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Mulberry (Morus L.) is an economically important tree being cultivated for its leaves to rear the silkworm Bombyx mori. Rearing of silkworm is an art and science popularly known as sericulture; an agrobased cottage industry provides employment to millions in China, India, Korea, Vietnam, etc. Mulberry is a perennial tree that maintains high heterozygosity due to the outbreeding reproductive system. It is recalcitrant to most of the conventional breeding methods, yet considerable improvement has been made in leaf yield and leaf quality. Conventional breeding in mulberry is a tedious, labour intensive and time taking process, which needs to be complemented with modern biotechnological methods to speed up the process. This article enumerates the problems, challenges, constraints and achievements in mulberry breeding along with recent advances in biotechnology and molecular biology to enable mulberry breeders to tackle specific problems more systematically and effectively.

Boil-off loss ratio is one of the most important economic traits to be considered during the course of silkworm breeding. The boil-off loss ratio varies among the breeds and seasons.The present study was undertaken with 5 oval and 5 peanut breeds and twenty five hybrids involving these parents to select the promising hybrids with desired boil-off loss ratio. Accordingly, studies were undertaken to estimate the heterosis and heterobeltiosis. It was observed that majority of the hybrids revealed negative heterosis for boil-off loss ratio which is desirable. Based on the heterosis and heterobeltiosis, among all the hybrids, the hybrid APBRO5 x APBRD5 exhibited highest negative heterosis for boil-off loss ratio and also exhibited highest EI value (64.5) for the quantitative and qualitative traits. Based on the hybrids performance, boil-off loss ratio, heterosis and heterobeltiosis and evaluation index, the hybrids viz. APBRO5 x APBRD5, APBRO1 x APBRD1 and APBRO3 x APBRD4 were identified for commercial exploitation. IntroductionTo face the global competitiveness in silk production there is a need to improve the quality of the raw silk and as such the sericulture industry requires good quality of silk to produce internationally gradable silk fabric to meet the requirement of the consumers across the world resulting in increased foreign exchange. To meet the specific requirement of the silk industry, the silkworm breeders have developed various hybrids such as productive breeds, robust breeds, breeds with special traits and sex limited races etc. Keeping this in view, most of the silkworm breeders have been concentrating on boil-off loss ratio to produce good quality silk as the boil-off loss ratio is one of the most important qualitative trait in silkworm breeding. The silkworm Bombyx mori L. spins a shell by extruding silk bave at the end of its larval period. The silk bave is composed of two silk proteins namely fibroin and sericin and also contains a small quantity of fatty, waxy, colouring and mineral matters. The fibroin protein occupies the middle portion of the Boil-off loss ratio in newly developed bivoltine silkworm hybrids 14 separation and assessment, 60 cocoon shells (30 each of female and male) were selected from each breed/ hybrid separately. Three replications were maintained each having 10 males and 10 females for conducting the experiment. Degumming was carried out by boiling the cocoon shells in soap solution using a standard procedure (Basavaraja et al., 2000). Two step boiling method as explained below was employed for the degumming of the cocoon shells and used neutral liquid soap for boiling. A quantity of 7g soap was dissolved in 1 liter of water for degumming and the material: liquor ratio was maintained as 1:40. First degummingThe liquor solution of the soap and soda was boiled in a copper vessel. When the boiling media solution reached the boiling point (>90 o C), the cocoon shell sample bags were immersed completely in boiling media kept tightly closed for 40 minutes. At an interval of 10 m...

The performance of five newly evolved cross breeds were evaluated across seasons to understand the genotype and environment interactions and their stability under fluctuating tropical environmental conditions along with control hybrids PM × CSR2 and APM1 × APS8. The data was collected on eight economic traits namely fecundity, yield per 10,000 larvae by number, yield per 10,000 larvae by weight, survival rate, cocoon weight, cocoon shell weight, cocoon shell ratio and filament length. The data was subjected for Analysis of Variance (ANOVA) and relevant statistical methods. The performance data obtained was further subjected for multiple trait evaluation index method. The ranks were adjudicated based on the index values. The two hybrids viz., MSO3 × APS45 and MSO1 × APS12 performed well under diversified environmental conditions indicating their overall stability and superiority. These hybrids revealed highly significant (p < 0.01) improvement for the majority of the traits over the control hybrids.

Effects of refrigeration (5 ± I'C) of newly hatchet! silkworm larvae on survival rate, growth and egg production were studied in two multivoltine races, Pure Mysore and Hosa Mysore. When refrigerated for 10 days, moth emergence (males: 83·3% vs 89·4% and females: 92% vs 90'2%) and fecundity (465'5 vs 458'3) did not differ significantly from the control. Reductions in cocoon weight by 4% (1,323 g vs 1·271 g) and 10·7% (1'323 g vs 1·181 g) were caused by 5 and 10 days of refrigeration. Marked increase in early stage (I and II instar), loss of larvae (12'9% vs 48,8%), decrease in effective rate of rearing (77'1% vs 33'5%), pupation rate (92,4% vs 65%) and reproductive rate (137,7 vs 36'9) were observed, when refrigerated for 10 days. Results on reproductive rate indicated one day's refrigeration as safe period in Hosa Mysore but not in Pure Mysore. In December season. both races showed higher tolerance and possibility of safe refrigeration upto 2 days.