Etiology of halo blight in Michigan hopyards

Plant Disease ◽  
2020 ◽  
Author(s):  
Douglas Higgins ◽  
Ross Joaquin Hatlen ◽  
Jan Byrne ◽  
Monique L Sakalidis ◽  
Timothy D Miles ◽  
...  
Keyword(s):  
Yield Loss ◽  
Elongation Factor ◽  
Single Spore ◽  
Halo Blight ◽  
Detached Leaf ◽  
Whole Plant ◽  
Likelihood Analysis ◽  
Symptomatic Tissue ◽  
Plant Assays ◽  
Management Challenge

Michigan’s hop acreage ranks fourth nationally, but the state’s growers contend with unique disease challenges resulting from frequent rainfall and high humidity. In August 2018, a Michigan hop grower reported necrosis and blighting of foliage and shattering of cones resulting in yield loss. Irregular-shaped lesions developed on leaves, surrounded by a halo of chlorotic tissue and cone bracts became brown. Pycnidia were observed in symptomatic tissue. The goal of this study was to identify and characterize the causal agent of symptoms in leaf and cone tissue. In symptomatic leaves, 15 of 19 isolates recovered had 96.4% internal transcribed spacer (ITSrDNA) homology with Diaporthe nomurai. Bayesian and maximum likelihood analysis were performed on a subset of isolates using ITSrDNA, histone H3, beta-tubulin, and elongation factor one alpha. Bootstrap and posterior probabilities supported a unique cluster of Diaporthe sp. 1-MI isolates most closely related to the D. arecae species complex, D. hongkongensis and D. multigutullata. Diaporthe sp. 1-MI was pathogenic in detached leaf and whole plant assays. Single-spore isolates from pycnidia originating from cones and leaves shared 100% ITSrDNA homology with Diaporthe sp. 1-MI obtained from the lesion margins of leaves collected in 2018. The distribution of Diaporthe sp. 1-MI was widespread amongst cones (n = 347) collected from Michigan hop yards (n = 15) and accounted for > 38% of fungi recovered from cones in three hop yards. Diaporthe sp. 1-MI causing halo and cone blight presents a new disease management challenge for Michigan hop growers.

scholarly journals Indications of Susceptibility to Calonectria pseudonaviculata in Some Common Groundcovers and Boxwood Companion Plants

Plant Disease ◽  
2020 ◽  
Vol 104 (4) ◽  
pp. 1127-1132 ◽  
Author(s):  
Patricia A. Richardson ◽  
Margery Daughtrey ◽  
Chuanxue Hong
Keyword(s):  
Disease Management ◽  
Plant Species ◽  
Natural Infection ◽  
Detached Leaf ◽  
Whole Plant ◽  
Galium Odoratum ◽  
Plant Assays ◽  
Companion Plants ◽  
Pachysandra Procumbens ◽  
Different Levels

Knowing the host range of a pathogen is critical to developing and implementing effective disease management programs. Calonectria pseudonaviculata (Cps) is known to attack a number of species, varieties, and cultivars in the genus Buxus as well as three Pachysandra species (Pachysandra terminalis, Pachysandra procumbens, and Pachysandra axillaris) and several Sarcococca species, all in the Buxaceae family. The objective of this study was to evaluate non-Buxaceae groundcovers and companion plants commonly associated with boxwood plantings for their susceptibility to Cps. Twenty-seven plant species belonging to 21 families were exposed to different levels of inoculum: 50 to 300 conidia per drop for detached leaf assays and 30,000 to 120,000 conidia per 1 ml for whole-plant assays. Inoculated plants were incubated in humid environments for at least 48 h to facilitate infection. Cps infection and sporulation were observed on 12 plant species: Alchemilla mollis, Arctostaphylos uva-ursi, Brunnera macrophylla, Epimedium × youngianum, Galium odoratum, Geranium sanguineum, Phlox subulata, Tiarella cordifolia, Callirhoe involucrata, Iberis sempervirens, Mazus reptans, and Vinca minor. These results suggest that there may be more hosts of Cps commonly grown in nurseries and landscapes. If corroborated by observations of natural infection, these findings have implications for the Boxwood Blight Cleanliness Program instituted by the National Plant Board and for planning disease mitigation at production and in the landscape.

Detached Leaf and Whole Plant Assays for Soybean Aphid Resistance: Differential Responses Among Resistance Sources and Biotypes

2010 ◽  
Vol 103 (3) ◽  
pp. 949-957 ◽  
Author(s):  
Andrew P. Michel ◽  
M. A. Rouf Mian ◽  
Nelson Horacio Davila-Olivas ◽  
Luis A. Cañas
Keyword(s):  
Soybean Aphid ◽  
Aphid Resistance ◽  
Resistance Sources ◽  
Detached Leaf ◽  
Whole Plant ◽  
Differential Responses ◽  
Plant Assays

Species and trichothecene genotype of pathogens causing Fusarium head blight of wheat in Nebraska, USA

2021 ◽  
Author(s):  
Esteban Valverde-Bogantes ◽  
Andreia Bianchini ◽  
Stephen Wegulo ◽  
Heather Hallen-Adams
Keyword(s):  
Fusarium Head Blight ◽  
Fusarium Species ◽  
Management Strategies ◽  
Elongation Factor ◽  
Head Blight ◽  
Single Spore ◽  
Additional Species ◽  
Growing Seasons ◽  
Worldwide Distribution ◽  
Pathogen Populations

Fusarium head blight (FHB) is an economically important disease caused by several Fusarium species affecting wheat and other small grain cereals. In recent years, reports of shifts in populations of FHB pathogens around the world have shown that these populations are dynamic and change continuously, often resulting in increased yield losses or changes in the mycotoxins produced in the grain, which highlights the need for increased vigilance. The objective of this research was to identify the species and trichothecene genotypes of FHB pathogens in Nebraska in order to monitor their populations and the major toxigenic risks in the state. A total of 74 single-spore Fusarium isolates were obtained from 42 FHB symptomatic wheat spikes collected from Nebraska fields during the growing seasons in 2015-2018. Most of the isolates were identified as F. graminearum (n=67) based on translation elongation factor 1α (TEF1), trichothecene 3-O-acetyltransferase (TRI101), and reductase (RED) sequences. Additional species included F. boothii (n=3), F. poae (n=2), F. acuminatum (n=1), and one isolate was an F. graminearum × F. boothii interspecific hybrid. All F. graminearum and F. boothii isolates had the 15-ADON trichothecene genotype. This study shows that F. graminearum is not the only pathogen causing FHB in Nebraska and helps expand knowledge on the worldwide distribution of F. boothii. The information obtained from this survey will be useful in developing effective FHB management strategies in Nebraska, since different pathogen populations can cause varying levels of disease intensity and can be selectively sensitive to management tactics.

scholarly journals Techniques for screening Cercospora leaf spot resistant fenugreek genotypes

2019 ◽  
Vol 99 (3) ◽  
pp. 324-337
Author(s):  
U. Subedi ◽  
S. Acharya ◽  
S. Chatterton ◽  
J. Thomas ◽  
D. Friebel
Keyword(s):  
Leaf Spot ◽  
Weather Conditions ◽  
Disease Spread ◽  
Temperature Sensitive ◽  
Cercospora Leaf Spot ◽  
Legume Crop ◽  
Whole Plant ◽  
Crop Field ◽  
Plant Assays ◽  
Trigonella Foenum Graecum L

Cercospora leaf spot (CLS) caused by Cercospora traversiana is an important phyto-pathological problem of fenugreek (Trigonella foenum-graecum L.), a multiuse legume crop. Field screenings for resistant plants, although accurate and effective, demand significant time and a sizable workforce to accomplish. Also, weather conditions in the field may not always be favourable for uniform disease spread, which eventually may lead to failure of the overall experiment. Whole-plant assays (WPA) and detached leaf assays (DLA) with artificial inoculation not only help in scaling up the number of plants screened but also reduce the space, time, and amount of inoculum needed for the experiment. The results from our two experiments indicate that both the WPA and DLA methods can be used reliably to differentiate resistant and susceptible genotypes of fenugreek. In addition, the correlation coefficient between WPA and DLA (r = 0.875, P < 0.01), derived from the mean disease score of each genotype, shows that they can be used interchangeably while screening fenugreek for CLS. DLA was found to be temperature-sensitive for the development of CLS symptoms and wounded leaves developed symptoms faster than non-wounded leaves. These indoor methods can be used for the development of CLS-resistant fenugreek cultivars in areas where disease development is difficult under field conditions.

scholarly journals Quantifying herbicide dose–response and resistance in Echinochloa spp. by measuring root length in growth pouches

2015 ◽  
Vol 95 (6) ◽  
pp. 1181-1192 ◽  
Author(s):  
C. J. Zhang ◽  
S. H. Lim ◽  
J. W. Kim ◽  
J. S. Song ◽  
M. J. Yook ◽  
...  
Keyword(s):  
Dose Response ◽  
Root Length ◽  
Cost Savings ◽  
Acetolactate Synthase ◽  
Rapid Diagnosis ◽  
Response Curves ◽  
Whole Plant ◽  
Accurate Dose ◽  
Plant Assays ◽  
Als Inhibitors

Zhang, C. J., Lim, S. H., Kim, J. W., Song, J. S., Yook, M. J., Nah, G., Valverde, N. E. and Kim, D. S. 2015. Quantifying herbicide dose–response and resistance in Echinochloa spp. by measuring root length in growth pouches. Can. J. Plant Sci. 95: 1181–1192. The aim of the presented study was to develop a bioassay for rapid diagnosis of herbicide dose–response and resistance in Echinochloa. Pre-germinated seeds of Echinochloa spp. were incubated in growth pouches (18 cm×16.5 cm) containing herbicide solutions in a range of concentrations. Shoot and root lengths were measured after 6 d of incubation. Dose–responses estimated by measuring root lengths in the growth pouches were well-described by the log-logistic dose–response model and similar to those estimated by a whole-plant assay. Accurate dose–response curves were successfully generated for several herbicides with different modes of action, suggesting that the growth pouch method can be used for herbicide bioassays. The suitability of the growth pouch method for rapid diagnosis of acetyl coenzyme-A carboxylase (ACCase) and acetolactate synthase (ALS) inhibitor resistance in Echinochloa spp. was also tested. For cyhalofop-butyl, resistant and susceptible biotypes were discriminated at 180–300 mg a.i. L−1 and 80–120 mg a.i. L−1 for barnyardgrass (E. crus-galli) and late watergrass (E. oryzicola), respectively. For penoxsulam, the discriminatory dosage was 350–500 mg a.i. L−1 for barnyardgrass and 650–1000 mg a.i. L−1 for late watergrass. The method was further used to identify late watergrass biotypes resistant and susceptible to two other ALS inhibitors, azimsulfuron and bispyribac-sodium. Our results show that the growth pouch method can be reliably used in herbicide dose–response studies and to diagnose herbicide resistance in Echinochloa spp., with significant time and cost savings compared with conventional whole-plant assays.

scholarly journals First Report of Fusarium oxysporum f. sp. lactucae Race 1 Causing Fusarium Wilt of Lettuce in Norway

Plant Disease ◽  
2021 ◽  
Author(s):  
Maria Luz Herrero ◽  
Nina Elisabeth Nagy ◽  
Halvor Solheim
Keyword(s):  
Costa Rica ◽  
Fusarium Oxysporum ◽  
Vascular Tissue ◽  
Uv Light ◽  
Elongation Factor ◽  
Aerial Mycelium ◽  
Light Cycle ◽  
Single Spore ◽  
Fungal Isolates ◽  
Race 1

Lettuce (Lactuca sativa L.) is produced in Norway both in field and greenhouses. In Norway, greenhouse lettuce is one of the most important vegetables grown year-round. In winter 2018, wilting symptoms were observed on soil-grown lettuce of the cultivar Frillice in a greenhouse in south east Norway (Buskerud county). Affected plants showed stunted growth, wilting of outer leaves, and brownish discoloration of vascular tissues of taproots and crowns. According to the producer, the disease led to an estimated 10% of yield losses. Fungal isolates were obtained from crowns and roots of diseased plants collected from the greenhouse in 2018 and 2019. Two single spore isolates, 231274 from 2018 and 231725 from 2019, were used in further studies. The isolates were incubated on synthetic nutrient-poor agar (SNA) at 18-20 ⁰C, and a 12 hours dark, 12 hours UV light cycle. Isolate 231274 produced abundant macro- and microconidia characteristics of Fusarium oxysporum while macroconidia were never observed in isolate 231725. On potato dextrose agar (PDA), colonies of isolate 231274 were purple in color and colonies of isolate 231725 were pinkish with abundant aerial mycelium. For PCR-assay, DNA from mycelia was extracted using Easy-DNA kit (Invitrogen). A portion of the translation elongation factor 1-α (EF1-α) gene was amplified using primers F-728F (Carbone and Kohn. 1999) and EF2 (O'Donnell et al. 1998) as described by Aas et al. 2018. Blast analysis of both sequences (accession no. MW316853 for 231274 and MW316854 for 231275) obtained a 99% homology with the sequence of Fusarium oxysporum f.sp. lactucae (FOL) race 1 strain S1 (accession no. DQ837657)(Mbofung et al. 2007). Both isolates were identified as race 1 by using specific primers Hani3’ and Hanilatt3rev (Pasquali et al. 2007) as described by Cabral et al. 2014. To complete Koch’s postulate, lettuce plants of the cultivar Frillice were used. Race identity was confirmed using the differential lettuce cultivars Costa Rica No.4 (resistant to FOL race 1), Banchu Red Fire (resistant to FOL races 2 and 4) and Romana Romabella (resistant to FOL races 1 and 2) (Gilardi et al. 2017) provided by the breeding company Rijk Zwaan (De Lier, The Netherlands). For inoculation, roots of six 2-weeks old seedlings per cultivar were dipped in a spore suspension (1 x 106 CFU/ml) for 1 min, while controls were dipped in distilled water. Seedlings were planted in 250 ml pots containing fertilized potting substrate, and were placed in a greenhouse with temperature ranging from 15 to 35 ⁰C and an average of 23 ⁰C. After 10 days reduced growth was observed in cultivars Frillice and Banchu Red Fire for both fungal isolates. After 25 days wilting was observed in both cultivars. Affected plants presented discoloration of vascular tissue. No difference in growth was observed between cultivars Romana Romabella and Costa Rica No. 4 and their respective controls. FOL was re-isolated from all inoculated cultivars but not from controls. The colony patterns of the recovered isolates were the same than those of the isolates used for inoculation. These results confirm that the isolate belongs to race 1. Greenhouse lettuce in Norway is mainly produced in hydroponics. FOL is here reported to cause damages in soil- grown lettuce. Nevertheless FOL in hydroponic systems has been reported in Japan (Fujinaga et al. 2003) and Thailand (Thongkamngam and Jaenaksorn 2017). Thus, the possibility of infections in hydroponics remain a big concern for lettuce production in Norway.

scholarly journals Location, location, location: Feeding site affects aphid performance by altering access and quality of nutrients

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0245380
Author(s):  
Vamsi J. Nalam ◽  
Jinlong Han ◽  
William Jacob Pitt ◽  
Shailesh Raj Acharya ◽  
Punya Nachappa
Keyword(s):  
Feeding Behavior ◽  
Negative Impact ◽  
Electrical Penetration Graph ◽  
Soybean Aphids ◽  
Whole Plant ◽  
Leaf Surfaces ◽  
Aphid Feeding ◽  
And Performance ◽  
Plant Assays

Aphid feeding behavior and performance on a given host plant are influenced by the plants’ physical and chemical traits, including structural characters such as trichomes and nutritional composition. In this study, we determined the feeding behavior and performance of soybean aphids (Aphis glycines) on the stem, the adaxial (upper), and the abaxial (lower) leaf surfaces during early vegetative growth of soybean plants. Using the electrical penetration graph technique, we found that aphids feeding on the stem took the longest time to begin probing. Once aphids began probing, the sieve elements were more conducive to feeding, as evidenced by less salivation on the stem than either leaf surface. In whole-plant assays, stems harbored higher aphid populations, and aphids had shorter development time on stems than the adaxial and the abaxial leaf surfaces. We compared trichome density and length on the stem, the adaxial, and the abaxial leaf surfaces to investigate whether plant trichomes affected aphid feeding and performance. There were higher density and longer trichomes on stems, which likely resulted in aphids taking a longer time to probe. Still a negative impact on aphid population growth was not observed. Analysis of phloem sap composition revealed that vascular sap-enriched exudates from stems had higher sugars and amino acids than exudates from leaves. In artificial diet feeding assays, the population of aphids reared on a diet supplemented with stem exudates was higher than on a diet supplemented with leaf petiole exudates which is in agreement with results of the whole-plant assays. In summary, our findings suggest that the performance of soybean aphids on a specific plant location is primarily driven by accessibility and the quality of phloem composition rather than structural traits.

scholarly journals First Report of Leaf Spot Caused by Alternaria alternata on Yucca gloriosa in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Qiang Zhang ◽  
Yanru Zhang ◽  
Hongli Shi ◽  
Yunfeng Huo
Keyword(s):  
Alternaria Alternata ◽  
Leaf Spot ◽  
Management Strategies ◽  
Elongation Factor ◽  
Morphological Characteristics ◽  
Internal Transcribed Spacers ◽  
Molecular Characteristics ◽  
Single Spore ◽  
Tissue Samples ◽  
First Report

Yucca gloriosa L. is introduced to China as a garden plant because of its attractive tubular flowers (Ding et al. 2020). In 2020 and 2021, a foliar disease occurred on approximately 10% of the Y. gloriosa plants in the campus of Henan Institute of Science and Technology, Xinxiang (35°18′N, 113°54′E), Henan Province, China. At the early stages, symptoms appeared as small brown spots on the tip of the leaves. As the disease developed, the spots gradually expanded and turned into necrotic tissue with a clear brown border. The length of lesions ranged from 1 to 3 cm. Infected tissue samples were cut into small pieces, surface sterilized with 75% ethanol for 30 s followed by 0.5% NaClO for 2 min, rinsed thrice with sterile water and plated on potato dextrose agar (PDA). After incubation at 25℃ for 3 days, five fungal isolates were collected and purified using single spore culturing. Morphological observations were made on the 7-day-old cultures. Colonies on PDA were white at first and then turned to dark olive or black along with profuse sporulation. Conidia were borne on branched conidiophores, light brown to dark brown, ellipsoidal to obpyriform, and 20.5 to 43.6 ×7.5 to 15.4 μm in size, with 2-6 transverse septa and 0-3 longitudinal septa (n = 50). The morphological characteristics of the five isolates were consistent with the description for Alternaria alternata (Simmons 2007). One representative isolate (ZQ20) was selected for molecular identification. The internal transcribed spacers (ITS)-rDNA, translation elongation factor-1 alpha (TEF-1α), Alternaria major allergen (Alt a1), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene regions were amplified with primer pairs ITS1/ITS4 (White et al. 1990), EFl-728F/ EFI-986R (Carbone and Kohn, 1999), Alt-for/Alt-rev (Hong et al. 2005), and gpd1/gpd2 (Berbee et al. 1999), respectively. Their sequences were submitted to GenBank (ITS, MW832377; TEF-1α, MW848791; Alt a1, MW848792; GAPDH, MW848793). BLAST searches showed ≥99% nucleotide identity to the sequences of A. alternata (ITS, 100% to KF465761; TEF-1α, 100% to MT133312; Alt a1, 100% to KY923227; and GAPDH, 99% to MK683863). Thus, the fungus was identified as A. alternata based on its morphological and molecular characteristics. To confirm its pathogenicity, 25 healthy leaves of five 2-year-old Y. gloriosa plants were used. Leaves were wounded with one sterile needle and inoculated with 5-mm-diameter fungal agar disks obtained from 5-day-old cultures. Sterile PDA disks of the same size were used as the controls. Treated plants were covered with a plastic bag at 12 to 25℃ for 48 h to ensure a high level of moisture. After 15 days, the inoculated plants developed the symptoms similar to those observed in naturally infected plants, whereas the control plants were symptomless. The fungus was reisolated from the symptomatic leaves with the same morphological and molecular characteristics as the original isolates, fulfilling the Koch's postulates. Leaf spot caused by A. alternata in the Yucca plants has been reported in India (Pandey 2019). To our knowledge, this is the first report of A. alternata causing leaf spot on Y. gloriosa in China. Identification of the cause of the disease is important to developing effective disease management strategies.

scholarly journals The Source of Rag5-Mediated Resistance to Soybean Aphids Is Located in the Stem

2021 ◽  
Vol 12 ◽  
Author(s):  
Kumud Joshi ◽  
Joshua L. Baumgardner ◽  
Madison MacPhail ◽  
Shailesh R. Acharya ◽  
Elizabeth Blotevogel ◽  
...  
Keyword(s):  
Management Strategies ◽  
The United States ◽  
Electrical Penetration Graph ◽  
Feeding Behaviors ◽  
Soybean Aphids ◽  
Whole Plant ◽  
Detached Leaves ◽  
Root Stock ◽  
Plant Assays ◽  
Whole Plants

The soybean aphid (Aphis glycines) continues to threaten soybean production in the United States. A suite of management strategies, such as planting aphid-resistant cultivars, has been successful in controlling soybean aphids. Several Rag genes (resistance against A. glycines) have been identified, and two are currently being deployed in commercial soybean cultivars. However, the mechanisms underlying Rag-mediated resistance are yet to be identified. In this study, we sought to determine the nature of resistance conferred by the Rag5 gene using behavioral, molecular biology, physiological, and biochemical approaches. We confirmed previous findings that plants carrying the Rag5 gene were resistant to soybean aphids in whole plant assays, and this resistance was absent in detached leaf assays. Analysis of aphid feeding behaviors using the electrical penetration graph technique on whole plants and detached leaves did not reveal differences between the Rag5 plants and Williams 82, a susceptible cultivar. In reciprocal grafting experiments, aphid populations were lower in the Rag5/rag5 (Scion/Root stock) chimera, suggesting that Rag5-mediated resistance is derived from the shoots. Further evidence for the role of stems comes from poor aphid performance in detached stem plus leaf assays. Gene expression analysis revealed that biosynthesis of the isoflavone kaempferol is upregulated in both leaves and stems in resistant Rag5 plants. Moreover, supplementing with kaempferol restored resistance in detached stems of plants carrying Rag5. This study demonstrates for the first time that Rag5-mediated resistance against soybean aphids is likely derived from stems.

scholarly journals Diagnosis and management of halo blight in Australian mungbeans: a review

2019 ◽  
Vol 70 (3) ◽  
pp. 195 ◽  
Author(s):  
Thomas J. Noble ◽  
Anthony J. Young ◽  
Colin A. Douglas ◽  
Brett Williams ◽  
Sagadevan Mundree
Keyword(s):  
Yield Loss ◽  
Management Strategies ◽  
Bacterial Disease ◽  
Atmospheric Nitrogen ◽  
Food Crop ◽  
Important Food ◽  
Weed Species ◽  
Nutritional Profile ◽  
Halo Blight ◽  
Significant Yield

Mungbean (Vigna radiata L. Wilczek var. radiata) is an important food crop cultivated on over 6 Mha throughout the world. Its short duration of 55–70 days, capacity to fix atmospheric nitrogen, and exceptional grain nutritional profile makes the crop a staple for smallholder and subsistence farmers. In Australia, mungbean is grown as a high-value export crop and established as a main summer rotation for dryland farmers. A major threat to the integrity of the industry is halo blight, a bacterial disease leading to necrotic lesions surrounded by a chlorotic halo that stunts and ultimately kills the plant. Caused by Pseudomonas savastanoi pv. phaseolicola, this seed-borne disease is extremely difficult to control, resulting in significant yield loss and production volatility. The challenge of managing halo blight is exacerbated by a wide host range that includes many legume and weed species, and the presence of multiple epidemiologically significant strains. Molecular technologies could play a pivotal role in addressing these issues. This review synthesises current and emerging technologies to develop improved management strategies for the control of halo blight in mungbean.

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