Variation in Virulence Within Meloidogyne chitwoodi, M. fallax, and M. hapla on Solanum spp

ABSTRACT The virulence of Meloidogyne hapla, M. chitwoodi, and M. fallax was studied on genotypes of Solanum spp. in a greenhouse. Juveniles of 11 M. hapla race A isolates, 3 M. hapla race B isolates, and 5 mono-female lines of a M. hapla race A isolate were inoculated on S. chacoense, S. hougasii, and S. sparsipilum. Juveniles of eight M. chitwoodi isolates, five M. fallax isolates, and six mono-female lines of a M. chitwoodi isolate were inoculated on S. bulbocastanum, S. chacoense, S. hougasii, S. stoloniferum, and S. tuberosum. Virulence was expressed as nematode reproduction 8 weeks after inoculation. Nematode reproduction was estimated by the number of egg masses and, in one experiment, by the number of hatched second-stage juveniles per inoculated juvenile. Considerable variation in virulence and resistance was observed among M. hapla isolates and plant genotypes, respectively. The M. hapla isolate-plant species interaction was highly significant. The response to M. chitwoodi ranged from susceptible (S. tuberosum and S. chacoense) to highly resistant (S. bulbocastanum and S. hougasii). S. tuberosum was susceptible to M. fallax, whereas all four wild species were resistant. In contrast to M. hapla, no significant isolate-plant genotype interaction was obtained for M. chitwoodi or M. fallax, indicating no or little intraspecific variation in virulence. M. chitwoodi juveniles in species mixtures with M. fallax isolates appeared to be able to break the resistance of S. bulbocastanum and S. hougasii. Significant differences among mono-female lines of M. hapla and M. chitwoodi were observed, indicating heterogeneity of pathogenicity within meiotic parthenogenic Meloidogyne populations.     

Nematode quantitative resistance conferred by the pepper genetic background presents additive effects and is stable against different isolates of Meloidogyne incognita

Root‐knot nematodes (RKNs), Meloidogyne spp., are a major disease problem in solanaceous crops worldwide, including pepper (Capsicum spp.). Genetic control provides an economically and environmentally sustainable protection alternative to soil fumigants. In pepper, resistance to the main RKN species (M. incognita, M. javanica and M. arenaria) is conferred by the major genes (R genes) Me1, Me3 and N. However, RKNs are able to develop virulence, thus endangering the efficiency of R genes. Quantitative resistance (QR) against Meloidogyne spp. is expected to provide an alternative to R genes, or to be combined with R genes, to increase the resistance efficiency and durability in pepper. In order to explore the ability of QR to protect pepper against RKNs, five pepper inbred lines, differing in their QR level, were tested directly, or after combination with the Me1 and Me3 genes, for their resistance to a panel of M. arenaria, M. javanica and M. incognita isolates. The M. arenaria and M. javanica isolates showed low pathogenicity to pepper, unlike the M. incognita isolates. The QR, controlled by the pepper genetic background, displayed a high resistance level with a broad spectrum of action, protecting pepper against Me3‐virulent as well as avirulent M. incognita isolates. The QR was also expressed when combined with the Me1 and Me3 genes, but presented additive genetic effects so that heterozygous F₁ hybrids proved less resistant than homozygous inbred lines. The discovery of this QR is expected to provide promising applications for preserving the efficiency and durability of nematode resistance.     

Occurrence of virulent root-knot nematode populations on tomatoes bearing the <Emphasis Type="Italic">Mi</Emphasis> gene in protected vegetable-growing areas of Turkey

Root-knot nematodes (Meloidogyne spp.; RKN) are one of the most important pathogens of vegetables in Turkey. Assessing the existing virulent RKN populations is of importance for pathogen mapping in the west Mediterranean region of Turkey. Therefore, 95 populations of RKN were collected from different protected vegetable-growing locations in the region. Pure cultures were obtained and identified by means of species-specific primers. Virulence of the populations against the Mi-1 gene conferring resistance to Meloidogyne incognita, M. javanica and M. arenaria was determined according to their egg masses and gall rating on resistant and susceptible tomato varieties. Results showed that seven populations of M. incognita and six populations of M. javanica were able to overcome the resistance controlled by the Mi-1 gene. The frequency of virulent populations of M. incognita and M. javanica collected from different protected-grown vegetables was 11.7% and 21.4%, respectively. To our knowledge, this is the first report of populations of RKN virulent to the Mi-1 gene in Turkey.     

<Emphasis Type="Italic">Solanum sisymbriifolium</Emphasis> - a new approach for the management of plant-parasitic nematodes

Plant-parasitic nematodes are serious pests causing important crop losses worldwide. After extensive screening of non-tuber-bearing Solanaceae, a resistant trap crop, Solanum sisymbriifolium, with a high production level of hatching agents, seemed an ideal control method for potato cyst nematodes (PCN), Globodera spp. Recently, root-knot nematodes (RKN), Meloidogyne spp., were found coexisting with PCN. Therefore, it is important to find alternative methods to control both nematode genera. The chemical properties of S. sisymbriifolium turns this plant into an excellent candidate for further nematicidal studies and to develop new crop production models. Studies concerning the effects of this plant on plant-parasitic nematodes are presented. Pathogenicity studies with four S. sisymbriifolium cvs (Domino, Pion, Sis 4004 and Sharp) and five Meloidogyne species showed that all cultivars of S. sisymbriifolium studied were resistant to M. chitwoodi and hypersusceptible to M. arenaria and M. hapla. For M. hispanica only cv Pion was susceptible. M. javanica induced different responses: cvs Pion and Sharp were susceptible; cv Domino resistant and Sis 4004 hypersusceptible. The studies of the hatching effects of root exudates from these cvs showed that they had an influence on the hatching inhibition of second stage juveniles of the five Meloidogyne species tested.     

Suitability of weed species prevailing in Spanish vineyards as hosts for root-knot nematodes

Commercial vineyards in southern Spain were surveyed and sampled during October to December 2004 to determine the extent to which common weeds present were suitable hosts of root-knot nematodes infesting soils of those vineyards. Seven weed species commonly growing in grapevine soils in southern Spain were found infected by either Meloidogyne incognita or M. javanica: Amaranthus retroflexus (redroot pigweed), Anchusa azurea (ox-tongue), Chenopodium album (goosefoot), Erodium moschatum (musk stork’s bill), Malva rotundifolia (low mallow), Sinapis alba (white mustard), and Solanum nigrum (black nightshade). The host suitability of the weeds to root-knot nematodes was evaluated on the basis of root galling severity and nematode population densities in soil and roots. Also, the host–parasite relationship in these naturally Meloidogyne-infected weeds was examined. All the weed species in the study were considered suitable hosts for M. incognita and M. javanica because: (a) high Meloidogyne spp. populations occurred in roots and surrounding soil of the weed species; (b) the severity of root galling was high, and (c) well-established permanent feeding sites were observed in the histopathological studies of infected root tissues. In addition, this study presents the first reports of S. alba and A. azurea as hosts for M. incognita, and of E. moschatum as a new host for M. javanica, thus increasing the list of reported weed hosts for Meloidogyne spp. These results indicate that noticeable population densities of M. incognita and M. javanica can be maintained or increased in these weeds, at population levels higher than those previously reported for the same nematodes infecting grapevine roots. The weeds infesting vineyards thus represent an important source of inoculum of Meloidogyne spp., and furthermore may act as reservoirs of these nematodes which can be disseminated within or among vineyards by agricultural operations.     

茄子砧木根系苯丙烷类代谢与抗南方根结线虫水平的关系

采用盆栽幼苗人工接种方法,研究南方根结线虫侵染对茄子砧木幼苗根系苯丙氨酸解氨酶(PAL)、酪氨酸解氨酶(TAL)及多酚氧化酶(PPO)活性和总酚、木质素含量的影响.结果表明,无论是否遭受南方根结线虫侵染,幼苗根系PAL、TAL、PPO活性及总酚、木质素含量均以托鲁巴姆显著高于赤茄.虽然南方根结线虫侵染使2个茄子砧木幼苗根系苯丙烷类物质含量及相关酶活性均有所增加,但以托鲁巴姆增幅较大,其PAL、TAL、PPO活性及总酚、木质素含量的最大增幅较对照分别高67.87%、82.13%、32.19%、62.14%和20.91%,而赤茄仅分别较对照高47.13%、45.52%、18.08%、35.38%、14.86%.整个侵染进程中,托鲁巴姆始终表现出强烈的抗性反应,而赤茄除在初次侵染前期表现出一定的抗性反应外,其余时间反应较弱,尤其在遭受二次侵染时,抗性反应显著低于初次侵染.表明苯丙烷类代谢产物及关键酶与茄子砧木抗南方根结线虫水平密切相关.     

Ribosomal Intergenic Spacer: A Polymerase Chain Reaction Diagnostic for Meloidogyne chitwoodi, M. fallax, and M. hapla

ABSTRACT Polymerase chain reaction amplification of the intergenic spacer region between the 5S and 18S genes from Meloidogyne chitwoodi, M. fallax, and M. hapla enabled these three important temperate species to be differentiated. Length polymorphism was found between M. chitwoodi and M. fallax as a result of differing numbers of short repeats located between the 5S and 18S genes. The presence of the 5S gene within the rDNA cistrons was confirmed in the Meloidogyne spp. included in this study. The region between the 28S and 5S genes for M. chitwoodi and M. fallax was short and lacked variability in repeated sequences compared with the main tropical Meloidogyne spp. and M. hapla. Differences in the number of these repeats resulted in intraspecific length polymorphism for M.hapla.     

Distribution and genetic diversity of root‐knot nematodes (Meloidogyne spp.) in potatoes from South Africa

A molecular‐based assay was employed to analyse and accurately identify various root‐knot nematodes (Meloidogyne spp.) parasitizing potatoes (Solanum tuberosum) in South Africa. Using the intergenic region (IGS) and the 28S D2–D3 expansion segments within the ribosomal DNA (rDNA), together with the region between the cytochrome oxidase subunit II (COII) and the 16S rRNA gene of the mtDNA, 78 composite potato tubers collected from seven major potato growing provinces were analysed and all Meloidogyne species present were identified. During this study, M. incognita, M. arenaria, M. javanica, M. hapla, M. chitwoodi and M. enterolobii were identified. The three tropical species M. javanica, M. incognita and M. arenaria were identified as the most prevalent species, occurring in almost every region sampled. Meloidogyne hapla and M. enterolobii occurred in Mpumalanga and KwaZulu‐Natal, respectively, while M. chitwoodi was isolated from two growers located within the Free State. Results presented here form part of the first comprehensive surveillance study of root‐knot nematodes to be carried out on potatoes in South Africa using a molecular‐based approach. The three genes were able to distinguish various Meloidogyne populations from one another, providing a reliable and robust method for future use in diagnostics within the potato industry for these phytoparasites.     

Behaviour of Solanum spp. on inoculation with different isolates of Fusarium oxysporum f. sp. melongenae*

Twelve wild Solanum accessions were tested in a glasshouse at the seedling stage for resistance to Fusarium oxysporum f. sp. melongenae, the causal agent of fusarium wilt of aubergine. Four isolates of the fungus (three Turkish and one Italian) were used. Solanum incanum and S. linneanum were highly susceptible, whereas S. sisymbrifolium, S. torvum and S. aethiopicum Gilo group (one accession) were resistant. In Solanum aethiopicum Aculeatum (two accessions), S. aethiopicum Gilo, S. viarum and S. macrocarpon there were both resistant and susceptible individuals. The sources of resistance found in these wild Solanum spp. could be conveniently used to breed aubergine cultivars resistant to fusarium wilt.     

Cucumis metuliferus is resistant to root‐knot nematode Mi1.2 gene (a)virulent isolates and a promising melon rootstock

Pot experiments were carried out to characterize the response of two Cucumis metuliferus accessions (BGV11135 and BGV10762) against Mi1.2 gene (a)virulent Meloidogyne arenaria, M. incognita and M. javanica isolates and to determine the compatibility and the effect on physicochemical properties of fruit melons. In addition, histopathological studies were conducted. One week after transplanting, plants were inoculated with one J2 cm^?3 of sterilized sand (200 cm³ pots) and maintained in a growth chamber at 25 °C for 40 days. The susceptible cucumber cv. Dasher II or melon cv. Paloma were included for comparison. The number of egg masses and number of eggs per plant were assessed, and the reproduction index (RI) was calculated as the percentage of eggs produced on the C. metuliferus accessions compared to those produced on the susceptible cultivars. The compatibility and fruit quality were assessed by grafting three scions, two of Charentais type and one of type piel de sapo, under commercial greenhouse conditions. The resistance level of both C. metuliferus accessions ranged from highly resistant (RI < 1%) to resistant (1% ≤ RI ≤ 10%) irrespective of Meloidogyne isolates. Melon plants grafted onto C. metuliferus accession BGV11135 grew as self‐grafted plants without negatively impacting fruit quality traits. Giant cells induced by Meloidogyne spp. on C. metuliferus were in general poorly developed compared to those on cucumber. Furthermore, necrotic areas surrounding the nematode were observed. Cucumis metuliferus accession BGV11135 could be a promising melon rootstock to manage Meloidogyne spp., irrespective of their Mi1.2 (a)virulence, without melon fruit quality reduction.     

Reaction of a heterozygous tomato hybrid bearing the Mi-1.2 gene to 15 Meloidogyne species

Many root-knot nematode (RKN) species (Meloidogyne spp.) are polyphagous and cultivated tomato (Solanum lycopersicum) is one of their preferential hosts, leading to significant losses. It is known that the dominant Mi-1.2 gene in tomato confers resistance to the three most important RKN species—M. incognita, M. javanica, and M. arenaria, and minor species—M. ethiopica, M. hispanica, and M. luci. However, little information is available about resistance of tomatoes carrying this gene to other tomato-infecting RKN species. In this study, resistance conferred by the Mi-1.2 gene/locus was evaluated against populations of 15 Meloidogyne species, employing tomato cultivars Santa Clara (homozygous recessive mi-1.2/mi-1.2, susceptible) and Debora Plus (heterozygous Mi-1.2/mi-1.2, resistant). Debora Plus was susceptible only to M. enterolobii and M. hapla, and was resistant to the other Brazilian populations of M. arenaria, M. ethiopica, M. exigua, M. hispanica, M. incognita, M. inornata, M. izalcoensis M. javanica, M. konaensis, M. luci, M. morocciensis, M. paranaensis, and M. petuniae. Mi-1.2 is located on tomato chromosome 6 within a cluster of seven homologous genes of the nucleotide-binding site leucine-rich repeat (NBS-LRR) family; further research is required to confirm if this multiple Meloidogyne spp. resistance phenotype is controlled exclusively by Mi-1.2 or by combined action of other closely linked genes. This evaluation of resistance of the Debora Plus cultivar to several Meloidogyne species suggests that the Mi-1.2 gene/locus may reduce losses induced by a wide range of Meloidogyne spp. Further studies using additional resistant cultivars and other populations of Meloidogyne spp. are needed to confirm these results.     

‘99昆明世博会参展植物寄生线虫的检疫初报

本次博览会参展植物种类多,来源广,带土普遍疫情复杂。在严处国内外的参展植物中截获矛线目和垫刃目的１３个科的５６个属,其中在参展植物中截获我国对外检疫潜在危险性线。     

The reproductive potential of the root-knot nematode <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> is affected by selection for virulence against major resistance genes from tomato and pepper

The emergence of virulent root-knot nematode populations, able to overcome the resistance conferred by some of the resistance genes (R-genes) in Solanaceous crops, i.e., Mi(s) in tomato, Me(s) in pepper, may constitute a severe limitation to their use in the field. Research has been conducted to evaluate the durability of these R-genes, by comparing the reproduction of several laboratory-selected and wild virulent Meloidogyne incognita isolates, on both susceptible and resistant tomatoes and peppers. We first show that the Me1 R-gene in pepper behaves as a robust R-gene controlling avirulent and virulent Me3, Me7 or Mi-1 isolates. Although the reproductive potential of the virulent isolates was highly variable on susceptible and resistant plants, we also confirm that virulence is highly specific to a determined R-gene on which selection has occurred. Another significant experimental result is the observation that a reproductive fitness cost is associated with nematode virulence against Mi-1 in tomato and Me3 and Me7 in pepper. The adaptative significance of trade-offs between selected characters and fitness-related traits, suggests that, although the resistance can be broken, it may be preserved in some conditions if the virulent nematodes are counter-selected in susceptible plants. All these results have important consequences for the management of plant resistance in the field.     

Resistance of Brassicaceae plants to root-knot nematode (Meloidogyne spp.) in northern Australia

Abstract

Brassicaceae plants have the potential as part of an integrated approach to replace fumigant nematicides, providing the biofumigation response following their incorporation is not offset by reproduction of plant-parasitic nematodes on their roots. Forty-three Brassicaceae cultivars were screened in a pot trial for their ability to reduce reproduction of three root-knot nematode isolates from north Queensland, Australia: M. arenaria (NQ1), M. javanica (NQ2) and M. arenaria race 2 (NQ5/7). No cultivar was found to consistently reduce nematode reproduction relative to forage sorghum, the current industry standard, although a commercial fodder radish (Raphanus sativus) and a white mustard (Sinapis alba) line were consistently as resistant to the formation of galls as forage sorghum. A second pot trial screened five commercially available Brassicaceae cultivars, selected for their biofumigation potential, for resistance to two nematode species, M. javanica (NQ2) and M. arenaria (NQ5/7). The fodder radish cv. Weedcheck, was found to be as resistant as forage sorghum to nematode reproduction. A multivariate cluster analysis using the resistance measurements, gall index, nematode number per g of root and multiplication for two nematode species (NQ2 and NQ5/7) confirmed the similarity in resistance between the radish cultivar and forage sorghum. A field trial confirmed the resistance of the fodder radish cv. Weedcheck, with a similar reduction in the number of Meloidogyne spp. juveniles recovered from the roots 8 weeks after planting. The use of fodder radish cultivars as biofumigation crops to manage root-knot nematodes in tropical vegetable production systems deserves further investigation.     

Comparison of two short DNA barcoding loci (COI and COII) and two longer ribosomal DNA genes (SSU & LSU rRNA) for specimen identification among quarantine root-knot nematodes (Meloidogyne spp.) and their close relatives

Root-knot nematodes (Meloidogyne spp.) are important pests of numerous crops worldwide. Some members of this genus have a quarantine status, and accurate species identification is required to prevent further spreading. DNA barcoding is a method for organism identification in non-complex DNA backgrounds based on informative motifs in short DNA stretches (≈600 bp). As part of the EU 7th Framework project QBOL, 15 Meloidogyne species were chosen to compare the resolutions offered by two typical DNA barcoding loci, COI and COII, with the distinguishing signals produced by two ribosomal DNA genes (small and large subunit rDNA; SSU?≈?1,700 and LSU?≈?3,400 bp). None of the four markers distinguished between the tropical species Meloidogyne incognita, M. javanica and M. arenaria. Taking P ID (Liberal) values ≥0.93 as a measure for species delimitation, the four mtDNA and rDNA markers performed well for the tropical Meloidogyne species complex, M. enterolobii, M. hapla, and M. maritima. Within cluster III A (Holterman et al. Phytopathology, 99, 227–235, 2009), SSU rDNA did not offer resolution at species level. Both mtDNA loci COI and COII did, whereas for LSU rDNA a longer fragment (≥700 bp) is required. The high level of mitochondrial heteroplasmy recently reported for M. chitwoodi (Humphreys-Pereira and Elling Nematology, 15, 315–327, 2013) was not found in the populations under investigation, suggesting this could be a regional phenomenon. For identification of RKNs, we suggest the combined use of SSU rDNA with one of three other markers presented here.     

Control of food legume nematodes in the Mediterranean Basin1

Control of food legume nematodes should consider the nematode species, type of crops, whether for grain or fresh pod production, environmental conditions and the economics of the crops. In general, 3–4-year crop rotations could provide sufficient control of Heterodera goettingiana and H. ciceri and to a lesser extent also of Meloidogyne artiellia. Soil solarization has shown promise in controlling Pratylenchus thornei and H. ciceri on chickpea and has also been reported to be effective against Meloidogyne spp. The use of fumigants such as 1,3-dichloropropene or 1,3-dichloropropene + methylisothiocyanate and also of non-volatile nematicides (aldicarb, oxamyl, carbofuran, thionazin and fenamiphos) gives good control of these nematodes resulting in impressive yield increases in heavily infested soil. However, both nematicides and soil solarization are expensive and their use may not be economic in most cases. The use of resistant cultivars is, so far, of little importance due to very limited number of those with good agronomic characteristics. To ensure good yield of faba bean, attention must also be paid to producing seed stocks free from Ditylenchus dipsaci. In addition, quarantine regulations must avoid spread of this nematode among different countries.     

Histological Characterization of Resistance to Different Root-Knot Nematode Species Related to Phenolics Accumulation in Capsicum annuum

ABSTRACT In the pepper Capsicum annuum CM334, which is used by breeders as a source of resistance to Phytophthora spp. and potyviruses, a resistance gene entirely suppresses reproduction of the root-knot nematode (Meloidogyne spp.). The current study compared the histological responses of this resistant line and a susceptible cultivar to infection with the three most damaging root-knot nematodes: M. arenaria, M. incognita, or M. javanica. Resistance of CM334 to root-knot nematodes was associated with unidentified factors that limited nematode penetration and with post-penetration biochemical responses, including the hypersensitive response, which apparently blocked nematode migration and thereby prevented juvenile development and reproduction. High-performance liquid chromatography analysis suggested that phenolic compounds, especially chlorogenic acid, may be involved in CM334 resistance. The response to infection in the resistant line varied with root-knot nematode species and was correlated with nematode behavior and pathogenicity in the susceptible cultivar: nematode species that quickly reached the vascular cylinder and initiated feeding sites in the susceptible cultivar were quickly recognized in CM334 and stopped in the epidermis or cortex. After comparing our data with those from other resistant pepper lines, we suggest that timing of the resistance response and the mechanism of resistance vary with plant genotype, resistance gene, and root-knot nematode species.     

Genetic diversity of Meloidogyne spp. from rice and identification of multiresistant sources in Oryza spp. accessions

Recently a Meloidogyne species complex was detected parasitizing and causing damage to irrigated rice in southern Brazil, highlighting the need to study the genetic diversity of these species and their pathogenicity to Oryza spp. in order to select genotypes of rice with multiple resistance. This study compared the genetic diversity of Brazilian Meloidogyne spp. isolates from irrigated rice and evaluated the reaction of four wild accessions of Oryza species (O. glumaepatula, O. longistaminata, O. grandiglumis, and O. alta) and two cultivated species, O. glaberrima and O. sativa (control) to M. ottersoni, M. oryzae, and two variants of M. graminicola (Est G2 and Est G3). Genetic variability was assessed using RAPD and AFLP markers. M. graminicola and M. ottersoni showed high intraspecific variability: 83.76% and 41.14%, respectively. Cluster analysis showed a clear separation among rice root-knot nematodes (RKNs) into subclades according to their esterase phenotypes with 100% bootstrap. For rice resistance screening, plants were inoculated with 5,000 eggs, and the nematode reproduction factor evaluated 90–120 days postinoculation. O. glumaepatula, an American wild species, was highly resistant or resistant to all rice RKNs tested and is a valuable source of multiple resistance. Overall, the other rice species also showed different levels of resistance. Conversely, O. longistaminata exhibited low levels of resistance. M. graminicola Est G3 was the most aggressive isolate. Sources of resistance against RKN in wild Oryza genotypes, especially in an AA genome like O. glumaepatula, may be of great interest for future breeding programmes in cultivated rice.     

Screening of common bean (Phaseolus vulgaris) for resistance against temperate root-knot nematodes (Meloidogyne spp.)

BACKGROUND: An important part of the production area of common bean (Phaseolus vulgaris L.) in Belgium is located on the sandy soils of the provinces of Antwerp and Limburg where Meloidogyne chitwoodi (Golden), M. fallax (Karssen) and M. hapla (Chitwood) are present. The host plant status of ten bean cultivars for root‐knot nematodes was determined by evaluating penetration, development and egg mass formation after inoculation with second‐stage juveniles. RESULTS: The tested cultivars were poor to good hosts for M. chitwoodi, non‐hosts or bad hosts for M. fallax and excellent hosts for M. hapla. Significantly fewer M. fallax were found in the roots, and their development was delayed. Penetration of M. hapla took place over a longer period than that of M. chitwoodi and M. fallax. The number of mature females of M. chitwoodi in cv. Polder 6 weeks after inoculation was no different from that in other cultivars, although fewer egg masses were found on this cultivar in the screening test. There was no influence of M. chitwoodi on vegetative growth of cv. Polder. CONCLUSION: The differences found in host plant status of bean cultivars stress the importance of a correct diagnosis of the Meloidogyne species in agricultural fields. Cultivar Polder showed potential as a trap crop for M. chitwoodi. Copyright © 2011 Society of Chemical Industry     

Screening of cultivated and wild adzuki bean for resistance to race 3 of <Emphasis Type="Italic">Cadophora gregata</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis>, cause of brown stem rot

Two diseases of adzuki bean, brown stem rot (BSR, caused by Cadophora gregata f. sp. adzukicola) and adzuki bean Fusarium wilt (AFW, caused by Fusarium oxysporum f. sp. adzukicola), are serious problems in Hokkaido and have been controlled using cultivars with multiple resistance. However, because a new race of BSR, designated race 3, was identified, sources of parental adzuki bean for resistance to race 3 were needed. Therefore, we examined 67 cultivars and lines of cultivated and wild adzuki bean maintained at the Tokachi Agricultural Experiment Station using a root-dip inoculation method. Consequently, nine adzuki bean cultivars, one wild adzuki bean accession and 30 lines (including two lines resistant to all the three races of BSR and AFW) were confirmed to be resistant or tolerant to race 3 of BSR, and we found a cultivar Akamame as well as a wild adzuki bean Acc2515 to be a new source for a resistance gene to the race 3. This cultivar also holds promise as a source of resistance against other races of BSR and AFW.