Reduction of Carbon Assimilation and Water Use Efficiency in Groundnut Ringspot Virus (GRSV)-Infected Groundnut Varieties

Groundnut (Arachis hypogaea L.) production is threatened by the advent of many emerging pests and diseases, key among them being Groundnut ringspot virus (GRSV). The numerous alternative host crops of the virus make its control particularly difficult, resulting in heightened virus transmission risk and increased yield loss. The mechanisms underlying yield loss, though not fully understood, have often been speculated to be a result of the reduction in photosynthesis and transpiration in infected leaves. This study was therefore aimed at testing the effect of GRSV infection on carbon assimilation and water use efficiency by four farmer preferred groundnut cultivars (Nkosuor, Otuhia, Sinka, and Yenyawoso) in Ghana. Seeds of virus indexed plants previously grown in a screen house were nursed in a screen house and artificially infected with GRSV by grafting infected groundnut scions onto them to be compared with plants onto which uninfected groundnut scions had been grafted. The rate of photosynthesis, transpiration, and stomatal conductance of the distal leaf of each plant was measured using the CO2/H2O gas analyzer (CID, Inc., Camas, WA, USA). The virus infection was found to reduce stomatal conductance, transpiration, net photosynthesis, and 100 seed weight in a genotype dependent manner. This highlights the effect of GRSV infection on water conservation through a reduction in transpirational water loss, constraining photosynthesis, or carbon assimilation in the process to confirm the trade-off between photosynthesis and transpiration through the stomata.