Genetic variability and pathogenicity of Rhizoctonia solani associated with black scurf of potato in New Zealand

Abstract

Isolates (a total of 129) of Rhizoctonia solani were collected from black scurf on potato tubers from different potatogrowing regions in New Zealand. Sequence analysis of the nuclear ribosomal DNA internal transcribed spacer (rDNA-ITS) regions from these isolates identified three anastomosis groups (AGs), AG-3PT, AG-2-1 and AG-5. Isolates classified as AG-3PT were widely distributed, whereas AG-2-1 and AG-5 were confined to distinct locations. Sequence heterogeneity was identified in the ITS regions of 100 AG-3PT and AG-2-1 isolates. Variation in the sequence and length of the rDNA-IGS1 region was also observed for selected isolates of AG-3PT and AG-2-1. Phylogenetic studies found all AG-2-1 isolates belong to AG-2Nt, a subset of AG-2-1 previously associated with solanaceous crops in other countries. AG-2-1 isolates were consistently more aggressive than those of AG-3PT. Delayed emergence, severe infection on stolons, formation of aerial tubers and considerable yield losses were associated with AG-2-1, but they caused negligible black scurf. In contrast, AG-3PT caused black scurf on progeny tubers but variable effects on stem emergence and stolons. Furthermore, AG-2-1 isolates caused severe tuber malformation, but isolates of other AGs did not. This is the first report on the AG composition, genetic variability and pathogenicity of R. solani isolates associated with black scurf of New Zealand potatoes.

Relative Contribution of Seed Tuber- and Soilborne Inoculum to Potato Disease Development and Changes in the Population Genetic Structure of Rhizoctonia solani AG 3-PT under Field Conditions in South Africa

“…Rhizoctonia solani species complex exists in many different groups and presently, 13 anastomosis groups (AGs) are recognized, with many subgroups (Carling et al 2002). The predominance and aggressiveness of R. solani AG 3 potato-inf ecting subgroup (AG 3-PT) on potatoes has been confirmed in South Africa (Muzhinji et al 2015) and elsewhere (Das et al 2014;Fiers et al 2011;Woodhall et al 2007). …”

Pathogenicity of Fungi Isolated from Atypical Skin Blemishes on Potatoes in South Africa and Zimbabwe

“…Previously, reports of tuber malformations were associated with R. solani AGs. R. solani AG 2Nt, a subset of AG 2-1 was associated with severe tuber malformations in New Zealand (Das et al 2014). BNR AGs were thought to be saprophytic and some were demonstrated to be biological control agents of plant pathogens (Carling and Leiner 1986;Escande and Echandi 1991).…”

Morphology and pathogenicity of Rhizoctonia solani Kühn associated with potato black scurf in Nariño (Colombia)

“…Developing tubers remain small or deformed, and the surface of tubers have black crusts or sclerotia, detracting from quality (Tsror, 2010;ICA, 2011). Worldwide, this disease causes important decreases in yield and quality and is responsible for losses of up to US$ 75million/year in several countries (Das et al, 2014).…”

“…To date, 13 AGs has been identified worldwide, and the more important are AG3 and AG4. AG3 is the most pathogenic and is characterized mainly by the formation of sclerotia on tubers (Ferrucho et al, 2012;Das et al, 2014;Muzhinji et al, 2015). In Venezuela, Ecuador and Colombia, AG3 has been determined as the most pathogenic in potato cultivars (Escalona et al, 2011;Alban, 2015;Ferrucho et al, 2012Ferrucho et al, , 2013).…”