Brassica juncea is an amphidiploid with Brassica nigra (L.) Koch (2n = 16) and Brassica rapa L. (2n = 20) as parents
Many African farmers use their own landraces of farm-saved seed. Brassica juncea can be reproduced by means of self-pollination, allowing for a rapid purification of new selections. East-West Seed Company in Thailand has developed cultivars especially for tropical conditions, e.g. ‘Mayur’ harvestable 30–35 days after sowing or 21–25 days after transplanting, and ‘Laguna’ with bolting tolerance at high temperatures and harvestable 40–45 days after sowing. ‘Suehlihung No.2’ is a cultivar from Taiwan that is resistant to soft rot and viruses. It can be grown year-round in Taiwan and be harvested 20 days after transplanting. The cultivar ‘King Mustard’ produces large and tender green-purple leaves.