138,373 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
Abnormal germling development by brown rust and powdery mildew on cer barley mutants
No full textThe barley leaf rust fungus forms appressoria over host leaf stomata and penetrates via the stomatal pore. High levels of avoidance to leaf rust fungi have been described in some wild accessions of Hordeum species where a prominent wax layer on the stomata inhibits triggering of fungal appressorium differentiation. Leaf rust avoidance has not yet been found in H. vulgare. Since cuticular leaf waxes are implicated in the avoidance trait, we screened 27 eceriferum (cer) mutant lines of H. vulgare for avoidance to barley leaf rust. These mutations affect leaf waxes. Reduction in numbers of germ tubes forming appressoria over stomata was found in some lines, but the greatest reduction (ca 30%) was less than previously found in wild barley spp. or in an accession of H. chilense used here as a check. In one line (cer-zh654), avoidance was due to a combination of factors. Firstly, fewer germ tubes oriented towards stomata and so failed to contact them. Secondly, some germ tubes that encountered stomata did not form appressoria but over-grew them. In this line, therefore, the fungus tended to fail both to locate and to respond to stomata. The appressoria of barley powdery mildew form on leaf epidermal cells that they penetrate directly. On certain cer lines, a proportion of germlings of the barley powdery mildew fungus developed abnormally, suggesting that germlings failed to recognise and/or respond to the leaf surface waxes on these mutants
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 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
Search for partial resistance to leaf rust in a collection of ancient Spanish wheats
No full textA collection of 917 accessions of Spanish durum and bread wheat was screened for resistance to leaf rust (Puccinia triticina) under field conditions at three locations. Resistance levels ranged from very low to very high, high susceptibility being most frequent. Relative disease severity (referred to the most susceptible accession = 100 %) was lower than 20 % in about 6 % of the accessions in each location. In the collection most of the lines (84 %)displayed a susceptible infection type. A final selection of seven accessions (one of them durum) displaying low severity level in the field and high infection type in a growth chamber was chosen for further studies. High levels of partial resistant with longer latency period and high percentage of early aborted colonies without necrosis were found. They might be used in breeding programmes
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
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