Drought (WS) and low phosphorus (LP) stress in groundnut: Water extraction pattern and tolerance related traits for breeding program

Drought (WS) and low soil phosphorus (LP) are major constraints of groundnut productivity. This study aims to (i) understand the relative importance of phosphorus (P) deficiency, water stress and their interaction, (ii )investigate water extraction pattern under WS and LP, and (iii) identify field and controlled conditions measured traits related to better performance of genotypes under WS and LP. Six groundnut varieties were assessed under field and lysimetre conditions. Two water regimes (WW, WS) and 2 phosphorus treatments (HP, LP) were imposed. Leaf Area Index (LAI), roots volume (RV), length density (RLD) and roots dry matter (RDM), water extraction (WEx), transpiration efficiency (TE), soil moisture content (SMC) and yield were investigated. LP stress decreased LAI and pod weight (Pwt) (42 and 28 % respectively). ICGV 12991 and 12CS-116 varieties showed the highest LAI and Pwt. LAI, correlated to Pwt(r2 = 0.77), revealed relevant trait for LP tolerance.LP and WS decreased roots and canopy measured traits. WS and LP decreased WEx (51 and 7% respectively). Combined LP and WS (WS-LP) decreased WEx up to 60%. ICG 12991 and 12CS-116 showed the highest WEx, RLD and RDM under WS-LP; RLDcould contribute to water uptake to avoid dehydration. Significant genotypic variation observed on SMC revealed different pattern of WEx. TE increased under WS and decreased under LP; factors driving TE would be different.12CS-116, 55-437 and ICG 12991 revealed high TEand tolerant to WS-LP but showed different tolerance mechanism. This study revealed that ICG 12991 and 12CS-116 were tolerant to WS-LP and LAI, RLD, while WEx and TE revealed relevant traits for groundnut improvement.