Evaluation of susceptibility of commercial citrus rootstocks to white root rot incited by Rosellinia necatrix

Spain reached the fifth position of citrus production and the first of fresh fruit exporter worldwide. Pre-harvest diseases caused by soil-borne pathogens can limit citrus crop production. Phytophthora spp. are considered the most serious soil-borne pathogens of citrus crops worldwide, but their management strategies are highly developed. Conversely, Rosellinia necatrix is another soil-borne pathogen with polyphagous behavior, including citrus trees, and without fully-effective control tools. In this sense, the aim of this study was to characterize the susceptibility of several commercial citrus rootstocks to R. necatrix disease. Potted plants from 10 different rootstocks were artificial inoculated with an isolate of R. necatrix. Plant physiological measurements of above-ground symptoms, chlorophyll content, biomass and leaf area were obtained. Flying Dragon and Forner-Alcaide 517 citrus rootstocks displayed the lowest disease incidence of SAUDPC, whereas Citrus macrophylla the highest symptoms rate. The highest chlorophyll content was found in Forner-Alcaide 517, and the lowest in Citrus macrophylla and Bitters C-22. Additionally, this last rootstock reached the highest reduction of biomass and the lowest leaf area rate. In conclusion, Forner-Alcaide 517 could be an interesting choice for those orchards with R. necatrix problems; contrarily, Citrus macrophylla and Bitters C-22 were the most sensitive candidates to this pathogen.