Dr.H.V. Anil Kumar
Associate Professor of Sericulture, Laboratory for Applied Biological Science
DVS College of Arts and Science, Shivamogga

Topic: Crop improvement in rain fed mulberry genotypes by EMS induced mutations and its impact on silk yield

Abstract:
Silk is a splendid gift of nature to mankind, an inimitable natural fiber synonymous with splendor, sibilant with luster and spectacular in vision. Silk is a protein biosynthesized by the silkworm Bombyx mori. L. Silkworm is monophagous and exclusively feeds on mulberry (Morus alba L.), hence mulberry is the sole forage for silkworm. The preference for mulberry by silkworm is probably due to chemical β-Sitosterol (beta-sitosterol) present in mulberry and special organs the silkworm is equipped with, that respond to the taste of leaves. Nearly 70% of the mulberry leaf protein is converted into silk protein through biosynthesis in silkworm. Thus, Mulberry leaf protein is the quintessence for synthesis of sericin and fibroin, main components of silk protein. Obviously mulberry is the central dogma in sericulture and the increased biomass (leaves) in mulberry variety is the principal determining factor of higher cocoon yield.

Realizing the significance of increased biomass (leaves) and nutritional value of mulberry leaves, the present investigation explored to achieve the enhancement in biomass coupled with quality of leaves, in rain fed mulberry genotype, through EMS induced chemical mutagenesis. The purpose of induced mutations is to enhance the mutation frequency rate in order to select appropriate variants for plant breeding. The mutation frequency rate of spontaneous mutations is rather very low and difficult to exploit by the plant breeders. Mutations are induced by physical (e.g. gamma radiation) and chemical (e.g. ethylmethane sulfonate) mutagen treatment of both seed and vegetatively propagated crops.

Ethyl Methane Sulphonate (EMS) is a potent chemical mutagen, extensively used in genetic research. It is a monofunctional-ethylating agent that has been found to be mutagenic in wide a variety of genetic test systems from virus to mammal. The alkyl group of an alkylating agent reacts with DNA, which may lead to a change in the nucleotide sequence and hence leads to point mutation. Since the alkylating agent like EMS reacts with DNA in variety of ways, a broad spectrum of mutagenic effects is manifested in the population. EMS has been found more potent for mulberry. Thus, EMS was conveniently used for induction of mutations in mulberry rain fed genotypes. Observations were recorded in M1V1 and M1V2 generations for early growth parameters and later morphometric characters. The results revealed that the 0.1% and 0.3% concentrations of EMS treatment were effective in significantly altering the early growth parameters and later morpho-economic traits. The higher concentration of 0.5% EMS reduced the survival rate and was found lethal, but the low concentrations 0.1% and 0.3% EMS were found to be safe and optimum for treatment. Thus, it infers that these vegetative parameters were mutagen dose dependent factors