Determination of acequinocyl and hydroxyacequinocyl on fruits and vegetables by HPLC-DAD

A method for determining residues of the new reduced-risk pesticide acequinocyl and its deacetylated derivative hydroxyacequinocyl on fruits and vegetables (grapes, lemons, pears, and tomatoes) by HPLC is described. The pesticides were extracted from the fruits and vegetables with hexane and ethyl acetate solution (1:1, v/v), determined by HPLC-DAD at 250 nm and confirmed by LC/MS. No cleanup was necessary. This method is characterized by recoveries (0.01-4 mg/kg) > 77%, while the coefficient of variation was determined to be less than 11%. The limit of quantitation for both acequinocyl and hydroxyacequinocyl was 0.01 mg/kg for all matrixes.     

Chemical immobilization of chimpanzees (Pan troglodytes) using a combination of detomidine and ketamine

Objective To determine if a combination of detomidine and ketamine can be used for effective chemical immobilization of chimpanzees. Study design Observational study. Animals Twenty‐one adult captive chimpanzees (12 males, nine females), age 8–46 years, weighing 40.4–68.4 kg. Methods The chimpanzees were immobilized with intramuscular (IM) detomidine and ketamine by a darting system. Based on estimated weights, doses administered were 50 μg kg^?1 detomidine and 4 mg kg^?1 ketamine in groups 1 and 2, and 60 μg kg^?1 and 5 mg kg^?1 respectively in group 3. Eight minutes in group 1 and 15 minutes in groups 2 and 3 were allowed from the time of apparent immobilization before removing the animals from their enclosures. Body temperature, arterial haemoglobin saturation and pulse rate were measured. The time from injection to induction (recumbency and absence of voluntary movement), total anaesthetic and recovery times (with or without atipamezole) were recorded. Results Immobilization occurred within 5 minutes after darting in most animals. Early handling of the chimpanzees often resulted in arousal and required further doses of ketamine IM. Most animals were hypoxaemic and hypothermic. Occasionally, bradycardia was observed. Atipamezole resulted in an acceptable quality of recovery 10 minutes after IM injection. The duration of immobilization varied widely when no antagonist was administered. Conclusions and clinical relevance The combination detomidine (60 μg kg^?1) and ketamine (5–6 mg kg^?1) can be used for the immobilization of chimpanzees for non‐ to minimally invasive procedures. A period of 15 minutes should be allowed before handling to avoid unwanted arousal. Oxygen administration is recommended to reduce hypoxaemia. Administration of atipamezole is justified to hasten recovery.     

Response of Potato Genotypes to Bacterial Wilt Caused by Ralstonia Solanacearum (Smith)(Yabuuchi et al.) In the Tropical Highlands

Potato varietal resistance to bacterial wilt disease caused by Ralstonia solanacearum Yabuuchi et al., (Microbiology and Immunology 39:897–904, 1995) is the best management of the disease. Because the causal pathogen exhibits strong host-pathogen-environment interaction, screening the potential parents for resistance under the target growing environmental conditions is the first important step for effective resistance breeding. The objective of this study was to determine the response to bacterial wilt of selected potato genotypes currently grown by farmers in Kenya and candidate clones from the International Potato Center to identify parents that can be used in the local breeding program to develop resistant cultivars. A study was carried out at Kabete, Kenya for three consecutive seasons between November 2011 and February 2013. Thirty six potato genotypes were planted on an inoculated field at the Kenya Agricultural Research Institute (KARI), Kabete using alpha lattice experimental design with three replications. Data collected were days from planting to onset of wilting (DTOW), bacterial wilt incidence (BWI), total tuber weight (ton ha^?1) (TTW), total tuber numbers/hectare (TTN), proportion of ware sized tubers (PWTTW), proportion of symptomatic tubers based on weight (PSTTW), proportion of symptomatic tubers based on tuber numbers (PSTTN) and latent infection (LI) of the tubers. Almost, all the potato genotypes evaluated in this study were susceptible to bacerial wilt. Ranking of genotypes based on resistance differed among the three seasons. On average, the three most resistant genotypes were Kenya Karibu, Kenya Sifa and Ingabire. The study identified eight potato genotypes (Meru, Ingabire, Kenya Karibu, Sherekea, Kihoro, Tigoni, Bishop Gitonga and Cangi) to be used as promising parents for subsequent crosses. The chosen genotypes are prolific in pollen production and popularly grown by Kenyan farmers.     

Inheritance of resistance to Fusarium wilt and yield traits in pigeonpea

Fusarium wilt is the main pigeonpea production constraint in Malawi. The purpose of the study was to understand the nature and mechanism of inheritance of F. wilt resistance, yield and secondary traits in pigeonpea. 48 crosses were generated in a 12 lines × 4 testers mating scheme. Some F₁ plants were selfed for segregation analysis for inheritance pattern of resistance, while others were evaluated for resistance, yield and secondary traits. There were significant variations among F₁ plants for F. wilt, days to 50 % flowering, seed/pod, and number of secondary branches. Specific combining ability (SCA) effects were predominant for F. wilt, days to 50 % flowering and number of secondary branches. The general combining ability (GCA) effects, mainly due to maternal genotypes, were preponderant for yield and other secondary traits. The significance of GCA and SCA effects suggested that variations were due to additive gene action in both the testers and parental lines arising from their interactions, and the dominance effects due to interactions of the parental lines. The χ² analysis suggested dominant patterns of inheritance for wilt in most of the F₂ populations. The segregation ratios of 3:1, 15:1, and 9:7 suggested the involvement of single or two independent/complementary dominant genes in the test donors. Involvement of a few genes governing wilt resistance suggested the ease of breeding for this trait. Pedigree breeding method would be recommended for incorporating various traits in pigeonpea.     

Iron distribution in the clay fraction of Cambisols as determined by Mössbauer spectroscopy,X-ray diffractometry and selective dissolution

Iron forms which characterize the clay fraction of four Cambisols from granite and the distribution of iron oxides in the soil profiles are studied by Mössbauer spectroscopy, X-ray diffractometry and selected chemical methods. The results obtained show that about 50 % of the Fe_t(6–10 % Fe) is not extracted by dithionite. The Fe_o/Fe_d ranges between 0.15 and 0.35. Oxalate dissolves goethite in different amounts, probably depending on the particle size and the Al-substitution level. The highest amount of hematite is found in the samples characterized by the lowest internal magnetic fields, suggesting that the soil distribution of hematite and goethite is related to environmental factors favouring or disfavouring Al-for-Fe substitution and crystallinity of the oxides.     

Genetic inheritance of resistance to cowpea aphid-borne mosaic virus in cowpea

Cowpea aphid-borne mosaic virus (CABMV) is a major virus disease in Uganda that causes substantial loss of the cowpea crop especially in growth and yield. The mode of gene action conferring resistance to the virus is not well understood. The objective of the study was to determine the genetic inheritance of resistance in cowpea crosses. Three susceptible (S) cowpea landraces that are commonly grown by farmers were crossed with five introduced resistant cowpea varieties in accordance with a North Carolina mating design II scheme. The F₁, F₂ and BC₁F₁ progenies generated were evaluated in the field together with their parents. They were then infected with two infection methods namely: by spreader-rows of S cultivar (Ebelat) and artificial inoculation of virus extracts. The results obtained showed that general combining ability (GCA) and specific combining ability (SCA) effects were significant, indicating that both additive and non-additive gene effects controlled virus infection. The results further demonstrated that the GCA effects (59.8?%) were more important than SCA effects (40.2?%) in determining virus resistance in the cowpea varieties. Utilisation of good general combiners of the varieties MU-93, IT82D-516-2, SECOW-2W and IT85F-2841 in hybridisation to improve virus resistance in cowpea crosses would be recommended. The result of this study provided an indication that CABMV resistance was conditioned by more than one recessive gene in eight populations, but also revealed resistance to be conditioned by a single recessive gene in the other seven populations. Observation of continuous distribution of progenies for severity data in the F₂ populations also confirmed significance of quantitative inheritance for CABMV resistance. Therefore, the significance of GCA effects suggests that recurrent selection could be applied to accumulate the additive genes for resistance in F₂ populations.     

Phytoplankton community structure and the drawdown of nutrients and CO2 in the southern ocean

Data from recent oceanographic cruises show that phytoplankton community structure in the Ross Sea is related to mixed layer depth. Diatoms dominate in highly stratified waters, whereas Phaeocystis antarctica assemblages dominate where waters are more deeply mixed. The drawdown of both carbon dioxide (CO2) and nitrate per mole of phosphate and the rate of new production by diatoms are much lower than that measured for P. antarctica. Consequently, the capacity of the biological community to draw down atmospheric CO2 and transport it to the deep ocean could diminish dramatically if predicted increases in upper ocean stratification due to climate warming should occur.