The location and characteristics of novel sources of resistance to Bremia Lactucae Regel (downy mildew) in wild Lactuca L. Species

Euphytica ◽  
1981 ◽  
Vol 30 (3) ◽  
pp. 659-668 ◽  
Author(s):  
Judith M. Norwood ◽  
I. R. Crute ◽  
A. Lebeda
Keyword(s):  
Downy Mildew ◽  
Bremia Lactucae ◽  
Sources Of Resistance

scholarly journals Mutants of downy mildew resistance in Lactuca sativa (lettuce).

Genetics ◽  
1994 ◽  
Vol 137 (3) ◽  
pp. 867-874
Author(s):  
P A Okubara ◽  
P A Anderson ◽  
O E Ochoa ◽  
R W Michelmore
Keyword(s):  
Molecular Marker ◽  
Downy Mildew ◽  
Genomic Dna ◽  
Spontaneous Mutation ◽  
Multigene Families ◽  
Downy Mildew Resistance ◽  
Bremia Lactucae ◽  
Wild Type ◽  
Mildew Resistance ◽  
Recessive Mutations

Abstract As part of our investigation of disease resistance in lettuce, we generated mutants that have lost resistance to Bremia lactucae, the casual fungus of downy mildew. Using a rapid and reliable screen, we identified 16 distinct mutants of Latuca sativa that have lost activity of one of four different downy mildew resistance genes (Dm). In all mutants, only a single Dm specificity was affected. Genetic analysis indicated that the lesions segregated as single, recessive mutations at the Dm loci. Dm3 was inactivated in nine of the mutants. One of five Dm 1 mutants was selected from a population of untreated seeds and therefore carried a spontaneous mutation. All other Dm1, Dm3, Dm5/8 and Dm7 mutants were derived from gamma- or fast neutron-irradiated seed. In two separate Dm 1 mutants and in each of the eight Dm3 mutants analyzed, at least one closely linked molecular marker was absent. Also, high molecular weight genomic DNA fragments that hybridized to a tightly linked molecular marker in wild type were either missing entirely or were truncated in two of the Dm3 mutants, providing additional evidence that deletions had occurred in these mutants. Absence of mutations at loci epistatic to the Dm genes suggested that such loci were either members of multigene families, were critical for plant survival, or encoded components of duplicated pathways for resistance; alternatively, the genes determining downy mildew resistance might be limited to the Dm loci.

scholarly journals Identification of new Bremia lactucae races in lettuce in São Paulo state

2012 ◽  
Vol 30 (2) ◽  
pp. 209-213 ◽  
Author(s):  
Renata Castoldi ◽  
Hamilton César de O Charlo ◽  
Tagli Dalpian ◽  
Danilo M Melo ◽  
Adelita P Botelho ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Sao Paulo ◽  
Leafy Vegetable ◽  
Susceptible Cultivar ◽  
São Paulo ◽  
Bremia Lactucae ◽  
Paulo State ◽  
São Paulo State

Lettuce is the most consumed leafy vegetable in Brazil. However, its production has faced increasing difficulties mainly due to the infestation of producing areas with Bremia lactucae, the causing agent of downy mildew, the worst disease in lettuce. The aim of this study was to identify B. lactucae races occurring in lettuce producing areas of São Paulo state, during 2008 and 2009. Lettuce leaf samples containing B. lactucae sporangia were collected in the major lettuce producing areas of São Paulo. Each sample was considered an isolate. After the multiplication of sporangia in the susceptible cultivar Solaris, with subsequent inoculation in the differentiating cultivars, the evaluations were performed on the same day of the first sporulation in the susceptible cultivar 'Cobham Green (DM 0)'. In 2008 one new B. lactucae code was identified. SPBl:05 was the denomination proposed to it. In 2009 one another B. lactucae code was identified, that is, 63/63/02/00, whose denomination was proposed to be SPBl:06.

scholarly journals Identification of new resistant sources against downy mildew disease from a selected set of cucumber germplasm and its wild relatives

2020 ◽  
Vol 80 (04) ◽  
Author(s):  
Jameel Akhtar ◽  
Dikshant Gautam ◽  
Ranjan Nath ◽  
A. B. Gaikwad ◽  
K. V. Bhat ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Plant Disease ◽  
Mapping Population ◽  
Disease Index ◽  
Sources Of Resistance ◽  
Resistant Accession ◽  
Genomic Regions ◽  
Moderately Resistant ◽  
Agroclimatic Zones ◽  
Downy Mildew Disease

This study was undertaken to identify new sources of resistance against downy mildew of cucumber caused by Pseudoperonospora cubensis [(Berk. and Cart.) Rostow]. Pot experiments were conducted with 16 accessions each of Cucumis sativus and C. hardwickii during the years 2017 and 2018 using 12 isolates of P. cubensis representing different agroclimatic zones of India. The accession, IC331627 from Dehradun, Uttarakhand showed plant disease index (PDI) ranging from 5.55-20.35 per cent with an average PDI of 11.56 and 11.87 per cent during the years, 2017 and 2018, respectively. Hence, IC331627 was identified to be resistant against the five isolates of P. cubesis (Pc12, Pc17, Pc19, Pc21 and Pc24) and moderately resistant against one isolate (Pc22). This resistant accession C. hardwickii (IC331627) could be utilized to develop mapping population to map genomic regions conferring the resistance to downy mildew in cucumber.

scholarly journals First Report of Bremia lactucae Causing Downy Mildew on Helichrysum bracteatum in Italy

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 315-315 ◽  
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Downy Mildew ◽  
Morphological Characteristics ◽  
The United States ◽  
Northern Italy ◽  
Plant Diseases ◽  
Bremia Lactucae ◽  
First Report ◽  
Parasitic Fungi ◽  
Commercial Farms ◽  
Helichrysum Bracteatum

Helichrysum bracteatum, also known as strawflower, is commonly grown for the production of dried flowers and, more recently, as a potted plant. This latter cultivation system is becoming increasingly important on the Liguria Coast in northern Italy. During the spring of 2002, severe oubreaks of a previously unknown disease were observed in commercial farms in the area of Albenga (northern Italy) on several cultivars of H. bracteatum. Leaves of infected plants appeared curled and blistered; the infected portions of leaves turned chlorotic. On the lower leaf surface of chlorotic areas, a dense, whitish growth was evident. Infected leaves eventually wilted without dropping. Basal leaves with poor air circulation were the most severely affected. Certain cultivars of H. bracteatum (such as ‘Florabella Pink’) were most seriously affected, while others (‘Florabella Gold’ and ‘Florabella White’) had less disease. Microscopic observations revealed sporangiophores emerging from the stomata that were dichotomically branched, ending with 4 to 7 sterigmata. The sporangia were globose and measured 15.5 to 16.8 μm in diameter. The pathogen was identified as Bremia lactucae based on the morphological characteristics. Pathogenicity was confirmed by inoculating healthy H. bracteatum (100-day-old ‘Florabella Gold’) as well as Lactuca sativa (25-day-old ‘Salad bowl’) plants with a sporangial suspension (1 × 105 sporangia/ml). Five plants of H. bracteatum and 10 of lettuce were used as replicates. Noninoculated plants served as controls. Inoculated and uninoculated plants were maintained in a growth chamber at 20°C and 90 to 95% relative humidity. After 7 to 10 days, typical symptoms of downy mildew developed on H. bracteatum and lettuce plants artificially inoculated. Bremia lactucae was observed on infected leaves. Uninoculated plants did not show symptoms. To our knowledge, this is the first report of Bremia lactucae on H. bracteatum in Italy. B lactucae was previously reported as the causal agent of downy mildew on H. bracteatum in several countries including the United Kingdom (3), the United States (1), and Egypt (2). References: (1) S. A. Alfieri et al. Index of plant diseases in Florida. Bull No. 11, 1984. (2) H. Elarosi and M. W. Assawah. Rev. Plant Prot. Res., 39:583, 1959. (3) W. C. Moore. British Parasitic Fungi. Cambridge University Press, Cambridge, 1959.

scholarly journals Host interactors of effector proteins of the lettuce downy mildew Bremia lactucae obtained by yeast two-hybrid screening

PLoS ONE ◽  
2020 ◽  
Vol 15 (5) ◽  
pp. e0226540 ◽  
Author(s):  
Alexandra J. E. Pelgrom ◽  
Claudia-Nicole Meisrimler ◽  
Joyce Elberse ◽  
Thijs Koorman ◽  
Mike Boxem ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Effector Proteins ◽  
Bremia Lactucae ◽  
Yeast Two Hybrid ◽  
Lettuce Downy Mildew ◽  
Two Hybrid ◽  
Hybrid Screening

scholarly journals Insensitivity to the Fungicide Fosetyl-Aluminum in California Isolates of the Lettuce Downy Mildew Pathogen, Bremia lactucae

Plant Disease ◽  
2004 ◽  
Vol 88 (5) ◽  
pp. 502-508 ◽  
Author(s):  
Sarah Brown ◽  
Steven T. Koike ◽  
Oswaldo E. Ochoa ◽  
Frank Laemmlen ◽  
Richard W. Michelmore
Keyword(s):  
Quantitative Analysis ◽  
Downy Mildew ◽  
Mating Type ◽  
Control Measures ◽  
Bremia Lactucae ◽  
Widespread Occurrence ◽  
Lettuce Downy Mildew ◽  
Normal Field ◽  
Growth Room ◽  
Disease Pressure

Lettuce downy mildew, caused by Bremia lactucae, is the most important foliar disease of lettuce in California. In recent years, there were apparent failures of fungicides containing fosetyl-aluminum (Aliette) to control downy mildew in commercial lettuce fields in California. Consequently, we characterized 134 isolates collected over 2 years from throughout the coastal growing areas of California for insensitivity to the fungicides fosetyl-aluminum and maneb, pathotype, and mating type. Tests using seedlings in controlled growth room conditions demonstrated the widespread occurrence of insensitivity to fosetyl-aluminum in California populations of B. lactucae. Fifty percent of the isolates assayed sporulated profusely in the presence of fosetyl-aluminum applied at rates twice the normal field dosage, and an additional 40% showed moderate sporulation at this rate. Fosetyl-aluminum-insensitive isolates were detected from all regions sampled. Insensitivity was also observed in multiple pathotypes. Insensitivity was not complete, however, because quantitative analysis of the number of lesions on older plants revealed that applications of fosetyl-aluminum could reduce the levels of disease by 50%. Therefore, while fosetyl-aluminum may have utility under low disease pressure in the field, other control measures are required to provide control under conditions favorable to the disease.

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