Root system plasticity enhances phosphorus acquisition in sorghum for a low-input farming system

Year 2025, Volume: 9 Issue: 2, 65 - 72

Benson Nyongesa

Abstract

Phosphorus (P) deficiency remains a significant constraint to sorghum (Sorghum bicolor L.) productivity, particularly in smallholder farming systems with limited access to fertilizers. This study aimed to evaluate root system architecture (RSA) plasticity among improved sorghum varieties under contrasting P conditions to identify varieties with superior P-foraging traits for low-input systems. Eight sorghum varieties were grown under low (5.38 mg/kg) and high (50 mg/kg) P levels, and their root traits were characterized using high-resolution imaging and RhizoVision analysis. Six RSA traits: total root length (TRL), number of root tips (NRT), branching points (NBP), surface area (SA), root diameter (AD), and root volume (RV), were analyzed in this study. Analysis of variance revealed significant variety (V), Phosphorus (P), and V × P interaction effects (p < 0.001) for all traits. Under low P, varieties showed enhanced RSA expression: TRL increased by 58%, NRT by 142%, NBP by 210%, SA by 89%, and RV by 133%, while AD declined by 32%, indicating strategic carbon investment in absorptive roots. Notably, KARI Mtama 1 exhibited constitutive robustness, while T30b demonstrated exceptional plasticity. TRL, SA, NA, NRT, and RV had over 74% of heritability, demonstrating strong genetic control. These findings underline RSA plasticity as a key adaptive strategy for nutrient acquisition, providing valuable breeding targets for P-efficient cultivars. Integrating these traits into breeding programs can enhance P-use efficiency, with KARI Mtama 1 and T30b serving as donor parents for developing elite sorghum lines suited to low P conditions.

Keywords

Low-input agriculture , Phenotypic plasticity , Phosphorus deficiency , Root system architecture , Sorghum

Ethical Statement

This study was exempted from ethical review and approval because the study did not involve human clinical trials or animal experiments. The Ethics and Review Committee of the University of Eldoret approved the study.

Supporting Institution

None

Project Number

20-085

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