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

Dule Zhao,Alice G Laborte,Kazuki Saito,Hidetoshi Asai,Cécile Grenier

doi:10.1080/1343943x.2018.1459751

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 self-sufficiency at national level. Breeding programs in Asia and Latin America have developed high-yielding 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.

Highlights

IntroductionWheat, and maize are the world’s three most important food crops. Of these, rice is the most consumed by humans, being eaten by more than half of the world’s population
Recent statistics from 71 countries from Asia, Latin America and sub-Saharan Africa show that lowland and upland rice account for 92 and 8% of total rice cultivation area, respectively, (Figure 1)
Recent breeding progress in upland rice in the tropics has replaced traditional upland rice varieties characterized by low yield, tall plants, and few tillers by improved varieties; in West Africa, the traditional varieties are often tropical japonica (Oryza sativa) or Oryza glaberrima, which is highly weed competitive, and resistant to local biotic and abiotic stresses (Arouna et al, 2017; Atlin et al, 2006; Futakuchi et al, 2012; Pinheiro et al, 2006; Saito & Futakuchi, 2009)

Summary

Introduction

Wheat, and maize are the world’s three most important food crops. Of these, rice is the most consumed by humans, being eaten by more than half of the world’s population. Toure, et al (2015) show that recent yield increases at national level are associated with share of irrigated area in total rice area in sub-Saharan Africa. This indicates that enhancing yield in rain-fed systems, including upland rice, remains a major challenge. Recent breeding progress in upland rice in the tropics has replaced traditional upland rice varieties characterized by low yield, tall plants, and few tillers by improved varieties; in West Africa, the traditional varieties are often tropical japonica (Oryza sativa) or Oryza glaberrima, which is highly weed competitive, and resistant to local biotic and abiotic stresses (Arouna et al, 2017; Atlin et al, 2006; Futakuchi et al, 2012; Pinheiro et al, 2006; Saito & Futakuchi, 2009). ‘aerobic rice varieties’ that are developed for ‘aerobic rice systems’ can be used as upland rice varieties, and grown in uplands having no severe drought

SAITO ET AL

Breeding efforts and genetic gains in the tropics

Latin America

Sub-Saharan Africa

Findings

Synthesis and conclusions