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Resistance Breeding (resistance + breeding)
Selected AbstractsIdentification of Two Blast Resistance Genes in a Rice Variety, DiguJOURNAL OF PHYTOPATHOLOGY, Issue 2 2004X. W. Chen Abstract Blast, caused by Magnaporthe grisea is one of most serious diseases of rice worldwide. A Chinese local rice variety, Digu, with durable blast resistance, is one of the important resources for rice breeding for resistance to blast (M. grisea) in China. The objectives of the current study were to assess the identity of the resistance genes in Digu and to determine the chromosomal location by molecular marker tagging. Two susceptible varieties to blast, Lijiangxintuanheigu (LTH) and Jiangnanxiangnuo (JNXN), a number of different varieties, each containing one blast resistance gene, Piks, Pia, Pik, Pi - b, Pi - kp, Pi - ta2, Pi - ta, Pi - z, Pi - i, Pi - km, Pi - zt, Pi - t and Pi-11, and the progeny populations from the crosses between Digu and each of these varieties were analysed with Chinese blast isolates. We found that the resistance of Digu to each of the two Chinese blast isolates, ZB13 and ZB15, were controlled by two single dominant genes, separately. The two genes are different from the known blast resistance genes and, therefore, designated as Pi-d(t)1 and Pi-d(t)2. By using bulked segregation method and molecular marker analysis in corresponding F2 populations, Pi-d(t)1 was located on chromosome 2 with a distance of 1.2 and 10.6 cM to restriction fragment length polymorphism (RFLP) markers G1314A and G45, respectively. And Pi-d(t)2 was located on chromosome 6 with a distance of 3.2 and 3.4 cM to simple sequence repeat markers RM527 and RM3, respectively. We also developed a novel strategy of resistance gene analogue (RGA) assay with uneven polymerase chain reaction (PCR) to further tag the two genes and successfully identified two RGA markers, SPO01 and SPO03, which were co-segregated toPi-d(t)1 and Pi-d(t)2, respectively, in their corresponding F2 populations. These results provide essential information for further utilization of the Digu's blast resistance genes in rice disease resistance breeding and positional cloning of these genes. [source] Linkage and quantitative trait locus mapping of foliage late blight resistance in the wild species Solanum verneiPLANT BREEDING, Issue 3 2006K. K. Sørensen Abstract The global cultivation of potato (Solanum tuberosum) is threatened by epidemics caused by new variants of the late blight pathogen, Phytophthora infestans. New sources of durable late blight resistance are urgently needed and these may be found in wild Solanum species. The diploid wild species, S. vernei, has not previously been subjected to mapping of quantitative trait loci (QTLs) for late blight resistance. Two populations designated HGIHJS and HGG, originating from a cross between a clone of S. vernei and two different S. tuberosum clones were evaluated in field trials for late blight infestation. The relative area under the disease progress curve (RAUDPC) was estimated and used for QTL mapping. A linkage map of S. vernei, comprising 11 linkage groups, nine of which could be assigned to chromosomes, was constructed. Results indicated that the resistance in S. vernei was quantitatively inherited. Significant QTLs for late blight resistance were identified on chromosomes VIII (HGG), VI and IX (HGIHJS). In addition, potential QTLs were detected on chromosomes VII (HGIHJS) and IX (HGG). A putative and a significant QTL for tuber yield were found on chromosomes VI and VII in HGG, but no linkage between yield and resistance was indicated. The QTL for late blight resistance, which mapped to chromosome IX, could be useful for late blight resistance breeding as it was located close to the microsatellite marker STM1051 in both populations. [source] Resistance to Leveillula taurica in the genus CapsicumPLANT PATHOLOGY, Issue 5 2003V. L. De Souza One hundred and sixty-two Capsicum genotypes were evaluated for powdery mildew (Leveillula taurica) resistance, following inoculations with a suspension of 5 × 104 conidia mL,1 on 10-leaved to 12-leaved plants. Genotypes were graded into five resistance classes, based on the areas under the disease progress curves calculated from disease incidence (percentage infected leaves per plant) and severity (total number of colonies per plant). Results revealed a continuum from resistance to susceptibility, with the majority (70%) of C. annuum materials being classified as moderately to highly susceptible to L. taurica. Conversely, C. baccatum, C. chinense and C. frutescens were most often resistant, indicating that resistance to L. taurica among Capsicum species is found mainly outside the C. annuum taxon. Nevertheless, some resistant C. annuum material was identified that may be useful for resistance breeding. Eight genotypes were identified as immune to the pathogen: H-V-12 and 4638 (previously reported), and CNPH 36, 38, 50, 52, 279 and 288. Only H-V-12 and 4638 are C. annuum, while all others belong to the C. baccatum taxon. Latent period of disease on a set of commercial sweet pepper genotypes varied, indicating diverse levels of polygenic resistance. The latent period progressively reduced with plant maturity, from 14·3 days in plants at the mid-vegetative stage to 8·6 days in plants at the fruiting stage. Young plants of all commercial genotypes tested at the early vegetative stage were immune, irrespective of the reaction of the genotype at later stages, demonstrating widespread juvenile resistance to L. taurica in the Capsicum germplasm. Inoculation of plants of different botanical taxa with a local isolate indicated a wide host range. Some hosts, including tomato (Lycopersicon esculentum), artichoke (Cynara scolymus) and poinsettia (Euphorbia pulcherrima), produced large amounts of secondary inoculum. Other hosts included okra (Abelmoschus esculentus), eggplant (Solanum melongena), cucumber (Cucumis sativus), Solanum gilo, Chenopodium ambrosioides and Nicandra physaloides. [source] Variation in the response of melon genotypes to Fusarium oxysporum f.sp. melonis race 1 determined by inoculation tests and molecular markersPLANT PATHOLOGY, Issue 2 2003Y. Burger Screening of genotypes of melon (Cucumis melo) for resistance to wilt caused by Fusarium oxysporum f.sp. melonis is often characterized by wide variability in their responses to inoculation, even under carefully controlled conditions. The variability at the seedling stage of 17 genotypes susceptible to race 1 was examined in growth-chamber experiments. Disease incidence varied from 0 to 100% in a genotype-dependent manner. Using four combinations of light (60 and 90 µE m,2 s,1) and temperatures of (27 and 31°C), only light intensity showed a statistically significant effect. Marker-assisted selection for fusarium resistance breeding using cleaved amplified polymorphic sequence (CAPS) and sequence-characterized amplified region (SCAR) markers were compared using a single set of genotypes that included 24 melon accessions and breeding lines whose genotype regarding the Fom-2 gene was well characterized. The practical value of the markers for discriminating a range of genotypes and clarifying the scoring of phenotypes was also tested using a segregating breeding population which showed codominant SCAR markers to be useful in marker-assisted selection. [source] Detection, distribution and control of Potato mop-top virus, a soil-borne virus, in northern EuropeANNALS OF APPLIED BIOLOGY, Issue 2 2010J. Santala Potato mop-top virus (PMTV; genus Pomovirus; family Virgaviridae) is transmitted by the soil-borne Spongospora subterranea f.sp. subterranea, a protoctist that causes powdery scab on potato. PMTV is distributed widely in the potato growing areas in South and North America, Japan and northwestern Europe. This article reviews the current knowledge on detection, distribution and control of PMTV with focus on the Baltic Sea region. Since the 1980s, PMTV has caused great economic losses to potato production in the Nordic countries (Norway, Sweden, Denmark and Finland), but its occurrence in other countries of the Baltic Sea region remained unknown. To fill this knowledge gap, harmonised sampling and virus detection procedures including bioassays and serological and molecular methods were employed by 21 research institutions to detect PMTV in potato tubers and soil samples in 2005,2008. Potato growing areas were widely contaminated with PMTV in the Nordic countries. Only the main seed potato production area in northern Sweden and the High Grade seed potato production zone in Finland were negative for PMTV. Intensive and systematic surveys in Poland in 2004,2008 found no evidence of PMTV, except a single PMTV-infected tuber detected in 2008. Surveys in the Baltic countries (Lithuania, Latvia and Estonia) and northwestern Russia (Leningrad province) were negative for PMTV, except infection of minitubers in a screenhouse in Latvia in 2005. Varying percentages of tubers expressing spraing symptoms in Sweden, Norway, Denmark and Poland were infected with Tobacco rattle virus, and bioassays indicated similar results for Russia. Incidence of symptomless infections with PMTV was high in tubers of many potato cultivars. Here, we discuss the contrasting patterns of distribution of PMTV in the Baltic Sea region, factors playing a role in dispersal and establishment of PMTV in new fields and means for controlling PMTV and its spread to new areas. We emphasise the use of the current virus-specific methods for the detection of PMTV in symptomless potato tubers and the high risks of disseminating PMTV to new fields and areas in viruliferous resting spores of S. subterranea in the soil adhering to seed tubers. PMTV-resistant potato cultivars will provide the only sustainable means for preventing yield losses in the infested fields and the prospects of resistance breeding are summarised. [source] | ||||||||||