Assessing resistance to spring black stem and leaf spot of alfalfa caused by Phoma spp.

2004 ◽  
Vol 84 (1) ◽  
pp. 311-317 ◽  
Author(s):  
H. Wang ◽  
S. F. Hwang ◽  
K. F. Chang ◽  
B. D. Gossen ◽  
G. D. Turnbull ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Leaf Spot ◽  
Similar Pattern ◽  
Disease Incidence ◽  
Field Trials ◽  
Disease Reaction ◽  
Detached Leaf ◽  
Controlled Conditions ◽  
Detached Leaves ◽  
Phoma Sclerotioides

The disease reaction of alfalfa (Medicago sativa) cultivars to spring black stem was evaluated in field trials and greenhouse experiments. In field trials, differences in cultivar reaction to leaf spot (predominantly spring black stem) were observed in 9 of 16 station years. The reaction of certain cultivars was consistent across most trials, but other cultivars were quite variable. Under controlled conditions, one isolate each of Phoma sclerotioides and P. exigua produced symptoms on alfalfa leaves that were similar to those caused by P. medicaginis. These results indicate that P. medicaginis is not the only pathogen responsible for symptoms of spring black stem on alfalfa in the prairie region. In a detached-leaf study, one isolate each of P. medicaginis, P. sclerotioides and P. exigua produced leaf lesions on all 18 alfalfa cultivars assessed. Disease incidence in Absolute, Algonquin, Pickseed 3006 and Anik (M. sativa subsp. falcata) was lower than in 630 and AC Blue J. Inoculation of eight selected cultivars using a range of spore concentrations under controlled conditions showed a similar pattern; all three isolates produced leaf lesions on all eight cultivars. Ino culation with conidial suspensions of P. medicaginis resulted in a lower disease incidence on Absolute than on Beaver. Key words: Medicago sativa, Medicago sativa subsp. falcata, Phoma medicaginis, P. sclerotioides, P. exigua, detached leaves.

scholarly journals Screening of French Bean (Phaseolus vulgaris L.) Genotypes against Alternaria Leaf Spot Caused by (Alternaria alternata) under Dryland Conditions of Kashmir

2021 ◽  
pp. 25-30
Author(s):  
Sabiya Bashir ◽  
Mohammad Najeeb Mughal ◽  
Zahida Rashid ◽  
Shabeena Majid ◽  
Sabeena Naseer ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Leaf Spot ◽  
Disease Incidence ◽  
French Bean ◽  
Phaseolus Vulgaris L ◽  
Dryland Agriculture ◽  
Disease Reaction ◽  
The Mean ◽  
Selection For ◽  
Resistant Genotypes

Sixty-three genotypes of  french bean was screened against leaf spot (Alternaria  alternata) in sick plots at Research Farm of Dryland Agriculture Research Srinagar, Rangreth during  Kharif  2018 and 2019. The highest mean disease incidence ranged from 0.00 to 85.00 per cent  with  the mean disease intensity ranged from 0.00 to 53.26 per cent .One genotype namely  ‘Local Pulwama’ was highly susceptible in their disease reaction. Among the screened germplasm, ‘Highly Resistant’ genotypes was SKU-R-601, SKUA-R-105, SKU-R-927, DARS-25, DARS-66, DARS-R-615,  while as ‘Susceptible’ genotypes was  DARS-8, DARS-12,  DARS-11, SKUAST-R-155, SKU-R-928, DARS-7, DARS-R-4, Bhaderwah (L),  Local  Kupwara black and Raj Jawala. Local Pulwama was found to be a highly susceptible (HS) genotype.  Twenty nine genotypes namely., DARS-16, DARS-9, DARS-54, DARS-39, VL-125, DARS-63, ENTO-504, SKUAST-204,SKU-R-925, DARS-60, DARS-109, DARS-43, DARS-44, SKU-R-23, DARS-4, DARS-74, SKU-R-105, DARS-40, DARS-23, DARS-18, SKU-R-71, WB-341, SKU-R-605, Uri local, Shopian (L), SKU-R-23, DARS-71, SSGB-729, DARS-R-19 showed resistant reaction to disease. The selection for resistance was based on the reaction of varieties on leaves.

Co-inoculation of lucerne (Medicago sativa) with an AM fungus and a rhizobium reduces occurrence of spring black stem and leaf spot caused by Phoma medicaginis

2018 ◽  
Vol 69 (9) ◽  
pp. 933 ◽  
Author(s):  
Ping Gao ◽  
Yingde Li ◽  
Yane Guo ◽  
Tingyu Duan
Keyword(s):  
Medicago Sativa ◽  
Leaf Spot ◽  
Root Nodules ◽  
Disease Incidence ◽  
Arbuscular Mycorrhizal ◽  
Dry Weight ◽  
Sinorhizobium Medicae ◽  
Phoma Medicaginis ◽  
Am Fungus ◽  
Serious Disease

Spring black stem and leaf spot of lucerne (alfalfa, Medicago sativa L.), caused by Phoma medicaginis, is an important disease in temperate regions of the world. It is now a serious disease threatening global lucerne production. This experiment was designed to test the combined effects of the arbuscular mycorrhizal (AM) fungus Funneliformis mosseae and the rhizobium Sinorhizobium medicae on growth, nutrient uptake and disease severity in lucerne. The results showed that F. mosseae increased plant phosphorus and nitrogen uptake and plant dry weight, and this beneficial effect was enhanced when in association with S. medicae. Rhizobial and AM fungal effects were mutually promoting; inoculation with AM fungus significantly increased the formation of root nodules, and inoculation with rhizobium increased the percentage of root length colonised by AM fungus (P < 0.05). After infection with P. medicaginis, typical leaf spot symptoms with the lowest disease incidence and disease index occurred on plants that were host to both F. mosseae and S. medicae. Plants with both symbiotic microorganisms had higher activities (concentrations) of phenylalanine ammonia-lyase, chitinase, β-1,3-glucanase, lignin, hydroxyproline-rich glycoprotein and jasmonic acid. Therefore, the tested AM fungus (F. mosseae) and rhizobium (S. medicae) have the potential to reduce damage and yield loss in lucerne from spring black stem and leaf spot caused by P. medicaginis.

Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: temporal spread and its influencing factors

2002 ◽  
Vol 53 (10) ◽  
pp. 1095 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price
Keyword(s):  
Chinese Cabbage ◽  
Wind Direction ◽  
Leaf Spot ◽  
Irrigation System ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Average Wind ◽  
Temporal Spread

Temporal spread of dark leaf spot on Chinese cabbage was studied in experimental plots for 2 years. The effect of row orientation, the orientation of inoculated plants, and irrigation system on disease incidence and the effect of average wind direction on disease spread were investigated. A line source of inoculum in each plot was used for the 1993–94 summer and the 1994 spring–summer field trials, and 3 line sources for a 1995 autumn field trial. Disease progressed more rapidly in the 1993–94 summer than in the 1995 autumn. Disease epidemic did not develop in the 1994 spring–summer when environmental conditions were unfavourable. Disease incidence was higher in plots with row orientation parallel to the average wind direction than in plots with row orientation at right angles to the average wind direction for both the 1993–94 summer and the 1995 autumn trials. In summer 1993–94, across-row inoculation resulted in higher disease incidence than row inoculation did. No difference in disease incidence occurred between channel irrigation and overhead irrigation plots. Secondary infections always occurred adjacent to the source of inoculum and disease spread was influenced by the prevalent wind direction.

scholarly journals Evaluation of Lisianthus Cultivars for Resistance to Botrytis cinerea

Plant Disease ◽  
2007 ◽  
Vol 91 (8) ◽  
pp. 997-1001 ◽  
Author(s):  
Stephen N. Wegulo ◽  
Miguel Vilchez
Keyword(s):  
Botrytis Cinerea ◽  
Disease Incidence ◽  
Lesion Length ◽  
Screening Methods ◽  
Leaf Discs ◽  
Detached Leaf ◽  
Stem Lesion ◽  
Spray Inoculation ◽  
Detached Leaves

Lisianthus (Eustoma grandiflorum) is a high-value cut flower. However, major yield losses often result from gray mold caused by Botrytis cinerea. Various techniques were used to evaluate 12 lisianthus cultivars for resistance B. cinerea. Disease evaluations from detached leaf, leaf disc, cut stem, and in vivo growth chamber stem (GC) assays were correlated with those from an in vivo greenhouse stem (GH) assay, in which commercial greenhouse production of lisianthus was simulated. In all assays, stems or leaves were wounded before inoculation with spores or mycelia of B. cinerea. There was a significant (P ≤ 0.03) positive correlation between stem lesion length in the GH assay and disease incidence in the same assay (R = 0.74), stem lesion length from spore spray inoculation in the GC assay (R = 0.62), and percent necrosis from spore spray inoculation of detached leaves (R = 0.71). Correlations between stem lesion length in the GH assay and disease evaluations from spore drop and mycelial inoculation of detached leaves, leaf discs, and cut stems were not significant at P = 0.05. Considering only screening methods with significant correlations, ‘Magic Champagne’ was the most resistant cultivar (mean rank [mr] = 2 of 12). ‘Echo White’ and ‘Echo Lavender’ were the least resistant cultivars (mr = 11). The other cultivars were ‘Magic White’ (mr = 4); ‘Avila Ivory’, ‘Balboa Yellow’, ‘Echo Pink’, and ‘Magic Rose’ (mr = 5); ‘Balboa Blue’ (mr = 6); ‘Avila Blue Rim’ (mr = 8); and ‘Avila Purple’ and ‘Catalina Purple’ (mr = 9). The results from this study indicate that in vivo disease incidence, in vivo stem assays, and detached leaf assays, all initiated with wounding followed by spore spray inoculation, may be more reliable in evaluating lisianthus cultivars for resistance to B. cinerea than spore drop and mycelial inoculation of detached leaves, leaf discs, and cut stems. The results also indicate that lisianthus cultivars with moderate resistance to B. cinerea are commercially available. These cultivars have potential for use as germplasm in breeding lisianthus for resistance to the pathogen.

Seasonal variation in lucerne foliar diseases and cultivar reaction to leaf spot pathogens in the field in southern Queensland

1993 ◽  
Vol 33 (3) ◽  
pp. 343 ◽  
Author(s):  
MJ Inch ◽  
JAG Irwin ◽  
RA Bray
Keyword(s):  
Seasonal Variation ◽  
Genetic Variability ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Breeding Line ◽  
Disease Reaction ◽  
Foliar Diseases ◽  
Foliar Pathogens ◽  
Major Pathogens

Detailed assessments were made of leaf and stem disease incidence and severity on 16 lucerne cultivars and lines over 10 months in the field near Gatton, Queensland (27�34'S., 152�17'E.). The 4 major pathogens encountered were Leptosphaerulina trifolii, Uromyces striatus, Pseudopeziza medicaginis, and Cercospora medicaginis. The diseases caused by these pathogens showed a seasonality in occurrence. Both U. striatus and P. medicaginis were more severe on older shoots, whereas L. trifolii caused highest disease levels on shoots sampled 2 weeks after cutting. The relative rankings of the lucerne entries changed across pathogens, but breeding line MSA showed the best resistance to rust, L. trifolii, and P. medicaginis. This work has indicated that there is genetic variability in disease reaction to foliar pathogens which could be exploited in the development of cultivars for subtropical Queensland.

A COMPARISON OF SAMPLING METHODS FOR SURVEYING ALFALFA FOLIAGE DISEASES

1977 ◽  
Vol 57 (4) ◽  
pp. 1091-1097 ◽  
Author(s):  
P. K. BASU ◽  
C. S. LIN ◽  
M. R. BINNS
Keyword(s):  
Medicago Sativa ◽  
Downy Mildew ◽  
Leaf Spot ◽  
Sampling Methods ◽  
Disease Incidence ◽  
Sampling Area ◽  
Stemphylium Botryosum ◽  
Entire Field ◽  
Medicago Sativa L ◽  
Eastern Ontario

Two surveys of eastern Ontario alfalfa (Medicago sativa L.) fields were conducted in 1973 and 1974 to study the effects of the size of sampling area, the pattern of sampling paths, and the spread among sampling sites in relation to the incidence of common leaf spot (Pseudopeziza medicaginis (Lib.) Sacc.), Stemphylium leaf spot (Stemphylium botryosum Wallr.), and downy mildew (Peronospora trifoliorum de Bary). Results of the 1973 survey of 17 fields by three methods indicated that sampling along a 90-m diagonal of a square area of size 4,047 m2 (1 acre) within a quadrant of a field was adequate when disease incidence was either below 20 or above 80%; however, when disease incidence was intermediate (20–80%), sampling along a W-shaped path covering the entire field was more appropriate. Results of the 1974 survey of 60 fields suggested that the total number of sampling sites per field could be reduced from 40 to 15 without reducing precision, provided they were well distributed throughout the field.

Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: spatial patterns

2005 ◽  
Vol 56 (7) ◽  
pp. 699 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price ◽  
M. J. Silvapulle
Keyword(s):  
Chinese Cabbage ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Distance Class ◽  
Maximum Information ◽  
Spatial Spread ◽  
Core Cluster

The spatial spread of dark leaf spot caused by Alternaria brassicicola on Chinese cabbage was characterised over 2 years. The study was conducted in 2 field trials using ordinary runs, mapping, spatial autocorrelation, and 2-dimensional distance class analyses. Diseased plants were generally clustered and cluster orientation coincided with the line of inoculation. Disease spread was greater within than across rows. The maximum number of spatial lags with significantly positive autocorrelations occurred when disease incidence levels reached 20–80% in summer 1993–94. Core cluster size generally increased with disease incidence. Two-dimensional distance class analysis was the best analytical method among those used in describing spatial spread of the disease as it did not only provide maximum information but also considered missing data.

scholarly journals Development of Lettuce Breeding Lines Resistant to Bacterial Leaf Spot

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1098A-1098 ◽  
Author(s):  
Ryan J. Hayes ◽  
Carolee T. Bull ◽  
Polly H. Goldman ◽  
Edward J. Ryder
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Disease Incidence ◽  
Field Trials ◽  
Control Measures ◽  
Bacterial Leaf Spot ◽  
Sources Of Resistance ◽  
Breeding Lines ◽  
Overhead Irrigation ◽  
Lettuce Breeding

Bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians (Xcv) is an important lettuce disease in California. No adequate control measures have been found, although resistance exists in several heirloom cultivars. Deployment of cultivars resistant to bacterial leaf spot will reduce these periodic and costly disease events. The objectives of this research were to 1) identify new sources of resistance within modern crisphead cultivars and 2) select for resistance in `Salad Crisp' × `Iceberg' progeny. Field plots were established and grown with overhead irrigation, and a three-strain mixture of Xcv was applied until runoff 1 week after thinning at 1 × 109 CFU/mL. Twenty-six crisphead cultivars were tested in unreplicated field trials and rated on a 1 (susceptible) to 4 (resistant) scale. Selection was carried out between and within families from the F2 to F4 generation. Sixteen F3 families were evaluated in unreplicated plots, and 12 F5 families were tested in replicated plots for disease incidence and severity. No usable levels of resistance were identified in the modern crisphead cultivars tested to date. All F3 families had resistance greater than `Iceberg', and 19 plants from eight families were selected for further breeding. Subsequently, 12 plants from two F4 families were selected. Replicated trials of 12 F5 families indicated that all lines have disease severity comparable to both parents. Breeding lines from crosses to `Salinas 88' are currently being developed.

The bioactivity and efficacy of benzovindiflupyr against Corynespora cassiicola, the causal agent of cucumber Corynespora leaf spot

Plant Disease ◽  
2021 ◽  
Author(s):  
Jiamei Zhu ◽  
Xiuhuan Li ◽  
Lingyan Zhang ◽  
Yangyang Gao ◽  
Wei Mu ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Integrated Management ◽  
Disease Incidence ◽  
Field Trials ◽  
Corynespora Cassiicola ◽  
Atp Production ◽  
Control Failure ◽  
Efficient Alternative ◽  
The Mean ◽  
And Control

Corynespora cassiicola, which causes Corynespora leaf spot, results in considerable yield loss of cucumber grown in greenhouses. Frequent reports of reduced efficacy and control failure of fungicides warrant new, efficient alternative chemistries. In the present study, the sensitivity of C. cassiicola to benzovindiflupyr was evaluated using a collection of 81 isolates collected from Shandong, China. The mean EC50 values for mycelial growth, spore germination and germ tube elongation of C. cassiicola were 0.69 ± 0.44, 0.12 ± 0.063 and 0.13 ± 0.076 µg mL-1, respectively. Benzovindiflupyr treatment led to a reduced respiration rate and ATP production of C. cassiicola and decreased spore pathogenicity by 21.9% on average. Additionally, detached cucumber leaves sprayed with fungicides before or after inoculation were used to assess the efficacy of benzovindiflupyr against C. cassiicola. Benzovindiflupyr (150 µg mL-1) exhibited preventive and curative efficacies of 86.9% and 77.1%, respectively. Benzovindiflupyr at 150 g a.i. ha-1 provided over 70% efficacy in field trials performed in 2018 and 2019, which was significantly higher than that of the reference fungicides fluopyram and fluxapyroxad at the same dose. Furthermore, the yield of commercial cucumber increased as disease incidence decreased. Our findings pave the way for the introduction of benzovindiflupyr in the integrated management of Corynespora leaf spot.

scholarly journals Development of a Protocol and a Diagrammatic Scale for Quantification of Bacterial Leaf Streak Disease on Young Plants of Maize

Plant Disease ◽  
2020 ◽  
Vol 104 (11) ◽  
pp. 2921-2927
Author(s):  
Renata Rodrigues Robaina ◽  
Talita Vigo Longhi ◽  
Douglas Mariani Zeffa ◽  
Leandro Simões Azeredo Gonçalves ◽  
Rui Pereira Leite
Keyword(s):  
Disease Incidence ◽  
The United States ◽  
Bacterial Suspension ◽  
Bacterial Leaf Streak ◽  
Experimental Conditions ◽  
Maize Production ◽  
Maize Hybrids ◽  
Controlled Conditions ◽  
Maize Plants ◽  
Diagrammatic Scale

Bacterial leaf streak (BLS), caused Xanthomonas vasicola pv. vasculorum (Xvv), has become a major concern for maize production, mainly in the United States and South America. Therefore, this study aimed to establish a protocol for Xvv inoculation in young maize plants under controlled conditions and to develop and validate a diagrammatic scale for evaluation of maize hybrids in regard to BLS resistance. The study was carried out in three steps: the establishment of a protocol for inoculation of Xvv in young maize plants under controlled conditions; the development and validation of a diagrammatic scale for BLS severity evaluation; and the screening for BLS resistance of 45 hybrids using the proposed protocol for bacterial inoculation and the diagrammatic scale developed in this study. Besides reproducing a more natural Xvv infection, the bacterial suspension spraying without injury inoculation method induced higher disease incidence and severity, as well as reproducibility of results under the experimental conditions established in this study. The proposed diagrammatic scale allowed evaluating BLS severity with up to 97.49% of the leaf area affected by the disease. Further, the use of the diagrammatic scale resulted in an increase of accuracy from 0.909 up to 0.992. The reaction of 45 maize hybrids to BLS allowed establishing six major groups of susceptibility to the disease. The most resistant maize hybrids to BLS formed a group of 13 hybrids, with disease severity below 5%.

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