days) , and seed shape (both kidney shaped), lodging susceptibility(12 to 11 % ). Terminal leaf shape (sub-globose). MS16, MS36 Major group B 26.66% This group consisted of both the Mesoamerican and intermediate seed size. Grouping of accessions with the same tendency for growth habit, four accessions had (Type I), two (type III) and two (Type IV). Number of days