Studies on the Management of Potato Mop-Top Virus-Induced Tuber Necrosis

Tuber necrosis caused by the Potato Mop-top Virus (PMTV) has become one of the most important tuber necrosis diseases in the United States. PMTV is transmitted by the powdery scab pathogen (Spongospora subterranea f.sp subterranea (Sss)) and no effective methods of control are currently available for these pathogens. Potato cultivars have been reported to exhibit natural variability in their reaction to PMTV infection, making cultivar selection a viable management option. This dissertation focuses on finding short to long term strategies for managing PMTV tuber necrosis. In the first study, potato cultivars were assessed for sensitivity to PMTV-induced tuber necrosis in three separate field trials. Results of tuber assessments demonstrated that sensitivity to PMTV-induced tuber necrosis among cultivars follows a continuum of tolerant to sensitive. In the second study, advanced breeding selections of potato were evaluated for sensitivity to PMTV-induced tuber necrosis. The results revealed high variability in PMTV-induced tuber necrosis incidence and severity among selections and identified 17 of them to be tolerant, nine – moderately tolerant, eight - moderately sensitive, while six were found to be sensitive. Results of the field trials show that russet-skinned cultivars and selections are less sensitive to PMTV tuber necrosis than red-, yellow- and white-skinned types. In the third study, a growth chamber experiment was conducted to investigate the potential of using moisture regime to manage PMTV tuber necrosis. The results showed significant differences in PMTV tuber necrosis and powdery scab infection among moisture regimes. Maintaining soil moisture level at 90% field capacity throughout the season resulted in significantly higher incidence and severity of PMTV tuber necrosis and powdery scab infection than keeping soil at 60% field capacity. The results also show that the potato plant may be susceptible to PMTV-induced tuber necrosis and powdery scab infection throughout the season. The results of these investigations offer potato growers the option to plant less sensitive cultivars in areas where PMTV and powdery scab exist. This information can be utilized in future breeding efforts to obtain resistant potato cultivars. Useful information on using soil moisture regime as a management strategy for PMTV tuber necrosis has been provided.Northern Plains Potato Growers AssociationU.S. Potato BoardMinnesota Area II Potato Grower

Cacao sustainability: The case of cacao swollen-shoot virus co-infection.

The cacao swollen shoot virus disease (CSSVD) is among the most economically damaging diseases of cacao trees and accounts for almost 15-50% of harvest losses in Ghana. This virus is transmitted by several species of mealybugs (Pseudococcidae, Homoptera) when they feed on cacao plants. One of the mitigation strategies for CSSVD investigated at the Cocoa Research Institute of Ghana (CRIG) is the use of mild-strain cross-protection of cacao trees against the effects of severe strains. In this study, simple deterministic, delay, and stochastic ordinary differential equation-based models to describe the dynamic of the disease and spread of the virus are suggested. Model parameters are estimated using detailed empirical data from CRIG. The modeling outcomes demonstrate a remarkable resemblance between real and simulated dynamics. We have found that models with delay approximate the data better and this agrees with the knowledge that CSSVD epidemics develop slowly. Also, since there are large variations in the data, stochastic models lead to better results. We show that these models can be used to gain useful informative insights about the nature of disease spread

Social network to inform and prevent the spread of cocoa swollen shoot virus disease in Ghana

The cocoa swollen shoot virus disease is a major factor limiting cocoa (Theobroma cacao L.) productivity for West African farmers. The only treatment against this disease is to cut infected trees and replant with disease-free planting material. Research has recommended the prevention measures: (i) cordon sanitaire (leaving 10-m-wide cocoa-free zone around cocoa), (ii) barrier cropping, (iii) using partly tolerant hybrids, and (iv) removing specific alternative host tree species. Here, we evaluate the current adoption of these measures and identify their adoption constraints. We conducted a quantitative survey with 396 farmers in the Eastern and Western Regions of Ghana, held six focus group discussions and hosted a multi-stakeholder validation workshop with 31 key actors in the cocoa value chain. Our results indicate that the adoption of prevention measure against the disease remains limited. Farmers with a more extensive social network (number of family members/close friends who already adopted a particular measure), a larger farm size, more secure land tenure rights, and more knowledge about the measures were more likely to adopt them, especially barrier cropping, hybrid seedlings, and removing alternative host trees. Lack of knowledge about the measures was the single biggest barrier for their adoption, with 51% of the participating farmers not even being aware of any prevention measures. Here, we show for the first time that the social network is the main information source for farmers, which agrees with the finding that the flow of information between farmers and other stakeholders is a critical factor affecting knowledge spread and consequently adoption. Our results provide crucial insights for the elaboration of an implementation action plan to boost the dissemination of feasible prevention measures against the cocoa swollen shoot virus disease in Ghana in order to efficiently cover farmers’ needs for information (technical advice) and inputs (access to hybrid seedlings).ISSN:1774-0746ISSN:1773-015

Записки о социологическом осмыслении настоящего глобального экономического кризиса

The approaches to obtain the prior goal of staving off the financial crisis and economic depression are considered in the context of a modern global economic crisis. Learning the contradictions and consequences of the present crisis means analyzing the contradictions of a modern society. Five constructively interconnected distinctions reflecting the specificity of its sociological aspect are suggested. = В контексте современного глобального экономического кризиса анализируются подходы к решению приоритетной задачи по предотвращению финансового краха и экономической депрессии. Изучение противоречий и последствий настоящего кризиса предполагает анализ противоречий современного общества. Приводится пять конструктивно взаимосвязанных признаков, отражающих специфику его социологического аспекта