The heritability of resistance to early blight in diploid potatoes (Solanum tuberosum, subsp.Phureja andStenotomum)
The heritability of resistance to early blight caused byAlternaria solani (Ell. & Martin) Son was estimated for field grown, diploid potatoes at Fletcher, North Carolina in 1981. Fourteen breeding lines, selected from a random mated hybrid population ofSolanum tuberosum, subsp.phureja andstenotomum, were used. Resistance was measured as the slope obtained by regressing the logit of the disease proportion Y, measured as % defoliation, on time. A wide range of resistance was found. Narrow-sense heritability, as determined by offspring-midparent regression, on an individual plant basis, was calculated to be 0.825.
Temporal sensitivity ofAlternaria solani to foliar fungicides
Alternaria solani Sorauer (Ellis) is a causal agent of early blight of potato (Solanum tuberosum L.). Sensitivity to chlorothalonil, triphenyl tin hydroxide (TPTH), and mancozeb was determined for field isolatesof A. solani in 1998 and 1999. Specifically, the relative sensitivity ofA. solani to foliar fungicides in field populations collected from several commercial fields was evaluated over the course of two growing seasons. Sensitivity to these foliar fungicides was determined with anin vitro spore-germination assay method. The fungicide concentration that inhibited conidial germination by 50% (EC50) was estimated for each isolate. Sensitivity ofA. solani isolates to TPTH and mancozeb varied little during the growing season, possibly because there were few TPTH and mancozeb applications made to the fields studied. At several locations, however, repeated exposure ofA. solani populations to chlorothalonil resulted in considerable variability in sensitivity, frequently causing isolates to have decreased sensitivity to this fungicide at the end of the growing season. In five of seven fields, isolates of A.solani collected at the end of the season were significantly less sensitive to chlorothalonil than isolates collected at the beginning of the season.ResumenAlternaria solani Sorauer (Ellis) es el agente causal del tizon temprano de la papa (Solanum tuberosum L.). La sensibilidad al clorotalonil, trifenil hidroxido de estaño (TPTH) y mancozeb se determinó para aislamientos de campo deA. solani en 1998 y 1999. Específicamente se evaluó la sensibilidad relativa deA. solani a los fungicidas foliares en poblaciones de campo colectadas de varios campos comerciales en el transcurso de dos campanas de cultivo. La sensibilidad a estos fungicidas foliares fue determinada con un métodoin vitro de germinación de esporas. Para cada aislamiento se estimó la concentratión de fungicida que inhibió la germinación de las conidias en un 50% (EC50). La sensibilidad de los aislamientos deA. solani al TPTH y al mancozeb variaron muy poco durante el período de cultivo, posiblemente porque se hicieron pocas aplicaciones de estos productos a los campos estudiados. En varios lugares, sin embargo, la repetida exposición de las poblaciones deA. solani al clorotalonil resultaron en una considerable variabilidad en sensibilidad, frecuentemente causando que los alslamientos disminuyan su sensibilidad a este fungicida al final de cada estación de cultivo. En cinco de siete campos, los aislamientos deA. solani colectados al final del cultivo fueron significativamente menos sensibles al clorotalonil que los aislamientos colectados al comienzo de la época de cultivo.
Intentional poisoning cases of animals with anticholinesterase pesticide-carbofuran in Sri Lanka.
Carbofuran is a broad spectrum insecticide and nematicide which inhibits acetyl cholinesterase. Several intentional poisoning cases of animals and birds including crows, dogs, cow, and elephant, using carbofuran were reported in Sri Lanka. Qualitative analysis of carbofuran in biological specimens was carried out using T.L.C and GC-MS. The quantitative analysis was carried out by HPLC using Zorbax Eclips XDB-C18 (150 x 4.6 mm I.D x 5 microm particle size) column with acetonitrile: water 25:75 v/v mobile phase and UV detection at 210 nm. The liquid-liquid extraction with chloroform was reproducible and sensitive. The procedure was validated in terms of linearity (0.996<r<0.999) for concentrations ranging from 1 to 200 microg/ml, repeatability (RSD 4.4% at 100 microg/ml, n=10) extraction recovery (91.7% at 100 microg/g, 77.3% at 20 microg/g), limit of detection (S/N ratio=3, 0.7 microg/ml) and limit of quantification (S/N ratio=10, 2.4 microg/ml). The method was found satisfactory and successfully applied in fatal cases of animals and birds due to carbofuran poisoning. The fatal carbofuran levels detected were in the range of 42-910 microg/g in crow's gizzard and contents, 50-800 microg/g in dog's stomach contents, 13-20 microg/g in dog's liver, 0.9 microg/g in cow's stomach and contents, 35 microg/g in elephant's stomach and contents.