Structure of populations and reciprocal inoculations of Xylella fastidiosa subsp. pauca occurring in neighboring cultures of Citrus sinensis and Coffea arabica in conditions of São Paulo.

Abstract

The bacteria Xylella fastidiosa is one of the most genomically known microorganisms with significantly advances at molecular levels throught the last ten years. On the other hand a restrict background was accumulated concerning the ecology of this multi-host microorganism that is vectored by a polyphago insect, the sharpshooters of Cicadellini and Preconnini tribes. In the Brazil these bacteria infect and are responsible by diseases in economically important crops such as in sweet orange (Citrus sinensis) causing the Citrus Variegated Chlorosis (CVC), in coffee (Coffea arabica) causing the coffee leaf scorch (CLS), and in plum, causing the plum leaf scorch (PLS). Approximately 35% of 200 millions of sweet orange plants spread through the 600,000 ha in Sao Paulo State are affected by CVC with expressive economic lost. The coffee farms are spread over a smaller area (200,000 ha) but with no official information about the CLS damage. In Central, East, and West regions of Sao Paulo State a significant number of farms shared both sweet orange and coffee crops, which are affect by the sub-specie pauca of Xyllela fastidiosa. On the other hand, uncertain information are known about the cross infection in citrus and coffee plants by Xylella fastidiosa and disease development, yet. According to previous published papers the main reason for this non-agreement are the few isolates used in the tests as well as the different inoculum concentration tested. Our null hypothesis (Ho) is that cross-inoculation is able to occur in natural conditions when citrus and coffee plants infected by Xylella fastidiosa are closely cultivated. The alternative hypothesis (H1) to be tested is that cross-infection could occur under artificial condition if solution with high titer of Xylella fastidiosa (>109 UFC/mL) were used as source of inoculum. Collection of Xylella fastidiosa isolates from sweet orange and coffee plant showing CVC and CLS, respectively, will be established on artificial medium using as source plants from Central, East, and West regions of Sao Paulo State. Molecular markers (SSR and MLST) will be used for typify those isolates and consequently to determined genetic clusters. Strains representative of those clusters will be used on artificial cross-infection assays to test the hypotheses.