scholarly journals Melon-Powdery Mildew Interactions Reveal Variation in Melon Cultigens and Podosphaera xanthii Races 1 and 2

2006 ◽  
Vol 131 (1) ◽  
pp. 59-65 ◽  
Author(s):  
James D. McCreight
Keyword(s):  
Powdery Mildew ◽  
Virulence Factors ◽  
Cucumis Melo ◽  
Podosphaera Xanthii ◽  
Sphaerotheca Fuliginea ◽  
Race 1 ◽  
New Races ◽  
Race 2 ◽  
Serious Disease ◽  
Greenhouse Tests

Powdery mildew is a serious disease of melon (Cucumis melo L.) worldwide. Twenty-two melon cultigens have been used to define 22 reported races of the pathogen Podosphaera xanthii (sect. Sphaerotheca) xanthii (Castag.) U. Braun & N. Shish. Comb. nov. [syn. Sphaerotheca fuliginea (Schlecht. ex Fr.) Poll.]. Discrepancies in the reactions of eight cultigens to populations of P. xanthii races 1 and 2 in California, Japan, and Spain revealed genetic differences among them that can be used to differentiate P. xanthii race 1 and 2 populations in these countries. Implicit in these results is the existence of previously unknown virulence factors in these populations of P. xanthii races 1 and 2 that permit designation of new races of P. xanthii on melon. Synthesis of these results with previous reports resulted in the identification of 28 putative races of P. xanthii on melon that include eight variants of race 1 and six variants of race 2. Six of the cultigens exhibited resistant blisters in response to heavy infection by P. xanthii in field and greenhouse tests.

scholarly journals Genes for Resistance to Powdery Mildew Races 1 and 2U.S. in Melon PI 313970

HortScience ◽  
2003 ◽  
Vol 38 (4) ◽  
pp. 591-594 ◽  
Author(s):  
James D. McCreight
Keyword(s):  
Powdery Mildew ◽  
Cucumis Melo ◽  
Powdery Mildew Resistance ◽  
Dominant Gene ◽  
Recessive Gene ◽  
Sphaerotheca Fuliginea ◽  
Limited Data ◽  
Race 1 ◽  
Resistance Reaction ◽  
Greenhouse Tests

Powdery mildew is a major problem in melon (Cucumis melo L.) production worldwide. Three genes for resistance to Sphaerotheca fuliginea (Schlecht. ex Fr.) Poll. race 1 and race 2U.S. were identified in growth chamber and greenhouse tests in the cross of PI 313970 × `Top Mark'. A recessive gene conditioned resistance of true leaves to race 1. A recessive gene appeared to condition resistance of cotyledons to race 2U.S., although a second recessive gene may be involved. A semi-dominant gene conditioned resistance of true leaves to race 2U.S. Limited data suggested linkage of the recessive gene for resistance to race 1 and the semi-dominant gene for resistance to race 2U.S. The resistance reaction of PI 313970 to infection of true leaves by race 2U.S. included water-soaked spots and resistant blisters, but segregation data for the resistant blister reaction were inconclusive. Allelic relationships of these genes with previously reported melon powdery mildew resistance genes remain to be determined.

scholarly journals Occurrence of Podosphaera xanthii Race 2 on Cucumis melo in Brazil

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1161-1161 ◽  
Author(s):  
R. F. Kobori ◽  
O. Suzuki ◽  
R. Wierzbicki ◽  
P. T. Della Vecchia ◽  
L. E. A. Camargo
Keyword(s):  
Cucumis Melo ◽  
Fungal Growth ◽  
Sao Paulo ◽  
Podosphaera Xanthii ◽  
São Paulo ◽  
Erysiphe Cichoracearum ◽  
Summer Squash ◽  
Golovinomyces Cichoracearum ◽  
Race 1 ◽  
Race 2

Powdery mildew is an important disease of melons (Cucumis melo L.) cultivated in greenhouses in Brazil. Currently, there are 5 races of Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) and 2 races of Golovinomyces cichoracearum (formerly known as Erysiphe cichoracearum) described on melons worldwide, but only race 1 of P. xanthii has been reported in Brazil (1). However, typical whitish powdery fungal growth was observed on an experimental hybrid yellow melon resistant to race 1 of P. xanthii during the summer of 2000 in a greenhouse in Bragança Paulista, State of São Paulo. Conidia collected from diseased leaves were spread onto 0.5% water agar medium and maintained at 22°C for 24 h with 12 h of light and 12 h of darkness. Most of the germinated conidia displayed fibrosin inclusion bodies when observed in a solution of 3% potassium hydroxide (KOH), and approximately 1 of 50 also displayed forked germ tubes. These features allowed us to identify P. xanthii as the causal agent. Conidia raised on the susceptible yellow melon ‘Amarelo CAC’ were used to inoculate cotyledons of the differential melon lines (2) ‘Hale's Best Jumbo’ (susceptible to races 1, 2, and 3 of P. xanthii), ‘PMR-45’ (resistant to race 1 and susceptible to races 2 and 3), and ‘PMR-6’ (resistant to races 1 and 2 and susceptible to race 3). Inoculations were performed on 10 plants of each differential line and replicated four times. The presence or absence of symptoms was evaluated 18 days after inoculation. ‘Hale's Best Jumbo’ and ‘PMR-45’ were rated as susceptible while ‘PMR-6’ was rated as resistant, thus indicating the presence of race 2 of P. xanthii in Brazil. During field surveys from 2001 to 2003, this race was found on squash (Cucurbita moschata), summer squash (C. pepo), and melons in São Paulo. References: (1) F. J. B. Reifschneider et al. Plant Dis. 69:1069, 1985. (2) C. E. Thomas et al. Cucurbit Genet. Coop. 7:126, 1984.

scholarly journals FIELD EVIDENCE FOR A NEW RACE OF POWDERY MILDEW ON MELON

HortScience ◽  
2005 ◽  
Vol 40 (3) ◽  
pp. 888a-888 ◽  
Author(s):  
James D. McCreight ◽  
Michael D. Coffey ◽  
Thomas A. Turini ◽  
Michael E. Matheron
Keyword(s):  
Powdery Mildew ◽  
Powdery Mildew Resistance ◽  
Genetic Resistance ◽  
Podosphaera Xanthii ◽  
Sphaerotheca Fuliginea ◽  
Imperial Valley ◽  
Field Evidence ◽  
Race 1 ◽  
New Race ◽  
The U.S

Races 1 and 2 of Podosphaera xanthii (syn. Sphaerotheca fuliginea) were defined in Imperial Valley, Calif. 1938 when P. xanthii overcame genetic resistance in `PMR 45'. Race 3 was first observed in the U.S. in 1976 in Texas; 15 additional races of P. xanthii have been reported in the literature since 1996. Races 1 and 2 have been common in Arizona and California based upon the effectiveness of the powdery mildew resistance genes in commercially available melon cultivars grown in these states. Field data from 11 commonly used melon P. xanthii race differentials in 2001 and 2002 indicated the presence of race 1 in the Imperial Valley and San Joaquin Valley of California, and Yuma, Arizona. In spring 2003, the powdery mildew race situation changed. The first evidence was the occurrence of a severe and widespread infection of powdery mildew in a commercial cantaloupe field. The 11 powdery mildew race differentials were susceptible to powdery mildew in a nearby replicated field test. PI 313970, a melon from India, was resistant to this apparent new race of powdery mildew.

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.

scholarly journals CHARACTERIZATION OF RESISTANCE TO ROOT-KNOT NEMATODES IN SWEETPOTATO

HortScience ◽  
2005 ◽  
Vol 40 (3) ◽  
pp. 868e-869
Author(s):  
J.A. Thies
Keyword(s):  
Meloidogyne Incognita ◽  
Ipomoea Batatas ◽  
Nematode Species ◽  
Plant Introduction ◽  
Root Knot Nematode ◽  
Race 1 ◽  
Race 2 ◽  
The U.S ◽  
Greenhouse Tests

Thirteen sweetpotato (Ipomoea batatas) genotypes were characterized for resistance to Meloidogyne incognita, M. javanica, M. hapla, and M. arenaria races 1 and 2 in greenhouse tests. The following sweetpotato genotypes representing a range of reactions to M. incognita were evaluated: U.S. Plant Introduction (PI) 399163 (highly resistant = HR), Sumor (HR), Nemagold (HR), Excel (HR), Tinian (HR), Hernandez (resistant = R), Jewel (R), Regal (R), Porto Rico (intermediate = I), Centennial (susceptible = S), Georgia Jet (S), Sulfur (S), and Beauregard (S). Meloidogyne incognita was most pathogenic to sweetpotato of the four Meloidogyne spp. evaluated in these studies. The U.S. Plant Introduction (PI) 399163 and Sumor were resistant to M. incognita in all tests. Only two genotypes, Beauregard and Porto Rico, were susceptible to M. javanica. All genotypes evaluated were resistant to M. hapla, M. arenaria race 1, and M. arenaria race 2. Sumor, U.S. PI 399163, and Nemagold appear to provide the highest levels of resistance against the four Meloidogyne spp. used in these studies. Since M. incognita is the most commonly occurring root-knot nematode species in sweetpotato growing areas of the southern U.S. and is pathogenic to most of the commonly grown sweetpotato cultivars, efforts to develop resistant cultivars that have desirable horticultural characteristics for the U.S. market should be directed toward this root-knot nematode species.

scholarly journals `PMR Delicious 51': An Improved Open-pollinated Melon with Resistance to Powdery Mildew

HortScience ◽  
2005 ◽  
Vol 40 (1) ◽  
pp. 261-262 ◽  
Author(s):  
Mark J. Henning ◽  
Henry M. Munger ◽  
Molly M. Jahn
Keyword(s):  
Powdery Mildew ◽  
Plant Breeding ◽  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Cucumis Melo ◽  
Agricultural Experiment Station ◽  
Cornell University ◽  
Experiment Station ◽  
Agricultural Experiment ◽  
Race 2

`PMR Delicious 51' is a new and improved version of the `Delicious 51' eastern type melon (Cucumis melo L.). It was developed in the Department of Plant Breeding at the Cornell University Agricultural Experiment Station in Ithaca, N.Y. It is well adapted for northeastern U.S. conditions and shows potential for good adaptation in the northwest. It is well suited for home gardeners, market gardeners, and commercial growers who want to grow an open-pollinated (OP) melon. `PMR Delicious 51' has excellent resistance to powdery mildew races 1 and 2 (Podosphaera xanthi) and resistance to fusarium wilt (Fusarium oxysporum f. sp. melonis) race 2.

scholarly journals Potential Sources of Resistance to Fusarium Wilt and Powdery Mildew in Melons

HortScience ◽  
2005 ◽  
Vol 40 (6) ◽  
pp. 1657-1660 ◽  
Author(s):  
José María Alvarez ◽  
Rafael González-Torres ◽  
Cristina Mallor ◽  
María Luisa Gómez-Guillamón
Keyword(s):  
Powdery Mildew ◽  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Cucumis Melo ◽  
Wild Relatives ◽  
Natural Resistance ◽  
Sphaerotheca Fuliginea ◽  
Sources Of Resistance ◽  
Potential Sources ◽  
Artificial Inoculations

In total, 139 Cucumis melo accessions were evaluated for resistance to races 0, 1, and 2 of Fusarium oxysporum fsp. melonis and 127 accessions were evaluated for resistance to races 1 and 2 of Sphaerotheca fuliginea. In addition, seven C. melo wild relatives were also tested. Artificial inoculations were performed and plants were scored for presence or absence of symptoms. The screening revealed that sources of natural resistance to these fungi are limited. However, several sources of resistance were found in C. melo accessions. Thus, the accession `CUM-334' from Tajikistan has shown resistance to the three races of F. oxysporum fsp. melonis, behaving similarly to the melon inbred line `MR1'. Two accessions of C. melo var. conomon, `CUM-190' and `Shiroubi Okayama', from Japan, were resistant to races 0 and 1 and twelve accessions were resistant to races 0 and 2. Intra-specific variability for resistance to powdery mildew in C. melo was found to be poor. Nevertheless, six Spanish cultivars and the accessions `TGR-1551', `CUM-313', and `CUM-129' were resistant to races 1 and 2 of S. fuliginea.

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