Reaction of lucerne cultivars to Phytophthora megasperma, the cause of a root rot in Queensland

1974 ◽  
Vol 14 (69) ◽  
pp. 561 ◽  
Author(s):  
JAG Irwin
Keyword(s):  
Medicago Sativa ◽  
Root Rot ◽  
Controlled Environment ◽  
Field Site ◽  
Causal Organism ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Disease Surveys ◽  
Infested Field ◽  
Experimental Strains

The causal organism of Phytophthora root rot of lucerne (Medicago sativa) in Queensland was identified as Phytophthora megasperma var. sojae and a brief description of the organism is included. The results of disease surveys show that Phytophthora root rot is widespread and causes serious losses in lucerne in south eastern Queensland. A collection of lucerne cultivars and strains was screened for resistance to P. megasperma var. sojae both in controlled environment chambers and in a naturally infested field site. The cultivar Lahontan and the experimental strains ESI, BDSI, ECRSI and Combined showed high levels of resistance in both situations.

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.

Lack of control of phytophthora root in lucerne (Medicago sativa) by foliar applications of phosphorus

1991 ◽  
Vol 31 (4) ◽  
pp. 503
Author(s):  
KF Lowe ◽  
MJ Ryley ◽  
TM Bowdler
Keyword(s):  
High Risk ◽  
Medicago Sativa ◽  
Root Rot ◽  
Dry Matter ◽  
Small Reduction ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Resistant Cultivars ◽  
Matter Production ◽  
Lack Of Control

Application of phosphonate was investigated as a means of controlling phytophthora root rot (Phytophthora megasperma f. sp. medicaginis) in lucerne (Medicago sativa). Foliar sprays of the chemical at rates of 2, 4 and 8 g/L did not improve the persistence or dry matter production of susceptible or resistant cultivars of lucerne, despite a small reduction in the degree of damage inflicted on lucerne plants by a severe epiphytotic of the disease. Regular monthly applications gave no better control than single applications at establishment or at the time of the development of an epiphytotic. It is concluded that phosphonate is not efficacious in controlling phytophthora root rot in lucerne and will not improve the performance of susceptible cultivars in high risk situations.

Selection for resistance to Phytophthora megasperma var. sojae in Hunter River lucerne

1978 ◽  
Vol 18 (94) ◽  
pp. 708 ◽  
Author(s):  
RA Bray ◽  
JAG Irwin
Keyword(s):  
Medicago Sativa ◽  
Root Rot ◽  
Dry Matter ◽  
Dry Matter Yield ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Laboratory Conditions ◽  
Two Generations ◽  
Selection For

Seedlings of lucerne (Medicago sativa) resistant to Phytophthora root rot were isolated from cv. Hunter River by two generations of selection under laboratory conditions. Screening of three-month-old seedlings confirmed the resistance of the selected populations. In the field, when compared with cv. Hunter River, the best population had greater survival, more resistant plants, and twice the dry matter yield.

AC Caribou alfalfa

1992 ◽  
Vol 72 (3) ◽  
pp. 845-847
Author(s):  
R. Michaud ◽  
C. Richard
Keyword(s):  
Medicago Sativa ◽  
Research Station ◽  
Clavibacter Michiganensis ◽  
Maritime Provinces ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Clavibacter Michiganensis Subsp ◽  
Cultivar Description ◽  
Medicago Sativa L ◽  
Moderately Resistant

AC Caribou alfalfa (Medicago sativa L.) is a cultivar developed by the Agriculture Canada Research Station in Sainte-Foy. It is similar to Iroquois in maturity, rate of growth, and fall dormancy. It is highly resistant to bacterial wilt (caused by Clavibacter michiganensis subsp. insidiosus (McCulloch) Davis, Gillaspie, Vidaver & Harris), resistant to verticillium wilt (caused by Verticillium albo-atrum Reinke & Berth.), and moderately resistant to phytophthora root rot (caused by Phytophthora megasperma Dreschs. f. sp. medicaginis T. Kuan & D. C. Erwin). AC Caribou, an alfalfa with fine leafy stems, is well suited for production in Quebec and the Maritime Provinces where winter survival may be a problem.Key words: Alfalfa, Medicago sativa, cultivar description

RCAT Persian soybean

1991 ◽  
Vol 71 (1) ◽  
pp. 175-176
Author(s):  
G. R. Ablett ◽  
W. D. Beversdorf
Keyword(s):  
Glycine Max ◽  
Root Rot ◽  
Yield Potential ◽  
Maturity Group ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Group I ◽  
Glycine Max L ◽  
Cultivar Description ◽  
Late Maturity

RCAT Persian is a mid-late Maturity Group I soybean [Glycine max L. (Merr.)] cultivar with excellent yield potential, good lodging tolerance and resistance to most races of phytophthora root rot caused by Phytophthora megasperma f. sp. glycinea (Pmg) found in Ontario. Key words: Soybean, cultivar description

Virulence of five Phytophthora species causing rhododendron root rot in Oregon.

Plant Disease ◽  
2021 ◽  
Author(s):  
Gabe O. Sacher ◽  
Carolyn F. Scagel ◽  
E. Anne Davis ◽  
Bryan R. Beck ◽  
Jerry E. Weiland
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Block Design ◽  
Abundant Species ◽  
Phytophthora Species ◽  
Phytophthora Root Rot ◽  
Moderate Disease ◽  
Randomized Complete Block Design ◽  
Infested Field ◽  
Production Areas

Phytophthora root rot is a destructive disease of rhododendron, causing substantial losses of this nursery crop in infested field and container production areas. Historically, Phytophthora cinnamomi was considered the main causal agent of the disease. However, a recent survey of soilborne Phytophthora species from symptomatic rhododendrons in Oregon revealed that P. plurivora is more common than P. cinnamomi and that several other Phytophthora species may also be involved. We investigated the ability of the five most abundant species from the survey to cause root rot: P. plurivora, P. cinnamomi, P. pini, P. pseudocryptogea, and P. cambivora. Three to four isolates were selected for each species from across six Oregon nurseries. Media of containerized Rhododendron catawbiense ‘Boursault’ was infested with single isolates in a randomized complete block design in a greenhouse. Phytophthora cinnamomi, P. pini, and P. plurivora rapidly caused ≥ 90% incidence of severe root rot while P. pseudocryptogea caused more moderate disease with 46% incidence of severe root rot. Phytophthora cambivora failed to produce enough inoculum and was used at a lower inoculum density than the other four species, but occasionally caused severe root rot (5% incidence). No differences in virulence were observed among isolates of same species, except for one isolate of P. plurivora that caused less disease than other P. plurivora isolates. This study demonstrates that all five Phytophthora species, which were representative of 94% of the survey isolates, are capable of causing severe root rot and plant death, but that not all species are equally virulent.

The development of lucerne with resistance to root rot in poorly aerated soils

1978 ◽  
Vol 18 (92) ◽  
pp. 434 ◽  
Author(s):  
VE Rogers ◽  
JAG Irwin ◽  
G Stovold
Keyword(s):  
Root Rot ◽  
New South ◽  
New South Wales ◽  
Mass Selection ◽  
Infested Soil ◽  
Yield Data ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
South Wales ◽  
Disease Free

Three cycles of recurrent mass selection in the field increased the level of resistance of lucerne (Medicago sativa) to Phytophthora root rot in irrigated heavy clay soil at Deniliquin, New South Wales. The breeding stocks were derived from Siro Peruvian and Lahontan. In each cycle between 45 and 80 vigorous, disease free plants were selected from soil naturally infested with Phytophthora megasperma var. sojae, and allowed to interpollinate. Yield data and ratings for root rot were obtained for half-sib families sown in rows. Progeny in cycle 1 were inoculated by isolates of P. megasperma from both New South Wales and Queensland, and there was substantial agreement between both sources in ratings for disease. In the third cycle of selection, progeny had a disease rating of 1.4 when inoculated with Queensland isolates of P. megasperma, compared with 3.6 and 4.1 for Hunter River and Siro Peruvian respectively (plants scored 1 or 2 considered resistant; 3, 4 or 5 susceptible). In a field trial, the percentage of disease-free plants after eight months of growth in infested soil was: cycle 3 selections, 44.4; Hunter River, 9.9; Siro Peruvian, 12.0. Cumulative dry matter production of the selections during that time was twice that of Hunter River.

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.

RCAT Angora soybean

1993 ◽  
Vol 73 (1) ◽  
pp. 179-180
Author(s):  
G. R. Ablett ◽  
J. W. Tanner
Keyword(s):  
Glycine Max ◽  
Key Words ◽  
Root Rot ◽  
Yield Potential ◽  
Maturity Group ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Glycine Max L ◽  
Cultivar Description ◽  
Late Maturity

RCAT Angora is a mid-late Maturity Group II soybean (Glycine max (L.) Merr.) cultivar with excellent yield potential and resistance to most races of phytophthora root rot caused by Phytophthora megasperma f. sp. glycinea (RMG) found in Ontario. Key words: Soybean, cultivar description

EFFECT OF Phytophthora megasperma ON YIELD AND SURVIVAL OF RESISTANT AND SUSCEPTIBLE ALFALFA CULTIVARS

1981 ◽  
Vol 61 (4) ◽  
pp. 955-960 ◽  
Author(s):  
M. A. FARIS ◽  
F. E. SABO
Keyword(s):  
Root Rot ◽  
Field Conditions ◽  
Yield Potential ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Resistant Cultivars ◽  
Central Experimental Farm

Performance of some artificially inoculated Phytophthora root rot (PRR) resistant and susceptible alfalfa cultivars was determined under field conditions at the Central Experimental Farm, Ottawa. Yields of both resistant and susceptible cultivars were reduced after inoculation; however, the resistant cultivars outyielded the susceptible ones. The resistant, inoculated cultivars showed less winterkill. There is still a need for improving PRR resistance in alfalfa, and thus increasing yield potential.

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