Abstract
Studies about phenotypic diversity are common in germplasm banks. The inference about this variability must be realized through several methods. The multidimensional scaling is a multivariate technique that has not yet been well explored in plant breeding programs. The objective of this study was to evaluate the phenotypic dispersion of landrace lima bean varieties using the non-metric multidimensional scaling technique (nMDS) based on seed morphology. Seeds of 25 lima bean accessions were characterized based on the morphological descriptors proposed by the International Plant Genetic Resources Institute. Distance matrices between the accessions were estimated based on the qualitative and quantitative variables, in addition to simultaneous analysis of the qualitative and quantitative data, using the Mahalanobis and Gower distances. The distances were represented by non-metric multidimensional scaling. The adjustment level of the nMDS mapping was calculated using Kruskal’s Stress. The scaling based on the quantitative and mixed data was efficient to represent the distances of the lima bean accessions in the bidimensional plane presenting Stress less than 20%. Divergent accessions, such as 11, 13, 17 and 25 were identified. The inclusion of qualitative characters provided the best discrimination of the accessions, confirming the importance of the simultaneous character analysis. The nMDS must be used as a complementary technique to those commonly employed in studies of phenotypic diversity in lima beans.
Highlights
Lima bean (Phaseolus lunatus L.) presents rusticity and adaptability to the environment (Vieira, 1992)
The seeds were characterized according to the following morphological descriptors for Phaseolus lunatus L., recommended by the International Plant Genetic Resources Institute (IPGRI, 2001): Seed Length (SL), Seed Width (SW), Seed thickness (ST), Seed color (SC), patter color of tegument (CPT), second patter color of tegument (SPC), pattern of seed tegument (SPTG), The seeds were classified according to their size (Mateo Box, cited by Vilhordo et al, 1996) and shape, by the coefficients Length/width (L/W) and thickness/width (T/W), according to Puerta Romero, cited by Vilhordo et al (1996)
The seed germplasm bank of the UFPI/CPCE, presents a great phenotypic diversity, evidenced by the dispersion represented by multidimensional scaling (Figure 1)
Summary
Lima bean (Phaseolus lunatus L.) presents rusticity and adaptability to the environment (Vieira, 1992). Its seeds are good sources of nutrients such as proteins, carbohydrates, fibers and minerals (Kathirvel & Kumudha, 2011). This crop has an important social aspect in many countries in South America. In Brazil, in the Northeast region, the lima bean germplasm used by farmers comes from their own crops and trading between rural communities (Penha et al, 2017). Often, this germplasm is maintained in landrace seed banks, presenting great genetic variability for agronomic traits of interest (Santos et al, 2002). Camacho-Pérez et al (2018) emphasize the reduction of genetic diversity in landrace varieties mainly due to changes in traditional agriculture and market preferences, assuming this as a global problem with high risk to the food security of future generations
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