Inheritance of nodal pigmentation in Indian mustard (Brassica juncea L. Czern & Coss)

Indian mustard (Brassica juncea L. Czern & Coss) is the predominant oilseed crop in India. In present scenario of safeguarding intellectual property rights, it is essential to establish distinctness among varieties for their easy identification. Morphological markers are very scanty in Indian mustard. Descriptors of rapeseed mustard varieties [1] suggests the need of additional characteristics to establish distinctness among varieties. Purple pigmentation at nodal regions has been reported in crops like rice [2] and cowpea [3]. Considering the importance of distinct morphological markers in identification of varieties, an experiment was conducted to study the genetics of purple nodal pigmentation. Four crosses were attempted during 2006-07 by crossing varieties devoid of pigmentation (NRCHB 101 and Rohini) with varieties having purple nodal pigmentation (PBR 97 and Jagannath). F sub(1) generation was raised during 2007-08 and F sub(2), BC sub(1) and BC sub(2) crosses were attempted. F sub(2) seeds were produced by selfing the F sub(1) plants to avoid any outcrossing. The F sub(2), BC sub(1) and BC sub(2) generations of all four crosses alongwith four parents were grown during winter of 2008-09 at Directorate of Rapeseed Mustard Research, Bharatpur. Observations on presence/absence of nodal pigmentation, days to appearance and disappearance of pigmentation, flower initiation and flower senescence were recorded. Presence/absence was recorded on single plant basis while days to appearance, disappearance, flower initiation and flower senescence were recorded on group of plants. On the basis of purple pigmentation, plants were grouped in to three distinct classes viz., pigmented, intermediate and absent. Chi-square test was applied to test the goodness of fit for the segregation ratio. Observations on presence/absence of pigmentation were recorded on single plant basis at the time of flowering.