An intraspecific genetic map of velvetbean (Mucuna sp.) based on AFLP markers

Velvetbean (Mucuna sp., n=11), a self-pollinated species, is an important legume used in tropical agricultural systems in rotation with other crops for nematode management and/or soil improvement. A genetic map of velvetbean was constructed in order to identify potential molecular markers linked to important morphological and agronomic traits that would be particularly useful for developing and improving the species. Traits such as seed coat color, pod color, and pod pubescence were among the main parameters observed in a process of genetic diversity estimation. Two slightly divergent velvetbean accessions, PI364362 and Edgar Farm White, a land race from Alabama, were used to make an intraspecific F₁ hybrid. Amplified fragment length polymorphism analysis (AFLP) detected an average of six polymorphic fragments per primer pair between the two parents. As expected for dominant markers, the sum of all AFLP bands from both parents was generally observed to be present in the AFLP profiles of the F₁ progeny, indicating full penetrance and the dominant nature of AFLP markers. An F₂ population was generated by self-pollinating a single F₁ plant. Using 37 AFLP primer pairs, we detected 233 polymorphic markers of which 164 (70.4%) segregated in 3:1 Mendelian ratios, while the remaining 69 (29.6%) both segregated and were scorable. The genetic linkage map constructed from this population comprised 166 markers, including two morphological traits (pod color and pod pubescence). Twenty linkage groups were found with an average distance between markers of 34.4 cM, covering a total of 687.9 cM. The linkage groups contained from 2 to 12 loci each and the distance between two consecutive loci ranged from 0 to 21.8 cM. The newly designated morphological traits pod color (pdc) and pod pubescence (pdp) co-segregated with each other at a distance of 4.2 cM. Two DNA markers designated ACGCAG2 and ACTCTG1 were located in the same group as pdc and pdp. The AFLP linkage map provides opportunities for use in marker-assisted selection and in the detection of loci controlling morphologically important traits.Communicated by J. Dvorak