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Susceptible Plants (susceptible + plant)
Selected AbstractsInheritance of resistance to wheat midge, Sitodiplosis mosellana, in spring wheatPLANT BREEDING, Issue 5 2002R. I. H. McKenzie Abstract Inheritance of resistance to a wheat midge, Sitodiplosis mosellana (Géhin), was investigated in spring wheats derived from nine resistant winter wheat cultivars. F1 hybrids were obtained from crosses between resistant winter wheats and susceptible spring wheats, and used to generate doubled haploid populations. These populations segregated in a ratio of 1:1 resistant to susceptible, indicating that a single gene confers the resistance. The F2 progeny from an intercross among spring wheats derived from the nine resistance sources did not segregate for resistance. Therefore, the same gene confers resistance in all nine sources of resistance, although other genes probably affect expression because the level of resistance varied among lines. Heterozygous plants from five crosses between diverse susceptible and resistant spring wheat parents all showed intermediate levels of response, indicating that resistance is partly dominant. Susceptible plants were reliably discriminated from heterozygous or homozygous resistant ones in laboratory tests, based on the survival and development of wheat midge larvae on one or two spikes. This powerful resistance gene, designated Sm1, is simply inherited and can be incorporated readily into breeding programmes for spring or winter wheat. However, the use of this gene by itself may lead to the evolution of a virulent population, once a resistant cultivar is widely grown. [source] Momordica charantia trypsin inhibitor II inhibits growth and development of Helicoverpa armigeraINSECT SCIENCE, Issue 5 2009Manasi Alok Telang Abstract, Bitter gourd (Momordica charantia L.) seeds contain several squash-type serine proteinase inhibitors (PIs), which inhibit the digestive proteinases of the polyphagous insect pest Helicoverpa armigera. In the present work isolation of a DNA sequence encoding the mature peptide of a trypsin inhibitor McTI-II, its cloning and expression as a recombinant protein using Pichia pastoris have been reported. Recombinant McTI-II inhibited bovine trypsin at 1: 1 molar ratio, as expected, but did not inhibit chymotrypsin or elastase. McTI-II also strongly inhibited trypsin-like proteinases (81% inhibition) as well as the total proteolytic activity of digestive proteinases (70% inhibition) from the midgut of H. armigera larvae. The insect larvae fed with McTI-II-incorporated artificial diet suffered over 70% reduction in the average larval weight after 12 days of feeding. Moreover, ingestion of McTI-II resulted in 23% mortality in the larval population. The strong antimetabolic activity of McTI-II toward H. armigera indicates its probable use in developing insect tolerance in susceptible plants. [source] Screening for Barley yellow dwarf virus -Resistant Barley Genotypes by Assessment of Virus Content in Inoculated SeedlingsJOURNAL OF PHYTOPATHOLOGY, Issue 6 2006Abstract The content of Barley yellow dwarf virus (BYDV) in roots and leaves of barley seedling plants differing in their level of resistance was assessed by quantitative ELISA 1,42 days after inoculation with the strain of BYDV (PAV). High virus accumulation in roots and low concentration in leaves was characteristic of the period 9,15 days after inoculation. In leaves, the differences in virus content between resistant and susceptible genotypes became significant after 15 days and resistance to virus accumulation was better expressed 30,39 days after inoculation. Roots of resistant materials exhibited evident retardation of virus accumulation and the greatest difference in virus content between resistant and susceptible plants was detected 9 days after inoculation. By these criteria, the selected winter and spring barley cultivars and lines (in total 44 materials) fell in to five groups according to field reactions and the presence or absence of the Yd2 resistance gene. There were highly significant and positive relations between ELISA values and 5-year field data on symptomatic reactions and grain-yield reductions due to infection. Using the described method, resistant and moderately resistant genotypes (both Yd2 and non- Yd2) were significantly differentiated from susceptible genotypes. The possible use of this method in screening for BYDV resistance is discussed. [source] Quantifying Phytophthora medicaginis in Susceptible and Resistant Alfalfa with a Real-Time Fluorescent PCR AssayJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2003G. J. Vandemark Abstract A real-time fluorescent PCR assay using a set of specific primers and a fluorochrome-labelled probe (TaqMan) was developed to quantify the amount of Phytophthora medicaginis DNA in alfalfa plants that were classified as either resistant or susceptible to the pathogen based on visual assessment of disease response. The assay clearly discriminated among three standard check alfalfa populations with different levels of resistance based on the analysis of DNA extracted from the roots of bulked plant samples. In two independent experiments, the Spearman rank correlation between pathogen DNA content and the number of susceptible plants in a bulked sample was greater than 0.89 and highly significant (P<0.0001). Significantly less pathogen DNA was detected in bulked samples of a highly resistant check population than in bulked samples from more susceptible check populations. Analysis of individual plants indicated that significantly less pathogen DNA was detected in resistant plants than in susceptible plants. Applications of the assay are considered for breeding programs and the study of microbial population dynamics in plants simultaneously infected with different pathogens. [source] Bean dwarf mosaic virus: a model system for the study of viral movementMOLECULAR PLANT PATHOLOGY, Issue 4 2010AVNER LEVY SUMMARY Taxonomy:Bean dwarf mosaic virus -[Colombia:1987] (BDMV-[CO:87]) is a single-stranded plant DNA virus, a member of the genus Begomovirus of the family Geminiviridae. Physical properties: BDMV virions are twinned incomplete isosahedra measuring 18 × 30 nm. The viral particle is composed of 110 subunits of coat protein, organized as 22 pentameric capsomers. Each subunit has a molecular mass of ,29 kDa. BDMV possesses two DNA components (designated DNA-A and DNA-B), each ,2.6 kb in size. Host range: The natural and most important host of BDMV is the common bean (Phaseolus vulgaris). Nicotiana benthamiana is often used as an experimental host. Common bean germplasm can be divided into two major gene pools: Andean materials, which are mostly susceptible to BDMV, and Middle American materials, which are mostly resistant to BDMV. Disease symptoms: The symptom intensity in common bean plants depends on the stage of infection. Early infection of susceptible bean seedlings will result in severe stunting and dwarfing, leaf distortion and mottling or mosaic, as well as chlorotic or yellow spots or blotches. BDMV-infected plants usually abort their flowers or produce severely distorted pods. Late infection of susceptible plants or early infection of moderately resistant genotypes may show a mild mosaic, mottle and crumpling or an irregular distribution of variegated patches. Biological properties: As a member of the Begomovirus group, BDMV is transmitted from plant to plant by the whitefly Bemisia tabaci. BDMV is a nonphloem-limited virus and can replicate and move in the epidermal, cortical and phloem cells. As a nonphloem-limited virus, it is sap-transmissible. [source] Non-host resistance in plants: new insights into an old phenomenonMOLECULAR PLANT PATHOLOGY, Issue 3 2005THORSTEN NÜRNBERGER SUMMARY Resistance of an entire plant species to all isolates of a microbial species is referred to as non-host or species resistance. An interplay of both constitutive barriers and inducible reactions comprises the basis for this most durable form of plant disease resistance. Activation of inducible plant defence responses is probably brought about by the recognition of invariant pathogen-associated molecular patterns (PAMP) that are characteristic of whole classes of microbial organisms. PAMP perception systems and PAMP-induced signalling cascades partially resemble those known to mediate activation of innate immune responses in animals, suggesting an evolutionarily ancient molecular concept of non-self recognition and immunity in eukaryotes. Genetic dissection has recently provided clues for SNARE-complex-mediated exocytosis and directed vesicle trafficking in executing plant non-host resistance. Recent functional analysis of bacterial effector proteins indicates that establishment of infection in susceptible plants is associated with suppression of plant species resistance. [source] Modelling binary mixtures of herbicides in populations resistant to one of the components: evaluation for resistance managementPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2009Bertrand Jacquemin Abstract BACKGROUND: Herbicide mixtures are commonly proposed to delay the selection of herbicide resistance in susceptible populations (called the SM strategy). However, in practice, herbicide mixtures are often used when resistance to one of the two active ingredients has already been detected in the targeted population (called the RM strategy). It is doubtful whether such a practice can select against resistance, as the corresponding selection pressure is still exerted. As a consequence, the effect of mixtures on the evolution of an already detected resistance to one of the herbicides in the combination remains largely unexplored. In the present work, a simple model was developed to explore further the necessary and sufficient conditions under which a binary RM strategy might stabilise or even reduce resistance frequency. RESULTS: Covering the hypothetical largest range of parameters, 39% of 9000 random simulations attest that the RM strategy might theoretically reduce resistance frequency. When strong enough, high genetic cost of resistance, negative cross-resistance between the herbicides associated in the mixture and reduced selection differential between resistant and susceptible plants can counterbalance the resistance advantage to one of the two applied herbicides. However, the required conditions for an RM strategy to ensure resistance containment in natural conditions seldom overlap with experimental parameter estimates given in the literature. CONCLUSION: It is concluded that the sufficient conditions for an RM strategy to be effective would rarely be encountered. As a consequence, the strategy of formulating mixtures with herbicides for which resistance has already been detected should be avoided. Copyright © 2008 Society of Chemical Industry [source] Post-infection development and histopathology of Meloidogyne arenaria race 1 on Arachis spp.PLANT PATHOLOGY, Issue 5 2008K. Proite The reproductive behaviour of the root-knot nematode Meloidogyne arenaria race 1 was compared on two wild species of Arachis (A. duranensis and A. stenosperma) and cultivated peanut (A. hypogaea cv. IAC-Tatu-ST). The three species were considered moderately susceptible, resistant, and susceptible, respectively. Penetration and development of the root-knot nematode in the resistant species was reduced in comparison with that occurring in susceptible plants. Several cell features, including dark blue cytoplasm and altered organelle structure were observed in the central cylinder of A. stenosperma, indicating a hypersensitive-like response (HR) of infested host cells. Neither giant cells, nor nematodes developed beyond the second stage, were found on A. stenosperma. Arachis duranensis showed a delay in the development of nematodes in the roots compared to A. hypogaea. The two wild peanut species were chosen to be the contrasting parents of a segregating population for mapping and further investigation of resistance genes. [source] Inhibition of the development of leaf rust (Puccinia recondita) by treatment of wheat with allopurinol and production of a hypersensitive-like reaction in a compatible hostPLANT PATHOLOGY, Issue 3 2000A. L. Ádám The effect of allopurinol [4-hydroxypyrazolo (3,4- d) pyrimidine], a purine analogue inhibitor of xanthine oxidase (XO) enzyme, was studied in the host,pathogen combination of Triticum aestivum,Puccinia recondita f.sp. tritici. Analysis of purines and pyrimidines in the allopurinol-treated wheat seedlings showed marked accumulation of xanthine, suggesting the inplanta inhibition of XO activity. In the incompatible wheat,rust interaction application of allopurinol as a drench, even at the highest concentration (50 ,m), did not change the hypersensitive reaction phenotype; only the number of lesions was slightly reduced. Allopurinol treatment decreased the augmented rate of electrolyte leakage and lipid peroxidation associated with the hypersensitive response (HR), an effect probably related to the inhibition of rust development by allopurinol. By contrast, in the case of the compatible wheat,leaf-rust combination the reaction type was strongly affected. The formation of uredia and production of uredospores were diminished or completely inhibited depending on the concentration of allopurinol, which was applied either as a drench (3.125,50 ,m) or as a foliar spray (100,400 ,m) to plants grown in perlite. At the highest allopurinol concentration in the drench, the compatible reaction type changed to a hypersensitive-like necrotic reaction. Significant increases in electrolyte leakage and lipid peroxidation (characteristic of the HR) were found 4,6 days after infection in susceptible plants treated with allopurinol. Staining of leaf slices from allopurinol-treated and compatible rust-infected plants with Evans blue indicated cell death surrounding the pustules, while at this stage no cell death was detected in infected leaves without allopurinol treatment. The above results suggest that XO is not the main source of the generation of active oxygen species in wheat during the HR to leaf rust. [source] Distinct physiological responses of two rice cultivars subjected to iron toxicity under field conditionsANNALS OF APPLIED BIOLOGY, Issue 2 2009R.J. Stein Abstract Iron toxicity is recognised as the most widely distributed nutritional disorder in lowland and irrigated rice, derived from the excessive amounts of ferrous ions generated by the reduction of iron oxides in flooded soils. Rice cultivars with variable degrees of tolerance to iron toxicity have been developed, and cultural practices such as water management and fertilisation can be used to reduce its negative impact. However, because of the complex nature of iron toxicity, few physiological data concerning tolerance mechanisms to excess iron in field conditions are available. To analyse the physiological responses of rice to iron excess in field conditions, two rice cultivars with distinct tolerance to iron toxicity [BR-IRGA 409 (susceptible) and IRGA 420 (tolerant)] were grown in two areas, with a well-established history of iron toxicity (in Camaquã, RS, Brazil) and without iron toxicity (in Cachoeirinha, RS, Brazil). Plants from the susceptible cultivar grown in the iron-toxic site showed lower levels of chlorophylls and soluble proteins (together with higher carbonyl levels) indicating photooxidative and oxidative damage. The toxic effects observed were because of the accumulation of high levels of iron and not because of any indirectly induced shoot deficiency of other nutrients. Higher activities of antioxidative enzymes were also observed in leaves of plants from the susceptible cultivar only in the iron-toxic site, probably as a result of oxidative stress rather than because of specific involvement in a tolerance mechanism. There was no difference between cultivars in iron accumulation in the symplastic and apoplastic space of leaves, with both cultivars accumulating 85,90% of total leaf iron in the symplast. However, susceptible plants accumulated higher levels of iron in low-molecular-mass fractions than tolerant plants. The accumulation of iron in the low-molecular-mass fraction probably has a direct influence on iron toxicity, and the adaptive strategy of tolerant plants may rely on their capacity to buffer the iron amounts present in the low mass fraction, a new parameter to be considered when evaluating tolerance to iron excess in field-cultivated rice plants. [source] | ||||||||||