Dissipation and Residues of Thiram in Potato and Soil

The residue levels of thiram during potato cultivation in open field were evaluated. Thiram residues were determined by methylation derivation method with high performance liquid chromatography (HPLC). Wettable powder (WP) formulation containing 25% thiram was applied at 2320 g active gradient hm−2(a.i. hm−2) dosage for the dissipation study. The decline rate in potato leave and soil followed first-order kinetics equation, and the half-life ranged from 2.8 to 5.4 days and 2.6 to 9.9 days, respectively. In terminal residue, the thiram was sprayed at 580 g a.i. hm−2(low concentration, recommended dosage) and 1160 g a.i. hm−2(high concentration, double of recommended dosage). The residues of thiram in potato and soil samples collected in the field at preharvest interval of 21 days and 30 days were all below 0.02 mg kg−1. The results show that thiram possesses low dietary risk in potato at harvest according to supervised residue field trial. It may be safe when used at recommended rate of application.

Optimized Extraction Technology for Chlorogenic Acid from Sweet Potato Leaf by CCD/RSM

The aim of this study was to optimized extraction chlorogenic acid from sweet potato leave by central composite design/response surface method (CCD/RSM). The effects of ethanol concentration, ratio of solid to liquid, and extraction time on the yield of chlorogenic acid were evaluated, and the yield of chlorogenic acid under analysis optimum condition was also forecasted. The optimized extraction conditions were as follows: extraction with a 20 fold volume of 70% aqueous ethanol solution for 2h. Under these conditions the theoretical yield of chlorogenic acid was 15.95 mg/g, and the measured value was 15.89 mg/g. This method is scientific, reasonable and feasible. It also laid a foundation for research and application of chlorogenic acid in sweet potato leaves.

Incidence of Potato Viruses in Different Districts of Khyber Pakhtunkhawa, Pakistan

Three consecutive potato crops are grown annually in Pakistan and Khyber Pakhtunkhawa (KPK) province is the main source for seed tubers. During the year 2010, 240 symptomatic and viral susceptible potato leave samples were collected from Swat, Dir, Abbottabad and Mansehra and serologically confirmed through Double Antibody Sandwich (DAS) Enzyme Linked Immunosorbant Assay (ELISA) against Potato virus X (PVX), Potato virus Y (PVY), Potato leaf roll virus (PLRV), Potato virus M (PVM), Potato virus S (PVS) and Potato virus A (PVA). The presence or absence of viruses was confirmed by observing the yellow and white color in ELISA plates respectively. According to ELISA results, overall percentage incidence of viral diseases was found highest in Swat (65%) followed by Mansehra (61%), Dir (53%) and Abbottabad (43.33%) while PVY and PVS were dominant in Swat (26.66%), Dir (20%), Mansehra (15%) and Abbottabad (21.66%) respectively. PVX was not detected in Abbottabad while Swat samples seemed to be free from PVM and PVA.