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

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.

Root and shoot responses of upland New Rice for Africa varieties to fluctuating soil moisture conditions as affected by different levels of nitrogen fertilization

“…Similar findings were reported in upland rice under cultivation environments in sub-Saharan Africa (Asch, Dingkuhn, Sow, & Audebert, 2005). We also showed that upland NERICA varieties did not enhance lateral root growth under severe drought conditions, while under mild to moderate drought conditions, approximately −18 to −48 kPa of soil water potential, varietal differences were observed among upland NERICAs in the ability to enhance lateral root growth (Menge et al, 2016). Moreover, Kato and Okami (2010) reported that stomatal behaviour under mild to moderate drought conditions differs depending on the variety.…”

“…This is consistent with reports by Niones et al (2012) and Suralta et al (2008b), who found genotypic differences in the ability to enhance root system development in response to fluctuating soil moisture conditions. In our previous study, NERICA 1 was found to have a greater ability to enhance lateral root growth than NERICA 4 under moderate drought stress (Menge et al, 2016). The same trend was demonstrated in this study by the fact that NERICA 1 exhibited greater root elongation under fluctuating soil moisture conditions than NERICA 4 (Tables 1 and 5 (Table 5).…”

Functional roles of root plasticity and its contribution to water uptake and dry matter production of CSSLs with the genetic background of KDML105 under soil moisture fluctuation

“…Previous studies have shown experimental evidences of genotypic variations in root plasticity expressed in response to heterogeneous soil environments for the adaptation of rice plants (Bañoc et al, 2000a;Siopongco et al, 2008;Kano-Nakata et al, 2013;2017;Kameoka et al, 2015;Menge et al, 2016;Niones et al, 2012;Nguyen et al, 2018;Owusu-Nketia et al, 2018;Suralta et al, 2010Suralta et al, , 2016Suralta et al, , 2018Tran et al, 2014). In this study, the CSSLs showed no significant differences in root system development with the recurrent parent under CWL in both experiments.…”

“…Digital images were then taken using an image scanner (EPSON Perfection V700 Photo) at 400 dpi resolution. The TRL was analyzed using WinRhizo software (Regent Instruments Inc., Saint-Foy, Canada) (Kameoka et al, 2015;Menge et al, 2016). A pixel threshold value of 175 was set for the root length analysis (Nguyen et al, 2018;Suralta et al, 2018).…”

“…In rice, the root plasticity such as promoted lateral root development were shown to be exhibited in response to varying water-deficit stress intensities (Kameoka, Suralta, Mitsuya, & Yamauchi, 2015;Kano, Inukai, Kitano, & Yamauchi, 2011;Kano-Nakata et al, 2013;Kano-Nakata, Inukai, Wade, Siopongco, & Yamauchi, 2011;Menge et al, 2016;Tran et al, 2014), continuous cycles of alternating waterlogged and drought stress (Niones et al, 2012;Owusu-Nketia et al, 2018), rewatering after drought (Bañoc, Yamauchi, Kamoshita, Wade, & Pardales, 2000a;Sandhu et al, 2016;Siopongco, Yamauchi, Salekdeh, Bennett, & Wade, 2005; and transient drought preceded by waterlogged and vice versa (Suralta et al, 2010;Suralta & Yamauchi, 2008), and to contribute to the maintenance of dry matter production and yield under such conditions. Khao Dawk Mali 105 (KDML105) is an elite cultivar of aromatic rice mainly grown in rainfed lowland areas of North and Northeast Thailand which are prone to abiotic and biotic stresses such as salinity, drought, submergence, diseases and pest (Jantaboon et al, 2011;Jongdee, Pantuwan, Fukai, & Fischer, 2006;Kanjoo et al, 2012;Siangliw, Jongdee, Pantuwan, & Toojinda, 2007;Toojinda, Siangliw, Tragoonrung, & Vanavichit, 2003;Toojinda et al, 2005).…”