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Inheritance of Resistance to Nuclear Polyhedrosis Virus in Silkworm, Bombyx mori
( Ratna Sen ),( S. K. Ashwath ),( R. K. Datta ) 한국잠사학회 2001 International Journal of Industrial Entomology Vol.3 No.2
Inheritance pattern of resistance to Bombyx mori nuclear polyhedrosis virus (BmNPV) was studied in an Indian silkworm stock TX by single back-cross test method. The resistant parent [TX], susceptible parent [HM], their Fl, F2, and Fl progeny back-crossed to TX [BC(R)] and HM [BC(S)] were inoculated per os with a fixed concentration of BmNPV (0.5×10(7) PIB/ml) on the first day of second stadium. The cumulative mortality was recorded until day 10th post-inoculation. The results show that the resistance to BmNPV in TX fellow mono Mendelian inheritance pattern. The resistance dominated over the susceptibility at Fl. At F2, the resistant and susceptible offspring segregated in 3:1 ratio whereas at BC(S), the resistant and susceptible offspring segregated in 1:1 ratio. The response of BC(R) was more or less like the resistant parent TX which confirms the involvement of a major dominant gene conferring resistance to BmNPV in TX. The possible mechanism of inheritance of resistance in TX is discussed.
Sen, Ratna,Nataraju, B.,Balavenkatasubbaiah, M.,Premalatha, V.,Thiagarajan, V.,Datta, R.K. Korean Society of Sericultural Science 2004 International Journal of Industrial Entomology Vol.9 No.1
Bombyx mori densonucleosis virus type 1 (BmDNV1)- a non occluded virus causes flacherie disease in the susceptible stocks of the silkworm, Bombyx mori. However, some stocks are non-susceptible. Non-susceptibility to BmDNV1 in B. mori is a unique case where the virus infection is completely inhibited by a single gene of the host. A survey conducted by this institute in some parts of Karnataka state has revealed that, 43.05% of the total incidence of flacherie disease caused by non-occluded viruses, are due to the synergistic infection of B. mori densonucleosis and infectious flacherie virus. Earlier study indicated that rearing of BmDNV1 resistant silkworm stock is effective in protecting silkworm against BmIFV also. In the present study the response of 78 silkworm stocks which include 42 of non-diapausing and 36 of diapausing groups, to BmDNV1 is investigated. Newly ecdysed third instar larvae were inoculated per-os with 10% inoculum of BmDNV1 extracted from the mid-gut of infected silkworm. One non-diapausing and three diapausing silkworm stocks were found to be resistant to BmDNV1. Eleven silkworm stocks were found to possess moderate resistance whereas rest sixty three were found to be susceptible to BmDNV1. Genetic analysis has shown that the resistance to BmDNV1 is autosomally inherited and controlled by a major dominant or a major recessive gene in different silkworm stocks. These resistant stocks can be utilized as the resource material to develop BmDNV1 resistant commercial hybrids. The selection strategies, depending upon the mode of inheritance of resistance in the resource material chosen, are discussed.
Inheritance of Resistance to Nuclear Polyhedrosis Virus in Silkworm, Bombyx mori
Sen, Ratna,Ashwath, S.K.,Datta, R.K. Korean Society of Sericultural Science 2001 International Journal of Industrial Entomology Vol.3 No.2
Inheritance pattern of resistance to Bombyx mori nuclear polyhedrosis virus (BmNPV) was studied in an Indian silkworm stock TX by single back-cross test method. The resistant parent [TX], susceptible parent [HM], their Fl, F2, and Fl progeny back-crossed to TX [BC(R)] and HM [BC(S)] were inoculated per os with a fixed concentration of BmNPV($0.5{\times}10^{th} PIB/ml$) on the first day of second stadium. The cumulative mortality was recorded until day $10^{\times}$ post-inoculation. The results show that the resistance to BmNPV in TX fellow mono Mendelian inheritance pattern. The resistance dominated over the susceptibility at Fl. At F2, the resistant and susceptible offspring segregated in 3:1 ratio whereas at BC(S), the resistant and susceptible offspring segregated in 1:1 ratio. The response of BC(R) was more or less like the resistant parent TX which confirms the involvement of a major dominant gene conferring resistance to BmNPV in TX. The possible mechanism of inheritance of resistance in TX is discussed.
Kumar L. Hemanth,Sen Ratna,Nataraju B.,Mamatha M. Korean Society of Sericultural Science 2006 International Journal of Industrial Entomology Vol.12 No.2
Central Sericultural Research and Training Institute, Mysore have evolved several highly productive bivoltine hybrids which can produce international grade raw silk. Among them $CSR2{\times}CSR4,\;CSR2{\times}CSR5,\;CSR3{\times}CSR6,\;CSR17{\times}CSR16,\;CSR18{\times}CSR19$ and $CSR12{\times}CSR6$ are being popularized in the field. There is a minimum difference in their economic characters but they appear to differ in survival. Though they are productive under high input management conditions, they are very susceptible to different diseases under normal rearing practices. No systematic attempts have been made to test their susceptibility status / resistance. Thus the present study is a modest attempt to screen the above six productive bivoltine hybrids to two important pathogens viz., Bombyx mori Nuclear Polyhedrosis Virus (BmNPV) and Bombyx mori Infectious Flacherie Virus (BmIFV) along with existing hybrid, $KA{\times}NB4D2$ to assess their susceptibility / resistance. The results shows that the productive hybrid $CSR2{\times}CSR4$ is the most resistant to BmNPV and it is suggested by its highest $LC_{50}$ value followed by $CSR12{\times}CSR6,\;KA{\times}NB4D2,\;CSR3{\times}CSR6,\;CSR17{\times}CSR16,\;CSR18{\times}CSR19,\;CSR2{\times}CSR5$. Based on the $LC_{50}$ value and $LT_{50}$ values for BmIFV, the hybrid $KA{\times}NB4D2$ was found to be the most resistant (1st position) one followed by $CSR3{\times}CSR6$ (2nd position) $CSR2{\times}CSR$ (3rd position) and $CSR12{\times}CSR6$ (4th position) $CSR17{\times}CSR16$, $CSR18{\times}CSR19$ (5th position) and $CSR2{\times}CSR5$ being the least. The response of 7 bivoltine hybrids to both the pathogens BmNPV and BmIFV indicates that, the hybrids $CSR2{\times}CSR4$, $CSR12{\times}CSR6$ and $KA{\times}NB4D2$ were found to be the most resistant when compared to others. Further, $KA{\times}NB4D2$ being less productive hybrid with a shell ratio of 20.08%, the other two hybrids $CSR2{\times}CSR4$ (Cocoon shell ratio, 21.44%) and $CSR12{\times}CSR6$ (cocoon shell ratio, 23.45%) can be considered to be most productive with superior quality cocoon and resistant to both BmNPV and BmIFV pathogens. The overall study indicated that the hybrid $CSR2{\times}CSR5$ is the most susceptible hybrid to both the pathogens.