An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm

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Najafi Najme; SEIDAVI ALIREZA; Mirhoseini Seyed Ziaeddin; Gharahveysi Shahabodin; Jingade Anuradha H.

Title

An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm

Author(s)

Keywords

Bombyx mori

Commercial exploitation

Evaluation index

Genetic diversity

Larval growth

Sub ordinate function

Abstract

Introduction: Silkworm (Bombyx mori) is an important economic insect which is used as experimental material for the evolution of economically important silkworm breeds. Breeds/strains thus evolved are maintained in germplasm stations for breeders and researchers to use (Chiang 1980). Silkworm germplasm resources have a very important role not only for use in sericulture and silkworm breeding, but also for experimentation in genetics and molecular biology research. Based on several parameters like nutrition, genetics, and biochemistry, silkworms have been classified into different inbred strains (ESCAP 1993). However, few studies are reported for classification of silkworm based on Larval growth potential. The Islamic Republic of Iran has valuable silkworm genetic resources which differ in cocoon shape. The present study was carried out to evaluate and identify oval cocoon bivoltine breeds suitable for rearing as germplasm resources under climatic conditions in Iran. Material and method: The present study was conducted in the Iran Silkworm Research Center (ISRC) and Islamic Azad University, Qaemshahr Branch, Iran. Fifty-four oval cocoon strains maintained by the Iran Silk Research Station (ISRC) were analyzed for the estimation of Evaluation index to study their genetic divergence. Silkworm rearing was carried out as a single batch rearing system. Disease free laying of these strains were incubated in a controlled environmental chamber. When the eggs attained the head pigmentation stage on the 8 th day of development, they were shaded with a black gobo for 48 hr to shield them from light, so as to obtain uniform hatching on the 10 th day. Neonates were brushed and reared separately on fresh mulberry (Morus alba) leaves. st Young 1 rd to 3 instar larvae were reared at 27– 28° C and 85-90% relative humidity. Late age larvae th viz., 4 th and 5 instars, were reared at 24-26° C and 70-80% relative humidity. The larvae were fed mulberry leaves ad libitum three times a day. 250 larvae each from all batches of all strains were retained for completion of the life cycle. Feeding and other conditions of larval rearing were conducted following standard procedures. Larval growth weight was recorded on day 1, 3, and 5 of th the 5 instar (3 replicates each), using a precision digital balance. Evaluation index and subordinate function values were calculated for performance indices based on changes in larval weight at the last larval instar. The Evaluation index and sub-ordinate function values for all traits were calculated separately and average index value was obtained. Silkworm strains were ranked based on the average of Evaluation index method and sub-ordinate function method. Hierarchical agglomerative clustering was done by using NTSYS-pc, version 2. 02e based on complete, single, UPGMA, UPGMC, and FLEXI approaches, and SAS-pc based on WARD and average approaches. However, the method of average linkage between groups (Romesburg 1984) under UPGMA (Unweighted Pair-Group Method using Arithmetic average) was considered as the major and final protocol for data conclusions and the resulting clusters were expressed as dendrograms. Results and discussion: ANOVA based on a completely randomized design indicated significant variations among the silkworm strains (P<0. 01). On the fifth day, strains 104×110, Shown, 102[Shown], 124-16-9[116] and Shaki A×D had significantly higher larval weights ranging from 4. 153– 3. 965 g (P<0. 01). Larval growth parameters revealed higher Evaluation index and higher sub-ordinate function values for strains 104×110 (197. 272 and 2. 857), 1001 (193. 268 and 2. 780), BH-4 (186. 365 and 2. 647), 124-16-9[116] (183. 023 and 2. 602), and Shown (180. 744 and 2. 556). In the present study, by adopting quantitative approaches, 54 silkworm oval strains with different geographical distribution were analyzed. Based on these results it was observed that strains of the same origin did not group together, indicating they have different biological background. Main groups were divided into various sub-groups. Some oval strains were grouped together and were placed far away from other silkworm strains, indicating they might be suitable for future crossing, maintenance of parental strains, and hybridization with peanut cocoon strains so as to maximize heterosis and to avoid inbreeding depression. Because of the low effective population size and each female mating only with one male (thus, all her offspring were full-sibs), the inbreeding rate for this study was very high. This could cause more differentiation among these strains. The grouping methods allowed us to subdivide observations into several subgroups in such a way that we obtained homogeneity inside the subgroups and heterogeneity between the subgroups. Present results confirmed and complemented the results of previous studies about the importance of evaluation and classification of Iranian silkworm strains based on economical and biological characters (Zhao et al. 2007; Zanatta et al. 2009). Silkworm oval strains could be clustered into different groups according to the geographic areas initially observed. Present results confirmed and complemented the results of previous studies about the importance of evaluation and classification of Iranian silkworm strains based on economical and biological characters (Sohn 2003). During selection of two parents for hybridization, some characters should be matched, including high silk yield, adversity-resistance, good combining ability, and excellent silk quality, so that hybrids have good characters of both parents. Effective utilization of selected germplasm plays an important role in saving time in the synthesis of new hybrids. Critical assessment of variability present in the breeding material is a pre-requisite for paving the way of combining most of the desirable traits present in different genotypes into a single hybrid combination. Generally, hybrids from distant background have high heterosis. The study of diversity is important for selection of useful races, use of the heterosis advantage and generating new races. The selection of high yielding breeds with wider adaptation and stable performance are important goals in breeding programs.

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APA: Copy

Najafi, Najme, SEIDAVI, ALIREZA, Mirhoseini, Seyed Ziaeddin, Gharahveysi, Shahabodin, & Jingade, Anuradha H.. (2020). An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm. ANIMAL SCIENCE RESEARCHES (FACULTY OF AGRICULTURE, UNIVERSITY OF TABRIZ), 30(2 ), 101-116. SID. https://sid.ir/paper/959789/en

Vancouver: Copy

Najafi Najme, SEIDAVI ALIREZA, Mirhoseini Seyed Ziaeddin, Gharahveysi Shahabodin, Jingade Anuradha H.. An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm. ANIMAL SCIENCE RESEARCHES (FACULTY OF AGRICULTURE, UNIVERSITY OF TABRIZ)[Internet]. 2020;30(2 ):101-116. Available from: https://sid.ir/paper/959789/en

IEEE: Copy

Najme Najafi, ALIREZA SEIDAVI, Seyed Ziaeddin Mirhoseini, Shahabodin Gharahveysi, and Anuradha H. Jingade, “An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm,” ANIMAL SCIENCE RESEARCHES (FACULTY OF AGRICULTURE, UNIVERSITY OF TABRIZ), vol. 30, no. 2 , pp. 101–116, 2020, [Online]. Available: https://sid.ir/paper/959789/en

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Scientific Information Database

ISSN: 2588-4824

Journal Paper

An analysis of oval cocoons strains of Iranian silkworm (Bombyx mori L. ) germplasm