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Oilseed Brassica crops play an important role in the vegetable oil economy of India and the world. There is an urgently felt need to increase their yield levels across varying growing conditions to meet the ever-growing demand for edible oil. The production level fluctuates widely over time and space mainly due to the challenges posed by various biotic and abiotic stresses. To combat these stresses that are very complex in nature, we need to have multi-pronged strategy by combining agronomical and breeding approaches. A major shift in yield level of any crop plant with increased tolerance to biotic and abiotic stresses is possible only with extensive genetic manipulation through breeding, and the breeding efforts in turn will require the continued collection, conservation, evaluation, and deployment of diverse crop genetic resources in a targeted way. Various activities enshrined in the management of rapeseed-mustard genetic resources are systematically explained in this chapter with an aim firstly to sensitize the readers about the importance of PGR and then to explain the principles and methodologies underlying the various activities involved in PGR management with special emphasis on rapeseed-mustard group of crops. Status of rapeseed-mustard germplasm in India and the world in terms of their number, characterization, evaluation, utilization so far, and future thrust area required are also discussed in this chapter.

Genetic diversity evaluation is one of the most important components of pre-breeding, which provides a clear understanding about the structure and variability inherited in a crop and thus helps in the identification of genetically diverse parents for breeding programmes. Rapeseed-mustard (RM) group of crops constitutes six economically important crops, of which five are oilseed crops and one, that is, Brassica oleracea, is an important vegetable crop. Among oilseed Brassica species, B. juncea (Indian mustard) is the most widely cultivated crop in many countries including India, Canada, Russia, China and Australia. In India, this crop contributes to more than 85% of RM acreage. Various efforts had been made in the past for genetic diversity characterization in Indian mustard germplasm and varieties using agro-morphological and biochemical markers. With the development of genomic resources in oilseed Brassica species, emphasis had been focused on using DNA/molecular markers including randomly amplified polymorphic DNA (RAPDs), inter-simple sequence repeats (ISSRs), restriction fragment length polymorphisms (RFLPs), amplified fragment length polymorphisms (AFLPs), simple sequence repeats (SSRs) and expressed sequence tags (ESTs). In this chapter, we have tried to compile various studies conducted for genetic diversity evaluation in Indian mustard using different types of molecular markers.