Abstract
The significance of nematodes for disease development caused by other soil-borne pathogens has been demonstrated in many crops throughout the world and specifically prevalent are interactions between plant-parasitic nematodes and species of plant pathogenic fungi. Here, the interaction between the fungus Rhizoctonia solani (AG2) and the migratory endoparasitic root-lesion nematode Pratylenchus penetrans was investigated on potato. The hypotheses were that the combination of R. solani and P. penetrans would result in more severe canker lesions, reduced quality of the tubers and lower tuber yield, and we also expected higher nematode levels to render more nematode damage. To test this, potato plants were grown in pots in two replicate experiments and the presence and/or abundance of the two pathogens were controlled. The first three hypotheses were rejected as (1) the tuber yield decreased when the fungus and nematode occurred together but not more than the sum of their separate effects, i.e. additive, (2) there was no effect of presence of nematodes on the incidence of stem canker, and (3) the quality of tubers was actually partly improved as the presence of the nematodes reduced the likelihood of elephant hide on the tubers in one of the experiments. As expected, there were more visible nematode damages with addition of more nematodes, but beyond that the different nematode levels rendered in most cases similar responses. To have knowledge about interactions between pathogens, as the one showed here, is essential for disease control through appropriate management methods.
Highlights
The development of disease in cultivated crops has long been known to depend on complex interactions between pathogen, host and prevailing environmental conditions
Stem canker and other symptoms caused by the plant pathogenic fungus Rhizoctonia solani Kühn are considered as major problems for potato growers in Sweden, especially in conventional growing systems, which often have shorter crop rotations
The potato plants in pots inoculated with R. solani were infected by stem canker and black scurf
Summary
The development of disease in cultivated crops has long been known to depend on complex interactions between pathogen, host and prevailing environmental conditions. Stem canker and other symptoms caused by the plant pathogenic fungus Rhizoctonia solani Kühn are considered as major problems for potato growers in Sweden, especially in conventional growing systems, which often have shorter crop rotations. Rhizoctonia solani attacks all parts of the potato plants; the germinating stem (stem canker), the roots and stolons become brown and the tubers are often developed close beneath the soil surface and are often covered with sclerotia on the skin (black scurf), have cracks in the skin (elephant hide), have narrow holes in the tuber (dry core) or are deformed (Bandy et al 1988; Banville 1989; Carling et al 1989; Hausmann 2006; Muzhinji et al 2014). The fungus is attracted to the plant through the root exudates released from the plant (Back et al 2010) and there is potential for interaction with plant-parasitic nematodes
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