37. CITRUS ROOTSTOCK HYBRIDS TOLERANTS TO CITRUS TRISTEZA VIRUS AND BAHIA BARK SCALING DISEASE

Citrus tristeza virus (CTV) and Bahia bark scaling disease (BBS) are the important viral disease of citrus in the Bahia state in Brazil. Evaluation of germsplasm bank and new hybrids for incidence and severity of these diseases is essential for developing new varieties. In this work 160 hybrids (grafted and un-grafted rootstocks) generated by the Citrus breeding program of Embrapa Cassava & Tropical Fruits were evaluated for CTV and BBS incidence under natural infection in the Reconcavo Southern of Bahia state. Severity of stem pitting of CTV and BBS symptoms were evaluated by using a rating scale. It was used serological method of ELISA (indirect method) to detect the presence of CTV. The samples were made of bark of young branches, diluted in carbonate buffer at 1:100, and for detection, it was used a polyclonal antiserum diluted 1:10,000 in PBS-Tween 0.05% adding 2% PVP and 0.2% egg albumin. The negative control was obtained from the bark of Poncirus trifoliata and the positive control from Mexican lime (Citrus aurantifolia Christm. Swing.) The confirmation of the results was performed by RT-PCR using two pairs of primers specific for genes p23 and p20. Hybrids immunes, tolerant and intolerant to CTV were identified. However, most of hybrids showed symptoms of BBS, mainly those generated using tangerine as a parent. Financial support: CNPq, FAPESP, Embrapa