Genetic Resources and Breeding of Tropical Grasses, Forages - Apomixis - Biofuel Feedstocks

Abstract

Farmers select landraces from wild plant populations. Landraces are useful for plant breeding. Genetic erosion is diminishing these valuable genetic resources and steps to retain these materials are required. Therefore, germplasm collection represents an important activity of agricultural scientists. From 1971 to 1973, two Japanese scientists made excursions to East Africa and collected ca. 2,000 accessions of tropical grasses, named the “Africa collection”. Within the collection, there are 140 guineagrass accessions, which is primarily a tetraploid (4x) form that reproduces through aposporous apomixis. A single, diploid (2x) sexual accession, GR297, was isolated from the collection and this accession played an important role for the breeding and molecular analysis of apomixis gene(s). During progeny testing of the open-pollinated GR297, a vigorous apomictic 4x hybrid plant, registered as cv. Natsukaze, was identified. Then, chromosome doubling of the GR297 was attempted to facilitate hybridization with 4x lines, and the 4x sexual line, Nekken No. 1 (Noh PL 1), was developed. This line has been utilized as a maternal parent for the development of new varieties, mapping and linkage analysis of apomixis. Even though the locus for apospory was identified, markers linked to the gene(s) exhibited no recombination. This apospory-specific genomic region was physically mapped by FISH to a single chromosome. Sorghum is cultivated as a forage crop in Japan. Germplasm of sorghum were collected with the cooperation of Myanmar and Kenya. Recently, sweet sorghum has attracted the interests of the biofuel industry for use as bioethanol feedstock. Radiation breeding has been applied to induce bm and bmr mutantions; which would be useful for efficient biofuel production. Mutation breeding elevates the frequency of natural mutation rates and can be efficiently utilized to develop new breeding materials. The importance of Genebank activities and mutation breeding towards biofuel production conducted within our center are discussed.