Feng, J., Hwang, R., Chang, K. F., Conner, R. L., Hwang, S. F., Strelkov, S. E., Gossen, B. D., McLaren, D. L. and Xue, A. G. 2011. Identification of microsatellite markers linked to quantitative trait loci controlling resistance to Fusarium root rot in field pea. Can. J. Plant Sci. 91: 199–204. Fusarium root rot, caused by Fusarium solani (Mart.) Sacc. f. sp. pisi (F. R. Jones) W. C. Snyder & H. N. Hans, is the most common root disease of field pea (Pisum sativum L.) in western Canada. In this study, a recombinant inbred line (RIL) population (n=71) of field pea, derived from crosses between a resistant cultivar Carman, and a susceptible cultivar Reward, was evaluated to identify quantitative trait loci (QTL) controlling resistance to Fusarium root rot. The parental genotypes and RILs were evaluated for resistance to root rot following inoculation with F. solani in field experiments during 2007 and 2008. The frequency distribution of disease severities among the RILs was continuous. Transgressive segregation for resistance was observed among the RILs, with five lines more resistant than Carman, but no lines were more susceptible than Reward. To identify DNA markers linked with the resistance, 213 microsatellite markers were screened with genomic DNA from the two parental cultivars. Only 14 markers were polymorphic between the two parents and were used to genotype each of the RILs. Quantitative trait loci analysis based on the mean disease severity data from 2007 and 2008 identified a QTL that explained 39.0% of the phenotypic variance in the RIL population. This QTL is flanked by markers AA416 and AB60 on linkage group VII. The microsatellite markers that are closely linked to this QTL may be useful for marker assisted selection to develop cultivars with superior Fusarium root rot resistance.

Conner, R. L., Chang, K. F., Hwang, S. F., Warkentin, T. D. and McRae, K. B. 2013. Assessment of tolerance for reducing yield losses in field pea caused by Aphanomyces root rot. Can. J. Plant Sci. 93: 473–482. Aphanomyces root rot, caused by Aphanomyces euteiches Drechs., is a serious disease of peas (Pisum sativum) that can severely reduce seed yield, and few effective control measures are available. The development of pea cultivars with tolerance or partial resistance to Aphanomyces root rot is generally considered to be one of the best options to reduce yield loss. A 4-yr field study was conducted at disease-free sites and at an Aphanomyces root rot site to compare the responses of cultivars and lines in the presence and absence of Aphanomyces root rot, identify breeding lines with tolerance and to evaluate the effects of tolerance on plant growth, disease severity and yield. At the Aphanomyces root rot site, a second test was established in which the phosphite fungicide Phostrol™ was applied as a soil drench treatment to the pea cultivars and lines. Aphanomyces root rot reduced seedling emergence, biomass production and yield in the susceptible pea genotypes. However, line 00-2067 consistently produced relatively high yields at all the field sites. At the Aphanomyces root rot site, yield was closely associated with plant vigour and shoot weight. Small, but significant, differences (P<0.05) in disease severity were observed between susceptible cultivars and tolerant lines indicating that the lines producing high yields at the Aphanomyces root rot site are tolerant rather than partially resistant. The root/shoot weight ratio was very low in the tolerant lines, indicating that even though their root systems were reduced and severely damaged by root rot, they were still able to produce high yields under favourable conditions for the disease. Drench application of the fungicide Phostrol™ did not significantly reduce root rot severity or improve the performance of any of the pea cultivars or lines.

Balasubramanian, P. M., Conner, R. L., McLaren, D. L., Chatterton, S. and Hou, A. 2014. Partial resistance to white mould in dry bean. Can. J. Plant Sci. 94: 683–691. White mould, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a constraint on dry bean (Phaseolus vulgaris L.) production across Canada. Under high disease pressure, dry bean cultivars succumb to the disease resulting in a severe loss of seed yield and quality. Disease development is highly influenced by environmental conditions. In the absence of complete resistance to white mould, dry bean cultivars with both field resistance (avoidance) and physiological resistance would be preferred by growers in order to reduce disease risk and production costs. The objective of this study was to characterize select dry bean genotypes for field resistance to white mould in inoculated disease nurseries, and physiological resistance in a controlled environment. White mould ratings ranged from moderately susceptible to susceptible. Dry bean cultivars lacked both field resistance and physiological resistance. Germplasm lines I9365-25, G122, A 195 and I9635-31 had low disease severity ratings (5.1 to 5.6 at 26 d after inoculation using a 1 to 9 visual disease rating scale) in controlled environment indicating physiological resistance. L 192, MO162, 92BG-7 and OAC Rico also had acceptable levels of physiological resistance (severity ratings of 5.8 to 6.2 at 26 d after inoculation). G122, A 195, L 192 and MO 162 had low white mould disease incidences (16 to 25%) in the field over 4 yr indicating field resistance to white mould. These genotypes may be used as parents in the development of dry bean cultivars with enhanced resistance to white mould.

. 2015. Impact of common bacterial blight on the yield, seed weight and seed discoloration of different market classes of dry beans (Phaseolus vulgaris L.). Can. J. Plant Sci. 95: 703Á710. Common bacterial blight (CBB) is a seed-borne disease of dry bean (Phaseolus vulgaris L.), causing significant economic loss to growers due to reductions in seed yield and quality and the need to annually purchase disease-free seed. Over the past decade a number of breeding lines and cultivars with resistance to CBB have been developed in several bean market classes including navy, black and cranberry beans. A comparison of three susceptible navy bean cultivars and seven resistant navy, three black and one cranberry bean entries in Manitoba revealed that most resistant navy and black bean lines had significantly reduced the incidence of leaf symptoms and their mean yield losses were reduced to less than 17%, while those of the susceptible lines were as high as 36% under severe disease pressure. Only the weakly resistant navy bean cultivar HR67 and the cranberry bean line F4GR1 failed to substantially reduce CBB symptoms or show a yield advantage. The Simple Sequence Repeat (SSR) marker PVctt001 in combination with Sequence Characterized Amplified Region (SCAR) marker SU91 was associated with a low incidence of CBB symptoms and a reduced yield loss in five navy bean lines, but not in the cranberry bean line F4GR1. Disease symptoms on the pods in the resistant black and navy beans and seed discoloration of navy beans caused by CBB were also significantly reduced by resistance. Seed weights were reduced by 2.1Á4.7% in the susceptible cultivars, but there was only a slight or no decrease or no effect on the seed weight of the CBB-resistant lines and cultivars. Generally the magnitude of the reductions in yield was much greater than the impact on seed weight, which suggests that yield losses were caused by a combination of reduced seed weight and the number of seeds per plant. 'une diminution du rendement et d'une de´te´rioration de la qualite´des graines, ensuite, de la ne´cessite´d'acheter chaque anne´e des semences indemnes de la maladie. Au cours des dix dernie`res anne´es, plusieurs ligne´es ge´ne´alogiques et cultivars re´sistants a`la bruˆlure bacte´rienne ont vu le jour dans diverses classes marchandes, y compris celles du petit haricot rond blanc, du haricot noir et du haricot canneberge. La comparaison de trois cultivars sensibles de petit haricot rond blanc a`sept varie´te´s re´sistantes, et at rois cultivars re´sistants de haricot noir ainsi qu'a`un autre de haricot canneberge au Manitoba re´ve`le que la plupart des ligne´es re´sistantes de petit haricot rond blanc et de haricot noir pre´sentent des symptoˆmes foliaires nettement moins e´tendus et une baisse de rendement moyenne infe´rieure a`17 %, alors que la diminution du rendement peut atteindre jusqu'a`36 % chez les ligne´es sensibles, quand la pression de la maladie se fait e´leve´e. Seuls le cultivar de petit haricot rond blanc peu re´sistant HR67 et la ligne´e d...

Chang, K. F., Conner, R. L., Hwang, S. F., Ahmed, H. U., McLaren, D. L., Gossen, B. D. and Turnbull, G. D. 2014. Effects of seed treatments and inoculum density of Fusarium avenaceum and Rhizoctonia solani on seedling blight and root rot of faba bean. Can. J. Plant Sci. 94: 693–700. Production of faba bean cultivars with tannin-free seed on the Canadian prairies has potential for use in human food and as a feedstock for livestock and aquaculture. However, root rot is a major constraint to production. The effects of fungicide seed treatments on root rot caused by Fusarium avenaceum and Rhizoctonia solani, and the effect of inoculum density on seedling emergence, nodulation, root rot severity and yield of faba bean were examined across 12 station years from 2009 to 2011 at sites in Manitoba and Alberta. Fusarium avenaceum reduced seedling emergence more than R.solani, but both pathogens had a similar impact on seed yield. The effects of inoculum density and seed treatment were generally significant for seedling emergence, root rot severity and seed yield for both pathogens. The interaction effects of inoculum density×seed treatment for F.avenaceum and R.solani were only significant for seed yield and seedling emergence. Seedling emergence and seed yield declined with increasing inoculum level for both F. avenaceum and R.solani. Fungicidal seed treatments with Apron Maxx (fludioxonil+metalaxyl) and Vitaflo 280 (carbathiin+thiram) consistently improved emergence and seed yield in trials inoculated with F.avenaceum or R.solani. This study demonstrated that seed treatment to manage root rot of faba bean is warranted.