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.

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.

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.

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.

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.

Breeding disease resistant, aphid resistant lucerne for subtropical Queensland

1984 ◽  
Vol 24 (125) ◽  
pp. 178 ◽  
Author(s):  
RJ Clements ◽  
JW Turner ◽  
JAG Irwin ◽  
PW Langdon ◽  
RA Bray
Keyword(s):  
Acyrthosiphon Pisum ◽  
Crown Rot ◽  
Research Station ◽  
Preliminary Evaluation ◽  
Progeny Testing ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Colletotrichum Trifolii ◽  
Winter Activity ◽  
Better Than

The breeding and preliminary evaluation of two new lucerne cultivars are described. Each is shown to possess a satisfactory level of resistance to Phytophthora megasperma f.sp. medicaginis (Phytophthora root rot), Colletotrichum trifolii (Colletotrichum crown rot), Therioaphis trifolii f, maculata (spotted alfalfa aphid) and Acyrthosiphon pisum (pea aphid) and a lower but adequate level of resistance to A. kondoi (blue-green aphid). The first cultivar, code-named APC Cycle 3 and subsequently released as cv. Trifecta, is a broadly based cultivar with a genetic background substantially based on cv. Hunter River. In a field trial at Gatton Research Station, it outyielded cv. CUF 101 by 19%, cv. Siriver by 24% and cv. Hunter River threefold over a 16-month period, and persisted significantly better than those cultivars. It showed some winter activity and was classified as winter active in Queensland. Polycross progeny testing showed that APC Cycle 3 contains significant genetic diversity for yield and persistence, and further response to selection for these characters could be obtained. Heritabilities ranged from 0.79 to 0.86 for yield and persistence. A positive genetic correlation (rg= 0.87) between winter yield and main season yield was measured, and yield was positively correlated genetically with persistence. The second cultivar, code-named SP Cycle 3 and subsequently released as cv. Sequel, was derived from cvv. Siro Peruvian and CUF 101. It is highly winter active.

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

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.

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.

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.

scholarly journals Resistance to Phytophthora Species among Rootstocks for Cultivated Prunus Species

HortScience ◽  
2017 ◽  
Vol 52 (11) ◽  
pp. 1471-1476 ◽  
Author(s):  
Gregory T. Browne
Keyword(s):  
Root Rot ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Prunus Species ◽  
Phytophthora Megasperma ◽  
Soil Flooding ◽  
Root And Crown Rot ◽  
Crown And Root Rot ◽  
Multiple Species

Many species of Phytophthora de Bary are important pathogens of cultivated Prunus L. species worldwide, often invading the trees via their rootstocks. In a series of greenhouse trials, resistance to Phytophthora was tested in new and standard rootstocks for cultivated stone fruits, including almond. Successive sets of the rootstocks, propagated as hardwood cuttings or via micropropagation, were transplanted into either noninfested potting soil or potting soil infested with Phytophthora cactorum (Lebert & Cohn) J. Schöt., Phytophthora citricola Sawada, Phytophthora megasperma Drechs, or Phytophthora niederhauserii Z.G. Abad & J.A. Abad. Soil flooding was included in all trials to facilitate pathogen infection. In some trials, soil flooding treatments were varied to examine their effects on the rootstocks in both the absence and presence of Phytophthora. Two to 3 months after transplanting, resistance to the pathogens was assessed based on the severity of root and crown rot. ‘Hansen 536’ was consistently more susceptible than ‘Lovell’, ‘Nemaguard’, ‘Atlas’, ‘Viking’, ‘Citation’, and ‘Marianna 2624’ to root and/or crown rot caused by P. cactorum, P. citricola, and P. megasperma. By contrast, susceptibility to P. niederhauserii was similarly high among all eight tested genotypes of peach, four genotypes of peach × almond, two genotypes of (almond × peach) × peach, and one genotype of plum × almond. Most plum hybrids were highly and consistently resistant to crown rot caused by P. niederhauserii, but only ‘Marianna 2624’ was highly resistant to both crown and root rot caused by all of the Phytophthora species. The results indicate that there is a broad tendency for susceptibility of peach × almond rootstocks and a broad tendency for resistance of plum hybrid rootstocks to multiple species of Phytophthora.

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