Is silicon beneficial for cassava (Manihot esculenta Crantz)?

Barhebwa Balangaliza, Fidèle [UCL] Li, Zimin [UCL] Bragard, Claude [UCL] Vanlauwe, Bernard Delvaux, Bruno [UCL]

Background and aim Ranked among the world’s top ten crops, cassava (Manihot esculenta Crantz) is the main staple food in sub-Saharan Africa. Its production is strongly limited by biotic and abiotic stresses, which proved to be mitigated in other plants by silicon (Si) uptake. The role of Si is unknown in cassava. Yet it has genes encoding specific aquaporins involved in plant water and Si influxes in numbers similar to those of some Si accumulating monocots. Methods Cassava Si and nutrient status were studied in four sites in South-Kivu, Democratic Republic of Congo, differing in altitude, climate and soil desilication stage. Out of 720 farms, 360 plots were selected for agronomic monitoring, of which 40 for foliar/topsoil analysis using germanium to trace Si. Results Regardless of soil type, Si concentration in cassava leaves ranged from 2 to 14 g kg−1 while root yield varied from 0.5 to 18 t ha−1 yr−1. Silicon accumulation formed fine-sized phytoliths of different morphotypes. Structural equation modelling showed that leaf Si mineralomass was an important predictor of yield, with a direct contribution of 45%. Silicon accumulation mitigated the altitude-mediated incidence of cassava mosaic disease (25%), notably through enhancing micronutrient uptake, while it could contribute to the plant tolerance to soil acidity. Conclusion Silicon accumulates substantially in cassava leaves. Our data highlight the potential role of Si in cassava production through direct and indirect effects by alleviating biotic and abiotic stresses. The function of Si in cassava thus deserves more attention than given until now.