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.

Factors contributing to poor lucerne persistence in southern Queensland

1977 ◽  
Vol 17 (89) ◽  
pp. 998 ◽  
Author(s):  
JAG Irwin
Keyword(s):  
Bacterial Wilt ◽  
Root Rot ◽  
Crown Rot ◽  
Wide Spread ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Colletotrichum Trifolii ◽  
Disease Survey ◽  
Disease Surveys ◽  
Made In

Lucerne disease surveys made in southern Queensland have shown the presence of seven fungal root and crown diseases. The two most wide spread and serious diseases are Phytophthora root rot (Phytophthora megasperma) and Colletotrichum crown rot (Colletotrichum trifolii). The general disease survey did not reveal the presence of bacterial wilt (Corynebacterium insidiosum) in Queensland. Studies made on the survival of lucerne populations for 2.5 years at three sites in Queensland have shown that disease was the major cause of all detected plant deaths.

scholarly journals Identification of Pisum sativum Germ Plasm with Resistance to Root Rot Caused by Multiple Strains of Aphanomyces euteiches

Plant Disease ◽  
1999 ◽  
Vol 83 (1) ◽  
pp. 51-54 ◽  
Author(s):  
D. K. Malvick ◽  
J. A. Percich
Keyword(s):  
Pisum Sativum ◽  
Root Rot ◽  
Plant Introduction ◽  
Aphanomyces Euteiches ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Pea Seedlings ◽  
Biomass Loss ◽  
Serious Disease ◽  
Multiple Strains

Aphanomyces root rot is a serious disease of pea (Pisum sativum), and additional sources of resistance are needed for development of disease-resistant cultivars. Accessions (n = 123) from the P. sativum Plant Introduction (PI) collection with the highest relative levels of resistance to one strain of Aphanomyces euteiches were previously identified from among approximately 2,500 accessions evaluated. The chosen 123 accessions were evaluated in this study for resistance to root rot caused by multiple strains of this pathogen. Five strains representing different US geographical locations and pathogenicity characteristics were used to evaluate pea seedlings in a greenhouse. Disease severity (DS) and percent loss of fresh biomass (inoculated vs. non-inoculated plants) were determined 15 days after inoculation. Significant differences (P = 0.05) in levels of DS and biomass loss (BL) occurred among the accessions after inoculation individually with the five strains. The relative rank of accessions based on DS and BL varied with the strain of A. euteiches used for inoculations. The 20 accessions with the lowest DS after inoculation with each strain were identified. Based on lowest DS, two accessions were among the 20 identified with all five individual strains, and four other accessions were among the 20 identified with four of the five strains. The results suggest that the P. sativum PI collection contains useful accessions for breeding programs aimed at developing pea varieties with resistance to A. euteiches.

scholarly journals Screening of Wild and Cultivated Capsicum Germplasm Reveals New Sources of Verticillium Wilt Resistance

Plant Disease ◽  
2015 ◽  
Vol 99 (10) ◽  
pp. 1404-1409 ◽  
Author(s):  
Suraj Gurung ◽  
Dylan P. G. Short ◽  
Xiaoping Hu ◽  
German V. Sandoya ◽  
Ryan J. Hayes ◽  
...  
Keyword(s):  
Verticillium Wilt ◽  
Root Rot ◽  
Breeding Programs ◽  
Phytophthora Root Rot ◽  
Soilborne Disease ◽  
Multiple Disease Resistance ◽  
Capsicum Species ◽  
National Plant Germplasm System ◽  
Rot Disease

Verticillium wilt caused by Verticillium dahliae is an important soilborne disease of pepper (Capsicum species) worldwide. Most commercial pepper cultivars lack resistance to this pathogen. Our objective was to identify resistance to two V. dahliae isolates in wild and cultivated Capsicum accessions from the core collection of the National Plant Germplasm System of the USDA. Screening of 397 Capsicum accessions against two V. dahliae isolates (Vdca59 and VdCf45) was performed in a greenhouse. Seventy-eight accessions selected from this screen were further evaluated in a follow-up experiment. In total, 21 (26.9%) and 13 (16.6%) Capsicum accessions tested were resistant to Verticillium wilt when inoculated with V. dahliae isolates VdCa59 and VdCf45, respectively. Eight accessions (Grif 9073, PI 281396, PI 281397, PI 438666, PI 439292, PI 439297, PI 555616, and PI 594125) were resistant to Verticillium wilt against both V. dahliae isolates. On the basis of Germplasm Resources Information Network data, two of the Capsicum annuum accessions (Grif 9073 and PI 439297) were also resistant to Phytophthora root rot disease. These sources of multiple disease resistance will be useful to pepper breeding programs.

scholarly journals Soil Salinity Enhances Phytophthora Root Rot of Tomato but Hinders Asexual Reproduction by Phytophthora parasitic

1991 ◽  
Vol 116 (3) ◽  
pp. 471-477 ◽  
Author(s):  
T.J. Swiecki ◽  
J.D. MacDonald
Keyword(s):  
Lycopersicon Esculentum ◽  
Asexual Reproduction ◽  
Root Rot ◽  
Crown Rot ◽  
Saline Soils ◽  
Phytophthora Root Rot ◽  
Tomato Plants ◽  
Zoospore Release ◽  
Root Necrosis ◽  
Root And Crown Rot

Exposure of tomato plants (Lycopersicon esculentum Mill.) to salinity stress either before or after inoculation with Phytophthora parasitica increased root and crown rot severity relative to nonstressed controls. The synergy between salinity and P. parasitic was most pronounced on young (prebloom) plants and least pronounced on older (postbloom) plants. Salt stressed, inoculated plants had significantly reduced top weight, significantly more root necrosis, greater incidence of crown necrosis, and significantly greater mortality. Increased disease severity occurred even though experiments showed salinity reduced zoospore release arid motility of P. parasitic, suggesting that even low inoculum levels can result in severe root rot on young tomato plants in saline soils.

Recurrent selection for resistance to Stemphylium vesicarium within the lucerne cultivars Trifecta and Sequel

1989 ◽  
Vol 29 (2) ◽  
pp. 189 ◽  
Author(s):  
RA Bray ◽  
JAG Irwin
Keyword(s):  
Leaf Spot ◽  
Root Rot ◽  
Recurrent Selection ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Stemphylium Vesicarium ◽  
Colletotrichum Trifolii ◽  
Resistant Lines ◽  
Selection For

Two cycles of recurrent selection for resistance to Stemphylium leaf spot (caused by Stemphylium vesicarium) based on half-sib family performance were made within the lucerne cultivars Trifecta and Sequel. Within Trifecta, 1 generation of selection was sufficient to increase the level of resistance to that of UC 1249 (resistant check), while 2 generations were necessary to obtain equivalent levels of resistance in Sequel. The Stemphylium resistant lines maintained adequate levels of resistance to anthracnose (caused by Colletotrichum trifolii) and Phytophthora root rot (caused by Phytophthora megasperma f. sp. medicaginis) on the basis of glasshouse tests.

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.

Performance of North American and Australian lucernes in the Queensland subtropics. 1. Field reaction to important root and crown diseases

1985 ◽  
Vol 25 (1) ◽  
pp. 76 ◽  
Author(s):  
D Gramshaw ◽  
PW Langdon ◽  
KF Lowe ◽  
DL Lloyd
Keyword(s):  
North America ◽  
North American ◽  
Root Rot ◽  
Crown Rot ◽  
Phytophthora Megasperma ◽  
Colletotrichum Trifolii ◽  
The North ◽  
Resistant Lines ◽  
Field Reaction ◽  
Better Than

Twenty-three lucernes from North America and five Australian lines were assessed for their sensitivity to root rot (Phytophthora megasperma f. sp. medicaginis), anthracnose/ crown rot (Colletotrichum trifolii) and root canker (Rhizoctonia solani). Plantings were spray irrigated or raingrown on sites representative of the major lucerne environments in southern Queensland. Ratings for each disease discriminated generally the same most susceptible and resistant lines across plantings, although significant sitexline interactions occurred, these being most pronounced for anthracnose. Nevertheless, mean ranking for reaction to each disease conformed to previous assessments conducted under more controlled conditions. For root rot, many of the North American lines showed resistances superior to those of the Australian lines Hunter River, Siro Peruvian and Paravivo, but not to Falkiner and HS Gen 3 Composite. None, however, were rated as having better resistance to anthracnose than Hunter River. Few of the introduced lines had better than moderate levels of combined resistance to root rot and anthracnose, a combination considered important for superior adaptation in the subtropics.

New sources of resistance in Trifolium subterraneum L. to root rot caused by two races of Phytophthora clandestina Taylor, Pascoe and Greenhalgh

2005 ◽  
Vol 56 (3) ◽  
pp. 271 ◽  
Author(s):  
M. P. You ◽  
M. J. Barbetti ◽  
P. G. H. Nichols
Keyword(s):  
Root Rot ◽  
Trifolium Subterraneum ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Breeding Lines ◽  
Late Flowering ◽  
Group 12 ◽  
New Cultivars

Eighty-four genotypes, comprising 71 ssp. subterraneum and ssp. yanninicum breeding lines of Trifolium subterraneum and 13 cultivars commonly used at the time of commencement of the experiment, were screened in the glasshouse for resistance to root rot caused by 2 races of Phytophthora clandestina that occur most widely in Australia. Resistance to race coded 001 was identified in 7 mid-season genotypes of ssp. subterraneum, including the new cultivar, Coolamon, and one genotype also showed resistance to race coded 373. Of the late flowering ssp. subterraneum genotypes tested, 13 showed resistance to race coded 001 and 4 of them also showed resistance to race coded 373. In the late flowering ssp. yanninicum group, 12 of 13 genotypes tested, including the new cultivar, Napier, showed resistance to both races. Of the mid-season ssp. yanninicum genotypes, all but 2 of 19 tested showed resistance to both races. The resistance observed in the majority of ssp. yanninicum and in some ssp. suberraneum genotypes, indicates that these are useful sources of resistance that can be exploited, either directly as new cultivars to minimise damage from this disease, or as parents in breeding programs to develop cultivars with improved resistance to P. clandestina. This study established the availability of 51 advanced lines and 11 cultivars as sources of resistance against P. clandestina race coded 001 and 36 lines and 4 cultivars for race coded 373, among which 36 lines and 4 cultivars were resistant against both races.

scholarly journals New Sources of Resistance in Winter Squash (Cucurbita moschata) to Phytophthora Crown Rot and Their Relationship to Cultivated Squash

2021 ◽  
Author(s):  
Chandrasekar S. Kousik ◽  
Gregory Vogel ◽  
Jennifer L. Ikerd ◽  
Mihir K. Mandal ◽  
Michael Mazourek ◽  
...  
Keyword(s):  
South Carolina ◽  
Root Rot ◽  
Rating Scale ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Human Consumption ◽  
Cucurbita Moschata ◽  
Sources Of Resistance ◽  
Plant Introductions ◽  
Crown And Root Rot

Butternut squash (Cucurbita moschata) is an important vegetable crop grown and consumed in most states in the USA. Cucurbita moschata lines and interspecific hybrids between Cucurbita species are also used as rootstocks for grafting watermelon and melon. However, currently most commercially available C. moschata squash varieties are highly susceptible to crown and root rot caused by the oomycete pathogen Phytophthora capsici, especially in the southeastern USA. All available plant introductions (PIs) of C. moschata (319 PIs) were evaluated for resistance to crown rot. Four-week-old plants were inoculated with 104 zoospores from a local South Carolina (SC) isolate of P. capsici. Plants were rated for disease severity three weeks after inoculation using a 0-5 rating scale (0=No symptoms and 5=Plant dead). The majority (87%) of the C. moschata PIs were highly susceptible to crown rot in the first evaluation and were rated as 5. Reevaluation of the promising PIs identified several potential new sources of resistance (e.g. Grif 935, PI 442272, PI 442264, PI 512142, PI 438724, PI 438778, PI 442280). Variability in resistance reaction among plants within a PI was also observed, and not all plants exhibited resistance. Further evaluation of S1 generation from the most resistant plants (rated ≤1) demonstrated that highly resistant plants could be selected from these PIs to develop lines for use in breeding programs. These new sources of resistance can be utilized for developing new crown and root rot resistant rootstocks for watermelon grafting and for developing resistant varieties for human consumption.

scholarly journals Potential Sources of Resistance in U.S. Cucumis melo PIs to Crown Rot Caused by Phytophthora capsici

HortScience ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 164-170 ◽  
Author(s):  
Ryan S. Donahoo ◽  
William W. Turechek ◽  
Judy A. Thies ◽  
Chandrasekar S. Kousik
Keyword(s):  
Cucumis Melo ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Fruit Rot ◽  
Broad Host Range ◽  
Post Inoculation ◽  
Vegetable Crops ◽  
Phytophthora Blight ◽  
Sources Of Resistance ◽  
Breeding Programs

Phytophthora capsici is an aggressive pathogen that is distributed worldwide with a broad host range infecting solanaceous, fabaceous, and cucurbitaceous crops. Over the past two decades, increased incidence of Phytophthora blight, particularly in eastern states, has threatened production of many vegetable crops. Cucumis melo L. (honeydew and muskmelon), although especially susceptible to fruit rot, is also highly susceptible to crown rot. Currently, little is known about host resistance to P. capsici in C. melo. To assess crown rot resistance in C. melo seedlings, 308 U.S. PIs, and two commercial cultivars (Athena and Dinero) were grown under greenhouse conditions. Seedlings with three to four true leaves were inoculated with a five-isolate zoospore suspension (1 × 104 zoospores per seedling) at the crown and monitored for 6 weeks. All the susceptible control plants of Athena died within 7 days post-inoculation. The majority of the PIs (281 of 308) were highly susceptible to crown rot and succumbed to the disease rapidly and had less than 20% of the plants survive. Several PIs (PI 181748, PI 182964, and PI 273438) succumbed to crown rot earlier than the susceptible melon cultivars. Eighty-seven PIs selected on the basis of the first screen were re-evaluated and of these PIs, 44 were less susceptible than cultivars Athena and Dinero. Twenty-five of the 87 PIs were evaluated again and of these six PI, greater than 80% of the plants survived in the two evaluations. Disease development was significantly slower on these PIs compared with the susceptible checks. High levels of resistance in S1 plants of PI 420180, PI 176936, and PI 176940 were observed, which suggests that development of resistant germplasm for use in breeding programs can be accomplished. Further screening and careful selection within each of these PIs can provide a framework for the development of resistant germplasm for use in breeding programs.

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