Evaluating Suitable Rootstocks for Grafting in Organic Pepper System

Organic farming systems are often plagued with challenges such as nutrient stress complexing with other biotic and abiotic issues. These issues can significantly affect the growth and productivity of vegetable crops, including peppers ( Capsicum spp.). Grafting with suitable rootstocks is a promising technique to address these challenges and improve the growth and productivity of peppers in low-input systems. In the United States, grafting is not as commonly practiced in pepper as compared with other solanaceous and cucurbit crops, in part because of limited availability of rootstocks. This study examined promising rootstocks with demonstrated disease resistance and further explored their suitability for organic systems under normal and reduced fertilization. A hybrid Italian sweet pepper ‘Mama Mia Giallo’ was used as scion and grafted onto four different rootstocks and grown in a greenhouse in summer with natural heat stress. The plants received organic fertilizer weekly or biweekly for a period of 5 weeks. Results showed that grafting plants with the rootstocks ‘CM-334’, ‘YC-207’, ‘Keystone Resistant Giant’, and ‘Scarface’ resulted in similar or improved growth relative to nongrafted and self-grafted plants under normal and reduced fertilization. The rootstocks showed promising traits that could be explored in further stress tolerance studies. Specifically, ‘YC-207’-grafted plants showed higher nitrogen utilization efficiency, shoot nitrate content, and phosphorous content as well as higher stomatal conductance, transpiration, and electron transport rate, which is indicative of stress tolerance. ‘YC-207’-grafted plants also had lower malondialdehyde content, indicating less oxidative damage to the cell membrane. ‘CM-334’-grafted plants showed higher antioxidant activity, nitrate reductase (NR) activity, and shoot nitrate content. This study provides evidence of the value of evaluating potential rootstocks and explores grafting as a promising technique for pepper crop to improve plant growth and performance under organic systems.