Multiple Sources Of Resistance Research Articles

Multiple Fusarium head blight resistance loci mapped and pyramided onto elite spring wheat Fhb1 backgrounds using an IBD-based linkage approach

Pyramiding QTL for FHB resistance from multiple sources presents an opportunity to enhance the Fhb1 derived resistance of elite spring wheat germplasm. Conventionally, pyramiding QTL using a marker assisted-selection approach requires preliminary mapping studies to identify the resistance QTL from each parental line and validation studies to assess the QTL effects in multiple genetic backgrounds. This study evaluates IBD-based linkage analysis for the purpose of mapping, validation and marker-assisted pyramiding of resistance QTL simultaneously in breeding populations. Eight hundred and twenty nine segregating F1 progeny from 43 four-way crosses among multiple sources of resistance were evaluated in the greenhouse and in field-based progeny tests. IBD-based linkage analysis was conducted using a mixed model extension of Haseman-Elston sib-pair regression. QTL for FHB resistance were identified on chromosomes 2A, 2B, 3B and 7B, cumulatively explaining 18–21 % of the variance for FHB severity in different evaluations. The QTL on chromosome 3B corresponded with Fhb1, and the QTL on chromosomes 2B and 7B are corroborated by previous mapping studies. The QTL mapped to chromosome 2A potentially represents a novel source of resistance derived from elite North American spring wheat germplasm. Marker haplotypes for these QTL regions are being used for marker-assisted selection of resistance alleles in subsequent generations of these breeding populations.

Inheritance and molecular mapping of anthracnose resistance genes present in sorghum line SC112-14

Anthracnose (Colletotrichum sublineolum) is one of the most destructive diseases of sorghum [Sorghum bicolor (L.) Moench], affecting all aerial tissues of the plant. The most effective strategy for its control is the incorporation of resistance genes. The anthracnose resistance response present in the sorghum line SC112-14 (Cs-SC112) was therefore studied against pathotypes from Puerto Rico, Texas, Arkansas, and Georgia using F2 progenies and recombinant inbred lines. The results show that a series of nearest single loci at the distal region of chromosome 5 control the resistance responses against pathotypes from Puerto Rico, Texas, and Arkansas. Resistance loci against pathotypes from Texas and Puerto Rico are tightly linked and flanked by simple sequence repeat (SSR) markers Ch5-55.0 and Ch5-56.1, while the resistance locus against pathotypes from Arkansas is 9.5 cM below SSR marker Ch5-56.1. The resistance locus against pathotypes from Georgia is not located in the distal region of chromosome 5, and its location could not be determined. Comparative analysis confirmed that the region associated with these three loci is not associated with the anthracnose resistance locus Cg1, which was previously mapped in the distal region of the same chromosome. The dominant mode of action against pathotypes from Puerto Rico suggests that these resistances sources can be beneficial for sorghum hybrid production. The durability of anthracnose resistance in sorghum depends on the adequate use of multiple resistance sources. Thus, the knowledge and genetic markers developed herein provide tools to initiate the pyramiding of multiple anthracnose resistance loci through marker-assisted selection.

BREEDING FOR DURABLE RESISTANCE TO DOWNY AND POWDERY MILDEW IN GRAPEVINE

The current strategy to control grapevine downy and powdery mildew relies on chemical treatments. An alternative solution to the use of chemicals is the development of varieties resistant to pathogens. Therefore a program to create new grapevine varieties with a durable resistance to downy and powdery mildew and with a berry quality suitable for high quality wine production was launched in 2000. The situation seemed very favourable to start up such a program: plenty of resistance sources were available, and several resistance QTLs with various effects had already been discovered. Nevertheless a first case of downy mildew resistance breakdown was described in the cultivar ?Bianca?. Even if resistance durability is a retrospective judgment, some principles can be considered to monitor the risk of resistance break-down: pyramiding resistance genes, taking into account the evolutionary potential of the pathogen or assessing the cost of virulence, from a practical point of view, a durable management of resistance meaning to reduce the selection pressure applied by the resistance genes on the pathogen population. Therefore we chose to use multiple sources of resistance as genitors. The genetic determinism of most of them was analysed and the molecular markers derived from these studies were quickly integrated to assist with selection. Concerning the shortening of the breeding process, we developed a greenhouse growing method allowing to go from seed to seed in one year and a resistance phenotyping platform to get the precise plant phenotype as early as possible in the process. Moreover all the field trials have been performed through an experimental network, which allows us to save time and to take into account the differences in environment conditions. The overall process of selection is organized into three steps and takes 16 years. We expect to propose our first varieties for registration in 2016.

Wild Sunflower Species as a Genetic Resource for Resistance to Sunflower Broomrape (Orobanche cumana Wallr.)

AbstractBroomrape (

Stacking Resistance Alleles from Wild and Domestic Soybean Sources Improves Soybean Cyst Nematode Resistance

ABSTRACTThe soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is the most economically important soybean [Glycine max (L.) Merr.] pathogen in the United States. Field SCN populations are adapting to the narrowly based SCN resistance currently deployed in soybean cultivars. The objective of our research was to measure the effects of combinations of SCN resistance genes or quantitative trait loci (QTL) from the wild soybean (Glycine soja Siebold & Zucc.) PI 468916 and the domesticated soybean accessions PI 88788 and PI 437654. Two populations were developed to test the combinations of QTL and genes. Both populations segregated for the G. soja resistance QTL cqSCN‐006 and cqSCN‐007. Population 1 also segregated for resistance from PI 88788 and Population 2 segregated for resistance from PI 437654. The populations were tested for resistance to three SCN isolates in a greenhouse and with single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. In both populations, the two G. soja resistance alleles significantly increased SCN resistance compared with the alternative alleles. The SCN resistance alleles rhg1 and Rhg4 from PI 437654 and rhg1‐b from PI 88788 also significantly increased resistance compared with the alternative alleles. The two G. soja QTL alleles significantly enhanced the resistance derived from PI 88788. These results show that SCN resistance can be increased through stacking genes and QTL from multiple resistance sources.

Improvements in Hazelnuts in the United States

In the mid-1980s, eastern filbert blight (EFB) fungus, Anisogramma anomala (Peck) E. Müller, was discovered in Oregon's main hazelnut-producing region and now is present throughout the hazelnut-producing area. Oregon State University's (OSU) Hazelnut Breeding Program responded by developing EFB-resistant cultivars, the first of which was released in 2005. The breeding program has also selected for other beneficial traits such as uniform early nut maturation, larger kernel size, and improved kernel quality. A 2008 OSU economic study on the costs of establishing and producing hazelnuts showed that the EFB-resistant cultivars enhanced economic viability of orchards, increasing cumulative cash flow during the 12-year establishment period by $12,243 per hectare. Several completely resistant cultivars have been released from the OSU Hazelnut Breeding program, all of which have ‘Gasaway’ as a resistance source, which transmits a dominant allele at a single locus that provides resistance to EFB. Additional EFB-resistant genotypes have also been identified from a diversity of origins that are being integrated into the OSU breeding program to produce new cultivars expressing multiple sources of genetic resistance. Interest in growing hazelnuts is increasing in other parts of the United States; for example, the Arbor Day Foundation began the Hazelnut Research Project in 1996 in Nebraska. A Hybrid Hazelnut Consortium was formed to join the leading hazelnut researchers in the United States. The Consortium's goal is to create a world-leading research and breeding program to develop hazelnuts as a widely adapted, high-yielding, and low-input sustainable crop that is competitive with annual crops for food, feed, or bioenergy. At Rutgers University, there has been a program of breeding and research for hazelnuts for the eastern United States since 1996. The program currently has ≈11,000 hazelnut seedlings undergoing evaluation. The Rutgers program is also looking for winter-hardy genotypes. They have been working closely with OSU to assess the response of OSU hazelnut selections that are resistant to EFB in Oregon when they are exposed to EFB isolates collected from across the eastern United States. This work has demonstrated the need for cultivars to express multiple sources of resistance and has prompted quarantine on importation of hazelnut plants into Oregon from other states where EFB strains may differ. Rutgers is also searching for new sources of resistance to EFB from seedling populations from Europe with the goal of integrating these sources into American germplasm. More effective Integrated Pest Management for EFB-susceptible hazelnut cultivars has been developed by OSU scientists. They recommend a management program that integrates scouting for and pruning infected tissue, fungicidal sprays, and the use of more resistant cultivars. Advances in hazelnut fertilizer management have included descriptions of patterns of nitrogen uptake, distribution, and use using isotopically labeled nitrogen.

Multiple-site identification of potato parent clones conferring high levels of late blight resistance with a corresponding genetic model for resistance

Toluca Valley, Mexico, is the putative center of origin and diversity forPhytophthora infestans (Mont.) de Bary, the oomycete pathogen responsible for late blight, making it an ideal location for screening potato breeding populations for late blight resistance. Approximately 21,500 progeny from the USDA-ARS, Aberdeen, Idaho potato breeding program were evaluated from 1996 through 2005 by estimating the percentage of defoliation due to late blight throughout the growing season. Comparisons of the number of resistant progeny and their degree of resistance response from resistant x susceptible (RxS) and resistant x resistant (RxR) crosses were made across years. A clone of each progeny planted in Toluca Valley was also planted the same year near Aberdeen, Idaho, to screen for acceptable tuber type. Promising progeny phenotypes were then screened the following year for tuber late blight resistance at field plots near Corvallis, Oregon. The RxR late blight crosses produced 64% resistant progeny compared to 29% of the RxS crosses. The segregation for late blight resistance in progeny from specific RxS crosses best fits a 1R:3S ratio. This segregation ratio is best explained by a gene model in which resistance is conferred by the presence of a dominant allele at each of two loci. The greater percentage of resistant progeny from RxR crosses indicates the benefits of pyramiding resistance genes from diverse germplasm. Three promising late blight resistant parental clones with acceptable tuber type resulted from family A95053. Family A95053 has multiple sources of resistance that includeSolarium demissum andSolarium stoloniferum, via female parent AWN86514-2 and male parent, B0718-3.

Identification of QTL for reaction to three races of Colletotrichum trifolii and further analysis of inheritance of resistance in autotetraploid lucerne

Anthracnose, caused by Colletotrichum trifolii, is one of the most serious diseases of lucerne worldwide. The disease is managed through deployment of resistant cultivars, but new pathotypes present a challenge to the successful implementation of this strategy. This paper reports the genetic map locations of quantitative trait loci (QTL) for reaction to races 1, 2 and 4 of C. trifolii in a single autotetraploid lucerne clone, designated W126 from the Australian cv. Trifecta. Resistance was mapped in a backcross population of 145 individuals, and reaction was assessed both by spray and injection inoculation of stems. Resistance to injection inoculation with races 1 and 4 was incompletely dominant and closely linked (phenotypic markers 2.2 cM apart); these resistances mapped to a linkage group homologous to Medicago truncatula linkage group 8. When the spray inoculation data were subjected to QTL analysis, the strongest QTL for resistance was located on linkage group 8; six QTL were identified for race 1 and four for race 4. Resistance to race 2 was incompletely recessive; four QTL were identified and these include one QTL on linkage group 4 that was also identified for race 1. Modelling of the interactions between individual QTL and marker effects allowed a total of 52-63% of the phenotypic variation to be described for each of the different races. These markers will have value in breeding lucerne, carrying multiple sources of resistance to the three known races of C. trifolii.

Sexuality Training, Education and Therapy in the Healthcare Environment: Taboo, Avoidance, Discomfort or Ignorance?

Multiple sources of resistance are present in the healthcare environment to comprehensive assessment and intervention efforts in regard to sexuality. The authors survey both the diversity of needs and values presented by consumers, and encourage providers to equip themselves educationally, emotionally and ethically so that they can deliver relevant, holistic services to consumers.

APPLICATION OF SCAR MARKERS LINKED TO A PUTATIVE PRSV-P RESISTANCE LOCUS FOR ASSISTED BREEDING OF RESISTANT C. PAPAYA CULTIVARS

Papaya ringspot virus type P (PRSV-P) is a serious disease of Carica papaya. Several wild relatives of the papaya, belonging to the genus Vasconcellea, exhibit complete resistance to PRSV-P, namely V. cundinamarcensis, V. cauliflora and V. quercifolia. Molecular genetic analysis of interspecific hybrids of V. cundinamarcensis and V. parviflora using Randomly Amplified DNA Fingerprinting (RAF) permitted the construction of genetic maps of these species. Identification and mapping of several DNA markers linked to a PRSV-P resistance gene locus in V. cundinamarcensis was possible, two of which (OPK41R and OPA115R), resulted from a Single Nucleotide Polymorphism (SNP), in close proximity to the PRSV-P resistance gene locus. The Sequence Characterised Amplified Regions (SCAR's), were shown to be present in both parents, and produced codominant markers, which were applied as reliable diagnostic markers for resistant and susceptible genotypes. The OPK41R SCAR was identified in 4 additional Vasconcellea species made available, including V. cauliflora and V. quercifolia, but not in C. papaya. The indel identified may be useful for the selection of PRSV-P resistant individuals in breeding programs with Vasconcellea and C. papaya to assist introgression of putative resistance genes. The markers were subsequently applied to an intergeneric hybrid population from C. papaya and V. quercifolia. Genetic characterisation of the hybrid population using RAF markers confirmed hybridity of the F1 and reduced V. quercifolia DNA content of back cross generations. The OPK41R and OPA115R SCARs were tested in the quercifolia hybrids, and did not identify linkage to PRSV-P resistance. From the results it can be inferred that Vasconcellea may contain multiple sources of resistance to PRSV-P. Overall these studies indicate that there is significant potential for the continued application of DNA markers in molecular breeding for PRSV-P resistant papaya genotypes.

Biology of Anticarsia gemmatalis on soybean genotypes with different degrees of resistance to insects

A knowledge of the mechanisms of resistance present in genetic materials should help breeding programs in developing cultivars resistant to insects. The biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) was studied on leaves of four soybean genotypes with different degrees of resistance to insects. The genotypes evaluated were cultivars IAC 17 and IAC 24, resistant to defoliators and stink bugs, line PI 229358, a source of multiple resistance to insects and used as parent in various lines selected for resistance to A. gemmatalis, and 'IAC PL-1', the susceptible control. The experiments were carried out in the laboratory, under controlled conditions of temperature (25 ± 2ºC), relative humidity (60 ± 10%) and photoperiod (14h). First instar larvae were placed in Petri dishes and fed leaves of each genotype, detached from plants at the R1 and R2 stages (beginning and full bloom). Later on, insect couples were maintained in 25 PVC cages to evaluate parameters of the adult stage. 'IAC 17' and 'IAC 24' promoted low viability of the larval, pupal, and egg stages, causing adult deformation and a reduction of the number of eggs per female. PI 229358 prolonged the immature stage and reduced pupal weight, egg viability, and adult longevity. Considering all tests, 'IAC 17' and 'IAC 24' were characterized as having antibiosis-type resistance, and 'IAC PL-1' demonstrated to be a genotype suitable for insect development.

Novel sources of multiple resistance to three races of Fusarium oxysporum f. sp. lycopersici in Lycopersicon germplasm

Fusarium wilt, caused by three races of Fusarium oxysporum f. sp. lycopersici, is worldwide one of the most important diseases of tomato (Lycopersicon esculentum Mill.). In Brazil, all races are now present offering a unique opportunity for a simultaneous evaluation of accessions to these pathogen variants. A germplasm collection comprising 94 Lycopersicon accessions was challenged with a race 3 isolate. A range of responses varying from immune-like resistance to high susceptibility was observed. A sub-group of 32 accessions displaying immune-like and highly resistant responses to race 3 was re-evaluated for the reaction to race 1, 2, and 3 isolates. Accessions combining high levels of resistance to all three races were identified in L. hirsutum, L. chilense, L. pennellii and L. peruvianum. The availability of distinct sources of resistance alleles/genes could be an important tool in breeding to anticipate future problems such as the emergence of other pathogen races besides 1, 2 and 3.

Potential Sources of Resistance for Melon to Nonpersistently Aphid-borne Viruses.

Two hundred and sixty-eight Cucumis melo and wild relative accessions were evaluated for resistance to Cucumber mosaic virus (CMV), Papaya ringspot virus strain W (PRSV-W), Watermelon mosaic virus (WMV), and Zucchini yellow mosaic virus (ZYMV). Symptom development and systemic infection based on double antibody sandwich enzyme-linked immunosorbent assays were monitored. Sources of resistance were scarce. However, a number of them were found among the C. melo accessions tested. Thus, the accession C-189 behaved similarly to PI 161375 and showed resistance to "common" CMV strains although it was infected by a "song" type CMV. For WMV, the accessions C-768 and C-425, although infected, exhibited very mild symptoms, and recovery from infection occurred in some occasions in the former. A similar trait was also found in C-105, although in this case symptoms rarely appear and part of the plants are not infected. In addition, C-105 was highly resistant to virus transmission by Aphis gossypii, similarly to PI 161375. Accessions C-885 and C-769 exhibited resistance to PRSV-W, WMV, and ZYMV; therefore they are potential sources of multiple resistance. Resistance traits were also found in wild relatives that could be exploited when interspecific barriers with C. melo can be circumvented.

Identification of stable sources of resistance in sorghum to midge and their reaction to leaf diseases

Sorghum midge ( Stenodiplosis (= Contarinia) sorghicola Coquillett) is an important pest of grain sorghum worldwide, and several sources of resistance have been identified in the world sorghum germplasm collection. DJ 6514 and the breading lines derived from it become susceptible to sorghum midge in Kenya. Therefore, we evaluated a diverse array of midge-resistant and -susceptible lines at Alupe, Kenya; and ICRISTAT Center, India, to identify lines with stable resistance across seasons and locations. The test material was also evaluated for resistance to leaf diseases at Alupe, Kenya; to identify lines with multiple resistance to sorghum midge and leaf diseases. Across seasons and locations; IS 3461, IS 8884, IS 8887, IS 8891, IS 19476, IS 22806, and AF 28 showed high to moderate levels of resistance to midge, and these lines will be useful for use in resistance breeding programs. Thirty-nine lines showed resistance to midge both under natural infestation and no-choice headcage screening at ICRISTAT Center, India, over four seasons, of which IS 18696, IS 22806, ICSV, 197, ICSV 745, ICSV 88032, PM 20710-2, DJ 6514, and AF 28 were highly resistant. Genotypes IS 3461, IS 8884, IS 8887, IS 8589, IS 19476, IS 22806, ICSV 736, ICSV 90003, and AF 28 showed moderate levels of resistance to both midge and leaf diseases at Alupe, Kenya; and these lines can be used as sources of multiple resistance to these pests. Lines IS 2766, IS 7148, IS 8733, and IS 8589, showed high levels of resistance to leaf diseases in Kenya. Resistance to midge breaks down in some lines at Alupe, Kenya; possibly because of the influence of environment on the expression of resistance or the possible differences in midge populations at different geographic locations.

Sources of Multiple Resistance to Rice Blast (Bl) and Bacterial Blight (BB) in Nepal

Sources of Multiple Resistance to Rice Blast (Bl) and Bacterial Blight (BB) in Nepal

Sources of multiple resistance to major diseases of sorghum in Tamil Nadu, India

Sources of multiple resistance to major diseases of sorghum in Tamil Nadu, India

Pink Bollworm Resistance, Lint Yield, and Earliness of Cotton Isolines in a Resistant Genetic Background 1

Natural resistance of cotton, Gosspyium hirsutum L., to pink bollworm (PBW), Pectinophora gossypiella (Saunders), may be increased by combining individual resistance traits. The objectives of this study were to determine: (i) the levels of resistance to PBW, as measured by seed damage, in germplasm lines carrying a single morphological resistance trait in a resistant genetic background; (ii) whether combinations of the morphological traits would increase the level of resistance; and (iii) the effects of those morphological traits in the resistant genetic background on lint yield and earliness. All possible combinations of the mutant traits nectariless (N), smoothleaf (S), and okra leaf (L), and of their normal counterparts in a resistant genetic background (AET-5), were grown for 2 yr in insecticide-free environments at Tempe, AZ. Check cultivars were the nectaried, semismoothleaf ‘Deltapine 61’ (DPL-61) and the nectariless, semismoothleaf ‘Deltapine NSL’ (DPL-N). Soil type was a Contine clay loam (fine, mixed, hyperthermic Typic Haplargid). Seed damage, lint yield, and earliness were determined from weekly harvests. The DPL-61 exhibited significantly more seed damage than any other cotton. The AET-5 showed more seed damage than the N, L, NL, and NSL isolines, but not more than the S, NS, or SL isolines or DPL-N. Contrary to expectations, AET-5NL did not have significantly less seed damage than AET-5N or AET-5L. In 1982, when PBW infestations were low, DPL-61 yielded significantly more lint than AET-5 or the isolines (except AET-5NSL). In 1983, when PBW infestations were high, DPL-61 yielded significantly less lint than all but the S isolines. The AET-5 and the N, L, and NL isolines were early maturing. The S isolines matured later and yielded as much lint as AET-5 and the other isolines in 1982, but significantly less in 1983. The low yield potential of AET-5 and of the N, L, and NL isolines emphasize that they should be used mainly as sources of multiple resistance to PBW for incorporation into more agronomically acceptable cottons rather than as cultivars themselves.

Gentamicin-resistant Klebsiella aerogenes as a clinically-significant source of transferable antibiotic resistance.

Of 108 epidemiologically-distinct strains of gentamicin-resistant Klebsiella aerogenes collected from 12 hospitals in six countries, 86 (80%) transferred multiple antibiotic resistance to Escherichia coli K12. For 77 (90%) of the successful donors the resistances were conferred by single plasmids with molecular weights of between 25 and 130 megadaltons. Forty-eight per cent of the donors transferred resistance to chloramphenicol, tetracycline, sulphamethoxazole, ampicillin/carbenicillin, in addition to resistance to at least two aminoglycosides and to one or more cephalosporins. Resistances to chloramphenicol, tetracycline, ampicillin/carbenicillin, sulphamethoxazole, gentamicin and trimethoprim were transferable in 89, 75, 74, 74, 67 and 58%, respectively, of strains that were resistant to these agents. Six ‘epidemic’ plasmids conferring extensive multiple resistance were found in 21 different serotypes from patients in single hospitals in London, Munich and Sydney. Three of these plasmids conferred resistances to gentamicin, trimethoprim and sulphamethoxazole. The frequency of transferable resistance and the intrageneric spread of single plasmids suggests that Klebsiella species serves as an important source of multiple resistance for this and other more pathogenic species.