Foliar Symptoms Caused by Potato mop-top virus on Potato Plants During Vegetative Propagation in Scotland and Their Association With Tuber Yield, Spraing and Tuber Infection

Abstract

The effect of foliar symptomatic infection by Potato mop-top virus (PMTV) on yield of tubers, spraing and infection in daughter tubers, and foliar symptom development and tuber infection in the following generations of propagation was investigated in commercial seed potato crops in Scotland. Six crops covering cvs Atlantic, Hermes, Nicola and Cara were studied between 2000 and 2006 by labelling paired replicates of plants with foliar symptoms and plants with no symptoms. Tubers from plants with no symptoms rarely produced plants with foliar symptoms in the following generation. Plants with no symptoms produced more infected tubers if they had been derived from plants with foliar symptoms the previous year than from plants with no symptoms. The proportion of daughter plants with foliar symptoms produced by tubers from plants with foliar symptoms in year 1 ranged from 19-41% and seemed to be associated with the severity of foliar symptoms. The detection of PMTV by ELISA in samples of leaves from plants with foliar symptoms ranged from 13% for cv. Cara to 59% for a crop of cv. Atlantic in 2004. The amounts of spraing were generally low but tended to be greater for tubers from plants with foliar symptoms than those from plants with no symptoms. These results indicate that roguing plants with foliar symptoms in seed potato crops could achieve an improvement in crop health but might be impractical when diseased plants are too prevalent.

The importance of the infected seed tuber and soil inoculum in transmitting Potato mop‐top virus to potato plants

“…This range is similar to the rates of 19–41% reported by Carnegie et al . () when testing daughter tubers of cv. Atlantic derived from seed tubers from plants with foliar symptoms of PMTV infection.…”

“…The symptoms on cvs Cara and Nicola were, however, similar to those reported by Carnegie et al . () for those cultivars in field crops. The incidence of symptomless foliar infection on plants of the susceptible cultivars Cara and Nicola derived from PMTV‐infected seed tubers was greater in 2005 when symptoms were less prevalent than in 2004 (Table ).…”

“…This is in agreement with the results of Carnegie et al . () who similarly tested plants of cv. Atlantic in field crops.…”

“…However, the development of foliar symptoms is strongly affected by environmental conditions (Calvert, 1968;Carnegie et al, 2010a) and thus their prevalence can vary considerably amongst the countries in which PMTV is present. For example, foliar symptoms are relatively common in the cool climate of Scotland (Carnegie et al, 2010b) but rare in Scandinavian countries with the exception of Norway (Santala et al, 2010).…”

Towards biological control of Spongospora subterranea f. sp. subterranea, the causal agent of powdery scab in potato

“…Mop-top virus has been reported 54 to cause yield losses of between 30 and 60% (Carnegie et al 2010) and tubers 55 expressing the characteristic 'spraing' symptoms are unacceptable at market. 56…”