Study On The Selection Of Cell Mutant Lines Resistant To Phytophthora Capsici In Pepper

In this study we used the cotyledons of three pepper Cv."2001","2056"and "2031"as explants induced the callus, the filtrate of Phytophthora capsici (crude toxin)as the selective agent. On the basis of research of bioactivities and culture condition of the crude toxin, the study select some cell mutant lines resistant to Phytophthora capsici by using of screening method at different concentration of crude toxin, and several mutant plants were obtained. 1. The crude toxin was obtained by means of liquid culture of the Phytophthora capsici with CFB medium. Using the crude toxin, the research investigated the effect of Phytophthora capsici on the leaf of pepper, the germination of pepper seeds, the growth of seedlings, the growth of pepper radicel, and the callus of pepper. The experimental results showed that the crude toxin of Phytophthora capsici could inhibit the germination of seeds, the growth of seedlings, and the growth of pepper radicel and the callus of pepper extremely. Therefore, the crude toxin of Phytophthora capsici can be used as selective agent in the following study. 2. The suitable culture condition of Phytophthora capsici to have the highest toxin production has been studied, such as medium, culture time, temperature, pH value. The results show that pepper seed treated by the liquid of Phytophthora capsici cultured 18 days in CFB medium at 25-30℃, at pH6-7 have the lowest germination rate, which means crude toxin cultured at this condition has the highest toxin production. The thermal stability of the crude toxin of Phytophthora capsici has also been studied. The treated crude toxin loses some of its toxin, but it still have extremely inhibition on the germination of pepper seeds, and the higher concentration treated crude toxin has the same effect as the lower concentration untreated one. 3. Using crude toxin as the selective agent, some cell mutant lines resistant to Phytophthora capsici were filtrated by means of callus induced by cotyledon in three pepper Cv. "2001", "2056"and "2031". The experimental results showed that the crude toxin of Phytophthora capsici inhibited the inducement, the growth of callus, and the differentiation frequency and the growth of buds. The inhibition increased with the increase of concentration of crude toxin. The experiment also found that different cultivars have different resistance to Phytophthora capsici. 4. Several regenerated plantlets resistant to Phytophthora capsici were obtained, and their resistant stability was detected. It was proved that mutant plantlets had a stable resistibility to Phytophthora capsici.