Elucidation of biological protective reaction of Porphyra cells aginst red rot disease and development of disease resistant strain

1.条斑紫菜红腐病是条斑紫菜上最严重的病害，由腐霉属真菌引起。在1/5 PES培养基中，13- 1/5 ℃，12 h暗12 h光循环，120 μ E/m^2/s光照强度下培养，在死亡的藻体中发现了未感染腐霉的抗病细胞。培养6个月后，分离的细胞生长为菌体。该叶状体对红腐病的抗性是商业化栽培紫菜的2倍左右.抗病因子的研究：抗病菌体中与细胞壁硬度有关的多糖、糖蛋白（extensine）、卟啉和3，6-脱水-L-半乳糖的含量明显低于商业化栽培紫菜。这些结果表明，壁多糖含量越低，抗病性越强.抗病性的连续性：获得的抗病菌株生长正常，这对实际应用具有重要意义。即使在最适宜病害发生的环境条件下，抗病品系的抗病性也比商业栽培条斑紫菜强3倍，这对了解条斑紫菜的抗病机制和抗病品系的选育具有重要意义。

1. Isolation and cultivation of red rot disease resistant cell : Red rot disease of Porphyra yezoensis is the most serious disease caused by the fungus Pythium. Disease resistant cell that was not infected with Pythium was found in the dead algal thallus, isolatedand cultivated at 13-15ﾟC on a 12 h dark and 12 h light cycle under the light intensities of120 muE/m^2/s in 1/5 PES medium. After 6 months cultivation, isolated cell grew to thallus. This thallus showed about 2 times strong resistance against the red rot disease compared to that of commercially cultivated Porphyra.2. Investigation of the factors responsible for disease resistance : In the disease resistant thallus, levels of polysaccharide, glycoprotein (extensine), porphyran and 3,6-anhydro-L-garactose related to hardness of cell wall are apparently lower than that of commercially cultivated Porphyra. These results suggest that the lower the contents of wall polysaccharides, the higher the disease resistance.3. The continuity of disease resistance : The disease resistant strain obtained grew in normal shape that is important to the practical use for cultivation. Even in the most suitable environmental conditions that the disease occurs, the resistant strain showed 3 times stronger resistance compared to that of commercially cultivated P.yezoensis.These results obtained above are useful to understand the mechanisms of disease resistance and to develop the disease resistant strain.