The Study On PLRV And PVY’s Influence On Growth, Development And Microtuber Production In In Vitro-Grown Shoots Of Potato

Potato(Solanum tuberosum) is the forth largest food crop in both the world and China. Viral diseases have long been threatened sustainable development of potato production. Potato leafroll virus(PLRV) and Potato virus Y(PVY) are the most damaging viruses attacking potato. Surveys on the commercial potato fields in Yuling, Shaanxi, showed that occurrence frequencies of PLRV and PVY were30-40%. Potato in vitro shoots were established using single nodes taken from the diseased field-grown plants, and used for investigations of effects of PLRV and PVY on vegetative growth, physiological metabolism and microtuber production. The results showed that parameters of shoot growth including bud break percentage, shoot length, and node number and length were markedly reduced in the diseased shoots. These negative effects were much more pronounced in shoots co-infected with PLRV and PVY than in those singly infected with either PLRV or PVY. The inhibitive effects on root development and growth measured by root number and length were observed only in shoots co-infected with PLRV and PVY. Virus-infected shoots showed a higher electrolyte leakage and relative water content than the healthy ones. Significantly lower contents of Chl a, Chl b and total chl were found in virus-infected shoots than in healthy ones. Contents of glucose, fructose and sucrose were significantly higher in healthy leaves compared with the infected leaves. However, the content of total soluble sugar was highest in shoots co-infected with PLRV and PVY, and lowest in the healthy shoots. There were striking differences in contents of total soluble protein observed between healthy shoots and PLVR and PVY co-infected ones. Furthermore, there were no significant differences found in the level of endogenous indole-acetic acid among healthy shoots verses virus infected shoots. However, the level of zeatin-ribosome was much higher in healthy shoots than in virus infected ones. Yet, both healthy and single PLRV infected shoots produced similar levels of gibberillic acid 3, which were much higher than those of PVY single-infected shoots and PLRV and PVY co-infected shoots. There were no significant differences in the number of microtubers among healthy shoots, PLVR single or PVY single infected shoots, but shoots co-infected with PLRV and PVY produced the lowest number of microtubers. Overall, the healthy shoots produced the largest size of microtubers and the highest percentage of microtubers≥5 mm in diameter. No obvious differences were observed on the content of K+ in microtubers induced in the healthy and virus-infected shoots. These data provide experimental evidence supporting use of virus-free potato tubers for achieving sustainable developmental of potato production.