~ 9 ~ ISSN Print: 2394-7500 ISSN Online: 2394-5869 Impact Factor: 5.2 IJAR 2017; 3(11): 09-17 www.allresearchjournal.com Received: 04-09-2017 Accepted: 06-10-2017 Usama Mohamed Ghazy Sericulture Research Department-Plant Protection Research Institute- Agricultural Research Center, Giza, Egypt Tahia Azooz Fouad Sericulture Research Department-Plant Protection Research Institute- Agricultural Research Center, Giza, Egypt Karima Haggag Textile Research Division, National Research Centre – Dock, Egypt Correspondence Usama Mohamed Ghazy Sericulture Research Department-Plant Protection Research Institute- Agricultural Research Center, Giza, Egypt New double hybrids of mulberry silkworm, Bombyx mori L. to be suitable for changed caused in Egyptian climate Usama Mohamed Ghazy, Tahia Azooz Fouad and Karima Haggag Abstract Breeding program of sericulture research department in Egypt has created many new mulberry silkworm, Bombyx mori L. races. Hybridization was made between some races to produce single hybrids. Hybrids used to create double hybrids. Double hybrids are feature to be tolerant to un-stability conditions. Nowadays the Egyptian climates are changed. So that, farmers needs the tolerant hybrids for unstable climate to increase their crops. Eleven races used for produced fifteen single hybrids. The resulted hybrids used to create fifteen double hybrids in the present investigation. Imported hybrid from Bulgaria reared as check parent. The double hybrids are reared under the normal Egyptian conditions. Criteria of fifth and total larval duration were recorded. Mortality percentage, weights of fresh cocoon, cocoon shell and pupae were registered. Cocoon shell ratio, silk productivity, cocooning percentage, pupation ratio, Number of cocoon per liter, crop by number and weight were tested. All data were analyzed using check parent value. As well as modified of evaluation index and subordinate function. Keywords: Double hybrids, new races, evaluation index, subordinate function, check parent, climate change 1. Introduction Impact of climate change on sericulture required modifying for methods of rearing and development silkworm hybrids to be suitable for changes. Genotypic expression affected by seasonal diversity of environmental component which expressed in phenotypic of silkworm traits such as cocoon characters. It is need to management of temperature and relative humidity for sustainable cocoon production (Rahmathulla, 2012) [11] . Sericulture scientists try to obtain hybrid suitable for the seasonal fluctuations conditions. They evaluate performance of bivoltine, multivoltine and multivoltine × bivoltine. Multivoltine × bivoltine hybrids represented very hardy with high survival rate and production under seasonal fluctuating conditions (Rao, 2006) [12] . Silkworm breeders evaluated the three- way and double hybrids comparison with single hybrids. They proved that, three way and double hybrids are suitable for climatic changes during Spring and Autumn seasons (Gowda et al. 2013, Gadgala and Singh 2016) [8, 4] . Mulberry silkworm is very sensitive insects for fluctuations in environmental factors such as temperature and humidity. This is may be return to very long time of domestication of silkworm. So, silkworm hybrids must be adoptable for the climatic conditions fluctuations. Silkworm breeding program of Sericulture Research Department in Egypt attempt to development the sericulture through creation many new silkworm races. As well as using different type of hybridization, single, three way and double hybrids. To face the climatic changed caused in Egyptian climate, which affected on sericulture viz., survival of silkworm as well as the cocoon traits and affected on sustainability of cocoon production. Environmental conditions represented the main factor which leads to success or un-success of the sericulture industry which divided to biotic and abiotic factors. Temperature factor among the abiotic affected on the growth and productivity (Ueda et al. 1975, Benchamin and Jolly, 1986) [15, 2] . International Journal of Applied Research 2017; 3(11): 09-17