Genetic diversity in oil and vegetable mustard (Brassica juncea) landraces revealed by SRAP markers

Mustard (Brassica juncea) is an important crop in both ancient and modern world. It has a broad resource of genetic diversity that is used primarily as oilseed but as vegetables, condiment and medicines also. Its superior tolerance to adverse environments, e.g., drought, high temperature and low fertility suggests its better adaptability in future possible harsh environments. Chinese vegetable mustard displays a wide spectrum of morphotypes. A collection of 95 accessions of B. juncea representing oil and vegetable mustards from China, France, India, Pakistan, and Japan were assessed to determine diversity at the molecular level using sequence-related amplified polymorphism (SRAP). Eight SRAP primer combinations identified a total of 326 scorable fragments of which 161 were polymorphic (49.39%). The percentage of polymorphism for each primer combination varied from 21.88 to 66.67%. Both Shannon-Weaver and Simpson genetic diversity index indicated that the level of genetic diversity within vegetable mustard is much higher than within oil mustard, and also winter oil mustards are genetically more diverse than spring oil mustards. Based on the Cluster and Principal Coordinates analysis, which were conducted on the similarity matrix of SRAP marker data, vegetable, spring oil and winter oil mustard were clearly divided into three distinct groups and among these three groups, spring and winter oil mustard are geneticlly closer than vegetable mustard. This suggests that bilateral gene exchange between oil and vegetable gene pools in the breeding program will effectively elevate the genetic potential in developing higher yields, more disease resistance, better quality and better adapted lines.