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

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.

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Etiology of halo blight in Michigan hopyards

Plant Disease ◽

10.1094/pdis-05-20-0924-re ◽

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.

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SSR marker diversity of soybean aphid resistance sources in North America

Genome ◽

10.1139/g07-090 ◽

2007 ◽

Vol 50 (12) ◽

pp. 1104-1111 ◽

Cited By ~ 9

Author(s):

Charles Y. Chen ◽

Cuihua Gu ◽

Clarice Mensah ◽

Randall L. Nelson ◽

Dechun Wang

Keyword(s):

North America ◽

Genetic Relationships ◽

Soybean Aphid ◽

Aphid Resistance ◽

Pedigree Information ◽

Clustering Methods ◽

Resistance Sources ◽

Ssr Loci ◽

Major Pest ◽

Aphis Glycines Matsumura

The soybean aphid ( Aphis glycines Matsumura) has become a major pest of soybean in North America since 2000. Seven aphid resistance sources, PI 71506, Dowling, Jackson, PI 567541B, PI 567598B, PI 567543C, and PI 567597C, have been identified. Knowledge of genetic relationships among these sources and their ancestral parents will help breeders develop new cultivars with different resistance genes. The objective of this research was to examine the genetic relationships among these resistance sources. Sixty-one lines were tested with 86 simple sequence repeat (SSR) markers from 20 linkage groups. Non-hierarchical (VARCLUS) and hierarchical (Ward’s) clustering and multidimensional scaling (MDS) were used to determine relationships among the 61 lines. Two hundred and sixty-two alleles of the 86 SSR loci were detected with a mean polymorphism information content of 0.36. The 61 lines were grouped into 4 clusters by both clustering methods and the MDS results consistently corresponded to the assigned clusters. The 7 resistance sources were clustered into 3 different groups corresponding to their geographical origins and known pedigree information, indicating genetic differences among these sources. The largest variation was found among individuals within different clusters by analysis of molecular variance.

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Variation in Soybean Aphid (Hemiptera: Aphididae) Biotypes Within Fields

Journal of Economic Entomology ◽

10.1093/jee/toab058 ◽

2021 ◽

Author(s):

S J Bhusal ◽

R L Koch ◽

A J Lorenz

Keyword(s):

Resistance Genes ◽

Environmental Sustainability ◽

Soybean Aphid ◽

Aphis Glycines ◽

Aphid Resistance ◽

Soybean Cultivars ◽

Major Pest ◽

Single Field ◽

Aphis Glycines Matsumura ◽

Multiple Resistance Genes

Abstract Soybean aphid (Aphis glycines Matsumura (Hemiptera: Aphididae)) has been a major pest of soybean in North America since its detection in this continent in 2000 and subsequent spread. Although several aphid resistance genes have been identified, at least four soybean aphid biotypes have been discovered, with three of them being virulent on soybean cultivars with certain soybean aphid resistance genes. These biotypes are known to vary across years and locations, but information on their variation within single fields is limited. An investigation was conducted to study the variation of soybean aphid biotypes within single townships and fields in Minnesota. Screening of 28 soybean aphid isolates collected from seven soybean fields (six soybean fields in Cairo and Wellington Townships of Renville County, MN and one field in Wilmar Township of Kandiyohi County, MN) revealed the existence of multiple known biotypes of soybean aphid within single fields of soybean. We found up to three biotypes of soybean aphid in a single field. Two biotypes were found in five fields while only one field had only a single biotype. Three isolates presented reactions on a panel of resistant and susceptible indicator lines that were different from known biotypes. These results highlight the importance of characterizing soybean aphid biotypes in small geographical areas and utilizing generated knowledge to develop soybean cultivars pyramided with multiple resistance genes. The outcome will be decreased use of insecticides, thereby improving economic and environmental sustainability of soybean production.

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Soybean Aphid Resistance in Soybean Jackson Is Controlled by a Single Dominant Gene

Crop Science ◽

10.2135/cropsci2007.01.0003er ◽

2007 ◽

Vol 47 (1) ◽

pp. 463-463

Author(s):

Curtis B. Hill ◽

Yan Li ◽

Glen L. Hartman

Keyword(s):

Dominant Gene ◽

Soybean Aphid ◽

Aphid Resistance ◽

Single Dominant Gene

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Techniques for screening Cercospora leaf spot resistant fenugreek genotypes

Canadian Journal of Plant Science ◽

10.1139/cjps-2018-0247 ◽

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.

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Identification and molecular mapping of two soybean aphid resistance genes in soybean PI 587732

Theoretical and Applied Genetics ◽

10.1007/s00122-014-2296-9 ◽

2014 ◽

Vol 127 (5) ◽

pp. 1251-1259 ◽

Cited By ~ 10

Author(s):

Ki-Seung Kim ◽

Anitha Chirumamilla ◽

Curtis B. Hill ◽

Glen L. Hartman ◽

Brian W. Diers

Keyword(s):

Resistance Genes ◽

Molecular Mapping ◽

Soybean Aphid ◽

Aphid Resistance

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

Canadian Journal of Plant Science ◽

10.4141/cjps-2015-122 ◽

2015 ◽

Vol 95 (6) ◽

pp. 1181-1192 ◽

Cited By ~ 3

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.

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