Assessment of physical purity of yellow common bean seeds in Tanzanian markets

Yellow bean trade is affected by limited information and unstructured system on production which has negative implications on seed supplies and other possible investments. The presence of improved varieties in seed markets shelves is a positive sign of a vibrant seed system. The aim of this study was to assess the physical purity of yellow bean varieties traded in the major markets in Tanzania using morphological traits basing on phenotypic traits of common beans. A total of 300 bean accessions were collected from Tanzanian markets and 14 inbreds reference samples were obtained from the International Centre for Tropical Agriculture (CIAT) gene bank in Uganda and the Tanzania Agricultural Research Institute (TARI). The accessions were grown to record their morphological traits to determine the level of phenotypic diversity of yellow bean varieties traded in the major markets in Tanzania. The samples were planted in augmented design and the data were collected from the growing plants at 50% of days to flowering, 50% of days of physiological maturity on number of pods per plant, number of seeds per pod, flower color and mature pod color. The analyses of variance (ANOVA), principal component analysis (PCA) and cluster analysis were conducted to characterize phenotypically the seed samples. The results of the ANOVA revealed significant (P<0.05) differences in six phenotypic traits out of eight traits that were studied. These were growth habit (GH), 50% of days to flowering (DF), flower color (FCOL), 50% of days to physiological maturity (DPM), mature pod color (MPDCOL) and seeds per pod (SDPD). The PCA distinguished the traits growth habit (DF), pods per plant (PDPL), 50% of days to physiological maturity (DPM), seeds per pod (SDPD) and seed weight (SW) as having greater variation. The study showed that there is phenotypic variation in yellow common beans in Tanzanian markets. Therefore, it was recommended that further investigation on the seed sold in the markets of Tanzania be done by periodically sending seed inspectors from the Seed Certifying Agency to these areas to collect seed samples from the markets for evaluation. Key words: Breeder seed, market seed samples, physical purity, seed systems, Tanzania, yellow bean