Tshewang Dorji, Geley Namgay, Tshering Penjor, Lhap Dorji, Loday Phuntsho, Sonam Gyeltshen, Pempa Lhamo Lepcha & Mandhira Acharya
Huanglongbing (Citrus Greening) is the most devastating citrus disease caused by phloem-inhabiting bacteria carried by the insect vector, Asian citrus psyllid (Diaphorina citri). In Bhutan, the production and movement of citrus seedlings and new orchard establishment have been restricted after the Citrus Greening disease was detected in most citrus orchards. To address this problem, Agriculture Research and Development Centre-Wengkhar has initiated research on clean citrus propagation through shoot tip grafting. This study assessed the efficiency of shoot tip grafting for the production of clean planting materials. Sweet orange was used as an indicator plant to study disease transmission and symptom expression in some of the potential and released citrus varieties. A total of 15 plants, 3 plants of each cultivar (AREP-1, AREP-2, Aoshima, Wengkhar Tshelu-2 and Yoshida Ponkan) produced through shoot tip grafting were used for bio-indexing. The cultivars were grafted on indicator plants using different grafting techniques (T-budding, side grafting, wedge, and split grafting). A total of twenty-six samples with two samples per cultivar was sent to the National Plant Protection Centre for PCR analysis. The result of PCR showed negative result for Huanglongbing. Thus, shoot tip grafting could be one potential method for clean citrus planting material production.
Keywords: Bio-indexing; Greening; Cultivar; Grafting, Symptoms; Shoot tip grafting