Relationships between stem canker, stolon canker, black scurf (Rhizoctonia solani) and yield of potato (Solanum tuberosum) under different agronomic conditions

Abstract

Relationships between diseases caused by Rhizoctonia solani on different parts of potato plants (Solanum tuberosum) at different stages of crop growth were investigated under selected agronomic conditions. The effects of different densities of tuber-borne inoculum, date of planting, irrigation, size of seed tubers and their interactions on the incidence of stem and stolon canker during crop growth, the incidence and severity of black scurf and the yield of progeny tubers at harvest were quantified in a multifactorial experiment. Differences in the incidence of stem canker, stolon canker and black scurf were dominated by the effect of density of inoculum on seed tubers at planting. Highly positive correlations between the disease variables indicated a close relationship between the incidence of disease at each stage of crop growth although the degree of association between variables measured at an early growth stage and those measured at progressively later stages of crop growth weakened as the time interval increased. Total yield of progeny tubers was not affected by the density of tuber-borne inoculum although there was a shift in the size distribution, with a decrease in the yield of main-sized tubers and an increase in the yield of baker-and oversized tubers at the higher density of inoculum. Of the remaining factors, the effect of season tended to be more pronounced than any of the agronomic treatments although the use of irrigation and later dates of planting did influence the incidence of infection to a limited extent.

Development of Rhizoctonia solani on Stems, Stolons and Tubers of Potatoes I. Effect of Inoculum Source

“…Our results indicate that seed inoculum levels of 12% of the tuber surface covered with black scurf are enough to consistently increase disease incidence and severity. Simons and Gilligan (1997) also found a similar relationship between seed inoculum level and the incidence of stem canker. In contrast, other authors have reported no influence of seed tuber inoculum levels of less than 15% to (Gudmestad et al 1979, James andMcKenzie 1972).…”

“…As stolons are pruned and tuber set is reduced, there are fewer tubers per plant to act as sinks for products of photosynthesis. This can lead to uneven tuber growth, thereby increasing yields of off-grade tubers (Simons and Gilligan 1997). The fungus may also form brown to black sclerotia on the surfaces of mature tubers, a symptom that is commonly referred to as black scurf.…”

Modifications in the potato rhizosphere during infestations of Globodera rostochiensis and subsequent effects on the growth of Rhizoctonia solani

“…This disrupts the movement of water and nutrients throughout the plant and eventually stems may be pruned (Back et al 2006). The collective name for these symptoms is widely known as stem canker (Read et al 1989;Simons and Gilligan 1997). In a similar manner, stolons and roots can also be infested and pruned by R. solani and the resulting symptoms are known as stolon and root canker, respectively.…”

“…Most reports claim that Rhizoctonia disease of potato does not usually reduce total tuber yield (e.g. Simons and Gilligan 1997). It may however substantially degrade tuber quality and marketability, which is the consequence of one or more of the following: (a) hard sclerotia on tuber surfaces (black scurf), (b) greater numbers of non-target size tubers, (c) tuber greening, (d) sessile tubers or 'little potato' and (e) malformed tubers (Scholte 1989;Simons and Gilligan 1997).…”

Interactions between field populations of the potato cyst nematode Globodera pallida and Rhizoctonia solani diseases of potatoes under controlled environment and glasshouse conditions

“…Rhizoctonia solani (AG3) is a soil-borne fungal pathogen that is widespread in potato (Solanum tuberosum L.) growing land in the UK (Wale et al, 2004;Woodhall et al, 2007), causing stem and stolon canker and black scurf at different growth stages of the plant (Hide et al, 1973;Scholte, 1989;Simons & Gilligan, 1997;Wale et al, 2008;Woodhall et al, 2008). Black scurf on tubers during plant senescence reduces tuber quality and causes marketable yield losses approaching 30% (Banville, 1989).…”