Waste Corn as a Source of Inoculum of Aspergillus Flavus, the Cause of Aflatoxin

Aspergillus Flavus occurs worldwide in diverse habitats on a variety of plant and animal substrates. In the United States, contamination of susceptible crops particularly maize, peanuts, cottonseed, and tree nuts has become a major health concern because of the development of the carcinogen, aflatoxin. Extensive research into all aspects of the biology of A. flavus over the past twenty years still has left many unanswered but very basic questions about the ecology of this important organism

Stability of sweet potato cultivars to Alternaria leaf and stem blight disease

Alternaria leaf petiole and stem blight is an economically important disease of sweet potato (Ipomoea batatus L.) in tropical and sub-tropical environments. Published research on cultivar resistance to the sweet potato disease is limited. To evaluate cultivar reaction and stability to the disease, multi-location and replicated experiments were established in 12 environments in Uganda. Disease severity (area under disease progress curves - AUDPC), and cultivar root yield were also assessed. Significant differences (P<0.001) in AUDPC were detected among cultivars. Mean AUDPC ranged from 46.3 (Araka Red) to 78.4 (New Kawogo) across locations and seasons and the genotypes Araka Red and Tanzania had the lowest disease values. The location and season effects accounted for 67.1% and 7.5% of the total variance of AUDPC recorded among cultivars. The ranking of cultivars based on predicted AUDPC from Additive Main Effect and Multiplicative Interactive model (AMMI) showed that the NASPOT 1, the susceptible check, and New Kawogo were most susceptible to the disease in 11 of the 12 environments. Low and stable disease was consistently recorded and predicted on NASPOT 3 and the landrace cultivars Tanzania, Dimbuca, and Araka Red across environments. These results suggest that landrace cultivars had relative stability to the disease and wide adaptation across environments. These results suggest that AMMI statistical model and other multivariate techniques can be utilized for prediction of Alternaria disease stability in these locations

Reporting on the Seminar - Risk interpretation and action (RIA): Decision making under conditions of uncertainty

The paper reports on the World Social Science (WSS) Fellows seminar on Risk Interpretation and Action (RIA), undertaken in New Zealand in December, 2013. This seminar was coordinated by the WSS Fellows program of the International Social Science Council (ISSC), the RIA working group of the Integrated Research on Disaster Risk (IRDR) program, the IRDR International Center of Excellence Taipei, the International START Secretariat and the Royal Society of New Zealand. Twenty-five early career researchers from around the world were selected to review the RIA framework under the theme of \u27decision-making under conditions of uncertainty\u27, and develop novel theoretical approaches to respond to and improve this framework. Six working groups emerged during the seminar: 1. the assessment of water-related risks in megacities; 2. rethinking risk communication; 3. the embodiment of uncertainty; 4. communication in resettlement and reconstruction phases; 5. the integration of indigenous knowledge in disaster risk reduction; and 6. multi-scale policy implementation for natural hazard risk reduction. This article documents the seminar and initial outcomes from the six groups organized; and concludes with the collective views of the participants on the RIA framework

Leaf petiole and stem blight disease of sweet potato caused by Alternaria bataticola in Uganda

In surveys conducted in 2001-03, the disease incidences in sweet potato ranged from 1 to 49% in Uganda. Symptoms typical of Alternaria leaf petiole and stem blight disease were observed. Symptoms initially manifested as small, dark gray to black oval lesions with lighter lesions centres on stems and petioles. Under humid conditions, lesions enlarged on stems and petioles resulting in petiole and stem girdling. Some leaves exhibited chlorotic and dry symptoms, while brown circular lesions with concentric rings were observed on older diseased leaves. In severe cases, defoliation occurred and soil beneath diseased vines was carpeted with blackened leaf debris. Based on pathogenicity tests and morphological observations, the causal organism was identified as Alternaria bataticola. This communication confirms previous record of sweet potato leaf petiole and stem blight disease caused by A. bataticola in Uganda

Occurrence and distribution of Alternaria leaf petiole and stem blight on sweetpotato in Uganda

Assessment of disease occurrence in relation to agroecological and cropping variables is essential for effective Alternaria leaf petiole and stem blight disease control. The occurrence and distribution of the disease was investigated in a systematic survey of the major sweet potato-producing districts in Uganda for two cropping seasons. The composition of the Alternaria sp. was determined from a random sample of diseased leaf tissues. Farmers' practices and perceptions on disease management were also investigated. A survey of the 35 districts in both years showed that Alternaria disease was widespread throughout Uganda. The predominant species observed were A. bataticola (55% of isolates) and A. alternata (40% of isolates). The severity of Alternaria disease was very low, however, the range in disease incidences were from 0 to 49.2%. The disease was more prevalent in the Lake Crescent Region than in the less humid regions of eastern and northern Uganda. No significant correlations were detected between altitude at which sweet potato cultivars were grown and disease severity or yield. Among the sweet potato cultivars surveyed, the lowest incidence of Alternaria disease was detected on cultivars Dimbuca and Silk. The study also noted that perception of farmers and disease practices were contributing factors to disease spread. These studies suggest that selective deployment of cultivars and cultural practices can limit the spread and damage attributed to Alternaria leaf petiole and stem blight disease of sweet potato. This is the first record of A. bataticola on sweet potato in Uganda

Impact of fungicide application and late blight development on potato growth parameters and yield in the tropical highlands of Kenya and Uganda

The effects of fungicide application and late blight development on potato varieties with different levels of resistance to late blight were quantified in Kenya and Uganda during the 1999 cropping seasons. Experiments were laid out in a randomised complete block design with three replications in three sites, Loreto and Kabete in Kenya and Kalengyere Research Station in Uganda. At each experimental site, plots consisted of 4 m rows with plants spaced at 0.75m x 0.3 m. Treatments consisted of three potato varieties and four application intervals of Dithane M-45 arranged in a factorial combination. Areas under disease progress curves (AUDPCs) was significantly lower in the sprayed plots than in the unsprayed plots. Disease levels were lower in plots with 7 days application interval and most severe in plots of 21 days spray interval. Yields were higher in the 7 days intervals and lower in the 14, 21-days intervals and in the unsprayed plots. Fresh tuber weights and dry tuber weights were higher in the sprayed plots and lower in the unsprayed plots, respectively. At Kabete, Kerr's Pink had the highest AUDPC value of 2139.3 and disease was least on Asante with an AUDPC value of 409.4. The corresponding AUDPC values for the control plots were 671.5, 945.6 and 2367.8 for Asante, Tigoni and Kerr's Pink, respectively. At Loreto, disease was also most severe on Kerr's Pink with an AUDPC value of 2076.3 and least severe on Tigoni that had an AUDPC value of 444.8. The corresponding AUDPC values for the control plots were 840.4, 1000.2 and 2740.0, for Tigoni, Asante and Kerr's Pink, respectively. The highest tuber yield of 41.3 t ha-1 recorded at Kabete for Asante was significantly higher than yields of Kerr's Pink (22.0 t ha-1) but was not different from the yields of Tigoni (39.9 t ha-1). At Loreto, Tigoni had the highest yields of 34.6 t ha-1 that was significantly different from that of Kerr's Pink (6.2 t ha-1) in the sprayed plots. At Kalengyere, disease levels were significantly (P = 0.05) lower in the sprayed plots than in the control plots and disease severity was least on variety Rutuku (AUDPC value of 17.9) in 7 day spray interval. Tuber yields were significantly (P = 0.05) higher in the sprayed plots and highest tuber yield was recorded on variety Kabale (39.5 t ha-1) in plots with 7 day spraying interval. Key Words: East Africa, fungicide, general resistance, growth parameters, late blight, yield (African Crop Science Journal 2001 9(1): 225-234

Evaluation of potato germplasm (Population A & B) for resistance to late blight in Kenya

Resistance of potato clones of populations A and B to late blight (Phytophthora infestans (Mont) de Bary) was evaluated in field studies during 1999-2000 long and short rains cropping seasons in Kenya at two locations, Kabete (1,800 masl) and Loreto (2,400 masl). Treatments consisted of germplasm materials introduced from International Potato Centre (CIP) headquarters in Lima, Peru from two populations arranged in a completely randomised block design with three replications. At Loreto, late blight was more severe during the long rains than in the short rains while at Kabete late blight was severe during the short rains than in the long rains. The most resistant late blight genotypes among the population A at Loreto were clones 387193.21 and KP93743.6 with AUDPC values of 204.9 and 269.4, and yields of 50.6 and 46.9 t ha-1, respectively. These two clones had also acceptable agronomic characteristics. Desiree (control) was the most susceptible with AUDPC value of 2674.0 and a yield of only 9.8 t ha-1. The most resistant genotype among the population B test materials at Loreto was clone 392640.28 with an AUDPC value of 252.9 and it had the highest yield of 53.4 t ha-1. Other resistant genotypes were 392640.13 and 392640.7 with an AUDPC values of less than 600 and also high yields of 41.8 and 40.5 t ha-1, respectively. The most resistant clone at Kabete was 390013.10 with an AUDPC value of 37.6 while the most susceptible one was 387969.1 with an AUDPC value of 671.9. Clone KP90182.4 had the highest yields of 35.0 t ha-1. Dutch Robjyn (susceptible check) had also a relatively low AUDPC value of 491.3 with a yield of 27.6 t ha-1. Generally, the low levels of disease observed at the two locations were due to low rainfall and relative humidity during the growing seasons. Potato tuber moth (PTM) infestation ranged between 0.5 to 20%. The high levels of PTM experienced were due to prolonged drought during the growing season. Key Words: Horizontal resistance, late blight, Kenya, potato tuber moth, Solanum tuberosum, Sub-Sahara Africa, yield (African Crop Science Journal 2001 9(1): 215-224