Genotypic variation in soil water use and root distribution and their implications for drought tolerance in chickpea

Abstract

Abstract. Chickpeas are often grown under receding soil moisture and suffer~50% yield losses due to drought stress. The timing of soil water use is considered critical for the efficient use of water under drought and to reduce yield losses. Therefore the root growth and the soil water uptake of 12 chickpea genotypes known for contrasts in drought and rooting response were monitored throughout the growth period both under drought and optimal irrigation. Root distribution reduced in the surface and increased in the deep soil layers below 30 cm in response to drought. Soil water uptake was the maximum at 45-60 cm soil depth under drought whereas it was the maximum at shallower (15-30 and 30-45 cm) soil depths when irrigated. The total water uptake under drought was 1-fold less than optimal irrigation. The amount of water left unused remained the same across watering regimes. All the drought sensitive chickpea genotypes were inferior in root distribution and soil water uptake but the timing of water uptake varied among drought tolerant genotypes. Superiority in water uptake in most stages and the total water use determined the best adaptation. The water use at 15-30 cm soil depth ensured greater uptake from lower depths and the soil water use from 90-120 cm soil was critical for best drought adaptation. Root length density and the soil water uptake across soil depths were closely associated except at the surface or the ultimate soil depths of root presence.

Root traits confer grain yield advantages under terminal drought in chickpea ( Cicer arietinum L.)

“…The water holding capacity of this field in lower limit: upper limit was 0.26:0.40 cm 3  cm −3 for the 0–15 cm soil layer, and 0.30:0.47 cm 3  cm −3 for the 105–120 cm soil layer. The available soil water up to 120 cm depth observed in this study was 216 mm in 2009–10 and 207 mm in 2010–11 (Purushothaman et al, 2016a). The bulk density was 1.35 g cm −3 for the 0–15 cm soil layer and 1.42 g cm −3 for the 105–120 cm soil layer (El-Swaify et al, 1985).…”

“…The emphasis placed upon RDp as an important trait for deeper soil water extraction to enhance reproductive growth and grain yield under DS (Saxena et al, 1993, Krishnamurthy et al, 2003, Zhang et al, 2004, Kashiwagi et al, 2005, Kirkegaard et al, 2007, Purushothaman et al, 2016a) had been confirmed to be appropriate with this work. The genotype ICC 4958 had a strong root system as early as 35 DAS, flowered and matured about 10 days earlier than mean flowering time.…”

“…These had displayed poor root growth throughout their life cycle and one among them produced very poor shoot biomass in 2010–11 and had a very low HI. Among the studied genotypes, these two drought sensitive genotypes had produced the least shoot biomass seemingly due to limited soil water uptake (Purushothaman et al, 2016a) and restricted transpiration as a consequence of their poor root growth. The best adapted genotype Annigeri was the next earliest to flower and mature after ICC 4958 completing its life cycle at least 7 days before the other genotypes.…”

“…For instance, Kirkegaard et al (2007) demonstrated through field-based direct root and soil water measurements, that a 30 cm rooting depth increase in root system can capture an extra 10 mm of deep soil water at the grain development stage and result in an extra 0.5 t grains per hectare. Large root system with greater root prolificacy and rooting depth, was shown to influence not only transpiration through soil moisture utilization but also shoot biomass production, harvest index (HI) under terminal DS (Kashiwagi et al, 2006, Kashiwagi et al, 2013, Zaman-Allah et al, 2011, Purushothaman et al, 2016a). On the contrary, a deeper and more profuse roots alone had been considered not that important for higher grain yields (Vadez et al, 2008) or as a needless biomass partitioning (Passioura, 1983) or as an unnecessary energy loss due to its vigorous respiration compared to the shoot system (Vanderwerf et al, 1988, Krauss and Deacon, 1994).…”

“…Association studies of the whole plant root system with the grain yield production may reveal a positive (Kell, 2011, Bishopp and Lynch, 2015) or negative or neutral association (CIAT, 2007, CIAT, 2008, Zaman-Allah et al, 2011, Schoppach et al, 2013) as all the segments of the whole root system (from surface to deep layer roots) are not actively involved in soil water extraction (Ali et al, 2002, Carvalho et al, 2014) due to variable soil water availability across soil depths (Purushothaman et al, 2016a). Such interactions deter researchers from arriving at the right conclusion on the contribution of root traits to grain yield.…”