D.E. Johnson

Growth and yield potential of Oryza sativa and O. glaberrima upland rice cultivars and their interspecific progenies

Abstract A recent breakthrough in generating fertile progeny from Oryza sativa × O. glaberrima crosses gives rice breeders access to a broader range of germplasm. Interspecific crosses might provide new solutions to the low productivity of upland rice systems prone to weed competition. Two field and one pot experiments conducted during 1995 and 1996 served to characterize growth and yield potential of CG14 ( O. glaberrima ), WAB56-104 ( O. sativa ) and their progeny. During the 1995 wet season and the 1996 dry and wet seasons, the lines were seeded in a well-drained upland field in Ivory Coast with supplemental sprinkler irrigation. A randomized complete-block design with three replications was used, with cultivar and nitrogen levels as sub-plots. Specific leaf area (SLA), leaf area index (LAI), leaf chlorophyll content (SPAD method) and tiller number were measured at 2-week intervals until flowering. Grain yield and yield components were measured at maturity. In all environments, CG14 produced two to three times the LAI and tiller numbers as WAB56-104. This was associated with a high SLA and low leaf chlorophyll content. Grain yields of CG14 did not respond to N inputs, although the sink potential did. The difference was mainly caused by grain shattering. The progenies had intermediate LAI, SLA and leaf chlorophyll content, but their grain yields, tiller numbers and resistance to lodging and grain shattering were similar to WAB56-104. Across lines, LAI and SLA were significantly correlated. A paddy field experiment confirmed the relationship between LAI and SLA for a wider range of rice cultivars and interspecific progenies. A pot experiment demonstrated that leaf net CO 2 assimilation rates ( A max ) followed a common linear function of areal leaf chlorophyll content across cultivars. The main common cause of differential LAI and A max appeared to have been genotypic patterns of SLA, which might be an important determinant of growth vigor and competitiveness with weeds. The possibility is discussed of combining, in a single line, high SLA during vegetative growth (for weed competitiveness) with low SLA during the reproductive growth phase (for high yield potential), to produce an efficient plant type for low-management conditions.

Realizing Africa's rice promise.

Africa Rice Center (AfricaRice), 01 BP 2031 Cotonou, Benin ABSTRACT Rice consumption in Africa is increasing rapidly because of changes in consumer preferences and urbanization. In 2009, the continent imported one-third of what is available on the world market, costing an estimated US

Realizing Africa's rice promise: priorities for action.

5 billion. Soaring and highly volatile rice prices and relatively low levels of global stocks are predicted to remain the norm over the next 10 years. As witnessed by the food crisis in 2008 this is a very risky, expensive and unsustainable situation, and it may lead to severe food insecurity and civil instability in some African countries. However Africa has the human, physical and economic resources to produce enough rice to feed itself and many national, regional and continental rice sector development initiatives have seen the light since the food crisis. The critical challenge facing the African rice sector is to enhance performance in production, processing and marketing to respond to a major concern to be turned into an opportunity: the growing demand for rice as a preferred staple. The Africa Rice Center (AfricaRice) is a pan-African research organization, that currently includes 24 member states, working to contribute to poverty alleviation and food security in Africa through research, development and partnership activities aimed at increasing the productivity and profitability of the rice sector in ways that ensure the sustainability of the farming environment. AfricaRice is also a member of the Consortium of International Agricultural Research Centers (CGIAR). During its 28th Ordinary Session, held in September 2011 in The Gambia, AfricaRice’s Council of Ministers approved the Center’s 2011-2020 Rice Research for Development strategy. Through a priority setting process, seven Research for Development (R4D) Priority Areas (PAs) were identified that are considered crucial to realize Africa’s rice promise: 1. Conserving rice genetic resources and providing climate-resilient rice varieties to smallholder farmers that are better adapted to production environments and consumer preferences 2. Improving rural livelihoods by closing yield gaps and through sustainable intensification and diversification of rice-based systems 3. Achieving socially-acceptable expansion of rice producing areas, while addressing environmental concerns 4. Creating market-opportunities for smallholder farmers and processors by improving the quality and the competitiveness of locally produced rice and rice products 5. Facilitating the development of the rice value chain through improved technology targeting and evidence-based policy making 6. Mobilizing co-investments and linking with development partners and the private sector to stimulate uptake of rice knowledge and technologies 7. Strengthening the capacities of national rice research and extension agents and rice value chain actors

Relationships between upland rice canopy characteristics and weed competitiveness

424 (eds M.C.S. Wopereis et al.) There are the producers and manufacturers of inputs (seeds, fertilizers, pesticides) and machinery, and the traders who sell these, while on the post-production side, there are processors, traders, wholesalers, retailers and consumers. This book deals with a diverse range of topics that are all of relevance to realizing ‘Africa’s rice promise’, defined in the Introduction: ‘Africa has sufficient land and water resources to produce enough rice to feed its own population and, in the long term, generate export revenues’. This concluding chapter brings together the main ideas presented in this book and traces a way forward to develop Africa’s rice sector in a sustainable and equitable manner. We will discuss a number of priorities that are grouped in four main action areas: