Resistance to Nucleopolyhedrosis Virus of Breeding stocks in Japanese Tusser, Antheraca Yamamai, GUERIN-MENEVILLE

通过抗病育种的尝试和对引起作物产量下降的核型多角体病毒感染的动物流行病学研究，研究了提高作物产量的方法。对31只雌性日本蚕蛾和49只雄性中国蚕蛾进行交配，比较其经济性状。与日本猎犬的杂交种(1)尽管母亲的受精率差，幼虫发育良好，并有很高的抵抗力，NPV infestation。茧层重量和茧层百分率也较高。利用杂交<F_1>后代获得了3个杂交组合：<F_1>X日本柞蚕、X日本柞蚕<F_1>和<F_1>X日本柞蚕<F_1>。(2)第二代及以后世代的杂交种在性状上没有表现出像杂交种那样显著的差异<F_1>。但3龄幼虫的第2 ~ 4节侧面出现黑点。这一繁殖阶段对应于睾丸肌细胞分裂活动的时间，其中含有染色体异倍性.对抗病原种（SR）和体色突变原种（MT）的幼虫生物学素质和茧丝品质与对照进行了比较。(1)SR和MT的孵化率和产茧量均高于对照。(2)SR雌虫产丝量较大。雄性和雌性MT生产的长丝在强度和拉伸性方面表现优异。本文就田间饲养中发生的核型多角体病病原菌与作物歉收的关系进行了探讨。(1)从麻栎（Quercus acutissima）的茎、叶中分离到大量的病原菌，引起了麻栎核多角体病的流行。(2)在（1）的基础上，假定了病原体通过寄生昆虫传播的模式。

Improvement of the crop productivity was studied by attempting breeding of disease-resistant stocks and by epizootiological approach to nucleopolyhedrosis virus infection which deteriorates the yield of crops .1 . Female Japanese tussers (n=31) and male Chinese tussers,Antheraea pernyi, GUERIN-MENEVILLE (n=49) were mated to compare the economical character of resultant! hybrids with those of Japanese tussers. (1) Despite poor fertilization ratios in mothers, larvae developed well and had high resistance to NPV-infction. Both the weight and percentage of cocoon shells were also higher. Using the <F_1> hybrids, 3 offspring combinations were obtained ; <F_1> X Japanese tusser, Japanese tusser X <F_1> and <F_1> X <F_1> . (2) Hybrids in the 2nd and later generations demonstrated no such remarkable differences in traits as the <F_1> hybrids. However, abnormality was found in the larvae of the 3rd instar which developed blackish dots on the lateral aspect of the 2nd to 4th segments. This breeding stage corresponds to the time of testicular mytotic activity which contained chromosomal heteroploidy.2 . The biological quality of larvae and quality of cocoon filament in the disease-resistant stock (SR) and body-color mutant stock (MT) were compared with controls. (1) The hatchability and cocoon productivity were higher in both SR and MT than controls. (2) SR females produced a larger weight of cocoon filament. Male and female MT produced filament that excelled in strength and stretchability.3 . The cause of poor crop was investigated in relation to pathogens of nucleopolyhedrosis occurring in field rearing. (1) A large amount of pathogens were isolated and recovered from the leaves and stems of oak, Quercus acutissima which caused a prevalance of nucleopolyhedrosis. (2) On the basis of (1), a pattern of pathogen propagation by inhabiting insets was postulated.