Plant extracts enhancers of defense response in ponkan mandarin Seedlings against Alternaria alternate f. spp. citri infection

The objective of this study was to determine the elicitor potential of plant extracts from Caatinga biome by enzyme activity and epidemiological components of Alternaria brown spot (Alternaria alternate f. spp. citri). These were prepared ethanolic, dichloromethanic, and aqueous extracts from 14 plants (Anadenanthera macrocarpa, Schinopsis brasiliensis, Maytenus rigida, Caesalpinia pyramidalis, C. ferrea, Peltophorum dubium, Capariscyn ophallophora, Ziziphus joazeiro, Mimosa hostilis, Momordica charantia, Erythrina velutina, Cleome hassleriana, Sideroxylum obtusifolium Spondias tuberosa) after dilution, (1mg/mL) they were sprayed on Citrus reticulate ‘Ponkan’seedlings and after 0, 24, 48, 72 and 96 h the leaves were collected for determination of polyphenol oxidase and peroxidase activity. For epidemiological disease components, leaves were collected 72 h after spraying, deposited on Petri dishes with moist paper, inoculated with a spore suspension of A. alternata f. spp. citri (2x105 conidia mL-1) and evaluated for 12 days initial and final severity, area below the progress curve of disease and protection. The extracts of A. macrocarpa and M. rigida potentiated the polyphenol oxidase and peroxidase activity which had great potential in the management of the disease, reducing the final severity and area under the disease progress curve, providing high levels of control. Key words: Citrus reticulata, alternaria brown spot, elicitor.