Abstract
[Context] Unpredictable water deficit (drought) and low soil phosphorus (LP) are major interacting constraints to groundnut growth and grain yield in Sahelian zones of West Africa. Combining breeding efforts for drought tolerance and P efficiency could lead to improve tolerance and grains yield in these zones. [Objectives] This study assessed six groundnut genotypes under lysimetric system to better understand the relative importance of P deficiency, water stress, and their interaction; investigate the water extraction pattern of genotypes under these constraints and identify tolerance related traits to accelerate development of more resilient varieties. [Methods] Thus, in experiment 1 (Exp.1) roots traits were investigated at 50% flowering, pod filling stage (60 days after sowing) and maturity stage (90 days after sowing) under high phosphorus (HP) and LP treatments. In experiment 2 (Exp.2), two water regimes (WW=well water, and WS = water stress) were imposed to HP and LP plants and parameters like total transpired water (TTW), transpiration efficiency (TE), water extraction (Wex), pods and haulm weights were investigated. [Results] Roots traits showed significant decrease due to LP stress, pod and haulm weights correlated significantly to roots length density (RLD) and roots dry matter (RDM). Genotypes 12CS-116 and ICGV 12991 revealed tolerant to LP stress while RLD and RDM revealed LP tolerance related traits in groundnut. Interacting effect of LP and drought stress (LPWS) was higher than separate effect of LP and WS. Under LPWS, Wex, TTW, TE, pod and haulm yields decreased significantly. This study suggests that RLD and RDM contributed to Wex in 12CS-116 and ICG 12991 under LPWS. 55-437 and JL-24 with highest TTW showed drought tolerance strategy while drought avoidance strategy could explain 12CS-116, 12CS-79, ICG 12991 and ICGV 97183 response to WS. Pod weight showed tight correlation (R2 =0.7) to TE only under LPWS suggesting that TE explains a large part of pod yield variation under LPWS conditions. TE revealed WS and LPWS tolerance related trait. The genotypic variation observed on Wex and TTW under LPWS suggests different patterns of water extraction and use among the groundnut genotypes.
Highlights
In Sahelian zones of the semi-arid tropics, groundnut (Arachis hypogaea L.) is widely cultivated in rainfed areas.Drought stress has adverse influence on water relations, photosynthesis, mineral nutrition, metabolism, growth and yield of groundnut [1]
Analyzed data of Water extraction (Wex) under WS revealed that genotypes 12CS-116, ICG 12991 and 12CS-79 extracted more water than 55-437, ICGV 97183 and JL-24. These findings suggest that roots length density (RLD) and roots dry matter (RDM) contributed to Wex in 12CS116 and ICG 12991 under low soil phosphorus (LP) and WS (LPWS) there is a lot of controversy around roots traits contribution to Wex [41]
This study showed that RLD and RDM were associated to high pod and haulm yield under LP and revealed tolerance related traits
Summary
In Sahelian zones of the semi-arid tropics, groundnut (Arachis hypogaea L.) is widely cultivated in rainfed areas.Drought stress has adverse influence on water relations, photosynthesis, mineral nutrition, metabolism, growth and yield of groundnut [1]. Intermittent drought, occurring almost each year in most of groundnut production Sahelian areas, leads to pods and haulm yields loss up to 55% [2]. Drought stress significantly reduced total dry matter (41%), transpiration (33%) and chlorophyll content (40%) across genotypes but significantly increased transpiration efficiency (20.5%) and Chlorophyll density (22%) in peanut [4]. These authors observed significant genotypic variation for transpiration efficiency and chlorophyll parameters. Drought at pod filling reduces growth, yield and seed quality of peanut (Arachis hypogaea L.) and great root system can reduce yield loss under water stress [8]. Useful traits, including rooting system and water uptake, to improve groundnut adaptation and productivity under drought are still needed
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