Mutants with increased sensitivity to caffeine

Mutants with increased sensitivity to caffein

Guanine-requiring mutants

Guanine-requiring mutant

Experience with the Applegate-Nelson-Metzenberg method of mutant enrichment in high sorbose medium

Experience with the Applegate-Nelson-Metzenberg method of mutant enrichment in high sorbose mediu

Estimation Of Reference Crop Evapotranspiration Using Fuzzy State Models

Daily evapotranspiration (ET) rates are needed for irrigation scheduling. Owing to the difficulty of obtaining accurate field measurements, ET rates are commonly estimated from weather parameters. A few empirical or semi–empirical methods have been developed for assessing daily reference crop ET, which is converted to actual crop ET using crop coefficients. The FAO Penman–Monteith method, which is now accepted as the standard method for the computation of daily reference ET, is sophisticated. It requires several input parameters, some of which have no actual measurements but are estimated from measured weather parameters. In this study, we examined the suitability of fuzzy logic for estimating daily reference ET with simpler and fewer parameters. Two fuzzy evapotranspiration models, using two or three input parameters, were developed and applied to estimate grass ET. Independent weather parameters from sites representing arid and humid climates were used to test the models. The fuzzy estimated ET values were compared with direct ET measurements from grass–covered weighing lysimeters, and with ET estimations obtained using the FAO Penman–Monteith and the Hargreaves–Samani equations. The estimated ET values from a fuzzy model using three input parameters (Syx = 0.54 mm, r2 = 0.90) were found to be comparable to ET values estimated with the FAO Penman–Monteith equation (Syx = 0.50 mm, r2 = 0.91) and were more accurate than those obtained by the Hargreaves–Samani equation (Syx = 0.66 mm, r2 = 0.53). These results show that fuzzy evapotranspiration models with simpler and fewer input parameters can yield accurate estimation of ET

Optimization Of Fuzzy Evapotranspiration Model Through Neural Training With Input–Output Examples

In a previous study, we demonstrated that fuzzy evapotranspiration (ET) models can achieve accurate estimation of daily ET comparable to the FAO Penman–Monteith equation, and showed the advantages of the fuzzy approach over other methods. The estimation accuracy of the fuzzy models, however, depended on the shape of the membership functions and the control rules built by trial–and–error methods. This paper shows how the trial and error drawback is eliminated with the application of a fuzzy–neural system, which combines the advantages of fuzzy logic (FL) and artificial neural networks (ANN). The strategy consisted of fusing the FL and ANN on a conceptual and structural basis. The neural component provided supervised learning capabilities for optimizing the membership functions and extracting fuzzy rules from a set of input–output examples selected to cover the data hyperspace of the sites evaluated. The model input parameters were solar irradiance, relative humidity, wind speed, and air temperature difference. The optimized model was applied to estimate reference ET using independent climatic data from the sites, and the estimates were compared with direct ET measurements from grass–covered lysimeters and estimations with the FAO Penman–Monteith equation. The model–estimated ET vs. lysimeter–measured ET gave a coefficient of determination (r2) value of 0.88 and a standard error of the estimate (Syx) of 0.48 mm d–1. For the same set of independent data, the FAO Penman–Monteith–estimated ET vs. lysimeter–measured ET gave an r2 value of 0.85 and an Syx value of 0.56 mm d–1. These results show that the optimized fuzzy–neural–model is reasonably accurate, and is comparable to the FAO Penman–Monteith equation. This approach can provide an easy and efficient means of tuning fuzzy ET models

A microbiological assay for host-specific fungal polyketide toxins

Genetic analysis of biosynthetic pathways for fungal secondary metabolites depends on availability of efficient and dependable assays for the end products. Some fungal plant pathogens produce secondary metabolites called host-specific toxins. Until recently, all bioassays for these toxins required use of whole plants or plant parts (Yoder 1981 In: Toxins in Plant Disease, Durbin ed., pp. 45-78). Since host-specific toxins, by definition, affect only plants that are susceptible to the toxin-producing fungus, other plants, animals and microorganisms are not sensitive and therefore cannot be used in bioassays

Complementation of Cochliobolus heterostrophus trp- mutants produced by gene replacement

Transformation systems for most filamentous fungi are based on selection for drug resistance. This strategy is advantageous becasue wild-type strains, including isolates collected directly from the field, can be used as recipients in transformation experiements

Evaluation Of Methods For Estimating Daily Reference Crop Evapotranspiration At A Site In The Humid Southeast United States

Estimated daily reference crop evapotranspiration (ETo) is normally used to determine the water requirement of crops using the crop factor method. Many ETo estimation methods have been developed for different types of climatic data, and the accuracy of these methods varies with climatic conditions. In this study, pair−wise comparisons were made between daily ETo estimated from eight different ETo equations and ETo measured by lysimeter to provide information helpful in selecting an appropriate ETo equation for the Cumberland Plateau located in the humid Southeast United States. Based on the standard error of the estimate (Syx), the relationship between the estimated and measured ETo was the best using the FAO−56 Penman−Monteith equation (coefficient of determination (r2) = 0.91, Syx = 0.31 mm d−1, and a coefficient of efficiency (E) = 0.87), followed by the Penman (1948) equation (r2 = 0.91, Syx = 0.34 mm d−1, and E = 0.88), and Turc’s equation (r2 = 0.90, Syx = 0.36 mm d−1, and E = 0.88). The FAO−24 Penman and Priestly−Taylor methods overestimated ETo, while the Makkink equation underestimated ETo. The results for the Hargreaves−Samani equation showed low correlation with lysimeter ETo data (r2 = 0.51, Syx = 0.68 mm d−1, and E = 0.20), while those for the Kimberly Penman were reasonable (r2 = 0.87, Syx = 0.40 mm d−1, and E = 0.87). These results support the adoption of the FAO−56 Penman−Monteith equation for the climatological conditions occurring in the humid Southeast. However, Turc’s equation may be an attractive alternative to the more complex Penman−Monteith method. The Turc method requires fewer input parameters, i.e., mean air temperature and solar irradiance data only

Linkage among melanin biosynthetic mutations in Cochliobolus heterostrophus

Melanin is synthesized by C. heterostrophus from acetate via pentaketide and several dihydroxynaphthalene intermediates (Tanaka et al. 1991 Mycol. Res. 95:49-56), as it is for certain other fungi (Bell and Wheeler 1986 Ann. Rev. Phytopathol. 24:411-451; Kubo et al. 1989 Exp. Mycol 13:77-84; Chumley and Valent 1990 Mol. Plant-Microbe Int. 3:135-143). Previously, five melanin deficient mutants of C. heterostrophus were analyzed by Tanaka et al. (Mycol. Res. 95:49-56), who were unable to establish complete linkage relationships because three of the mutations (alb1, alb3, and brn1) showed no recombination when crossed to each other, and were unlinked to the other two (sal1 and pgr1), which mapped about 12 cM apart. A sixth color mutation, scr1, represented a third linkage group, but there was no evidence of its involvement in melanin biosynthesis. Independently, we have recovered six melanin-deficient mutants, one of which (alb1, Leach et al. 1982 J. Gen. Microbiol. 128:1719-1729) was included in the study of Tanaka et al. and maps to chromosome 1 on the C. heterostrophus RFLP map (Tzeng et al. 1992 Genetics 130:81-96). We report here that our remaining five melanin-deficient mutants [crm1 (light cream), crm2 (dark cream), brn1 (brown), rsy1 (rose), and probably gra3 (gray)] are linked to, but are not allelic with, alb1 (white) and constitute a gene cluster on chromosome

Split-Marker Recombination for Efficient Targeted Deletion of Fungal Genes

A commonly used method for fungal gene deletion is introduction of linear DNA consisting of a selectable marker gene flanked on both sides by short stretches of DNA that target a gene of interest (Wirsel et al 1996 Curr. Genet 29:241-249). Gene deletion in Cochliobolus heterostrophus and Gibberella zeae occurs efficiently with this approach. To facilitate deletion construct synthesis, we have applied the split-marker” deletion strategy previously developed for Saccharomyces cerevisiae (Fairhead et al. 1996 Yeast 12:1439-57; Fairhead et al. 1998 Gene 223:33-46). Here, we describe both fusion PCR-based and plasmid-based deletion methods using this strategy with PEG-mediated protoplast transformation (Turgeon et al, 1985 Mol. Gen. Genet. 201:450-453). These methods are predicted to work well with any transformable fungus that undergoes homologous recombination between chromosomal and introduced DNA sequences