Development of Disease and Growth on Six Scion/Rootstock Combinations of Citrus Seedlings under Huanglongbing Pressure

Huanglongbing (HLB) disease is the most serious threat to citrus production in Indonesia. Commonly, the planted rootstocks/scion varieties expressed severely damaged to HLB. This research aimed to study effects of six citrus rootstock/scion combination of varieties on intensity of HLB disease, presence of Candidatus Liberibacter asiaticus (CLas), and growth of the seedlings. The grafting combination of three rootstock varieties- Japansche citroen (Citrus limonia Osbeck), Volkamer lemon (C. volkameriana V. Ten & Pasq), ‘Salam’ (local name), and two scions varieties- ‘Siem Pontianak’ (C. nobilis Lour) and ‘Keprok Tejakula’. ‘Keprok Tejakula’ (C. reticulata Blanco) were used for examination the effect rootstock/scion combination to HLB. Based on symptoms, the onset of disease intensity was observed in eight months after CLas inoculation, except on ‘Salam’ rootstock. The status of CLas inoculation, rootstock/scions varieties and the duration of plant infection influenced to CLas titers. There were inconsistency between HLB symptoms and CLas titers. According to measurement of plant height, and diameter of rootstocks and scion stem, the plant growth of Volkamer lemon rootstock grafted with ‘Siam Purworejo’ scion or ‘Keprok Tejakula’ scion was better than grafted with Japansche citroen and ‘Salam’ rootstocks. Japansche citroen rootstock was more susceptible to HLB than Volkamer lemon and ‘Salam’ rootstocks. Combination of rootstock/scion varieties affected plant tolerance against HLB.