Burlakoti, P., Rivera, V., Secor, G. A., Qi, A., Del Rio-Mendoza, L. E., and Khan, M. F. R. 2012. Comparative pathogenicity and virulence of Fusarium species on sugar beet. Plant Dis. 96:1291-1296.In all, 98 isolates of three Eusarium spp. (18 Fusarium oxysporum, 30 F. graminearum, and 50 Eusarium sp. nov.) obtained from sugar beet in Minnesota were characterized for pathogenicity and virulence on sugar beet in the greenhouse by a bare-root inoculation method. Among the 98 isolates tested, 80% of isolates were pathogenic: 83% of the E oxysporum isolates, 57% of the F. graminearum isolates, and 92% of the Eusarium sp. nov. isolates. Symptoms varied from slight to moderate wilting of the foliage, interveinal chlorosis and necrosis, and vascular discoloration of the taproot without any external root symptoms. Among the pathogenic isolates, 14% were highly virulent and 12% were moderately virulent. Most of the highly virulent isolates (91%) and moderately virulent isolates (89%) were Eusarium sp. nov. All pathogenic isolates of E graminearum and most pathogenic isolates (87%) of E. oxysporum were less virulent. In general, more-virulent isolates induced first foliar symptoms earlier compared with lessvirulent isolates. This study indicates that both E. oxysporum and Eusarium sp. nov. should be used in greenhouse and be presen: in field studies used for screening and developing sugar beet cultivars resistant to Fusarium yellows complex for Minnesota and North Dakota.

Fusarium graminearum causes fusarium head blight (FHB) of wheat and gibberella ear rot (GER) of corn in Canada and also contaminates grains with trichothecene mycotoxins. Very little is known about trichothecene diversity and population structure of the fungus from corn in Ontario, central Canada. Trichothecene genotypes of F. graminearum isolated from corn (n = 452) and wheat (n = 110) from 2010 to 2012 were identified. All the isolates were deoxynivalenol (DON) type. About 96% of corn isolates and 98% of wheat isolates were 15-acetyl deoxynivalenol (15ADON) type. The fungal population structures from corn (n = 313) and wheat (n = 73) were compared using 10 variable number tandem repeat (VNTR) markers. The fungal populations and subpopulations categorized based on host, cultivar groups, years and geography showed high gene (H = 0.818-0.928) and genotypic (GD = 0.999-1.00) diversity. Gene flow was also high between corn and wheat population pairs (Nm = 8.212), and subpopulation pairs within corn (Nm = 7.13-23.614) or wheat (Nm = 19.483) populations. Phylogenetic analysis revealed that isolates from both hosts were F. graminearum clade 7. These findings provide baseline data on 3-acetyl deoxynivalenol (3ADON) and 15ADON profiles of F. graminearum isolates from corn in Canada and are useful in evaluating mycotoxin contamination risks in corn and wheat grains. Understanding the fungal genetic structure will assist evaluation and development of resistant cultivars/germplasm for FHB on wheat and GER on corn.

Baseline sensitivity was determined using in vitro radial growth assay for Fusarium oxysporum, Fusarium graminearum, and a novel uncharacterized Fusarium sp. nov. from sugarbeet, and F. sambucinum from potato, to metconazole, triticonazole, and thiabendazole. All the isolates from sugarbeet and a thiabendazole-sensitive F. sambucinum isolate were sensitive to the tested fungicides. A thiabendazole-resistant isolate of F. sambucinum was resistant to thiabendazole but sensitive to the other two fungicides. The EC 50 values of F. oxysporum, F. graminearum, and F. sp. nov. for triticonazole were 0.51 µg ml-1 , 2.15 µg ml-1 , and 0.04 µg ml-1 , respectively. The EC 50 values of F. oxysporum, F. graminearum, and F. sp. nov. for metconazole were 0.04 µg ml-1 , 0.03 µg ml-1 , and 0.02 µg ml-1 , respectively. The EC 50 values of F. oxysporum, F. graminearum, and F. sp. nov. for thiabendazole were 0.57 µg ml-1 , 0.54 µg ml-1 , and 0.64 µg ml-1 , respectively. Generally, a higher concentration of triticonazole and thiabendazole compared to metconazole were required to reduce colony growth by 50%. The low EC 50 values of metconazole, triticonazole, and thiabendazole for the Fusarium species tested suggest that they are potential candidates for control of Fusarium diseases of sugarbeet. Research is needed to determine the

Numerous challenges exist in organic tomato production, one of the largest being a lack of amendments that can effectively serve as crop nutrients or pest controls and still be considered organic. Compost is a recognized organic input, and a recent development is the use of compost tea in fertility and biocontrol applications. Aerobic compost tea (ACT) is produced by aerating compost and water and allowing microbial activity to increase over a few days. An investigation into the biocontrol and fertility efficacy of different ACT formulations, as well as ACT crop application methods was completed. Four batches of ACT, two based on Sustane (commercial compost from poultry litter) and two based on spent mushroom compost, with or without nutritional additives, were made at a ratio of 31:1 water to substrate. In vitro antifungal bioassays revealed that all Sustane and spent mushroom compost ACTs reduced the growth of Phytophthora capsici whereas only ACT based on spent mushroom compost reduced the growth of Botrytis cinerea. A greenhouse trial using the tomato cultivar 'Glamour' was completed and ACT was applied by spraying the shoots or drenching the potting mixture either preinoculation or pre-and post-inoculation with P. capsici. All ACTs reduced disease progress although there were differences across application methods. Generally, drenching ACT reduced disease more than spraying and applying ACT twice (before and after pathogen inoculation) was also better than applying ACT once before inoculation. The percent reduction in disease progress ranged from an average of 6.4% for spraying ACT once to an average of 73.4% for drenching ACT twice. This same trend was observed in the plant biomass data. In addition, the biomass data suggests that ACT also offered fertility benefits to the tomato plants. ACT therefore holds promise as a sustainable biocontrol treatment as well as a source of plant nutrients for organically grown tomato.

Choy sum (Brassica rapa var. parachinensis), leafy mustard (Brassica juncea) and pak choi (B. rapa var. chinensis) are highly nutritious components of diets in Taiwan and other Asian countries, and bacterial black rot caused by Xanthomonas campestris pv. campestris (Xcc) is a major biotic constraint in these crops. As very little was known about the Xcc strains from these crops in these regions, including their cross‐pathogenicity and aggressiveness on different hosts, Xcc strains were obtained from cabbage (Brassica oleracea var. capitata), choy sum, leafy mustard and pak choi crops in Taiwan. Two previously published PCR‐based assays reliably distinguished the Xcc strains from other Xanthomonas species and subspecies. Phylogenetic analysis based on repetitive sequence‐based PCR assays placed the Xcc strains in a clade distinct from other Xanthomonas species, and also showed host specificity. Although all of the Xcc strains from the different host species were pathogenic on all five Brassica test species in both a detached leaf assay and an intact plant assay, in the intact plant assay they showed differences in virulence or aggression on the different test hosts. The Xcc strains from leafy mustard and pak choi were consistently highly aggressive on all the test host genotypes, but the strains from choy sum and cabbage were less aggressive on leafy mustard and choy sum. The intact plant assay proved more discriminating and reliable than the detached leaf assay for comparing the aggressiveness of Xcc strains on different host genotypes, and so, with the new Xcc strains isolated in this study, will be useful for screening leafy brassica germplasm accessions for resistance to black rot.