Occurrence and management of root rot of field pea caused by Aphanomyces euteiches

• Author / Creator

  Longfei, Wu

• Aphanomyces euteiches causes Aphanomyces root rot (ARR), an important disease of field pea (Pisum sativum). The development of ARR results in severe root damage, wilting and large yield losses under wet soil conditions. A survey of field pea crops in central Alberta in 2016 found an average incidence of root rot of 57.6%, ranging from 2% to 100%. Species of Fusarium were recovered most frequently from symptomatic roots, followed by Pythium spp., A. euteiches and Rhizoctonia spp. Inoculum density experiments under greenhouse and field conditions demonstrated an adverse effect of increasing A. euteiches inoculum concentration on pea seedling emergence, root nodulation and plant vigor. Seed treatment with the fungicides Apron Advance (thiabendazole + fludioxonil + metalaxyl) + Vibrance (difenoconazole+ metalaxyl-M+ sedaxane), Intego Solo (ethaboxam), BAS 516F (boscalid + pyraclostrobin), BAS 720F (metalaxyl + pyraclostrobin + fluxapyroxad) or BAS 516F + BAS 720F (3:1) were evaluated for their efficacy against ARR. All seed treatments except Apron Advance suppressed ARR development under controlled conditions. Twenty-two pea lines and cultivars were evaluated for resistance to ARR in field plot experiments, with the genotype 00-2067 found to be most tolerant to the disease. A recombinant inbred line (RIL) pea population was obtained by single-seed descent from the cross 00-2067 (ARR tolerant) × Reward (ARR susceptible) and used to identify quantitative trait loci (QTLs) associated with root rot severity, height, vigor, root weight and foliar weight in greenhouse and field trials. A total of 212 simple sequence repeat (SSR) markers were screened by bulk segregant analysis and the polymorphic markers used for linkage map construction. Composite interval mapping identified a total of six QTLs associated with tolerance to ARR, root weight, foliar weight and height. Two of the QTLs, PARR-LGI and PRW-LGI on linkage group I (LGI), explained 52.5% and 34.2% of the variation in root rot severity and root weight, respectively, in one greenhouse replication, while the four other QTLs, PRW-LGII, PFW-LGII-1, PFWLGII-2 and PH-LGII on linkage group II (LGII), explained 14.0-17.1% of the phenotypic data in greenhouse and field experiments. The results of this study suggest that an integrated approach, which incorporates the use of seed treatments and QTLs associated with tolerance to the ARR, will be required for the sustainable management of ARR of field pea in Canada.

• Subjects / Keywords

  • Aphanomyces euteiches
  • field pea
  • root rot
  • occurrence
  • fungicides
  • inoculum density
  • resistance
  • quantitative trait loci

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R34J0BC6K

• License

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