Drought-induced root plasticity of two upland NERICA varieties under conditions with contrasting soil depth characteristics

Daniel Makori Menge,Emi Kameoka,Mana Kano-Nakata,Akira Yamauchi,Shuichi Asanuma,Hidetoshi Asai,Mayumi Kikuta,Roel Rodriguez Suralta,Takuya Koyama,Thiem Thi Tran,Joel D L C Siopongco,Shiro Mitsuya,Yoshiaki Inukai,Daigo Makihara

doi:10.1080/1343943x.2016.1146908

Abstract

To identify differences in root plasticity patterns of two upland New Rice for Africa (NERICA) varieties, NERICA 1 and 4, in response to drought under conditions with contrasting soil profile characteristics, soil moisture gradients were imposed using a sloping bed system with depths ranging 30–65 cm and a line-source sprinkler system with a uniformly shallow soil layer of 20 cm depth. Varietal differences in shoot and root growths were identified only under moderate drought conditions, 11–18% v/v soil moisture content. Further, under moderate drought soil conditions where roots could penetrate into the deep soil layer, deep root development was greater in NERICA 4 than in NERICA 1, which contributed to maintaining dry matter production. However, under soil conditions with underground impediment to deep root development, higher shoot dry weight was noted for NERICA 1 than for NERICA 4 at 11–18% v/v soil moisture content, which was attributed to increased lateral root development in the shallow soil layer in NERICA 1. Enhanced lateral root development in the 0–20-cm soil layer was identified in NERICA 1 even under soil conditions without an impediment to deep root development; however, this did not contribute to maintaining dry matter production in upland rice. Thus, we show different root developmental traits associated with drought avoidance in the two NERICA varieties, and that desirable root traits for upland rice cultivation vary depending on the target soil environment, such as the distribution of soil moisture and root penetration resistance.

Highlights

In sub-Saharan Africa, where rice consumption has increased rapidly in recent years, the major ecosystem for rice cultivation is rainfed uplands which account for approximately 40% of sub-Saharan Africa’s total rice area (IRRI, 2013)
These results indicated that the sloping bed and line-source sprinkler systems are practical for simulating drought conditions under soil environments where the soil starts drying from the surface while maintaining wet conditions in deep soil layers and soil environments where deep root penetration to the subsoil strata is inhibited due to the presence of a hard soil layer, respectively
We aimed to evaluate the differences in drought avoidance-related root traits between New Rice for Africa (NERICA) 1 and NERICA 4, plasticity in deep root development and lateral root development, by using sloping bed and line-source sprinkler systems

Summary

Introduction

In sub-Saharan Africa, where rice consumption has increased rapidly in recent years, the major ecosystem for rice cultivation is rainfed uplands which account for approximately 40% of sub-Saharan Africa’s total rice area (IRRI, 2013). This is more than double the overall global proportion of rice crops that are rainfed upland rice, which is 15% or approximately 19 million hectares (Thanh et al, 1999). There are currently 18 varieties suited for upland growth conditions (NERICA 1 to NERICA 18) (Wainaina et al, 2015) The use of these improved rice varieties is expected to achieve remarkable yield improvements (Kijima et al, 2006) and catalyze a rice green revolution in sub-Saharan Africa (Matsumoto et al, 2014)

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