333,110 research outputs found
Combating stem and leaf rust of wheat: Historical perspective, impacts, and lessons learned
No full textmillions fed, food security, wheat rust, stem rust, leaf rust, Norman Borlaug,
Sources of resistance to yellow rust and stem rust in wheat-alien introgressions
No full textWheat is the staple food and the main source of caloric intake in most developing countries, and thereby an important source in order to maintain food security for the growing populations in those countries. Stem rust Puccinia graminis f. sp. tritici, and yellow rust P. striiformis f. sp. tritici of wheat continues to cause severe damage locally and globally, thereby contributing to food insecurity. In this paper biology and taxonomy of stem rust and yellow rust, breeding for resistance, utilization of resistance sources from different gene pools, molecular characterization and genetic dissection of resistance to rusts are discussed
Morphology of the rust fungus Puccinia boroniae revisited
No full textPuccinia boroniae Henns. is a rust fungus endemic to Australia, infecting various Boronia spp. This study describes and illustrates, using light and scanning electron microscopy, the telial stage, teliospore germination and basidiospore production of specimens collected from commercial Boronia plantations in Western Australia. Unusual formation of a single basidiospore per germinating teliospore, and the pycnial stage, observed on Boronia megastigma leaves, are reported for the first time for P. boroniae
Interrelations between citrus rust mite, Hirsutella thompsonii and greasy spot on citrus in Surinam
No full textCounts of citrus rust mite (Phyllocoptruta oleivora (Ashm.)) on leaves and fruit of citrus rose to a peak in the two dry seasons, the build up taking 4-5 weeks. It then decreased partly through infection by the entomogenous fungus Hirsutellathompsonii Fisher and partly through a decline in feed quality. The low counts in the wet seasons were associated with rain rather than humidity, temperature or infections by H. thompsonii. Spraying with suspensions of fragmented mycelium of H. thompsonii (mass concentration 0.5-1.0 g litre -1) prevented the build up of citrus rust mite.The severity of greasy spot (Stenella sp.) was positively correlated with counts of citrus rust mite. Defoliation of citrus trees after greasy spot infection was associated with high counts of mite.Control of citrus rust mite (with chlorobenzilate: mass concentration of a.i. 2 g litre -1at 500 litre ha -1) was warranted when 25% of fruit or 15% of leaves bore at least one mite per lens field (1.5 cm 2). Greasy spot could be controlled by preventing build-ups of citrus rust mite
Economic Impacts of Soybean Rust on the US Soybean Sector
No full textThe spread of Asian Soybean Rust (ASR) represents a real threat to the U.S. soybean sector. We assess the potential impacts of ASR on domestic soybean production and commodity markets as well as the competitive position of the US in the soybean export market. We develop a mathematical stochastic dynamic sector model with endogenous prices to assess the economic impacts of ASR on US agriculture. The model takes into account the disease spread during the cropping season, the inherent uncertainty regarding the risk of infection, and the dichotomous decisions that farmers make (no treatment, preventive treatment, and curative treatment) facing the risk of infection. Our results suggest substantial impacts from potential ASR spread on agricultural output, prices and exports. Our simulation results suggest that substantial losses to the US soybean producers may be avoided by establishing effective soybean rust controls. ASR control policies can be particularly efficient if applied in the gateway regions on the path of the ASR spread. On the other hand, our results indicate a possible gradual shift in soybean production from lower-latitude states toward higher-latitude statesAsian Soybean Rust, Stochastic Models, Dynamic Models, Crop Production/Industries, C61, Q13,
Economic Impacts of Soybean Rust on the US Soybean Sector
No full textThe spread of Asian Soybean Rust (ASR) represents a real threat to the U.S. soybean sector. We assess the potential impacts of ASR on domestic soybean production and commodity markets as well as the competitive position of the US in the soybean export market. We develop a mathematical stochastic dynamic sector model with endogenous prices to assess the economic impacts of ASR on US agriculture. The model takes into account the disease spread during the cropping season, the inherent uncertainty regarding the risk of infection, and the dichotomous decisions that farmers make (no treatment, preventive treatment, and curative treatment) facing the risk of infection. Our results suggest substantial impacts from potential ASR spread on agricultural output, prices and exports. Our simulation results suggest that substantial losses to the US soybean producers may be avoided by establishing effective soybean rust controls. ASR control policies can be particularly efficient if applied in the gateway regions on the path of the ASR spread. On the other hand, our results indicate a possible gradual shift in soybean production from lower-latitude states toward higher-latitude states.Asian Soybean Rust, Stochastic Models, Dynamic Models, Agribusiness, Marketing, C61, Q13,
Decision Support System for Soybean Rust (Phakopsora pachyrhizi) Management using QnD
No full textThe objective of this project is to design a decision support system for soybean rust management using gaming software that incorporates farmer's decision making in the face of risks from soybean rust. Learning from past actions and neighbor's actions are also incorporated. Farmers observe rust outbreak in the current and past periods and decide over how much of land to allocate between soybean, corn and other crops. This decision is influenced by maximization of expected profits criterion which entails crop rotation choices that are based upon perceived risks, yield drags and input costs from altering optimum rotation patterns. Adoption of new technology in terms of selecting better rust management practices is also analyzed in an adaptive management framework. The software meets the need of guiding policy formulation besides training stakeholders in making economically sound choices in the absence of empirical data over pest infestation.Research Methods/ Statistical Methods,
Morphology of the microcyclic rust fungus, Puccina boroniae, in Western Australia
No full textBoronia is an aromatic Australian native wildflower. Several species endemic to Western Australia are commercially cultivated for the cut flower market.
Puccinia boroniae is an important rust pathogen of the two most common Boronia species grown commercially, B. heterophylla and B. megastigma, and was first described by Hennings in 1903., Only the telial stage has been observed in the field and recorded. P. boroniae has been described as a microcyclic rust fungus with teliospores able to germinate without a period of dormancy, however no reference to germination structures or host inoculations confirming this have been published.
The objectives of this study were to provide a current and detailed morphological description of the various spore stages observed in the field, to describe the teliospore germination structures and basidiospores, and to confirm the lifecyc1e of P.boroniae
Characterization of Lr46, a gene conferring partial resistance to wheat leaf rust
No full textComponents of resistance conferred by the Lr46 gene, reported as causing "slow rusting" resistance to leaf rust in wheat, were studied and compared with the effects of Lr34 and genes for quantitative resistance in cv. Akabozu. Lr34 is a gene that confers non-hypersensitive type of resistance. The effect of Lr46 resembles that of Lr34 and other wheats reported with partial resistance. At macroscopic level, Lr46 produced a longer latency period than observed on the susceptible recurrent parent Lalbahadur, and a reduction of the infection frequency not associated with hypersensitivity. Microscopically, Lr46 increased the percentage of early aborted infection units not associated with host cell necrosis and decreased the colony size. The effect of Lr46 is comparable to that of Lr34 in adult plant stage, but in seedling stage its effect is weaker than that of Lr34
Rust resistance in Salix to Melampsora larici-epitea
No full textA total of 174 Salix (willow) clones belonging to 57 species and 14 interspecific hybrids were inoculated with seven pathotypes of Melampsora larici-epitea using the leaf disc method. Infection types were scored based on the uredinial pustule area data and the inoculum density. A close correlation (R-2 = 0.82) was found between the average pustule area and the average number of spores produced. Most of the willows were also assessed in the field for rust in 1999. Most willow clones belonging to the species native to western Europe were infected by the rust. In inoculation experiments, uredinia developed on 46 S. viminalis clones, out of a total of 47. In the field, all the S. viminalis clones were infected by rust. Within the subgenus Vetrix, eight out of the 17 willow species that originated from North and South America produced rust pustules in inoculation experiments. Of these, S. pellita was most susceptible. Salix irrorata and S. lasiolepsis var. bracelinae produced well developed pustules after inoculation but no rust infections were detected in the field. In both leaf disc tests and field assessments, no rust infections were found on S. candida, S. cordata, S. drummondiana, S. eriocephala, S. hookeriana, S. houghtonii, S. humilis, S. rigida var. mackenziana and S. syrticola. Of 12 species of subgenus Vetrix native to northeast Asia and Japan, only S. kochiana was susceptible both in inoculation tests and in the field. Salix rossica produced no symptoms in leaf disc tests but showed low levels of infection in the field. The maximum infection type scores in leaf disc tests were highly significantly correlated with field disease severity scores (Spearman rank correlation coefficient was 0.76, P < 1 x 10(-10))
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