Methods to isolate fungi from single spores are outlined. These methods are specifically designed for mycological laboratories which are not necessarily well funded. Therefore, they involve a simple procedure, are relatively inexpensive, and most importantly effective. Furthermore, only basic equipment is required. By using these methods, most fungi, with the exception of those that do not germinate on artificial medium, can be isolated. Some approaches are suggested to prevent mite infestations and to reduce the risk of bacterial contamination.
Minnesota is the top sugar beet (Beta vulgaris L.) producing state in the United States. In 2020, sugar beet plants were observed for the first time in which the two to three oldest leaves had light brown to dark brown necrotic leaf lesions that eventually became yellow or brown and died but remained attached to the plant. Morphological data and sequences of internal transcribed spacer regions identified the pathogen as Sclerotinia sclerotiorum. Because over 90% of the plants in identified fields were infected it was difficult to quantify loss in yield or quality caused by this disease. All fields with symptomatic plants had soybean or edible beans in the rotation. One field planted to several different varieties indicated that all the varieties were symptomatic. It will be useful to determine any economic loss caused by S. sclerotiorum and any known varietal resistance to this pathogen.
Establishing an adequate plant population is one of the first challenges of sugar beet production. Reduced sugar beet emergence results in a decision between a lower than desired plant population or replanting the field. The objective of this study was to determine the plant population that warrants replanting a field to maximize extractable sugar ha -1 . The study was conducted in three environments during the 2016 and 2017 growing seasons. Two planting dates and six plant populations were utilized in each environment. The two planting dates were separated by 19 or 20 days to simulate a replant situation. Sugar beets in each planting date were hand thinned to six populations of 44
IntroductionSugarbeets account for 55 to 60% of U.S. sugar production. Cercospora leaf spot (CLS), primarily caused by the fungal pathogen Cercospora beticola, is a major foliar disease of sugarbeet. Since leaf tissue is a primary site of pathogen survival between growing seasons, this study evaluated management strategies to reduce this source of inoculum.MethodsFall- and spring-applied treatments were evaluated over three years at two study sites. Treatments included standard plowing or tilling immediately post-harvest, as well as the following alternatives to tillage: a propane-fueled heat treatment either in the fall immediately pre-harvest or in the spring prior to planting, and a desiccant (saflufenacil) application seven days pre-harvest. After fall treatments, leaf samples were evaluated to determine C. beticola viability. The following season, inoculum pressure was measured by monitoring CLS severity in a susceptible beet variety planted into the same plots and by counting lesions on highly susceptible sentinel beets placed into the field at weekly intervals (fall treatments only).ResultsNo significant reductions in C. beticola survival or CLS were observed following fall-applied desiccant. The fall heat treatment, however, significantly reduced lesion sporulation (2019-20 and 2020-21, P < 0.0001; 2021-22, P < 0.05) and C. beticola isolation (2019-20, P < 0.05) in at-harvest samples. Fall heat treatments also significantly reduced detectable sporulation for up to 70- (2021-22, P < 0.01) or 90-days post-harvest (2020-21, P < 0.05). Reduced numbers of CLS lesions were observed on sentinel beets in heat-treated plots from May 26-June 2 (P < 0.05) and June 2-9 (P < 0.01) in 2019, as well as June 15-22 (P < 0.01) in 2020. Both fall- and spring-applied heat treatments also reduced the area under the disease progress curve for CLS assessed the season after treatments were applied (Michigan 2020 and 2021, P < 0.05; Minnesota 2019, P < 0.05; 2021, P < 0.0001).DiscussionOverall, heat treatments resulted in CLS reductions at levels comparable to standard tillage, with more consistent reductions across year and location. Based on these results, heat treatment of fresh or overwintered leaf tissue could be used as an integrated tillage-alternative practice to aid in CLS management.
Sugar beet (Beta vulgaris L.) is an important crop grown for its sucrose content used in sugar production around the world. Tomato bushy stunt virus (TBSV) is an RNA virus that belongs to the Tombusvirus genus of the family Tombusviridae (Hearne et al., 1990). The virus was first isolated from tomato, and it is known to infect a wide range of plants (Smith, 1935; Martelli et al., 1988; Hafez et al., 2010). In 1980, a natural infection of TBSV was reported in sugar beet leaves with chlorotic and necrotic ring spots and line pattern symptoms based on serological affinity to TBSV anti-sera in Czechoslovakia (Novak and Lanzova, 1980). In March 2021, sugarbeet plants showing stunted and bushy growth with yellowing and necrotic leaves were observed in a production field in the Imperial Valley of California. Harvested roots exhibited stunted and abnormal growth compared to roots from healthy plants (sFig. 1A). These symptoms prompted a screen for potential infection by TBSV. Root-tissue harvested from the symptomatic sugar beet was initially screened using a TBSV double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA; Agdia, Inc., Elkhart, IN), which reacted positive for TBSV. To obtain the full-length sequence of TBSV and potentially other viruses in the sample, total RNA isolated using the RNeasy Plant Mini Kit (Qiagen, Valencia, CA) from the root-tissue was subjected to high-throughput sequencing (HTS). Libraries were prepared using the TruSeq Stranded Total RNA Library Prep kit (Illumina, San Diego, CA) and sequenced using Illumina NovoSeq 6000 paired-end platform (Novogene, Sacramento, CA). A total of 52 million reads were obtained after removing the adapters and reads mapping to the host genome. These high-quality reads were de novo assembled into 75,891 contigs that are larger than 500 base pairs using the SPAdes assembler (Bankevitch et al., 2012; Prjibelski et al., 2020). The resulting contigs were searched for matching sequences to known viruses using the NCBI non-redundant database. A single contig of 4770 nts representing the full-length genome of TBSV was generated (Accession number OP477335), which showed 100% coverage to previously reported TBSV isolates ‘statice’ (AJ249740.1) and ‘nipplefruit’ (AY579432.1) with 92.19% and 91.25% nucleotide sequence identities, respectively, and thus confirming the presence of TBSV in sugar beet root-tissue. However, it showed 74% coverage with only 87% nucleotide identity to a previously reported Lettuce necrotic stunt virus (LNSV) from sugar beet, a tombusvirus that was re-classified as Moroccan pepper virus (MPV) due to high degree (>97%) of sequence identity (Obermeier et al., 2001; Wintermantel and Anchieta, 2012; Wintermantel and Hladky, 2013). The coat protein is conserved within species in tombusvirus, and it plays a significant role by providing serological relationships to tombusvirus taxonomy. The coat protein of TBSV-isolate of this study shared 98.45% and 96.91% identities at amino acid level with TBSV ‘nipplefruit’ (AY579432.1) and TBSV ‘statice’ (AJ249740.1) isolates, respectively. In contrast, it showed only 61.56% identity with the coat protein of MPV as shown in the phylogenetic tree indicating that the TBSV-isolate reported here is different from MPV (sFig. 2). To confirm the presence of TBSV, reverse-transcription (RT)-PCR was performed using the total RNA isolated from the root-tissue with primers (VR306: 5’-CGCTCACGAGCCCAGCATCCTTGA-3’ and VR297: 5’-ACACCGCCACAGGAGCCATGATTG-3’) designed based on the HTS data to amplify a portion of the TBSV genome. Sequencing of the RT-PCR product confirmed the presence of TBSV sequence with 99.1% identity to the TBSV-isolate identified in this study. Further, mechanical inoculation of total RNA isolated from the symptomatic sugar beet roots produced local lesions and systemic necrosis symptoms on the leaves of Chenopodium quinoa (sFig. 1B). Sequencing of the amplicon obtained using RT-PCR with primers VR306 and VR297 confirmed the presence of TBSV in C. quinoa. In addition to TBSV, several viral contigs representing Beet necrotic yellow vein virus were identified in the root-tissue indicating mixed infection in the field. To our knowledge, this is the first report that documents the occurrence of TBSV in sugar beet in the United States. Since TBSV is a soil-borne virus, our findings indicate the need for further studies focused on the frequency and coexistence of the TBSV with BNYVV in sugar beet production fields to understand the disease complexity resulting from potential mixed infections.
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