Progress in varietal improvement for increasing upland rice productivity in the tropics

Abstract

Enhancing rice yield in upland rice systems through genetic improvement remains a major challenge in the tropics. This review aims to provide the trends on upland rice cultivation over the last 30 years and recent distribution of upland rice in the tropics, and to report progress in studies on genetic improvement for enhancing productivity in Africa, Asia, and Latin America. While upland rice cultivation area has reduced in Asia and Latin America over the last 30 years, the area in Africa has increased. The current share of upland rice area in total rice area is related to rainfall and gross national income per capita, especially in Africa, and higher share is associated with lower rice selfsufficiency at national level. Breeding programs in Asia and Latin America have developed highyielding varieties using indica materials as parents. In Africa, New Rice for Africa (NERICA) varieties were developed from crosses between improved tropical japonica and Oryza glaberrima. However, recent studies report that there is scope for improving existing NERICA using upland indica materials from Asia. In highlands of Africa, there are ongoing breeding programs using japonica varieties, such as the Nepalese Chhomrong Dhan. Key important plant traits used in the breeding programs are not largely different across regions, especially intermediate plant height and tillering capacity (which may be related to weed-suppressive ability), and high harvest index. In conclusion, we propose an international network for breeding upland rice with accelerating seed exchange across regions that could enhance upland rice productivity through genetic improvement.

Pores for Thought: Can Genetic Manipulation of Stomatal Density Protect Future Rice Yields?

“…On the other hand, given that freshwater insecurities and exposure to drought will likely become increasingly prevalent in areas of rice cultivation (Kang et al, 2009;Quentin Grafton, 2017), rice crops that use water more efficiently might be of greater importance in the future climate. This will be especially important in Africa where, as a result of water limitations, rainfed upland rice production is steadily increasing, despite this method being particularly susceptible to drought (Saito et al, 2018). Promisingly, OsEPF1oe lines with decreased SD exhibit improved water conservation and tolerance to drought without yield penalties (Caine et al, 2019).…”

Improved Upland Rice: Adaptability, Agronomic and Farmer Acceptability Assessment under Semi-Arid Conditions of South Western Uganda

“…The current decline in the lowland rice yield in Uganda, which is partly attributed to prolonged drought, insufficient water availability and low soil fertility, is a threat to food security and income especially in regions that are highly dependent on this commodity. Effort to develop high yielding varieties that are adaptable to the diverse environments and tolerant to drought are on-going in Africa [17], and specifically in Uganda where many improved upland rice varieties have been recently released [12]. The current upland rice average yield of milled rice in Uganda is 1.7 t/ha, but it is projected to rise to 2.9 t/ha with increased use of improved technologies [18].…”

“…Typically, when plants shorten their growth period in event of abrupt water scarcity, yield deficits occur. Although Uganda is still advantaged because its higher soil fertility and relatively high annual rainfall (800 -1200 mm per year) compared to other African countries, the climate change threat may severely affect rice production if well adaptable varieties are not developed [17]. Therefore, the current focus on developing climate change resilient rice through breeding early maturing, high drought tolerant and high yielding varieties, is the appropriate strategy.…”

Multidisciplinary assessment of agricultural innovation and its impact: a case study of lowland rice variety WITA 9 in Côte d’Ivoire

“…To alleviate abiotic and biotic stresses and enhance domestic rice production in sub-Saharan Africa, research and development activities have developed and delivered new rice varieties (Saito, Asai, Zhao, Laborte & Greiner, 2018;Saito, Azoma & Sie, 2010;Saito, Azoma & Sokei, 2010;Saito, Sokei & Wopereis, 2012;Sikirou et al, 2015;Tollens et al, 2013). Breeding efforts have been focused on the development of varieties that have higher paddy yield as well as resistance to abiotic and biotic stresses, with limited focus on grain quality.…”

“…Although such efforts to disseminate WITA 9 were reported by local media such as newspapers, the success story of the upland 'New Rice for Africa' (NERICA) varieties diverted attention from the success of WITA varieties that preceded the NERICA varieties; there have been many studies and publications related to NERICA varieties (e.g. M. Matsunami, Matsunami & Kokubun, 2009;Saito et al, 2018;Saito, Fikuta, Yanagihara, Ahouanton, & Sokei, 2014;Saito et al, 2012;Sekiya et al, 2013;Watanabe, Futakuchi, Jones & Sobambo, 2006). As a result, the agronomic characteristics, adoption and impact in farmers' fields, and marketability of WITA 9 have not been studied until recently.…”