Performance evaluation of three peanut cultivars grown under elevated CO2 concentrations

This study explored the performance and physiological responses of three commercially used peanut cultivars in Australian farming systems under ambient and elevated CO2 conditions, aiming to identify the most suitable genotype for dual-purpose (grain and graze) cropping experiments. The experiment utilized an open-top chamber (OTC) facility to regulate CO2 concentrations. The elevated CO2 (EC) treatment targeted approximately 650 ± 50 µmol mol−1, while both ambient CO2 (AC) and control plots operated at a concentration of approximately 400 µmol mol−1. Notably, control plots without chambers served as a reference for current CO2 and environmental conditions. In contrast, despite having the same ambient CO2 concentration, AC plots were enclosed in chambers, allowing for plant growth comparisons with EC plots with the same environmental conditions aside from CO2 levels. The analyses revealed significant effects of CO2 enrichment on peanut plants. In particular, the EC treatment led to enhanced photosynthetic rates (20% in Kairi, 31% in Holt, and 19% in Alloway), alongside reduced stomatal conductance (−55% in Kairi, −32% in Holt, and −40% in Alloway), transpiration, and increased water use efficiency compared to AC conditions. Elevated CO2 levels positively influenced pod yields in Kairi (+41%) and Alloway (+36%). However, CO2 enrichment did not significantly alter the protein content, total phenolic content, cupric-reducing antioxidant capacity, and ferric-reducing antioxidant power of peanut plant material. Furthermore, no significant differences were observed in the phytochemical composition among the three cultivars under ambient or elevated CO2 conditions. On the other hand, analysis of the fibre structure conducted on peanut stover harvested at plant maturity suggested potential declines in feedstock quality. Based on the findings of this research, further investigations and testing, including simulated grazing trials, will be carried out to identify a single breed line suitable for dual-purpose management under future elevated CO2 conditions.