Efficient Regeneration In Cowpea (Vigna Unguiculata L.) From Embryonic Tip Explants

The embryonic tips of 12 cowpea varieties, including Cheng Jiang 7, Te Chang 901,Youqing Bigui cowpea, Red cowpea, Te Chang Qingtiao 1, American dwarf cowpea, Hongdaxue cowpea, Baizitai cowpea, Guangdong Jinguan cowpea, Baisha 17, were used as plant material in this experiment, especially Cheng Jiang 7. We investigated the effects of seed soaking time, induction time, disinfection method, hormone type and concentration on pollution rate, adventitious bud induction frequency and rooting rate of explants, compared the disinfection efficiency of 2% sodium hypochlorite,0.1% mercuric chloride and chlorine, established and optimized the embryonic tip regeneration system. The results are as follows:1. The disinfection method:soaking seed in 2% sodium hypochlorite for 5 minutes was the best disinfection method for Cheng Jiang 7; soaking seed in mercuric chloride for 5 min worked for all the cowpea varieties, but after treatment, vitrification of explants occurred; using chlorine had achieved great results and it would not hurt the explants. Besides, it is very convenient to get the plant material after disinfection. But it took a long time and toxic.2. During the cultivating process in MSB5 medium, the difference of adventitious bud induction rate between various cowpea varieties were found.3. For mature cowpea seed, adventitious bud induction rate varied between different soaking time. The time of Seed imbibition was different across the 12 genotypes. Soaking seed for 8h was best in Chengjiang 7, while other cultivars need more than 10 hours soaking time. Over-soaking will result in seed rot, and the embryonic tips will be dead after inoculation.4. Different induction time of plant hormone 6-BA had a remarkable effect on the adventitious bud generation of Chengjiang 7.5. The concentration of different hormones in medium affected the regeneration of embryonic tip. The optimal concentration of 6-BA was 2.5mg/L-4.0mg/L,2.0 mg/L,2.5 mg/L,4.0mg/L,4.0 mg/L,4.0 mg/L,2.0mg/L,2.5 mg/L,2.5-3.0mg/L,2.5mg/L for Chengjiang 7, Te Chang 901 cowpea, Youqing Bigui cowpea, red cowpea, Te Chang Qingtiao 1, American dwarf cowpea, Hongdaxue cowpea, Baizitai cowpea, Guangdong Jinguan cowpea, Baisha 17 cowpea, respectively. Each explant can generate 2-3 adventitious buds on average.6. The optimal concentration of IBA in rooting medium was 1 mg/L. Although 2 mg/L IBA can make the root stout, the survival rate after transplanting was poor. As the concentration of IBA rised, the root become thick and the number of fibrous root increased.