Molecular identification and pathogenicity of Rhizoctonia spp. recovered from seed and soil samples of the main bean growing area of Argentina

Abstract

The objective of this study was to perform the molecular and pathogenic characterization of Rhizoctonia solani in bean seed and soil samples from fields with root rot symptoms in northwestern Argentina. Fifty-two Rhizoctonia spp. isolates were collected in ten naturally infested bean fields and characterized by morphological traits, DNA sequencing, and pathogenicity. The mycelium color, the pattern of sclerotia formation, and the number of nuclei per hyphal cell were determined for each isolate. According to the variability in the rDNA-ITS region, isolates were identified as R. solani (85%), Waitea circinata var. zeae (Rhizoctonia zeae) (2%) and Rhizoctonia spp. (13%). Most isolates of R. solani (92%) were found to belong to the anastomosis group (AG) AG 4, including seven AG 4 HG-I and nine AG 4 HG-III isolates. AGs obtained from soil samples were more variable than those obtained from seed samples. Molecular identification of the isolates was in agreement with their morphological characterization. In addition, aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. Four virulence categories were defined according to the disease reaction on root and foliar tissues, which showed great variability in virulence among the isolates. Our results suggest that both seed and soil-borne inoculum may play a significant role in pathogen dispersal in the region. This is the first study on Rhizoctonia species and AGs in bean seed and soil in this region and it may contribute towards an efficient control strategy for bean diseases caused by Rhizoctonia species.

Characterization of Actinobacterial Strains as Potential Biocontrol Agents against Macrophomina phaseolina and Rhizoctonia solani, the Main Soil-Borne Pathogens of Phaseolus vulgaris in Cuba

“…In addition, [ 5 ] pointed out that the incidence and severity of root rot diseases caused by these fungi depend on the climatic factors prevailing at each sowing time, as well as the characteristics of the microclimates existing in each region of the country where common beans are grown. Among them, M. phaseolina and R. solani are considered the most prevalent fungal pathogens associated with root rot diseases of common bean worldwide [ 6 , 7 ].…”

“…On the other hand, R. solani (Basidiomycota) is the causal agent of rhizoctonia blight, also commonly known as damping off [ 11 ]. This soil-borne pathogen can affect more than 500 plant species, including cultivated and wild plants, and causes damping off in stands, necrotic lesions in roots, seeds and stems, as well as foliar lesions with a worldwide distribution [ 7 , 12 ]. This fungus affects young seedlings much more than adult plant tissues.…”

Characterization of fungal pathogens and germplasm screening for disease resistance in the main production area of the common bean in Argentina

“…There are cultivars that in some countries have moderate levels of resistance to WB while in other countries they are more susceptible to the disease ( Poltronieri and Ferreira de Oliveira, 1989 ), emphasizing the fact that local pathogenic WB isolates, characterized by their anastomosis group, should be used in germplasm screening to allow for the identification of sources of genetic resistance ( Beaver et al, 2021 ). Considering this, 23 common bean cultivars inoculated with two highly virulent AG 2-2 isolates collected in northwestern Argentina were evaluated for WB resistance by Spedaletti et al (2017) . Based on the disease incidence (DI) on foliar tissue, the Leales B30 and Leales CR5 cultivars, developed by the Instituto Nacional de Tecnologia Agropecuaria (INTA) from Argentina, were classified as resistant (1 = DI < 3) to both isolates.…”

“…Root and hypocotyl rot have been reported to be caused by isolates of R. solani AG 1, AG 2, AG 4, and AG 5 (Galindo et al, 1982;Abawi, 1989;Tu et al, 1996;Eken and Demirci, 2004;Nerey et al, 2010;Valentín Torres et al, 2016). Moreover, AG 4 has been reported to be the prevalent group associated with root and hypocotyl rot in Argentina and other common bean growing areas worldwide, such as Brazil, Cuba, Iran, Turkey and the Democratic Republic of the Congo (Muyolo et al, 1993;Meinhardt et al, 2002;Nerey et al, 2010;Haratian et al, 2013;Kiliçoǧlu and Özkoç, 2013;Spedaletti et al, 2017). In Argentina, the presence of various R. solani AGs in seed and soil samples from bean fields naturally infested with RR has been reported (Spedaletti et al, 2017).…”

Isolation and identification of pathogenic fungi and oomycetes associated with beans and cowpea root diseases in Oman

“…Several fungal genera have been reported to associate with foliar and root diseases on beans, peas and other legumes. These include Alternaria , Aphanomyces , Aspergillus , Curvularia , Drechslera , Fusarium , Penicillium , Rhizoctonia and Rhizopus species which have been detected on P. vulgaris , Vicia faba , Vigna unguiculata and Pisum sativum (Abdulwehab, El-Nagerabi & Elshafie, 2015; Gossen et al, 2016; Sousa et al, 2017; Spedaletti et al, 2017; Zeng et al, 2017). Vural & Soylu (2012) reported root and foliage infection of kidney bean with soil-borne fungal pathogens including Fusarium solani (Mart.)…”