Karyotype analysis of Brassica juncea cv. Hong Kong Hakka Mustard

Brassica juncea was one of the important leaf vegetables which had important edible value, and was popular with consumers. Brassica juncea cv. Hong Kong Hakka Mustard had characteristics of flesh crispy, tasted sweet and delicious, and had been widely cultivated in many places of China. In this research, we try to obtain cytological parameters on ‘Hong Kong Hakka Mustard’. Seven chromosomal parameters were measured and calculated: chromosome length, relative length, index of relative length, type of relative length, arm ratio, centromere index and centromere type. The experiment results showed that the maximum chromosome length was measured 4.10 µm and max arm ratio was determined 1.66, relative length ranged between 2.48% to 7.94%. There are four types of relative length, including long (L), medium long (M2), medium short (M1) and short (S) chromosomes. In addition, the maximum centromeric index was measured in 46.49%, centromere type were metacentric (m) chromosomes. Karyotype asymmetry index was 58.81%, and the karyotype formula was 2n=36=36m (2SAT). The karyotype characteristics was type 1B according to Stebbins’s classification criteria. According to the above information, we can draw a conclusion that ‘Hong Kong Hakka Mustard’ is a relatively primitive mustard variety. The findings revealed its karyotypic characteristics of ’Hong Kong Hakka Mustard’ from the cytogenetic aspects.