Effect of potato virus Y on growth, yield and chemical composition of flue-cured tobacco in Northern Vietnam
Potato virus Y (PVY) is a plant virus that causes significant losses to tobacco. PVY damage is severe in the tobacco growing provinces Lang Son and Bac Giang with disease rates from 10-45 %, with some areas infected 100 %. The objective of this study was to evaluate the effect of PVY on growth, yield and chemical composition to form the basis for managing disease in the field. An experiment was carried out using mechanical inoculation on tobacco cultivars C9-1 and GL7 in 2017. Treatments were replicated three times in a randomized block design. Only plants in the center two rows of each plot were inoculated. The infected leaves were collected and ground in a potassium phosphate buffer with 1 g infected leaf/2 ml buffer. Before inoculation, leaves of experimental plants were dusted with Carburundum 600 mesh. Each treatment was inoculated 15, 35, 50 and 60 days after transplanting. Control plants were not inoculated. The result of the experiment showed that early inoculation of C9-1 (15, 25 and 35 days after transplanting) caused height reduction of 47,4 %-62,0 % and yield reduction of 45,9 %-58,6 %. Similarly, to C9-1, GL7 experienced height reductions of 57,0 %-73,8 % and yield reductions of 49,4 %-58,9 % when inoculated 15-35 days after transplanting. PVY also modified the chemical composition of flue-cured leaves. Nicotine content was always lower in cured leaves from diseased plants than in cured leaves from healthy controls. This occurred especially when inoculation was done 15-35 days after transplanting, with nicotine reduced by 21,8 %-42,9 % and sugar by 6,1 %-56,5 %. Inoculation done 50 and 60 days after transplanting lightly affected yield and chemical composition but did not affect the total number of leaves and the height of the tobacco plant. From the results, efforts should be made to prevent the spread of PVY during the first month after transplanting by destroying infected plants and treating aphids.