Studies On The Numerical Taxonomy Of Common Bean (Phaseolus Vulgaris L.) And Its Related Species

Common bean (Phaseolus vulgaris L.) is an important vegetable in China. Although common bean cultivation in China is a long history, germplasm resources are not rich enough. Shortage of germplasm has been one of the bottle-neck in common bean breeding. On the other hand, the classification of common beans and its related species is controversial. In the present experiment, 24 cultivars of common bean, 3 cultivars of lima bean (Phaseolus lunatus L.), 1 cultivar of mung bean (Phaseolus aureus Roxb), 1 cultivar of red bean (Phaseolus angularis Wight), and 2 cultivars of asparagus bean (Vigna sesquipedalis Wight) were used to study the numerical taxonomy based on botany morphological traits and pollen environmental scanning electron microscope submicroscopic morphological traits. The main results were as follows:1. Selected 49 botany morphology characters of 31 species were investigated. The result of Q cluster analysis showed that the block distances between cultivars varied from 0.026 to 0.986, and all 31 cultivars could be grouped into 4 clusters at the coefficient level 0.366, i.e. 'Phaseolus vulgaris L.' group, 'Phaseolus lunatus L.' group, 'Phaseolus aureus Roxb and Phaseolus angularis Wight' group, ' Vigna sesquipedalis Wight' group, and the 24 Phaseolus vulgaris L. cultivars could be grouped into 4 small groups at the coefficient level 0.226, including one dwarf bean cluster, one semi-vine bean cluster, and two vine bean clusters. Result of R cluster analysis verified that the 49 selected botany morphology characters used to classify common bean cultivars and the cultivars related to common bean were appropriate. The discriminant analysis results showed that a new bean samples (Phaseolus vulgaris L., Phaseolus lunatus L., Phaseolus aureus Roxb and Phaseolus angularis Wight, Vigna sesquipedalis Wight) could be effective classified by observation results of 27 morphology characters.2. The pollens of 7 cultivars of Phaseolus vulgaris L. and 4 cultivars of its related species were observed through environmental scanning electron microscope (ESEM). The results showed that the pollen shapes were near spherical in equatorial view. The pollen size changed greatly among cultivars. There were certain differences in pollen extine sculpture and germinal pore. Cluster analysis was applied to classify the 11 cultivars by using the selected 14 pollen submicroscopic morphology characters. All selected cultivars were grouped by running SPSS cluster program. It was found that the block distances were ranged from 0.000 to 1.000. The cultivars could be grouped into 4 groups by Q cluser analysis at the coefficient level 0.118, i.e., 'Phaseolus vulgaris L. and Phaseolus lunatus L.' group, 'Phaseolus aureus Roxb' group, 'Phaseolus angularis Wight' group and ' Vigna sesquipedalis Wight' group. The 'Phaseolus vulgaris L. and Phaseolus lunatus L.' group could be grouped into dwarf bean cluster, vinecommon bean cluster and lima bean cluster at the coefficient level 0.042. R cluster analysis of 11 pollen submicroscopic morphology characters verified that the pollen submicroscopic morphology characters were appropriate. The discriminant analysis results showed that a new bean samples (Phaseolus vulgaris L. and Phaseolus lunatus L., Phaseolus aureus Roxb, Phaseolus angularis Wight, Vigna sesquipedalis Wight) could be effective classified by observation results of 5 pollen submicroscopic morphology characters.3. The cluster results were unanimous both by using botany morphology characters and by using pollen submicroscopic morphology characters. Clustering analysis using botany morphology and pollen submicroscopic morphology characters showed that the cultivars could be grouped into 4 groups at the coefficient level 0.315, i.e. 'Phaseolus vulgaris L.' group, 'Phaseolus lunatus L.' group, ''Phaseolus aureus Roxb and Phaseolus angularis Wight' group, and ' Vigna sesquipedalis Wight' group. And the 11 cultivars could be grouped into 6 small groups, named 'Phaseolus vulgaris L. var. humilis Alef.' cluster, 'Phaseolus vulgaris L.' cluster, 'Phaseolus lunatus L.' cluster, 'Phaseolus aureus Roxb' cluster, 'Phaseolus angularis Wight' cluster and 'Vigna sesquipedalis Wight' cluster, at the coefficient level 0.181. The discriminant analysis results showed that a new bean sample (Phaseolus vulgaris L., Phaseolus lunatus L., Phaseolus aureus Roxb and Phaseolus angularis Wight, Vigna sesquipedalis Wight) could be effective classified based on 6 pollen submicroscopic morphology characters (pollen length of polar axis (P), pollen width of equatorial axis (E), P/EU pollen aperture diameter, pollen aperture height, tumor on the surface of aperture membrane) and one botany morphology character (stem color).According to the principles of numerical taxonomy, the nearer the genetic relatives was, the earlier the cultivars were grouped. As the results showed above, Phaseolus vulgaris L. and Phaseolus lunatus L. had the closest genetic relatives than the others, and the farthest genetic relative was found between 'Phaseolus vulgaris L.' and 'Vigna sesquipedalis Wight'. The genetic distance between Phaseolus aureus Roxb, Phaseolus angularis Wight and Phaseolus vulgaris L. was relative near, as compared with the genetic distance between Phaseolus aureus Roxb, Phaseolus angularis Wight and Vigna sesquipedalis Wight.