Evaluation of potato clones for resistance to stem canker and tuber black scurf in field studies following artificial inoculation withRhizoctonia solaniAG-3 in Maine∗

Abstract

Potato clones were evaluated for resistance to Rhizoctonia stem canker, stolon lesion and black scurf in field experiments during the 1997 and 1998 growing seasons. Seed pieces were inoculated with Rhizoctonia solani Anastomosis group 3 (AG-3) by dipping them in a slurry or suspension of inoculum. Uninoculated controls were also planted. Seed emergence was assessed beginning at two weeks after planting. After 60 days, incidence and severity (%) of stem and stolon cankers were assessed. The numbers of root and stolon lesions were also quantified. At harvest, the incidence of black scurf on tuber yield and numbers were also determined. Significant differences in emergence of potato seed pieces (%) were detected between inoculated and control treatments and the incidence of stem and root cankers differed among clones in both years. The incidence and severity of stem cankers and the numbers of stem and root lesions were not significantly correlated with the black scurf incidence on tubers. These studies suggest that various symptom types incited by Rhizoctonia can be important epidemiological factors in disease development.

Improving Evaluation of Potato Resistance to Rhizoctonia solani infection by Optimizing Inoculum Method Combined with Toxin-based Assay

“…The severity of stem canker is usually positively correlated with the subsequent formation of black scurf on progeny tubers [27,32,33]. However, this is not always the case [19,34,35,36,37]. We also have found the correlation between stem canker and black scurf in 2009, but not so in 2010 [38].…”

“…genotypes is very limited [11,13,14,15,16,17,18,19]. There are few potato cultivars that have high resistance or tolerance to R. solani [13,16,17,18,19]. On a list of potato cultivars in Canada, only 10% of the 111 cultivars are considered resistant [20] (Anonymous.…”

A simple method based on laboratory inoculum and field inoculum for evaluating potato resistance to black scurf caused by <i>Rhizoctonia solani</i>

“…To date, there are few available potato cultivars with high resistance to species of Rhizoctonia ( Bains et al 2002 , Djébali and Belhassen 2010 , Leach and Webb 1993 , Naz et al 2008 , Olanya et al 2009 , Scholte 1989 , Yanar et al 2005 ). Most of the conventional cultivars are susceptible and may show severe stem canker and tuber black scurf.…”

“…Accordingly, the selection and cultivation of resistant cultivars has become one of the most economical and effective way to control tuber black scurf ( Naz et al 2008 ). However, few resistant cultivars are available to date ( Bains et al 2002 , Djébali and Belhassen 2010 , Khandaker et al 2011 , Leach and Webb 1993 , Naz et al 2008 , Olanya et al 2009 , Scholte 1989 , Yanar et al 2005 ). Mikheeva (1988) studied with some potato cultivars for field resistant to R. solani and found that the Erfolg cultivar was highly resistant to R. solani , which showed almost no infection of the tubers and roots.…”

“…Traditionally, resistance to fungal diseases such as Rhizoctonia black scurf, have been scarcely considered in any potato breeding program, because of the extremely wide host range of the pathogen ( Bakali and Martín 2006 , Ogoshi 1987 , Woodhall et al 2007 ) and the saprophytic life cycle ( Grosch et al 2005 ). Some reports found the differences in disease expression of cultivars and breeding lines, which has encouraged the screening for varietal differences in susceptibility ( Bains et al 2002 , Djébali and Belhassen 2010 , Leach and Webb 1993 , Naz et al 2008 , Olanya et al 2009 , Scholte 1989 , Yanar et al 2005 ). Therefore, it is essential to develop effective resistance appraisal techniques for accurately screening potato germplasm.…”