Assessing genetic diversity in the web blight pathogen Thanatephorus cucumeris (anamorph = Rhizoctonia solani) subgroups AG-1-IE and AG-1-IF with molecular markers

Abstract

genetic diversity in the web blight pathogen Thanatephorus cucumeris (anamorph = Rhizoctonia solani) subgroups AG-1-IE and AG-1-IF with molecular markers" (2012). Papers in Plant Pathology. 273. http://digitalcommons.unl.edu/plantpathpapers/273 Abstract Web blight, an important foliar disease of dry beans in the Americas, is a challenge to manage. We studied genetic variation of 92 isolates of Rhizoctonia solani subgroups AG-1-IE and AG-1-IF using DNA fingerprinting methods and mycelial compatibility grouping. The isolates were collected over 13 years from bean fields in the Dominican Republic, Honduras and Puerto Rico. Cluster and AMOVA analysis of combined data from two universal rice primers and two internal sequence repeats revealed significant genetic variation among and within populations of both subgroups. Variation was influenced by geographic origin and sampling year for AG-1-IE isolates and geographic origin for AG-1-IF isolates. Mycelial compatibility of paired isolates was mostly scored as incompatible in both subgroups and supported many unique phenotypes. Only two isolates of AG-1-IE displayed mycelial compatibility and DNA fingerprints, suggesting clonal origin. Genetic variation in these AG-1-IE and AG-1-IF isolate populations may explain the lack of durable resistance to web blight reported in dry beans.

Genetic Characterization and Pathogenicity of Rhizoctonia solani Associated with Common Bean Web Blight in the Main Bean Growing area of Argentina

“…This finding was in agreement with previous reports of variation at the ITS1 region of R. solani isolates within AGs (Justesen et al 2003;Gonzalez et al 2012). However, Gonzalez et al (2012) included a greater number of isolates per site and observed intragroup variation when analysing the rDNA-ITS sequence. However, Gonzalez et al (2012) included a greater number of isolates per site and observed intragroup variation when analysing the rDNA-ITS sequence.…”

“…Low levels of variability in ITS sequences of AG1-IE and AG-1IF isolates from Latin America and the Caribbean have been reported by Godoy-Lutz et al (2008). Moreover, their results were in agreement with the analysis based on URP and ISSR molecular markers and mycelial compatibility (Gonzalez et al 2012). Moreover, their results were in agreement with the analysis based on URP and ISSR molecular markers and mycelial compatibility (Gonzalez et al 2012).…”

“…Sequence alignment and phylogenetic analysis of the rDNA-ITS region confirmed the identification of the isolates as AG 2-2WB, suggesting that specific primers and the ITS sequencing are powerful tools for R. solani AG identification and phylogenetic analysis, as previously reported (Kuninaga et al 1997;Carling et al 2002;Godoy-Lutz et al 2008;Gonzalez et al 2012;Mora-Umaña et al 2013). The existence of polymorphisms within the AG group was evidenced, as a 100% match was observed only in a few sequences.…”

“…Web blight is also a limiting factor in other regions of Africa, Latin America and the Caribbean (Galvez et al 1989;Godoy-Lutz et al 2008;Mora-Umaña et al 2013), where yield losses from 20 to 100% have been reported (Galvez et al 1989;Costa-Coelho et al 2014). As commercial varieties with WB resistance are not available, the use of costly fungicides and minimum tillage is some of the cultural practices commonly used for the disease management (Godoy-Lutz et al 2008;Gonzalez et al 2012). As commercial varieties with WB resistance are not available, the use of costly fungicides and minimum tillage is some of the cultural practices commonly used for the disease management (Godoy-Lutz et al 2008;Gonzalez et al 2012).…”

Virulence and molecular characterization of Costa Rican isolates of Rhizoctonia solani from common bean

“…Worldwide, 14 AGs and numerous subgroups have been identified based on physical, chemical, pathogenic and molecular characteristics. Isolates can exist as multinucleate homokaryons or heterokaryons and present diverse mating strategies (homothallic or heterothallic) (González et al, 2012). Phaseolus vulgaris isolates belong mainly to AG 1 (6 subgroups), AG 2 (4 subgroups) and AG 4 (Carling, 1996;Schneider et al, 1997;Carling et al, 1999;Carling et al, 2002;Godoy-Lutz et al, 2003;GodoyLutz et al, 2008;González et al, 2006).…”