Abstract
1. Objectives and Importance. Many silkworms have been damaged by nuclear polyhedrosis virus diseases thoughout the country every year causing a decease in cocoon production by approximately ten per cent per year. The damage caused by the infections virus has occured in spite of complete disinfection. In this respect, it is well known it is impossible, at the present time, to protect the silkworm from these virus infections through chemical and physical control methods. Therefore, this author has attempted to solve this urgent problem from the view point of heredity and breeding, discovering the different resistances and heritabilities among 120 stains collected from throughout the country, and selecting the ones with highest resistance for the basic materials in the silkworm breeding. 2. Results of work 1) The strains with strong resistance to the nuclear polyhedrosis virus diseases are N$_4$, N$\sub$15/, N$\sub$48/, C$\sub$55/ and Em. the log ED$\sub$50/ values of them vary between 0.799 and 1.611. The susceptible strains are N$\sub$20/, C$\sub$62/, N$\sub$76/, N$\sub$79/ and C$\sub$108/, the log ED$\sub$50/ values of them vary between 5.159 and 7.258. (Reference Table 4) The Japanese strain with a log ED$\sub$50/, value of 3.770 is the strongest, followed by the Chinese strain with a log ED$\sub$50/ value of 3.564. The weakest is the European strain with a log ED$\sub$50/ value of 3.3381. The direction coefficient of the regression equation of the susceptibility varies between 0.1 and 0.6, the uniformness of the resistance of the preserved strains of this country is comparatively low. The hereditary henomena of the resistance of each strain and the conerete method of its application for silkworm breeding main the subjects for later studies. 2) The content of water and ash in silkworm has not been correlated with the capability for resistance to the virus diseases(Reference. Table 8). but it is very significantly correlated with mortality rate (in common reaning). In the case of the silkworms which have just completed the fourth moulting the content of water and ash is not related to the mortality rate. In the case of the silkworms which have just completed the third moulting, however, the water( +0.326) and ash (+0.362) registered a high significance. The ash content in the first ($\div$0.520) and second ($\div$0.386) moults is highly significant but water content in both cases is not significant (Reference Table 7). 3) The No. 205 strain proved to be the best in character among the various F$_1$ hybrids. No. 204 was very good in strength but a little lower in cocoon character than the control. No. 212 was a little low in coccon character and mortality was average, but the cocoon harvest was the best among all the varieties offered for (Reference Table 9). 4), In short, the above mentioned strains which are known to have strong resistance to the virus disease are expected to provide basic data for breeding strong varieties. It is proposed that continued research should be conducted on the characteristics of various strains for a satisfactory preservation of various characteristics.research should be conducted on the characteristics of various strains for a satisfactory preservation of various characteristics.
1. 본 조사는 현재 우리나라에 보존되어 있는 계통을 전부 수집하여 Virus병에 대한 저항성을 계통별로 조사함으로써 잠견생산에 막대한 피해를 주는 Virus병에 대하여 저항성이 강한 계통을 선발하는 동시에 선발된 결과는 앞으로 저항성품종 육성제료로 삼고저 하였다. 2. 가잠의 핵형다각체 Virus병에 대하여 저항성이 강한 계통은 N$_4$, N$_{6}$, N$_{46}$, $C_{85}$, E$_{111}$로써 log ED$_{50}$ 값이 0.799~1.611 범위내에 있으며 강한 계통으로서는 N$_{10}$, $C_{62}$, N$_{70}$, N$_{79}$, $C_{106}$이고 log ED$_{50}$의 값은 5.159~7.258 범위내에 있다(표 4참조) 그러고 일본계통이 가장 강하여 log ED$_{50}$이 3.770이 3.770이고 중국계통의 log ED$_{50}$은 3.564로서 다음이고 가주계통의 log ED$_{50}$이 3.381로서 가장 강한 계통으로 나타났다. 감염율의 회귀방정식의 방향계수는 0.1~0.6범위로서 우리나라 보존계통의 저항성의 균일성이 비교적 작을 경향을 다타냈다. ra계통별 저항성의 유전현상에 대한 해명과 품질육성을 위한 구체적인 응용방법에 관한 구명은 차후의 숙제로 남게 되었다. 3. 잠체의 수분 및 회분과 Virus병에 대한 저항성과는 상관관계가 없었고(표 8참조) 다만 감잠비율(보통 사육법에 의하여 조사된 것)과는 고도의 상관관계가 있다. 즉 4면 기잠에서는 수분 및 회분과는 관계가 없었고 3면 기잠에서는 수분은 +0.326 회분은 +0.326으로서 고도의 유의성을 나타냈고 1면과 2면의 회분에서는 각각 +0.520과 ＋386으로서 고도의 유의성을 나타냈으나 수분에서는 유의성이 없었다(표7 참조). 4. 교배조간에 있어서는 기호 205가 모든 형질에 있어서 가장 우수하였다. 특히 204는 강건성이 매우 좋았으나 견질에 있어서 대조구보다 약간 떨어진다. 기호 212는 견질을 약간 떨어지고 감잠비율은 보통이나 수견량이 공시품종중 가장 많았다(표 11). 5. 종합적으로 기술하면 Virus에 대한 저항성이 강한 상기 몇 계통은 강건성 품종？성을 위한 기초자료가 될것이며 계속 여러 계통외 특성을 조사하여 특성 보존을 위한 품종보존의 완벽을 기하여야겠다.다.