PHENOTYPIC VARIATION AND THE RELATIONSHIPS AMONG MUSTARD (BRASSICA-JUNCEA L.) GERMPLASM FROM PAKISTAN

An investigation was conducted to determine the extent of diversity an d relationships among the Brassica juncea germplasm from Pakistan usin g morphological characters. A total of 52 accessions, including the co llected germplasm as well as commercial cultivars/improved lines, were studied under field conditions at Tsukuba, Japan during 1995 and 1996 . All the accessions were characterized for 35 agro-morphological char acters from seedling emergence to crop maturity. Morphological data we re analyzed by numerical taxonomic techniques using two complementary procedures: cluster and principal component analyses. Phenograms based on Euclidean distance placed the accessions into six groups during bo th years. Landrace groups were primarily associated with morphological differences among the accessions and secondarily with the breeding ob jectives and horticultural uses. The mustard germplasm collected from Pakistan showed a comparatively low level of phenotypic variation amon gst themselves and were genetically similar to the oilseed cultivars. However, the oilseed forms and vegetable cultivars were genetically di stinct. This study revealed that the evaluated germplasm appears to ha ve a narrow genetic base which undergoes a high level of genetic erosi on. This is perhaps due to the use of the same ancestors in the select ion of new lines for similar horticultural traits, replacement by majo r crops and changes in agricultural land uses.