Association of greening bacterium with fruit morphological disorder ‘Waywar’ in monsoon cropping of Nagpur mandarin (Citrus reticulata Blanco) grown in central India

Abstract In the Vidarbha region of Maharashtra and the surrounding parts of central India, Waywar (citrus greening bacterium) fruit disorder, also known as wasteful fruit disorder, is a common manifestation of Nagpur mandarin fruit. In Vidarbha, the condition is also known as cock bund , while in China, it is called ‘Red Nose.’ According to early research, this condition is caused by abiotic stress factors, such as poor nutrition, too much moisture in the root zone, and other incorrect cultural practices. Recent research, however, has unequivocally shown that Candidatus Liberobacter asiaticus , the citrus greening bacterium, is responsible for this illness. When compared to normal growing fruits (0.82–0.89), the length to diameter ratio of Waywar fruits at the peak of incidence was reported in the range of 0.95–1.09, indicating their oblong shape. Premature Waywar fruits had higher acidity levels (1.75 to 2.04%) than normal fruits (1.65 to 2.03%) and produced seeds that were not viable. The cultural treatments applied to reduce the ill effects of the disorder improved the physico-chemical characteristics of Nagpur mandarin fruit at the time of harvesting. When compared to the untreated control, foliar spraying with growth regulators 2,4-D (15 ppm) and GA 3 (15 ppm) enhanced the amount of fruit retained per plant at harvest. The critical fruit quality parameters like TSS (10.10%) and vitamin C (39.37 mg/100 ml) were highest in GA 3 treated fruits. Maximum TSS/Acid ratio (14.00) and minimum acidity (0.69%) were noted with phosphorus applied at three times the RDF level at harvest.