PCR-based determination of colonization patterns during potato tuber infection by single and multiple pathogens

Abstract

Potato tubers piled in storage are prone to infection by numerous pathogens. Each pathogen can cause damage alone, but severe losses often arise when more than one pathogen is involved. Currently, only a visual diagnosis is practiced on potato tubers before storing them, which does not allow any prediction of further disease spread. The aim of the present study was to determine differences in patterns of tissue colonization by several tuber decay pathogens and how late blight infection affects further tuber colonization by other important tuber pathogens. This study was conducted using artificial inoculation of potato tubers and PCR to provide an early and accurate diagnosis of disease development for major potato tuber rots, and to assess potential synergism/antagonism between Phytophthora infestans and other pathogens in stored tubers. In order to accurately follow the progress of each pathogen in tuber tissues, samples were collected over time from both the surface (peel, 0-2 mm depth) and internal tissues (flesh, depth > 2 mm) of the tubers at various distances from the inoculation site, at 3, 5, 7, 10, 12, 14, 17, and 19 days after inoculation. Successful detection of single or multiple pathogens was achieved using specific PCR-primers for each pathogen. Pathogens were always detected several centimeters ahead of the visible lesions. This tracking enabled us to determine the extent of colonization both on the tuber's surface and in internal tissues by each tested pathogen, either after single or multiple infections involving P. infestans as the primary pathogen. The presence of P. infestans was shown to enhance the development of Pectobacterium atrosepticum and to slow down that of P. erythrospetica and Pythium ultimum. No noticeable effect on further tuber colonization by F. sambucinum, V. dahliae or V. albo-atrum was observed in the presence of P. infestans. This approach involving more than one pathogen is more realistic than classical studies considering single pathogens, and may be helpful in monitoring the sanitary status of stored tubers. Our results make the outcome of certain combinations of pathogens in potato tubers more predictable and may result in more efficient preventive measures.

Interactions between Magnaporthiopsis maydis and Macrophomina phaseolina, the Causes of Wilt Diseases in Maize and Cotton

“…Antagonistic interactions between phytoparasitic fungi have previously been reported in other host-pathogen species pairs [23], as detailed in the Introduction. In many of those studies, the molecular DNA tracing proved to be an essential research tool [25,27,42]. An example that is very similar to the current research is one of the most documented antagonisms among root pathogens, the suppression of Cochliobolus sativus by Fusarium (roseum) species [42].…”

“…A recent meta-analysis suggests that these interactions are probably much more prevalent than previously estimated [23]. Reports on pathogen-pathogen antagonisms encompass diverse plant disease systems, including tree pathogens and wood-rotting fungi [24], storage-rotting fungi [25], foliar pathogens [26], and root rots [27]. Studies of foliar pathogens are most common, with antagonisms being reported among foliar pathogens of wheat, barley, and peas (see, for example, [26,28,29]).…”

Competition Between Fusarium pseudograminearum and Cochliobolus sativus Observed in Field and Greenhouse Studies

“…A recent meta-analysis suggests that these interactions are probably much more prevalent than previously appreciated (Stephens et al 2013). Reported pathogen-on-pathogen antagonisms encompass a diverse cross section of plant disease systems, including tree pathogens and wood rotting fungi (Boddy 2000;Gibbs and Smith 1978), storage rotting fungi (El Hadrami et al 2007;Yang et al 2008), foliar pathogens (Le May et al 2009;Nolan et al 1999), and root rots (Ledingham 1942;Moya-Elizondo et al 2011a;Scardaci and Webster 1981). Studies of foliar pathogens appear most common, with antagonisms reported among foliar pathogens of wheat, barley, and pea (da Luz and Bergstrom 1987;Le May et al 2009;Nolan et al 1999;Round and Wheeler 1978).…”