Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)4. A wide range of non-food crops, which could include the production of pharmaceuticals,industrial oils, renewable materials and crops which could be used directly in theproduction of energy and fuel. Production for fuel could become increasingly attractive inthe event of more favorable revenue conditions applying to bio-fuels.The GM seed market represents about 10% of the commercial seed market worldwide.The total GM seed market in India has an estimated value of US$25 million. India increased its BTcotton area by 100%; India placed 8 th partition with 0.1 million hectares production. GEAC hasapproved the commercialized cultivation of BT cotton in April 2002 in six states in the country,which include Maharashtra, Gujarat, M.P., A.P., Tamil Nadu and Karnataka. Other crops such asmustard, soybean corn and potatoes are expected to receive approval in the near future. The GMseeds segment in India is dominated by various companies such as Mahyco, Monrto, ProAgro,Aduantor, Mahyco Monsanto.Biotechnological tool for maintenance of hybridityBarnase-barstar system : Gene barnase encodes an RNAse which kills the cells in which it isexpressed by degrading RNA. The expression of barnase was confined to tapetal cells by fusing itwith the promoter of tobacco tapetum specific gene TA29 ( gene construct : pTA29- barnase; ppromoter ). When the chimaeric gene construct was transferred and expressed in tobacco andoilseed rape, the tapetal cells of anthers were destroyed and there was no pollen development.However there was no effect on female fertility. Since the male sterility due to barnase isdominant, the male sterile lines are always heterozygous (barnase/- ; the – sign indicates absenceof barnase gene in homologous chromosome) and they have to be maintained by crossing to anynormal, non transformed male fertile line (-/-; barnase gene absent). Thus male sterile lines (barnase/-) will have to be crossed to be normal fertile lines (-/-), and only 50% of the progeny fromsuch crosses will be male sterile while rest 50% will be male fertile (-/-). In a hybrid seedproduction programme the male fertile plants present in male sterile line must be identified andeasily eliminated. This has been done by linking the barnase gene with the bar gene fromStreptomyces: bar gene confers resistance to herbicide phosphinothricin. When such male sterile (barnase-bar/-) plants are maintained by crossing with normal male fertile (-/-), all the male sterileprogeny ( barnase-bar/- ) are resistant to the herbicide, while all the male fertile plants (-/-) areherbicide susceptible. The male fertile plants are therefore eliminated by a herbicide spray at anearly stage of plant growth.The male fertility of barnase male steriles is restored by another gene, barstar, of thebacterium B. amyloliquefaciens. The gene barstar encodes a specific inhibitor of barnase encodedRNase. The barstar product forms a highly stable 1:1 non-covalently bound complex with the barnaseRNase; this reaction provides protection to the bacterial cells from their own RNase product.Transgenic plants expressing barstar are male fertile without any phenotypic effect, and are easilymaintained in the homozygous state. When a homozygous barstar male fertile line is crossed with abarnase male sterile all the progeny plants are male fertile since barstar gene product effectively- 193 -