James D. McCreight

Melon: Cucumis melo L.

Publisher Summary Melon is a member of the genus Cucumis, subtribe Cucumerinae, tribe Melothrieae, subfamily Cucurbitoideae, and family Cucurbitaceae. Immature melons are used fresh in salads, cooked—soup, stew, curry, stir-fry—or pickled. Mature fruit is eaten fresh as a dessert fruit or in a canned form or used for syrup or jam; dehydrated slices—lightly processed—for short-term or moderate-term storage can be reconstituted, and the pressed juice may be canned. Melon seeds are a dietary source of unsaturated vegetable oil and protein and may be lightly roasted and eaten like nuts. Melon has a base chromosome number of 12 and is a diploid species, 2n = 24. Polysomatic cells regularly occur in melon. Seven polyploid—allopolyploid and autopolyploid—Cucumis species occur but none appears to be closely related to melon. The 96 genes reported in melon can be roughly classified into six categories with different categories and number of genes in each: (1) plant, 24, (2) flower, 16, (3) fruit, 19, (4) disease resistance, 22, (5) insect resistance, 5, and (6) isozyme, 14. Inheritance and dominance relationships of economically important plant and fruit characters of melon are not as simple as their quantitative descriptions and gene symbols imply. Sex expression is one of the more challenging genetic problems in front of melon breeders. This chapter discusses the germplasm resources and reproductive biology of melon. It further reviews the selection of breeding methods for melon and the breeding methods and strategies used for melon. It also discusses some objectives of breeding in melon.

Effect of planting date, cultivar, and stage of plant development on incidence of fusarium wilt of lettuce in desert production fields

Fusarium wilt of lettuce, first recognized in Japan in 1955, has since been discovered in the United States (California in 1990, Arizona in 2001), Iran (1995), Taiwan (1998), and Italy (2001). In Arizona, the causal agent, Fusarium oxysporum f. sp. lactucae, has been recovered from lettuce plants in 27 different lettuce fields during the 2001 to 2003 production seasons. Studies were initiated to examine the impact of planting date, cultivar, and stage of plant development on the incidence of disease in the field. In 2002 and 2003, tested lettuce cultivars were sown in at least one of the following planting windows; early-season (September), mid-season (October), and late-season (December). Within each planting window, significant differences in disease incidence among lettuce cultivars were noted at plant maturity. The mean incidence of Fusarium wilt on cultivars sown in September, October, and December was 92.3, 15.1, and 2.0%, respectively, in 2002 and 74.2, 5.1, and 0.7%, respectively, in 2003. The mean soil temperatures at the10-cm depth during the September, October, and December plantings for both years were 26, 14, and 14°C, respectively. Initial symptoms of Fusarium wilt were apparent as early as 14 days after seeding, with increasing incidence of disease noted as the crop developed and reached maturity. Among all lettuce cultivars planted in September, only one and two cultivars of romaine in 2002 and 2003, respectively, reached maturity with ≤5% incidence of Fusarium wilt, whereas the lowest incidence of disease among crisphead, green leaf, red leaf, or butterhead cultivars was 73.7, 27.0, 20.2, and 65.7%, respectively, in 2002 and 62.1, 29.0, 100, and 100%, respectively, in 2003. For October plantings, all romaine cultivars had ≤5% incidence of Fusarium wilt at maturity, whereas disease incidence among tested cultivars of crisphead lettuce in 2002 and 2003 ranged from 0.8 to 66.8% and 0.3 to 43.3%, respectively. When planted in December, 82 and 88% of tested cultivars, including all romaine entries, reached maturity with ≤1% incidence of Fusarium wilt. Selection of appropriate lettuce cultivars and planting times should allow successful production of lettuce in the southwestern Arizona production region with minimal or no incidence of disease in fields infested with F. oxysporum f. sp. lactucae. On the other hand, successful production of lettuce in infested fields when temperatures favor disease development will not be possible until lettuce cultivars are developed that possess high tolerance or resistance to the pathogen.

Cucurbit powdery mildews: methodology for objective determination and denomination of races

Cucurbit powdery mildew (CPM), a disease on field and greenhouse cucurbit crops worldwide, is caused most frequently by two obligate erysiphaceous ectoparasites (Golovinomyces orontii s.l., Podosphaera xanthii) that are highly variable in their pathogenicity and virulence. Various independent systems of CPM race determination and denomination are used worldwide, having to date been differentiated on different cultivars or lines of melon (Cucumis melo L.). We briefly review historical perspectives and the current state of understanding of the virulence variation of the two CPM pathogens at the pathogenic race level, their differentiation and their designation. Furthermore, we propose for use by the international CPM research, breeding, seed and production community new tools to enhance research, communication and management of CPM. These tools consist of five components: 1) a set of 21 differential genotypes of Cucumis melo L. for the identification of CPM races; 2) a triple-part, septet code for meaningful, concise designation of CPM races; 3) protocols for maintaining CPM isolates and differential genotypes and for laboratory assays to examine the virulence of CPM isolates; 4) rules and principles of practical application of this system in breeding, seed production and cucurbit growing, including a proposal of a race denomination suitable for practical application; and 5) crucial activities leading to the implementation and running of new tools for CPM research and management. The five components of this package have equal importance, forming a compact system, and none of them can be omitted.

Host-Specific Relationship Between Virus Titer and Whitefly Transmission of Cucurbit yellow stunting disorder virus

Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus, family Closteroviridae) was identified in the melon (Cucumis melo) production regions of the desert southwestern United States in fall 2006. It is now well established in the region, where it is transmitted efficiently by the sweet potato whitefly, Bemisia tabaci biotype B (MEAM1). In order to evaluate the spread and establishment of the virus, nearly all spring and fall cucurbit fields planted in the Imperial Valley of California from 2007 to 2009 were surveyed and representative plants were tested for CYSDV infection. Incidence of CYSDV in spring melon fields was initially low and limited to a small number of fields in 2007 but increased to 63% of fields by spring 2009. Virus incidence in fall melon fields was 100% in each year. These results suggested that the virus had become established in native vegetation, weeds, and other crop species, and represented an increasing threat to melon production in the southwestern United States. Therefore, a select set of weed and crop species which grow or are cultivated in the Imperial Valley were evaluated as CYSDV reservoir hosts. For each species, we determined the capacity of CYSDV to accumulate, the relationship between virus titer in these source plants and transmission by whiteflies, as well as subsequent accumulation in inoculated cucurbit plants. Among these hosts, there was considerable variation in virus accumulation and transmission rates. Cucurbit hosts had the highest CYSDV titers, were efficient sources for virus acquisition, and showed a positive correlation between titer in source plants and transmission. Noncucurbit hosts had significantly lower CYSDV titers and varied in their capacity to serve as sources for transmission. CYSDV titers in some noncucurbit source plants, specifically common bean (Phaseolus vulgaris) and shepherds purse (Capsella bursa-pastoris), were not positively correlated with transmission, demonstrating that additional environmental, physical, or biochemical factors were involved. These results demonstrate that multiple factors influence the efficiency with which a host plant species will be a reservoir for vector transmission of virus to crops.

Genome-Wide Differentiation of Various Melon Horticultural Groups for Use in GWAS for Fruit Firmness and Construction of a High Resolution Genetic Map.

Melon (Cucumis melo L.) is a phenotypically diverse eudicot diploid (2n = 2x = 24) has climacteric and non-climacteric morphotypes and show wide variation for fruit firmness, an important trait for transportation and shelf life. We generated 13,789 SNP markers using genotyping-by-sequencing (GBS) and anchored them to chromosomes to understand genome-wide fixation indices (Fst) between various melon morphotypes and genomewide linkage disequilibrium (LD) decay. The FST between accessions of cantalupensis and inodorus was 0.23. The FST between cantalupensis and various agrestis accessions was in a range of 0.19–0.53 and between inodorus and agrestis accessions was in a range of 0.21–0.59 indicating sporadic to wide ranging introgression. The EM (Expectation Maximization) algorithm was used for estimation of 1436 haplotypes. Average genome-wide LD decay for the melon genome was noted to be 9.27 Kb. In the current research, we focused on the genome-wide divergence underlying diverse melon horticultural groups. A high-resolution genetic map with 7153 loci was constructed. Genome-wide segregation distortion and recombination rate across various chromosomes were characterized. Melon has climacteric and non-climacteric morphotypes and wide variation for fruit firmness, a very important trait for transportation and shelf life. Various levels of QTLs were identified with high to moderate stringency and linked to fruit firmness using both genome-wide association study (GWAS) and biparental mapping. Gene annotation revealed some of the SNPs are located in β-D-xylosidase, glyoxysomal malate synthase, chloroplastic anthranilate phosphoribosyltransferase, and histidine kinase, the genes that were previously characterized for fruit ripening and softening in other crops.

Histological aspects of Cucumis melo PI 313970 resistance to Podosphaera xanthii and Golovinomyces cichoracearum.

Cucumis melo accession PI 313970 possesses numerous genes for race-specific resistance to powdery mildew incited by Podosphaera xanthii. It also exhibits resistant blister (RB) leaf reactions, characteristic for non-race-specificity, to several races of P. xanthii in California, U.S.A. Microscopic examination confirmed the presence of mycelia, conidiophores and conidia, and limited number of necrotic cells within and limited to RB tissue. PI 313970 was susceptible to inoculation with Czech isolates of P. xanthii and Golovinomyces cichoracearum on leaf discs. Frequency of conidial germination did not differ between pathogen species, or between PI 313970 and the susceptible cucumber cv. ‘Stela’ control, but number of germ tubes and appressoria, mycelial growth and conidial production of both pathogens through 144 hours post-inoculation were reduced in comparison with the susceptible control. Hypersensitive responses (HR) were not observed in ‘Stela’, but occurred to a limited extent in PI 313970 where = 3% of examined sites had necrotic spots. These responses indicate two different resistance mechanisms to these powdery mildew isolates in PI 313970. The first mechanism targets conidial germination and appressoria formation. The second mechanism reduces pathogen growth and reproduction with minimal or no HR involvement and may be influenced by the first mechanism. Resistant blisters, observed only on intact leaves evidence a third and non-race-specific mechanism to P. xanthii and G.cichoracearum in PI 313970, based on our histological study.ZusammenfassungDie Akzession PI 313970 der Melone (Cucumis melo) besitzt zahlreiche rassenspezifische Resistenzgene gegenüber dem durch Podosphaera xanthii verursachten Echten Gurkenmehltau. Sie bildet darüber hinaus blasenförmige, nicht rassenspezifische Resistenzsymptome gegenüber zahlreichen kali- fornischen Rassen dieses Erregers auf den Blättern aus. Mikroskopische Untersuchungen bestätigten das Vorhandensein von Myzel, Konidiophoren und Konidien sowie eine begrenzte und auf das blasenförmig umgewandelte Gewebe beschränkte Anzahl nekrotisierter Zellen. Blattscheiben der Melonenakzession PI 313970 waren änfällig gegenüber tschechischen Isolaten von P. xanthii und des zweiten Erregers des Echten Gurkenmehltaus, Golovinomyces cichoracearum. Die Keimungsraten der Konidien unterschieden sich nicht zwischen den Erregerarten sowie zwischen PI 313970 und der als Kontrolle untersuchten anfälligen Gurkensorte ‘Stela’, aber die Anzahl der Keimschläuche und Appressorien, das Myzelwachstum und die Konidienbildung beider Erreger waren bis 144 Stunden nach der Inokulation gegenüber der anfälligen Kontrolle vermindert. Eine hypersensitive Reaktion wurde bei ‘Stela’ nicht beobachtet, während sie in begrenztem Umfang bei PI 313970 auftrat, wo = 3% der untersuchten Bereiche nekrotische Flecken aufwiesen. Diese Resistenzreaktionen von PI 313970 gegenüber den Erregern des Echten Gurkenmehltaus beruhen auf zwei verschiedenen Mechanismen. Der erste Resistenzmechanismus zielt auf die Konidienkeimung und die Appressorienbildung. Der zweite vermindert Wachstum und Vermehrung der Erreger mit minimaler oder nicht ausgelöster hypersensitiver Reaktion und könnte durch den ersten Mechanismus beeinflusst sein. Blasenförmige Blattveränderungen wurden nicht auf Blattscheiben, sondern nur auf intakten Blättern von PI 313070 mittels histologischer Verfahren beobachtet. Sie deuten auf das Vorhandensein eines dritten, nicht rassenspezifischen Resistenzmechanismus gegenüber P. xanthii und G. cichoracearum in PI 313970 hin.

Microwave enhanced staining for plant virus inclusions.

Plant virus inclusion bodies can be stained specifically with established staining methods for light microscopy. The procedure can be augmented by a short microwave treatment to provide better staining intensity and reduced staining time. The method is useful for preliminary sampling prior to collection for electron microscopy and for plant pathologists, plant breeders, and diagnosticians as a rapid means of plant virus characterization.

Cucurbits powdery mildew race identity and reaction of melon genotypes1

1. Manuscript received in Sep./2017 and accepted for publication in Dec./2017 (http://dx.doi.org/10.1590/1983-40632017v4749537). 2. Universidade Estadual Paulista “Júlio de Mesquita Filho”, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Produção Vegetal, Jaboticabal, SP, Brasil. E-mails: hudsonorabelo@gmail.com, lucasmelhorista@gmail.com, guilhermemdiniz@hotmail.com, marcusvmarin@gmail.com, leilatb@fcav.unesp.br. 3. United States Department of Agriculture, Agricultural Research Service, U.S. Agricultural Research Station, Salinas, CA, USA. E-mail: jim.mccreight@ars.usda.gov. Genetic resistance is one of the most suitable strategies to control cucurbit powdery mildew (CPM) on melon, incited by Podosphaera xanthii or Golovinomyces orontii. However, many races of these pathogens have been reported worldwide in recent years, what may compromise the effectiveness of this method. Thus, annual surveys of CPM races and the screening of germplasm for new sources of genetic resistance provide a vital support to melon breeding programs. This study aimed at identifying a natural population of CPM race under greenhouse conditions, as well as evaluating the reaction of local and exotic melon germplasm for CPM-resistance. CPM race identity was based on the reaction of eight race differentials: Védrantais, Nantais Oblong, PMR 45, PMR 5, WMR 29, Edisto 47, PI 414723 and PI 124111. Fifty-nine melon genotypes were evaluated, 53 of them being germplasm accessions, and six net melon elite-inbred lines, besides two net melon-type cultivars (Louis and Fantasy). Plants were evaluated using a visual scale for leaf lesions. The causal pathogen was confirmed to be P. xanthii, based on the presence of fibrosin bodies in conidia and the complete resistance response of winter melon (Benincasa hispida). Race 4 was identified for the first time in the São Paulo state, Brazil. Genotypes A19, A30, A32, C67, C384, JAB-3, JAB-7, JAB-9, JAB-11, JAB-18, JAB-20 and Solarking showed to be resistant to the race 4.

Cucurbit Genomics Database (CuGenDB): a central portal for comparative and functional genomics of cucurbit crops

Abstract The Cucurbitaceae family (cucurbit) includes several economically important crops, such as melon, cucumber, watermelon, pumpkin, squash and gourds. During the past several years, genomic and genetic data have been rapidly accumulated for cucurbits. To store, mine, analyze, integrate and disseminate these large-scale datasets and to provide a central portal for the cucurbit research and breeding community, we have developed the Cucurbit Genomics Database (CuGenDB; http://cucurbitgenomics.org) using the Tripal toolkit. The database currently contains all available genome and expressed sequence tag (EST) sequences, genetic maps, and transcriptome profiles for cucurbit species, as well as sequence annotations, biochemical pathways and comparative genomic analysis results such as synteny blocks and homologous gene pairs between different cucurbit species. A set of analysis and visualization tools and user-friendly query interfaces have been implemented in the database to facilitate the usage of these large-scale data by the community. In particular, two new tools have been developed in the database, a ‘SyntenyViewer’ to view genome synteny between different cucurbit species and an ‘RNA-Seq’ module to analyze and visualize gene expression profiles. Both tools have been packed as Tripal extension modules that can be adopted in other genomics databases developed using the Tripal system.

Cucurbit Powdery Mildew-resistant Bitter Gourd Breeding Lines Reveal Four Races of Podosphaera xanthii in Asia

Bitter gourd (Momordica charantia L.) is a commercially and nutritionally important market vegetable in Asia cultivated mainly by smallholder farmers. Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is a nearly ubiquitous and serious fungal disease of bitter gourd. Five bitter gourd breeding lines (THMC 113, THMC 143, THMC 153, THMC 167, and THMC 170) were selected at theWorld Vegetable Center for resistance to a local isolate of Px in Kamphaeng Saen, Thailand.We evaluated the resistance potential of these five inbred lines against local isolates of Px at 12 locations in five Asian countries. Plants were inoculated with the respective local Px isolate 15 and 30 days after transplanting and additional Px-infected plants of the inoculated control were interplanted throughout each test. Plants were rated 60 days after transplanting for CPM reaction using a 0 (no evidence of infection) to 5 (>75% infection evident on individual leaves) disease severity scale. THMC 153 and THMC 167 were resistant to the local race of Px in all locations, whereas THMC 143 was observed resistant in all test locations except one in China. THMC 113 was resistant in each location except one in India. THMC 170 was susceptible in three locations in India. The multilocation tests revealed four unique Px races on bitter gourd in different Asian countries and sources of resistance for breeding CPM-resistant bitter gourd cultivars. Six strains of Px isolated from other cucurbits (Cucumis and Cucurbita) and representing five melon CPM races were unable to infect the susceptibleM. charantia accession THMC 144 and the five resistant breeding lines, indicating pathotype differences between them and an isolate of M. charantia origin typed as race 1 on melon. THMC 143 and THMC 167, which originated from India, exhibited good yield potential in trials conducted in Thailand, Myanmar, Vietnam, and Bangladesh. HORTSCIENCE VOL. 53(3) MARCH 2018 337 Bitter gourd (M. charantia L.) is an important cucurbitaceous market vegetable in Asia, where more than 340,000 ha are devoted to its cultivation annually (McCreight et al., 2013). Its cultivation is gaining popularity in some African countries such as Ghana, Zambia, Congo, and Madagascar for local consumption or for export to Europe and the Middle East to cater the demand of emigrant Asian communities. It is also cultivated to a lesser extent in the southern United States and Australia (Northern Territory, Queensland, New South Wales, and Victoria), where popular Asian hybrid cultivars are cultivated for consumption mainly by ethnic communities from Asia (Morgan and Midmore, 2002). Bitter gourd fruit is a rich source of betacarotene, vitamin C, folic acid, magnesium, phosphorus, and potassium (Dhillon et al., 2017; Yuwai et al., 1991). The health and pharmacological properties of bitter gourd have been well documented (Tan et al., 2016). Currently, 422 million people worldwide have diabetes (World Health Organization, 2016) and Type 2 diabetes accounts for around 90% (379 million). Bitter gourd fruit is used in folk medicine to manage Type 2 diabetes (Abascal and Yarnell, 2005; Grover and Yadav, 2004; Lans, 2006). Cucurbit powdery mildew (CPM) caused by Px is a serious fungal foliar disease of cucurbit production in open fields and greenhouses. Disease outbreak brings reduction in plant growth, premature foliage loss, and reduction in yield and fruit quality (Keinath and DuBose, 2004). CPM on bitter gourd is currently controlled by fungicides, although fungicide resistance has developed in some areas (Lebeda et al., 2010; McGrath, 2006). The pathogen is highly variable in virulence and represented by many pathotypes (Lebeda et al., 2011) and races (Lebeda et al., 2016). The use of disease-resistant varieties is an economical and safe approach for disease management. Accessions resistant to CPM have been identified in melon (Cucumis melo; Dhillon et al., 2012), watermelon (Citrullus lanatus; Thomas et al., 2005), cucumber (Cucumis sativus; Block and Reitsma, 2005), squash (Cucurbita pepo; Lebeda and K rístkov a, 1996), pumpkin (Cucurbita moschata; Wessel-Beaver, 1993), and bottle gourd (Lagenaria siceraria; Kousik et al., 2008). Resistance to CPM is, however, often race-specific and not durable (Lebeda et al., 2008, 2016). Commercial cultivars of bitter gourd resistant to CPM are not currently available. We developed five inbred lines resistant to CPM after screening 150 accessions of a global collection of bitter gourd in the World Vegetable Center genebank against the local CPM population at Kamphaeng Saen (Thailand). A single resistant plant was identified in each of five segregating populations derived from five genebank accessions that originated from India, Thailand, Taiwan, and Belize. Multiple cycles of inbreeding and selection led to the development of the five CPM-resistant inbred lines. We evaluated four of these inbred lines in 2011 against local isolates of Px in Thailand, Taiwan, and the United States (South Carolina, Florida, California) (Dhillon et al., 2015). We report here the reactions of the five bitter gourd CPM-resistant inbred lines against local isolates of Px at 12 locations in five Asian countries (China, India, Thailand, Vietnam, and Philippines) in 2013 and 2014. In addition, we sought to relate Asian CPM– bitter gourd interactions to the more developed body of knowledge of CPM–melon interactions, first by challenging these lines with European and the Mediterranean CPM isolates, and second by challenging a set of melon CPM race differentials with a singlespore strain isolated from a local isolate of Px on bitter gourd from Kamphaeng Saen, Thailand. The latter test also challenged representatives of cucumber, summer squash, and watermelon, cucurbit species on which few CPM races have been identified, with the exception of watermelon where four CPM races have been defined (Davis et al., 2007; Kousik et al., 2011; Mercier et al., 2014; Zhang et al., 2011). Furthermore, we evaluated horticultural fruit characters of the CPM-resistant bitter gourd breeding lines in the field test at Kamphaeng Saen, Thailand in 2014, and assessed the yield potential of two of the lines in Thailand, Myanmar, Vietnam, and Bangladesh in 2016, to assess their horticultural value as sources of CPM resistance. Materials and Methods Germplasm and field test sites. Five bitter gourd CPM-resistant inbred lines and a susceptible bitter gourd check line were evaluated against the respective local Px isolates at 12 locations in five countries in 2013 and 2014 (Table 1). Each field test was planted in a randomized complete block design with three replications of five plants per plot. Entries were planted on raised, 1.6-m wide beds covered with black plastic mulch. Plots were 5-m long on a single bed; each consisted of five transplants spaced 1-m apart. Plants were trellised on the plastic net erected on vertical bamboo poles. Field test. At each location, a spore suspension was prepared by detaching heavily sporulating leaves of susceptible THMC 144 and washing them with a spray of 100 mL of water and filtering through a double layer of cheesecloth. The suspension was diluted to a concentration of 4 · 10 conidia/mL of water as determined by a hemocytometer. This was freshly prepared as required for each inoculation. Seedlings were inoculated 15 and 30 d after transplanting, at the threeleaf stage of growth, at each location. The spore suspension was sprayed over the plants until runoff, by using a pressurized sprayer. THMC 144 plants with abundantly sporulating CPMwere used as spreader plants, placed between rows as additional sources of powdery mildew inoculum. Disease severity was rated on leaves of individual plants 30 d after the second inoculation using a 0–5 visual rating scale, where 0 = no symptom; 1 = 1% to 10%; 2 = 11% to 25%; 3 = 26% to 50%; 4 = 51% to 75%; and 5 = >75% of leaf surface covered by mycelium. Plant ratings of 0 and 1 were considered resistant. The susceptible check had a mean rating of 5.0 at all test locations. The 0–5 scale was converted to percentage usingmidpoints: 0 = 0%, 1= 5.5%, 2= 18%, 3= 38%, 4 = 63%, and 5 = 97% and the data were subjected to analysis of variance (ANOVA) using SAS general linear model (GLM) procedure (SAS Institute, Cary, NC). Mean separation was performed using Fisher’s least significant differences (LSD) at P# 0.05. Growth chamber tests. There were two growth chamber tests. The first evaluated the five breeding lines against European and Mediterranean CPM isolates, whereas the second evaluated various cucurbits with a single-spore CPM strain from Kamphaeng Saen, Thailand. Five plants, each of the five bitter gourd CPM-resistant inbred lines, and a susceptible check (Table 2) were inoculated at two-leaf stage, similarly as explained previously, with six CPM strains isolated from cucurbits in Europe and the Mediterranean area and typed for race on melon: Sm3 (race 1), S87-7 (race 2F), 00Sm39 (race 3), 98Sm65 (race 5), and 04Sm2 and 08Sm9 (race 3.5). A singlespore CPM strain isolated from M. charantia grown in an open field in Kamphaeng Saen, Thailand, was inoculated on five plants each of ‘Marketer’ cucumber, ‘Diamant’ summer squash, ‘Sugar Baby’ watermelon, and melon CPM race differentials [‘V edrantais’, ‘PMR 45’, ‘PMR 5’, WMR 29, PI 124112, 90625 (PI 313970), and AR Hale’s Best Jumbo]. Plants were raised in a glasshouse until the second leaf stage and then incubated after inoculation in a growth chamber (16 h day 26 C/8 h night 20 C) at GAFL, INRA, Montfavet, France. Disease severity was rated on leaves of individual plants after 10–14 d of inoculation, using 0–3 visual rating scale, where 0 = no visible Received for publication 2 Oct. 2017. Accepted for publication 11 Jan. 2018. Funding for this research was provided by the Federal Ministry for Economic Cooperation and Development, Germany (BMZ), Japan Ministry of Agriculture, Forestry and Fish