Fusarium proliferatum and F. verticillioides are mycotoxin-producing, seedborne pathogens of maize. They are often asymptomatic in seed, eluding symptom-based detection. Experiments were conducted in nonsterile soil to determine whether interspecific competition influenced establishment in maize plants of an introduced isolate of F. proliferatum or F. verticillioides. Hygromycin-resistant, green fluorescent protein (GFP) transformed (GFP-tagged) F. proliferatum (F. proliferatum-green) and hygromycin-resistant, monomeric red fluorescent protein (mRFP) transformed (mRFP-tagged) F. verticillioides (F. verticillioides-red) strains were developed to provide molecular markers to track fungal establishment. Heat-killed Fusarium-free maize seed, colonized with F. proliferatum-green or F. verticillioides-red by immersion in a spore suspension for 16 h, served as the source of inoculum. The ability of F. proliferatum-green and F. verticillioides-red to colonize viable maize plants already colonized by the other species was determined. Maize plants were retrieved from soil after 14 days and DNA was extracted from three consecutive root segments and three consecutive stem segments. A TaqMan multiplex real-time quantitative PCR protocol was developed to identify and quantify F. proliferatum-green and F. verticillioides-red from each plant segment from each treatment; the experiment was repeated three times. This experiment confirmed that F. proliferatum-green and F. verticillioides-red effectively colonized roots and stems of the maize plant already colonized with the other species. Prior colonization of maize tissues by F. verticillioides-red (P = 0.6749) and other seedborne microorganisms (P = 0.1910) reduced but did not prevent subsequent colonization by F. proliferatum-green. Similarly, prior colonization of maize tissues by F. proliferatum-green (P = 0.7032) and other seedborne microorganisms (P = 0.1447) reduced but did not prevent subsequent colonization by F. verticillioides-red.

Sixty percent of the $109 million processed red raspberry industry of the United States occurs in northern Washington State. In 2012, late-summer symptoms of vascular wilt and root disease were observed in many raspberry plantings. These symptoms were initially attributed to Verticillium dahliae. However, diagnostic tests for the pathogen were often contradictory and other soilborne pathogens (Phytophthora rubi and Pratylenchus penetrans) or Raspberry bushy dwarf virus (RBDV) might also have been involved. Therefore, a survey was conducted in 2013 and 2014 to (i) establish the incidence and soil population levels of V. dahliae in red raspberry production fields, (ii) compare among diagnostic methods and laboratories for detecting and quantifying V. dahliae from raspberry field soil, and (iii) assess which pathogens are associated with late-summer disease symptoms of raspberry. Plant and soil samples were collected from 51 disease sites and 20 healthy sites located in 24 production fields. Samples were analyzed for the presence and quantity of each pathogen using traditional plating and extraction methods (V. dahliae, P. rubi, and P. penetrans), quantitative polymerase chain reaction (qPCR) (V. dahliae and P. rubi), and enzyme-linked immunosorbent assay (RBDV). Results showed that V. dahliae was present in 88% of the production fields and that detection of the pathogen differed by method and by laboratory: qPCR detected V. dahliae in the soil from approximately three times as many sites (51 of 71 total sites) as by plating on NP10 semi-selective medium (15 of 71 total sites). Soil populations of V. dahliae were slightly greater at disease sites, but the pathogen was detected with similar frequency from healthy sites and it was rarely isolated from diseased plants (4%). P. rubi, P. penetrans, and RBDV were also common in production fields (79, 91, and 53% of fields, respectively). Both P. rubi (soil and root samples) and P. penetrans (root populations only), but not RBDV, were more frequently found at disease sites than healthy sites, and the amount of P. rubi detected by qPCR was greater from disease sites than healthy sites. In addition, P. rubi was isolated from 27% of the symptomatic plants located at disease sites. Regardless of detection method, V. dahliae, P. rubi, and P. penetrans, either with or without RBDV, were more likely to co-occur at disease sites (73%) than healthy sites (35%), suggesting that a soilborne disease complex is present in raspberry production fields. Results indicate that P. rubi is the primary pathogen most strongly associated with late-summer symptoms of disease, but root populations of P. penetrans and higher soil populations of V. dahliae may also be of concern. Therefore, disease control methods should focus on all three soilborne pathogens.

Advances in plant nutrition can be achieved by improving the delivery of micronutrients to the plants. The objective of this research was to compare the efficiency of uptake of different sources of zinc, copper and manganese (sulfates, Ethylenediaminetetraacetic acid (EDTA) and oxides) and boron (boric anhydride and colemanite). We conducted all experiments in maize, repeated the experiment twice, using five replicates per treatment, and used two different media. Results showed that for cations, the soluble sources of micronutrients (sulfate and EDTA) in both media were more efficiently taken up. One-way ANOVA with post hoc Tukey for multiple comparisons of means (95% confidence level) was used for all statistical analyses. Sulfate sources were significantly different when compared to the negative control and to the oxide sources. EDTA sources were significantly different when compared to the negative control and to the oxide sources. Oxide sources were not significantly different from the negative control. For boron, we found a similar trend, with boric anhydride being significantly different when compared to the negative control and to colemanite. Colemanite was significantly different when compared to the negative control. This study generated important information about uptake of soluble and insoluble sources of four micronutrients that can be used for the development of new formulations.

The genus Verticillium contains 10 plant pathogenic species that are responsible for billions of dollars of crop losses annually on more than 400 plant species worldwide. On alfalfa, Verticillium alfalfae causes Verticillium wilt, a disease with the potential to reduce yields of susceptible cultivars by the second harvest year and to limit the productive stand life to less than 3 years. Susceptible alfalfa cultivars exhibit disease symptoms that include chlorotic V-shaped lesions at the leaf tip that cause entire leaflets to become bleached and twisted, leading to defoliation. Stems often remain green after all leaflets have desiccated, and discolouration, stunting and wilting of shoots is visible. Internally, the taproot can show yellow to brown vascular discolouration. International quarantines sometimes prohibit the entry of alfalfa samples contaminated with the Verticillium pathogen. In this investigation, we developed a recombinase polymerase amplification (RPA) assay coupled with a lateral flow device for the specific and sensitive detection of V. alfalfae. The primers targeted the translation elongation factor 1α (TEF-1α) gene and were designed with mismatches to increase the specificity of the assay. This assay detected as little as 800 fg of DNA from all tested isolates of V. alfalfae. Moreover, non-specific amplification of closely related V. nonalfalfae or other Verticillium species was not observed. Detection of V. alfalfae in inoculated alfalfa cultivars with high or low resistance further demonstrated the specificity and sensitivity of the diagnostic assay. Additionally, RPA detected V. alfalfae from inoculated plants using a crude DNA extraction method. The assay is easy to use and will allow growers, diagnostic labs and regulatory agencies to determine if V. alfalfae is present in alfalfa products.