Screening of Commercially Available Satsuma (Citrus unshiu and C. reticulata) Cultivars for Their Susceptibility to Citrus Canker Caused by Xanthomonas axonopodis pv. citri

Abstract

Citrus canker presents major challenges in citrus production worldwide. The disease spreads and develops rapidly under conducive environmental conditions, and Louisiana’s hot and humid weather provides highly favorable conditions for citrus canker development in both commercial and backyard citrus production. Despite being considered eradicated in late 1940s, citrus canker was reconfirmed in Louisiana in 2013. Citrus is the most popular fruit tree grown commercially and in backyards in Louisiana, and satsumas dominate with 63% of total citrus acreage. The results from an annual citrus cooperative agricultural pest survey from 2014 to 2016 revealed that satsumas are highly tolerant to citrus canker with only 2.5% disease incidence, but the survey lacked information on the types of satsuma cultivar. The main objective of this study was to screen commercially available satsuma cultivars including Brown’s Select, Louisiana Early, Miho, Owari, and St. Ann for their susceptibility to citrus canker under natural field disease inoculum conditions with a goal to provide citrus growers with alternate disease management tactics. The results showed that there were significant differences in disease severity (average number of lesions per leaf) among the satsuma cultivars. Of the five satsuma cultivars, Brown’s Select and Miho consistently showed less disease severity with delayed incidence. Additionally, both Brown’s Select and Miho exhibited significantly smaller lesion size, which could lower canker inoculum production for secondary infections. This work provides Louisiana growers with scientific field-based data to make sound decisions in selecting less-susceptible satsuma cultivars for future plantings to mitigate disease spread and development in the state.