한성흑란계통누에의 몇가지 실용형질향상을 위한 교잡방법

Breeding to Improve some of the Economic Characters of the Sex-limited Dark Egg Color Strains.

잠업시험장에서 육성중인 한성흑란계통잠의 실용형질향상을 위한 효율적인 교잡방법의 탐색을 위해 동아구교잡, 연속교잡, 단계 및 복계여교잡의 4가지 육종방법이 교잡원종세대(P)로부터 F6세대까지 비교검토되었다. 1. 화용비율의 경우 4가지 육종방법 공히 세대간에 또는 교잡방법간에 매우 변화가 심하였고 교잡효과의 양상은 연속교잡>동아구교잡·복계교잡>단계여교잡의 순으로 낮아졌다. 2. 전견중, 견층중, 견층비율의 경우 동아구교잡을 제외한 3가지 방법 공히 비교적 우수한 육종방법으로 생각된다. 3. 세대별 형질발현의 추이를 보면 화룡비율은 세대별 변화가 매우 심하여 일정한 경향이 없고, 전견중, 견층중, 견층비율은 교잡방법에 불구하고 P세대에서 F2,세대간은 교잡효과가 급상승하나 그 이후세대에서는 매우 둔화되는 양상을 보였다. 4. 육성중인 본 근성흑란계통누에의 실용형질은 육성중인 비전좌계통의 원종과 대차없다. 5. 본 근성흑란 암누에의 실용형질 발현도(E)는 정상잠에 가까워 전좌염색체편에 의한 생리적 결여가 매우 미소한 것으로 생각된다. 6. 이상의 결과에서 F7세대 이후의 근성흑란계통 누에의 실용형질 향상은 교잡육종에 의한 계통분리법이 좋을 것으로 생각되고, 아울러 형질고정도도 향상시켜야 할 것으로 생각된다.

To investigate suitable breeding system for the improvement of economic characters of the sexlimited dark egg colour strains, the four kinds of breeding methods which are represented as sibmating, repeated backcrossing, multi-backcrossing every other generation, and repeated hybridization were detected from the P to the F6. 1. Pupation ratio was varied between the four kinds of breeding methods and decreased gradually in order of repeated hybridization, mult-backcrossing every other generation and sib-matinv, and repeated backcrossing. 2. Repeated backcrossing, multi-backcrossing every other generation, and repeated hybridization with the exception of sib-mating were consiered as available breeding methods to improve single cocoon weight, cocoon shell weight and cocoon shell ratio of the sex-limited dark egg colour strains. 3. As for the responses of the economic characters form the P to the F6, pupation ratio was fluctuant and unstable, on the other hand single cocoon weight, cocoon shell weight and cocoon shell ratio increased remarkably in the F2, but in the subsequant generatios the increasing rate of each characters were fluctuant irregularly. 4. After the original sex-limited dark egg colour strains were bred under the corresponding breeding methods, from the P to the F6 the economic characters were approached to the level of normal breeding silkworm lines'. 5. It came to the consideration that the autosomal fragment which was translocated on the W chromosome had no physiologically significant effect on the expression of the economic characters because the Expression index (E) of the sex-limited dark egg colour strains was similar to that of normal silkworm lines. 6. From the results, it comes to the conclusion that the useful breeding methods to improve the economic characters of the sex-limited dark egg colour strains will be a line separation including fixation of the characters.