Takashi Kumashiro

Expression of ArabidopsisDREB1C improves survival, growth, and yield of upland New Rice for Africa (NERICA) under drought

Dehydration-responsive-element-binding protein 1 genes have important roles in response to stress. To improve the drought tolerance of an upland rice cultivar NERICA1, we introduced ArabidopsisAtDREB1C or rice OsDREB1B driven by a stress-inducible rice lip9 promoter. Plants of some transgenic lines survived better than non-transgenic plants under severe drought. AtDREB1C transgenic plants had higher dry weights than non-transgenic plants when grown under moderate drought until the late vegetative growth stage. On the other hand, OsDREB1B transgenic plants had lower dry weights than non-transgenic plants under the same condition. Similar results were obtained under osmotic stress. The AtDREB1C transgenic plants headed earlier, had a larger sink capacity, and had more filled grains than non-transgenic plants. These results suggest that AtDREB1C expressed in NERICA1 improves not only survival under severe drought, but also growth and yield under moderate drought.

Genetic characterization of rainfed upland New Rice for Africa (NERICA) varieties

A total of 18 rainfed upland New Rice for Africa (NERICA) varieties were categorized as the heavy panicle and low tillering types and early heading, in compared with 32 different varieties. These chromosome components were clarified using 243 SSR markers which showed polymorphism among NERICA varieties and their parents, CG 14 (O. glaberrima Steud.) and one of the recurrent parents, WAB-56-104 (O. sativa L.). NERICA varieties were classified into three groups, which corresponded with these parents’ continuation including two exceptions, NERICAs 14 and 17, by a cluster analysis using polymorphism data of SSR markers and 14 differential markers among them were selected to classify NERICA varieties. However, three groups: NERICAs, 3 and 4, NERICAs, 8, 9 and 11 and NERICAs, 15 and 16 were not distinguishable. Association analysis was carried out for characterization of NERICA varieties by using SSR markers genotype and phenotype of agronomic traits. A total of 131 quantitative trait loci between SSR markers and 11 agronomic traits were detected. The characteristics of early maturity and heavy panicle of upland NERICA varieties were succeeded from Asian rice varieties and the characteristics of high dry matter production and late heading were introduced from CG 14 and the other varieties.

Genetic variation in blast resistance in rice germplasm from West Africa

The genetic variation in resistance to blast (Pyricularia oryzae Cavara) in 195 rice accessions comprising 3 species of the AA genome complex (Asian rice [Oryza sativa L.], African rice [Oryza glaberrima Steud.] and wild rice [Oryza barthii]) was investigated based on their patterns of reaction to standard differential blast isolates (SDBIs) and SSR marker polymorphism data. Cluster analysis of the polymorphism data of 61 SSR markers identified 3 major clusters: cluster A (mainly Japonica Group or upland accessions), cluster B (mainly Indica Group or lowland accessions) and cluster C (O. glaberrima and O. barthii). The accessions were classified again into 3 resistance groups based on reactions to SDBIs: group Ia (susceptible), group Ib (middle resistance) and group II (high resistance). Group Ia included only a few differential varieties, susceptible controls and the Japonica Group cultivar Nipponbare. Accessions in clusters A and B included all 3 resistance groups and showed a wide variation in blast resistance, but cluster C contained only group Ib. These results demonstrated that variations in Asian rice (O. sativa) accessions in West Africa were skewed toward high resistance and that variations in O. glaberrima and O. barthii were limited and lower than the Asian rice accessions.