Genotypic variations in the plasticity of nodal root penetration through the hardpan during soil moisture fluctuations among four rice varieties

Dinh Thi Ngoc Nguyen,Roel Rodriguez Suralta,Mana Kano-Nakata,Shiro Mitsuya,Stella Owusu-Nketia,Akira Yamauchi

doi:10.1080/1343943x.2018.1439757

Dinh Thi Ngoc Nguyen, Roel Rodriguez Suralta + Show 4 more

Open Access

https://doi.org/10.1080/1343943x.2018.1439757

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Abstract

Rainfed lowland rice fields are characterized by soil moisture fluctuations (SMF) and the presence of hardpan that impedes deep rooting and thus limits water extraction from deep soil layer during the periods of drought. In this study, we used rootboxes with three layers; shallow layer, artificial hardpan, and deep and wet layer below the hardpan, to evaluate differences in the plasticity of nodal roots elongation through the hardpan and promote root branching below the hardpan in response to SMF among four rice varieties; Sasanishiki, Habataki, Nipponbare, and Kasalath. Experiments were conducted during the summer and autumn seasons. Plasticity was computed as the difference in root traits within each variety between the SMF and continuously well-watered treatments. In both experiments, Habataki consistently tended to exhibit higher root plasticity than the other three varieties by increasing number of nodal roots that penetrated the hardpan during rewatering period in SMF, when the soil moisture increased and penetration resistance decreased. This root plasticity then contributed to greater water use at the deeper soil during the subsequent drought period and overall shoot dry matter production. Habataki had significantly higher δ13C value in roots at deep layer than roots at the shallow and hardpan layers under SMF, which may indicate that these were relatively newly grown roots as a consequence of root plasticity. This study also indicates that CSSLs derived from Sasanishiki and Habataki varieties may be suitable for the analysis of QTLs associated with root plasticity expression in rainfed lowland with hardpan and experiencing SMF.

Highlights

19% of the world’s rice production comes from 52 million ha of rainfed lowlands (IRRI, 2013)
Among four varieties (Sasanishiki, Habataki, Nipponbare, and Kasalath) examined in two experiments, Habataki tended to exhibit higher plasticity in nodal root elongation, which resulted in hardpan penetration, and deep root development than the other varieties under soil moisture fluctuation (SMF) conditions
We showed that such plasticity in nodal root elongation through the hardpan occurred during the rewatering period in SMF, when the soil moisture increased and penetration resistance decreased

Summary

Introduction

19% of the world’s rice production comes from 52 million ha of rainfed lowlands (IRRI, 2013). Soil moisture fluctuation (SMF) or the alternating recurrence of drought and rewetting depending on the rainfall patterns, are two of the main limiting factors that reduce production (Suralta et al, 2016). Typical rainfed lowland fields are characterized by a 5-cm high bulk density hardpan layer underneath the cultivated layer at approximately 20 cm depth (Samson et al, 2002; Yano et al, 2006). The presence of hardpan is important for reducing the loss of irrigated water in lowland fields but it can hinder both the penetration of root to deeper soil layer as well as the movement of water between soil layers (Cairns et al, 2011). The ability of roots to penetrate the hardpan is one of the key traits for deep root system development (Fukai & Cooper, 1995), where water supply at the shallow layer is limited during periods of drought (Henry et al, 2011; Siopongco et al, 2009)

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