Pathogenic specialisation within Colletotrichum trifolii in Australia, and lucerne cultivar reactions to all known Australian pathotypes

2003 ◽  
Vol 54 (9) ◽  
pp. 829 ◽  
Author(s):  
J. M. Mackie ◽  
J. M. Musial ◽  
N. R. O'Neill ◽  
J. A. G. Irwin
Keyword(s):  
North American ◽  
Crown Rot ◽  
Sources Of Resistance ◽  
Colletotrichum Trifolii ◽  
Race 1 ◽  
Host Origin ◽  
New Races ◽  
Race 2 ◽  
Race 4 ◽  
First Time

Anthracnose and crown rot, caused by Colletotrichum trifolii, are serious diseases of lucerne (Medicago sativa L.) in humid regions of the world. A race survey was conducted by inoculating individual lucerne clones (genotypes) with C. trifolii isolates collected from a range of Medicago hosts, locations, and years in south-eastern Queensland. This survey revealed for the first time in Australia the presence of race 2 (virulence on anthracnose resistance gene An1) and the first world report of race 4 (virulence on An2). A collection of North American race 1 and race 2 C. trifolii isolates, when inoculated onto the Australian differential clones, gave responses that were in agreement with their North American reactions. A RAPD analysis was conducted on 9 Australian C. trifolii isolates including races 1, 2, and 4; two C. destructivum and one C. gloeosporioides isolate were included as known outliers. For the C. trifolii isolates, 94.6% similarity was found regardless of host origin or race, compared with 2.2% similarity between this group and the C. gloeosporioides and C. destructivum isolates, confirming that the new races belong to C. trifolii. Currently, it is hypothesised that only plants carrying genes An1 and An2 are resistant to the 3 races. Of 22 cultivars screened against the 3 races, only UQL-1, Hallmark, and Pioneer 54Q53 had >30% of plants resistant to the 3 races in separate screenings. The research highlights the need to find new sources of resistance to C. trifolii in lucerne.

scholarly journals A New Race of Colletotrichum trifolii Identified on Alfalfa in Ohio

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1362-1362 ◽  
Author(s):  
J. J. Ariss ◽  
L. H. Rhodes
Keyword(s):  
United States ◽  
North American ◽  
The United States ◽  
Morphological Characters ◽  
First Report ◽  
Anthracnose Resistance ◽  
Colletotrichum Trifolii ◽  
Race 1 ◽  
Race 2 ◽  
Race 4

Anthracnose of alfalfa (Medicago sativa L.), caused by the fungus Colletotrichum trifolii Bain & Essary, was identified as a potential problem of alfalfa in the United States in the late 1960s. Races 1 and 2 are known in the United States, and recently, race 4 was described in Australia (1). An additional race, race 3, had previously been reported in the United States, but isolates of this proposed race were not preserved and its status as a distinct race of C. trifolii is unclear. In June 2003, an isolate of C. trifolii was collected in Columbus, OH from a 4-year-old alfalfa stand of cv. 520. The isolate was obtained from typical anthracnose stem lesions. Stem sections with lesions were scraped with a sterile inoculation loop, and conidia were directly streaked onto acidified potato dextrose agar. Individual colonies were transferred to half-strength oatmeal agar. Morphological characters (conidia, acervuli, and setae) of this isolate, designated OH-WA-520, were consistent with those of other C. trifolii isolates and clearly distinguishable from C. destructivum or other Colletotrichum spp. that occur on alfalfa. The alfalfa differential cultivars Arc (resistant to race 1 and susceptible to race 2 of C. trifolii), Saranac AR (resistant to race 1 and race 2), and Saranac (susceptible to both races) were inoculated with conidia of isolate OH-WA-520 per the North American Alfalfa Improvement Conference standard protocol for determining anthracnose resistance (2). Isolate OH-WA-520 was avirulent on Arc but virulent on Saranac AR and Saranac. In each of three repetitions of the protocol, more than 65% of Arc plants survived, while less than 18% of Saranac and Saranac AR plants survived. These results indicate a physiological race inconsistent in reaction with C. trifolii race 1 or race 2, but similar in reaction to race 4 isolates previously described only from Australia (1). To our knowledge, this is the first report of a C. trifolii isolate virulent on Saranac AR but avirulent on Arc. This is also the first report of C. trifolii race 4 in the United States. References: (1) J. M. Mackie et al. Aust. J. Agric. Res. 54:829, 2003. (2) N. R. O'Neill. Anthracnose resistance. Page D-1 in: Standard Tests to Characterize Alfalfa Cultivars. Online publication. North American Alfalfa Improvement Conference, Beltsville, MD, 1991.

scholarly journals First Report of Race 2 of Colletotrichum trifolii Causing Anthracnose on Alfalfa (Medicago sativa) in Wisconsin

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 843-843 ◽  
Author(s):  
D. A. Samac ◽  
S. Allen ◽  
D. Witte ◽  
D. Miller ◽  
J. Peterson
Keyword(s):  
United States ◽  
Medicago Sativa ◽  
The United States ◽  
Crown Rot ◽  
Growth Chamber ◽  
Its Sequence ◽  
Colletotrichum Trifolii ◽  
Differential Cultivars ◽  
Race 1 ◽  
Race 2

Anthracnose of alfalfa (Medicago sativa), caused by Colletotrichum trifolii, is widespread in the United States. In addition to loss of forage due to death of stems, the pathogen causes crown rot, reducing stand life and winter survival (2), making it one of the most serious diseases of alfalfa. Three physiological races have been described (2). Race 1 is reported to be the dominant race that is present wherever alfalfa is grown, while race 2 was reported in a limited area in the Mid-Atlantic states, and race 4 was found in Ohio (1). Conspicuous, straw-colored dead stems with a “shepherd's crook” wilt and large, sunken, diamond-shaped lesions with a dark border were observed in experimental plots and breeding nurseries of experimental lines in Clinton and West Salem, WI, in August 2011 and in West Salem, WI, in mid-August 2012. Acervuli with black setae and orange spore masses were observed in lesions placed in moist chambers for 2 days at room temperature with ambient room lighting. Conidia were germinated on 1% water agar and then single hyphae were transferred to potato dextrose agar (PDA) plates. DNA was extracted from pure cultures of strains DA-1 (Clinton, WI) and FGI-3 (West Salem, WI), the rDNA ITS1-5.8S-ITS2 region was amplified with primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′), the products sequenced directly, and the sequences compared to the ITS region of known race 1 and race 2 strains of C. trifolii. The sequences from DA-1 and FGI-3 were identical to the ITS sequence of C. trifolii 2sp2 (race 1; KF444778) and C. trifolii SB-2 (race 2; KF444779), but distinct from the ITS sequence of C. destructivum (JQ005764) and C. dematium (JX567507), which can cause anthracnose on alfalfa (1). Conidia from DA-1 and FGI-3 were harvested from 7-day-old cultures grown on PDA plates, diluted to 2 × 106 conidia/ml, and sprayed to runoff on 10-day-old growth chamber grown plants of three differential cultivars: Saranac (susceptible to races 1 and 2), Arc (resistant to race 1, susceptible to race 2), and Saranac AR (resistant to races 1 and 2). Plants were maintained at 100% relative humidity for 48 h and then grown in a growth chamber at 24°C with a 16-h photoperiod. Symptoms were rated at 14 days after inoculation. In the three repetitions of the experiment using 75 plants of each cultivar in each experiment, less than 10% of the Saranac and Arc plants survived, while survival of Saranac AR was 31 to 44%. The approximate expected survival of differential cultivars inoculated with race 1 is 1% for Saranac, 65 to 70% for Arc, and 45% for Saranac AR (2). Aggressiveness of race 2 strains on Saranac AR is variable, ranging from 12 to 68% plant survival (3). The susceptibility of Arc when inoculated with DA-1 and FGI-3 is consistent with the reaction to race 2 strains, indicating that both strains are race 2. The isolation of race 2 strains in major alfalfa growing regions in Wisconsin indicates that this physiological race is currently more widespread than previously observed. Although most modern alfalfa cultivars have resistance to race 1, few cultivars with resistance to race 2 are available. The occurrence of C. trifolii race 2 in the Midwest United States should be considered in alfalfa breeding programs when developing multi-pest resistant alfalfa cultivars. References: (1) J. J. Ariss and L. H. Rhodes. Plant Dis. 91:1362, 2007. (2) N. R. O'Neill. Plant Dis. 80:450, 1996. (3) N. R. O'Neill et al. Phytopathology 79:750, 1989.

Pathogenic Specialization of Venturia nashicola, Causal Agent of Asian Pear Scab, and Resistance of Pear Cultivars Kinchaku and Xiangli

2020 ◽  
Author(s):  
Hideo Ishii ◽  
Kumiko Nishimura ◽  
Kenji Tanabe ◽  
Yuichi Yamaoka
Keyword(s):  
Resistance Breeding ◽  
Scab Resistance ◽  
Japanese Pear ◽  
Pyrus Pyrifolia ◽  
Asian Pear ◽  
Sexual Recombination ◽  
Venturia Nashicola ◽  
Race 1 ◽  
New Races ◽  
Race 2

Scab, caused by Venturia nashicola is one of the most serious diseases of Asian pears including Japanese pear (Pyrus pyrifolia var. culta) and Chinese pears (P. bretschneideri and P. ussuriensis). Breeding of scab-resistant pear cultivars is essential to minimize the use of fungicides and the risk of fungicide resistance developing in the pathogen. A survey of pathogenic specialization in V. nashicola is needed to ensure durable scab resistance in cultivated pears. Race 1, 2, and 3 isolates of V. nashicola, each differing in pathogenicity to Japanese pear cv. Kousui and Asian pear strain Mamenashi 12, have been reported from Japan. In the present study, isolates collected from scabbed pears in China and Taiwan were classified as V. nashicola based on conidial size and mating ability. However, various isolates were found to have pathogenicity distinct from races 1, 2, and 3 in tests on seven differential host genotypes: Kousui; Mamenashi 12; Chinese pear cvs. Jingbaili, Yali, Linyuli, Nanguoli; and Taiwanese pear cv. Hengshanli. The new races were designated as races 4 to 7. Progenies characteristic of race 3 isolates were produced in a cross between race 1 and race 2 isolates, suggesting the possible role of sexual recombination in the emergence of novel races. Japanese pear cv. Kinchaku and cv. Xiangli of P. sinkiangensis (Korla fragrant pear grown in China) didn’t show visible symptoms after inoculation with any of the seven races. The broad scab resistance in Kinchaku and Xiangli makes them a promising genetic resource for resistance breeding programs.

The proportion of individual lucerne plants resistant to Phytophthora medicaginis and Colletotrichum trifolii in Australian cultivars

1998 ◽  
Vol 38 (1) ◽  
pp. 41 ◽  
Author(s):  
J. M. Mackie ◽  
J. A. G. Irwin
Keyword(s):  
Root Rot ◽  
Crown Rot ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Phytophthora Root Rot ◽  
Colletotrichum Trifolii ◽  
Eastern Australia

Summary. Phytophthora root rot (Phytophthora medicaginis) and colletotrichum crown rot (Colletotrichum trifolii) are the 2 most serious pathogens of lucerne in eastern Australia. Work reported in this paper shows that in glasshouse tests of the 11 most commonly grown Australian lucerne cultivars, the proportion of individual plants with resistance to both pathogens ranges from 0 (Hunter River and Aurora) through to a maximum of 19.8% (Sequel HR). Within 9 of the cultivars, the proportion of individual plants resistant to the 2 pathogens was <7%. Since these 2 diseases are known to cause serious losses in eastern Australia, the results indicate further improvement in lucerne production can be obtained by increasing the proportion of individual plants in a cultivar resistant to both pathogens. This would be best achieved by identifying dominant sources of resistance and incorporating this into on-going lucerne breeding programs.

scholarly journals Virulence and Molecular Genotyping Studies of Sporisorium reilianum Isolates in Sorghum

Plant Disease ◽  
2011 ◽  
Vol 95 (5) ◽  
pp. 523-529 ◽  
Author(s):  
Louis K. Prom ◽  
Ramasamy Perumal ◽  
Saradha R. Erattaimuthu ◽  
John E. Erpelding ◽  
Noe Montes ◽  
...  
Keyword(s):  
Fragment Length Polymorphism ◽  
South Texas ◽  
Pathogen Virulence ◽  
Inoculation Techniques ◽  
Sporisorium Reilianum ◽  
Race 1 ◽  
Race 2 ◽  
Small Clusters ◽  
Race 4 ◽  
Syringe Injection

Head smut, caused by the fungal pathogen Sporisorium reilianum, has been reported with increasing frequency in the grain sorghum growing areas of Texas. To facilitate analysis of changes in pathogen virulence, four inoculation techniques were examined: soil and teliospore mixture, seed coating, media placement, and syringe injection. Of the four, syringe injection was determined to be the most effective. Inoculations of sorghum host differentials BTx643, BTx7078, BTx635, SC170-6-17 (TAM2571), SA281 (Early Hegari), and Tx414 showed 23 of 32 Texas isolates were race 4. Two isolates from College Station, TX, were classified as race 1, but no race 2 or 3 isolates were found. New, virulent races 5 and 6 were identified among isolates from south Texas. Using 16 amplified fragment length polymorphism (AFLP) primer combinations, genetic diversity was assessed in DNA samples from 49 S. reilianum isolates, including 44 sorghum isolates from Texas, two from Uganda, and one from Mali; and two maize isolates from Mexico. Single-base extensions with EcoRI and MseI primers in the selective amplification increased the number of informative polymorphic bands. High genetic dissimilarity (50%) was observed between isolates originating from maize and those originating from sorghum. The resultant dendrogram, made using cluster analysis, grouped the Texas S. reilianum isolates into four small clusters with ≥82% similarity. Other than for two race 6 isolates from Weslaco, TX, no evidence for geographical or other restrictions on gene flow was evident.

Characterisation of Strains of Fusarium oxysporum f.sp. cubense by Production of Volatiles

1991 ◽  
Vol 39 (2) ◽  
pp. 161 ◽  
Author(s):  
NY Moore ◽  
PA Hargreaves ◽  
KG Pegg ◽  
JAG Irwin
Keyword(s):  
Fusarium Oxysporum ◽  
Vegetative Compatibility ◽  
Vegetative Compatibility Group ◽  
Compatibility Group ◽  
Race 1 ◽  
Race 2 ◽  
Race 4

The production of volatiles on steamed rice by Australian isolates of Fusarium oxysporum f. sp. cubense correlated well with race and vegetative compatibility group (VCG). All race 4 isolates (VCGs 0120, 0129) produced distinctive volatile odours which gave characteristic gas chromatograms where the num- ber of peaks equated to VCG. Race 1 (VCGs 0124, 0125) and race 2 (VCG 0128) isolates, as well as non-pathogenic isolates of F. oxysporum from the banana rhizosphere, did not produce detectable volatiles and gave chromatograms without significant peaks.

scholarly journals First Report of Race 3 of Fusarium oxysporum f. sp. lycopersici in Southeastern Florida

Plant Disease ◽  
2000 ◽  
Vol 84 (2) ◽  
pp. 199-199
Author(s):  
R. C. Ploetz ◽  
J. L. Haynes
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Personal Communication ◽  
Crown Rot ◽  
Basal Cells ◽  
Single Spore ◽  
Tomato Cultivar ◽  
Race 1 ◽  
Race 2 ◽  
Research And Education

Race 3 of Fusarium oxysporum f. sp. lycopersici, cause of Fusarium wilt of tomato, Lycopersicon esculentum, was first recognized in Florida in 1982 on the west coast (Hillsborough and Manatee counties) (2). Approximately 10 years later, race 3 was reported in northeastern production areas of the state (Gadsden County) (1) and was observed on the east coast (Ft. Pierce area) (D. O. Chellemi, personal communication). During the 1998 to 1999 season, mature plants of Sanibel, a commercial tomato cultivar with resistance to races 1 and 2, were observed with symptoms of Fusarium wilt at the University of Florida's Tropical Research and Education Center in Homestead. Approximately 20% of the plants were conspicuously wilted, chlorotic, and necrotic in all or unilateral portions of the canopy. Internal, vascular discoloration in affected plants extended far into the canopy, distinguishing the disease from Fusarium crown rot, caused by F. oxysporum f. sp. radicis-lycopersici. Pure colonies of fungi were isolated from surface-disinfested (10 s with 70% ethanol, 2 min with 10% bleach) stem segments on potato dextrose agar (PDA) amended with streptomycin (100 mg/liter), rifamycin (50 mg/liter), and a commercial miticide (Danitol 2EHC [4 drops/liter]). Isolates were identified as F. oxysporum due to their production of typical falcate macroconidia with foot-shaped basal cells, microconidia borne in false heads only on mono-phialides, and chlamydospores. In replicated (three) greenhouse trials, six single-spore isolates were used to root-dip inoculate (107 conidia per ml) seedlings of differential tomato cultivars (Bonnie Best, no resistance; Manapal, race 1 resistance; Walter, race 1 and race 2 resistance). All isolates were pathogenic on each of the differential cultivars, and one isolate, 2-1, caused severe damage on Walter (mean rating of 3.5 on a 1 to 5 scale). The results were repeated in a second trial with the most virulent isolate. In both trials, pure colonies of F. oxysporum were recovered from symptomatic seedlings. Southeastern Florida is the last major tomatoproduction area in Florida to be affected by race 3 of F. oxysporum f. sp. lycopersici. References: (1) D. O. Chellemi and H. A. Dankers. Plant Dis. 76:861, 1992. (2) R. B. Volin and J. P. Jones. Proc. Fla. State Hortic. Soc. 95:268, 1982.

scholarly journals Characterization of Capsicum chinense Cultigens for Resistance to Meloidogyne arenaria, M. hapla, and M. javanica

Plant Disease ◽  
2001 ◽  
Vol 85 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Judy A. Thies ◽  
Richard L. Fery
Keyword(s):  
High Resistance ◽  
Meloidogyne Incognita ◽  
Capsicum Chinense ◽  
Sources Of Resistance ◽  
Alternative Source ◽  
Highly Pathogenic ◽  
Habanero Pepper ◽  
Race 1 ◽  
Race 2

Four Capsicum chinense cultigens with known reactions to Meloidogyne incognita were characterized for resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica, in greenhouse and growth-chamber tests. The M. incognita-resistant cultigens PA-353, PA-398, and PA-426 exhibited high resistance to M. arenaria race 1; the M. incognita-susceptible PA-350 was susceptible to M. arenaria race 1. M. arenaria race 2 and M. javanica were not highly pathogenic to any of the C. chinense cultigens. PA-353, PA-398, and PA-426, however, supported an average of 98.1 and 94.8% fewer (P < 0.05) M. arenaria race 2 and M. javanica eggs per gram fresh root, respectively, than PA-350. M. hapla was pathogenic to all four C. chinense cultigens. PA-353, PA-398, and PA-426 will be useful sources of resistance to M. arenaria races 1 and 2, M. javanica, and M. incognita, for developing resistant habanero pepper cultivars; however, an alternative source of resistance must be identified for M. hapla.

scholarly journals Identification of Sources of Resistance to Xanthomonas campestris pv. campestris in Brassica napus Crops

Plant Disease ◽  
2011 ◽  
Vol 95 (3) ◽  
pp. 292-297 ◽  
Author(s):  
M. Lema ◽  
P. Soengas ◽  
P. Velasco ◽  
M. Francisco ◽  
M. E. Cartea
Keyword(s):  
Brassica Napus ◽  
Xanthomonas Campestris ◽  
Specific Resistance ◽  
Sources Of Resistance ◽  
Nonspecific Resistance ◽  
Breeding Programs ◽  
Race 1 ◽  
Improved Cultivars ◽  
Race 4 ◽  
Xanthomonas Campestris Pv Campestris

Black rot, caused by Xanthomonas campestris pv. campestris, is one of the most important diseases affecting Brassica crops worldwide. Nine races have been differentiated in X. campestris pv. campestris, with races 1 and 4 being the most virulent and widespread. The objective of this work was to identify sources of resistance to races 1 and 4 of X. campestris pv. campestris in different Brassica napus crops, mainly in the underexplored pabularia group. Seventy-six accessions belonging to four B. napus groups were screened for resistance to two X. campestris pv. campestris races (1 and 4). The strain of race 1 used in this study was more virulent on the tested materials than the strain of race 4. No race-specific resistance was found to race 1. Most cultivars were susceptible except Russian kale, from the pabularia group, which showed some resistant plants and some other accessions with some partially resistant plants. High levels of race-specific resistance to race 4 were found in the pabularia group, and great variability within accessions was identified. Three improved cultivars (Ragged Jack kale, Friese Gele, and Valle del Oro) and four landraces (Russian kale, MBG-BRS0037, MBG-BRS0041, and MBG-BRS0131) showed plants with some degree of resistance to both races, which may indicate that race-nonspecific resistance is involved. These accessions could be directly used in breeding programs, either as improved cultivars or as donors of race-specific resistance to other Brassica cultivars.

Variability within Kabatiella caulivora Race 1 and Race 2 revealed by cultural and molecular analyses

2003 ◽  
Vol 54 (1) ◽  
pp. 77 ◽  
Author(s):  
K. L. Bayliss ◽  
L. Spindler ◽  
E. S. Lagudah ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Aflp Analysis ◽  
Similarity Coefficients ◽  
Breeding Lines ◽  
Disease Site ◽  
Race 1 ◽  
Kabatiella Caulivora ◽  
Race Comparison ◽  
New Races ◽  
Race 2 ◽  
Clover Scorch

Kabatiella caulivora is the causal agent of clover scorch, a fungal disease of clover (Trifolium) species. Variability within and between K. caulivora Race 1 and Race 2 was determined by cultural characteristics, isozymes, and amplified fragment length polymorphisms (AFLP). Cultural studies indicated isolates from both races were highly variable. No differences were identified within or between races by isozyme analysis. Similarity coefficients, determined from AFLP analysis, indicated that isolates from different races were often more similar than isolates from the same race. Comparison of single representative isolates from Race 1 and Race 2, collected at a Denmark (Western Australia) disease site, with isolates collected from another site of clover scorch outbreak at Esperance, 300 km east of Denmark, indicated most of the isolates causing the second outbreak were similar to Race�2, confirming previously conducted pathogenicity tests. It is hypothesised that Race 2 may have evolved from Race 1, and that the level of variability in the pathogen indicates the potential for development of further new races of K. caulivora. The requirement for improved selection strategies, including the screening of new cultivars and breeding lines with multiple isolates of the pathogen, is discussed in relation to these findings.

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