A phenomenological model of dry matter partitioning among plant organs for simulation of potato growth

A mathematical model of the process of dry matter partitioning among plant organs during the autotrophic period of potato development is presented. The model consists of a system of differential equations based on the concept of a sink. The sink strength is proportional to the dry matter (DM) biomass, subject to total photosynthesis production. The ageing process is taken into account. The equations contain a set of parameters which are estimated by fitting the numerical solution to the empirical data recorded from growth analysis in field experiments.     

A model for simulation of potato growth on the plant community level

A model for the main processes in potato growth is developed and used for the simulation of crop production under different meteorological conditions. The main control factors considered in the model are irrigation, fertilization and timing of harvest. The model is constructed on the level of the plant community. The time interval for the simulation of general dynamic processes is one day. To describe some important physiological processes during a day, the simulation is performed by subroutines with hourly time steps.     

Vegetative propagation of Vitellaria paradoxa by grafting

Vitellaria paradoxa or karité is a wild fruit-bearing tree species of sudano-sahelian parklands that plays an important socio-economic role in Sub-Saharan Africa due to the commercial and domestic value of the fruits. Principal constraints of karité fruit production are: long juvenile phase, slow growth, genetic variability and lack of knowledge regarding the cultivation of the species. To address these constraints and to enhance productivity and quality, five methods of grafting (side cleft, top cleft, tongue, chip budding and side veneer), two methods of pre-treatment of scions and rootstocks (washing with 10% sodium hypochlorite to wash off latex and sterilise and a control without washing), and two methods of protection of grafts against desiccation (covering with white plastic sheet and aluminium foil) were tested. The results showed decreasing success of survival of grafts 16 weeks after grafting for the five grafting techniques: side cleft (86.1%), tongue (80.9%), top cleft (78.1%), chip budding (38.1%) and side veneer (20.7%) grafting methods. The results also showed May to be the optimum time for grafting, with high rates of shoot growth and survival of grafts. The average annual growth rate of grafts was 12.6 cm. The pre-treatment of scions with 10% sodium hypochlorite, however, had no significant effect on survival of scions. There was also no significant difference in survival of scions between the two methods of protection of grafts against desiccation (aluminium foil and plastic sheet). Two grafts produced fruits two years after grafting using side veneer grafting.This revised version was published online in November 2005 with corrections to the Cover Date.     

Mathematical modelling and evaluation of the different routes of transmission of lumpy skin disease virus

ABSTRACT: Lumpy skin disease (LSD) is a severe viral disease of cattle. Circumstantial evidence suggests that the virus is transmitted mechanically by blood-feeding arthropods. We compared the importance of transmission via direct and indirect contact in field conditions by using mathematical tools. We analyzed a dataset collected during the LSD outbreak in 2006 in a large dairy herd, which included ten separated cattle groups. Outbreak dynamics and risk factors for LSD were assessed by a transmission model. Transmission by three contact modes was modelled; indirect contact between the groups within a herd, direct contact or contact via common drinking water within the groups and transmission by contact during milking procedure. Indirect transmission was the only parameter that could solely explain the entire outbreak dynamics and was estimated to have an overall effect that was over 5 times larger than all other possible routes of transmission, combined. The R0 value induced by indirect transmission per the presence of an infectious cow for 1 day in the herd was 15.7, while the R0 induced by direct transmission was 0.36. Sensitivity analysis showed that this result is robust to a wide range of assumptions regarding mean and standard deviation of incubation period and regarding the existence of sub-clinically infected cattle. These results indicate that LSD virus spread within the affected herd could hardly be attributed to direct contact between cattle or contact through the milking procedure. It is therefore concluded that transmission mostly occurs by indirect contact, probably by flying, blood-sucking insects. This has important implications for control of LSD.     

Management of insect pests in celery and potato crops by pneumatic removal

Over the course of 4 years, five sets of trials were run in celery and potato crops to evaluate the efficacy of a field-scale vacuum (FSV) unit for use in insect pest management. The unit was designed to dislodge insects by blowing air from lateral vents onto the plants while simultaneously vacuuming from above. Efficacy was evaluated by field observations, yellow sticky traps and hand vacuum sampling before and after the FSV. All insects evaluated were effectively removed by the vacuum unit; typically, population reductions of 50–75% were achieved with whiteflies, leafhoppers, and aphids. In some trials, reductions were achieved that lasted from week to week. Additionally, agromyzid leafminers were significantly reduced in number, but population reductions were temporary because of their strong flying ability.     

Continuous Drug Release by Sea Anemone Nematostella vectensis Stinging Microcapsules

Transdermal delivery is an attractive option for drug delivery. Nevertheless, the skin is a tough barrier and only a limited number of drugs can be delivered through it. The most difficult to deliver are hydrophilic drugs. The stinging mechanism of the cnidarians is a sophisticated injection system consisting of microcapsular nematocysts, which utilize built-in high osmotic pressures to inject a submicron tubule that penetrates and delivers their contents to the prey. Here we show, for the first time, that the nematocysts of the starlet sea anemone Nematostella vectensis can be isolated and incorporated into a topical formulation for continuous drug delivery. We demonstrate quantitative delivery of nicotinamide and lidocaine hydrochloride as a function of microcapsular dose or drug exposure. We also show how the released submicron tubules can be exploited as a skin penetration enhancer prior to and independently of drug application. The microcapsules are non-irritant and may offer an attractive alternative for hydrophilic transdermal drug delivery.     

Diagnosing agrosilvopastoral practices using Bayesian networks

This article discusses the potential of BNs to complement the analytical toolkit of agricultural extension. Statistical modelling of the adoption of agricultural practices has tended to use categorical (logit/probit) regression models focusing on a single technology or practice, explained by a number of household and farm characteristics. Here, a Bayesian network (BN) is used to model household-level data on adoption of agrosilvopastoral practices in Tiby, Mali. We discuss the advantages of BNs in modelling more complex data structures, including (i) multiple practices implemented jointly on farms, (ii) correlation between probabilities of implementation of those practices and (iii) correlation between household and farm characteristics. This paper demonstrates the use of BNs for ‘deductive’ reasoning regarding adoption of practices, answering questions regarding the probability of implementation of combinations of practices, conditional on household characteristics. As such, BNs is a complementary modelling approach to logistic regression analysis, which facilitates exploring causal structures in the data before deciding on a reduced form regression model. More uniquely, BNs can be used ‘inductively’ to answer questions regarding the likelihood of certain household characteristics conditional on certain practices being adopted.