Study On The Selection Of Cell Mutant Lines Resistant To Capsicum Wilt In Pepper

This study established the program of a high efficient in vitro regeneration procedure of five pepper cultivars. The effect of genotypes, explants, hormones, and days of seedlings on the tissue culture in pepper was investigated systematically. Furthermore, the study had a research on the degree of damage of the crude toxin derived from capsicum wilt pathogen to the germination of seeds, growth of seedlings, and elongation of radicel in pepper. On the basis of these steps, the study selected some cell mutant lines resistant capsicum wilt in pepper by use of the crude toxin, and obtained several plants regenerated in vitro. Some conclusions were drawn as following.1. Three cultivars of pepper (Capsicum annuum L.), 'Nongchengjiao 2', '0127', and '0171', were screened out of five cultivars for their high capacity of regeneration. The experimental results showed that the cotyledon explants taken from 12-day-old seedlings displayed the highest shoot-buds regeneration capacity. As far as culture medium was concerned, the buds induced well on MS+3% sucrose+0.6% agar + 5. 0mg/L BA+0.5-1.0mg/L IAA, which made the shoot buds differentiation frequency of 98%. Moreover, 45.7% of induced buds elongated well on the medium of MS+3% sucrose+0.6% agar+3.0mg/L BA+1.0mg/L IAA+2.0mg/L GA3+10.0mg/L AgNO3. The regenerated plants were transplanted into nutrient soil and developed into normal plants. So, an efficient program for plant regeneration from explants of pepper had been developed.2. The crude toxin was obtained by means of liquid culture of the capsicum wilt pathogen with Czapek's liquid medium. Using the crude toxin, the study investigated the effect of capsicum wilt on the germination of seeds, the growth of seedlings, and the elongation of radicel in three cultivars of pepper, 'Nongchengjiao 2', '0127', and '0171'. The experimental results showed that the crude toxin of capsicum wilt pathogen had the capacity of thermal stability, and can not only extremely inhibit both the germination of seeds and the growth of seedlings, but also do great harm to the elongation of radicel. Under the same concentration of crude toxin, the degree of damage was different from varied genotypes. The crude toxin inhibit the growth of seedlings of cultivar '0127' more extremely than that of cultivar 'Nongchengjiao 2' and '0171', which indicated that the resistance of cultivar '0127' to capsicum wilt was less than cultivar 'Nongchengjiao 2' and '0171' to some extent.3. Using crude toxin, some cell mutant lines resistant to capsicum wilt were filtrated in vitro by means of callus induced by cotyledon explants in two pepper cultivars, 'Nongchengjiao 2' and '0127'. The experimental results meant that the resistance to capsicum wilt can be showed in vitro because of different capacity of disease resistance between varied genotypes. The crude toxin had sharply negative effect on both the inducement and the growth of callus. Also, it done great harm to the regeneration of buds differentiated from the callus. Compared with the degree of the damage to callus, the crude toxin inhibited both the differentiation frequency and the growth of the buds more strongly.4. Several plants resistant to capsicum wilt were obtained in vitro. It was proved that their cell mutant lines had a stable resistibility to capsicum wilt through the identification and analysis.