Otim, Michael HillaryOmara, TomWamani, SamOcitti, Patrick...
11页
查看更多>>摘要：Cassava whitefly are a group of cryptic species within the Bemisia tabaci sensu lato complex that causes significant damage to cassava in Africa. B. tabaci Sub-Saharan Africa 1 (SSA1) is the major species in the study region which transmits plant-virus diseases to cassava and causes direct feeding damage. Benefits from management of cassava viral diseases through deployment of resistant varieties are being undermined by their susceptibility to B. tabaci SSA1 and the problem is exacerbated by high populations of B. tabaci in cassava fields. To develop a clean seed system that is disease-free, the judicious use of insecticides is required to manage this pest and vector. This study evaluated the effect of timing of insecticide application on controlling B. tabaci SSA1 population abundance and damage to cassava. Field trials were carried out between 2017 and 2018 in Kamuli and Wakiso districts of Uganda using the widely available insecticide Imidacloprid. Three cassava cultivars (NAROCASS1, SAUTI, KBH/ 2002/026) were planted in a randomized complete block trial design replicated three times. The insecticide was applied in split-plots designated as: (i) no protection (NP), no insecticide applied (control), (ii) early protection (EP), insecticide applied 2 times between 0 and 4 months after planting, (iii) long protection (LP), insecticide applied 3 times between 0 and 8 months after planting, and (iv) total protection (TP), insecticide applied 4 times between 0 and 12 months after planting. Except for control plots, stem cuttings were first dipped into a diluted solution of Imidacloprid prior to planting. Bi-monthly data were collected on the B. tabaci population, feeding damage, cassava mosaic disease and cassava brown streak disease. Stem cuttings and root yields were determined at harvest. The marginal rate of return for each treatment was calculated to determine cost effectiveness. Insecticide application effectively reduced B. tabaci populations, feeding damage and disease spread. Cassava yield differed significantly with insecticide treatment and amongst cultivars. Root and stem yield losses of >60% was recorded in unprotected control plots. The marginal rate of return of the early protection (0-4 MAP) program was 163%. We discuss these findings and the implication for judicious use of insecticides as part of a cassava clean seed system.
Doungous, OumarMasky, BoutouLevai, Dopgima L.Bahoya, Joseph A. L....
7页
查看更多>>摘要：Cassava plays a key role in the food security and economy of Cameroon, but its production is constrained by cassava mosaic disease (CMD). However, comprehensive surveys of CMD in Cameroon have been lacking. This study aimed at evaluating the current status of CMD and its whitefly vector. Field surveys were conducted in 2020 using a sampling, diagnostics and data storage protocol that has been harmonized across 10 West and Central African countries for ease of comparison. Thirty plants per field were assessed for CMD severity, whitefly abundance and source of infection. Surveys were conducted in 343 fields and confirmed the presence of CMD in all 10 regions of Cameroon. Among the 10,057 assessed plants, 33.07% were deemed healthy (asymptomatic). At the field level, only 6.7% fields were found to be healthy. The mean CMD incidence across the country was 66.93%, and the mean severity score was 2.28. The main mode of infection was likely through contaminated cuttings. The mean whitefly count per plant was 5.78. This study is the first countrywide survey of CMD in Cameroon and provides insights that can be useful for improving the country's CMD intervention and management strategies.
Patrocinio, Nara Georgia R. B.Niella, Givaldo RochaSolis, KarinaPenaherrera, Sofia...
9页
查看更多>>摘要：Moniliophthora perniciosa is a hemibiotrophic plant pathogen that causes witches' broom disease (WBD) in Theobroma, Herrania, and other plant species. This disease is one of the primary threats that reduce the yield of cacao and cupuacu plantations in Tropical America. Thereby, there is a growing concern that the pathogen may spread to other areas. The fungus can infect flowers, pods, and stems, causing various symptoms, including stem swellings and dark brown necrotic pods. In some cases, these symptomatologies are very similar to other cacao diseases, such as the black pod (Phytophthora spp.) and frosty pod rot (M. roreri) of cacao. Pathogens isolation and identification from diseased samples need expertise. Thus, the objective of this work was to develop a diagnostic guide with standard procedures with the aid of a molecular marker for M. perniciosa identification that is specific, sensitive, and cost-effective. A genomics-based approach was used to identify unique primer pairs to M. perniciosa. The specificity of 24 primer pairs in identifying M. perniciosa from pure culture gDNA was evaluated by conventional polymerase chain reaction (PCR) with approximately 400 isolates from ten fungal species of common occurrence in cacao plantations, including M. roreri. No amplicon was detected from other fungal species, confirming the high specificity and sensibility of the M. perniciosa specific markers Mp44 and Mp47 for molecular identification of M. perniciosa from pure culture. Finally, the present study provides a set of standardized WBD diagnosis procedures that associate a classical with a molecular approach by PCR-based identification of M. perniciosa.
Arncken, C.Hirschvogel, C.Messmer, M. M.Leska, A....
7页
查看更多>>摘要：White lupin (Lupinus albus L.) is a promising crop to meet the rising global demand for plant-based protein. The seed-borne pathogen Colletotrichum lupini, however, threatens lupin cultivation worldwide. Seed dressings using synthetic fungicides were shown effective to reduce infection levels, but their negative environmental impact and exclusion from organic production calls for more sustainable solutions. In this study, a total of eleven different alternative seed treatments were tested in field trials in Switzerland between 2018 and 2021. Treatment types consisted of: hot water, steam, electron, long-term storage, elevated partial pressure of oxygen (EPPO), vinegar, plant extracts and biological control agents (BCAs). The BCAs were tested for potential antagonistic activity against C. lupini during white lupin infection under controlled conditions prior to field trials. Long-term storage and vinegar treatments successfully reduced disease incidence and increased yield to levels similar to those observed for certified seeds, without significantly affecting germination rate. Although promising, effectiveness of these treatments needs further validation. Four BCAs showed significant disease reductions under controlled conditions. Besides lowering disease severity, two BCAs also reduced C. lupini DNA in stem tissue. These reductions, however, were not observed in the field, highlighting the importance of field validations. The treatments identified in this study provide a solid basis for the development of sustainable and effective seed protection strategies in white lupin to control C. lupini successfully.
Garnica, Vinicius C.Jhala, Amit J.Harveson, Robert M.Giesler, Loren J....
8页
查看更多>>摘要：A multi-environmental field study was conducted in 2017 and 2018 in Nebraska to investigate potential interactions between soybean seedling diseases and soil-applied residual pre-emergence (PRE) herbicides. Experiments were established from mid-May to early June in fine-textured, poorly drained soils with a history of seedling establishment problems. PRE herbicides consisted of chlorimuron-ethyl, flumioxazin, metribuzin, saflufenacil, and sulfentrazone applied at labeled rates, in addition to non-treated control. Assessments included soybean injury, seedling root lesion severity (DSI), plant height, population, biomass, and yield. Additionally, symptomatic seedling roots were sampled for fungal and oomycete organisms to expand comprehension of potential biotic associations. Greater soybean injury and reduced root biomass were observed in two distinctive environments following PPO-inhibiting PRE herbicide applications. Exceptionally in one environment, where DSI seemed (P = 0.07) lower for metribuzin in comparison to saflufenacil, PRE herbicides did not affect seedling root rot severity and no yield differences occurred among treatments. Community composition depicting Fusarium, Phytophthora, Pythium, and Rhizoctonia genera varied considerably across environments (P < 0.001) and DSI classes (P = 0.002), representing distinctive ecological environments under investigation. Phytophthora structured a large portion (>40%) of the total primary pathogenic isolates recovered in the highest DSI environment, whereas Pythium frequency ranged from 4.6% to 22% across all surveyed environments, and Rhizoctonia recovery was low (<10.3%) and sporadic. Across environments with varying DSI and soilborne pathogen composition, results indicated a lack of consistent interaction between soil-applied residual PRE herbicides and the incidence of soybean seedling diseases in optimal to delayed planting situations.
查看更多>>摘要：The disease caused by strawberry vein banding virus (SVBV) is one of the main virus diseases affecting the growth and development of strawberries, and the development of an on-site method for rapid detection of SVBV would be useful for breeding virus-free strawberry seedlings. In this study, we used isothermal recombinant polymerase amplification (RPA) combined with lateral flow strip (LF strip) testing to achieve rapid diagnosis of SVBV following on-site rapid DNA extraction. The DNA target for the SVBV-RPA amplification was the specific nucleotide region, which is conserved between different SVBV isolates in China. This assay allowed detection of SVBV within 30 min, comprising rapid N3 DNA extraction for 10 min, DNA amplification with RPA for 15 min at 40 degrees C, and visualization of the amplicons by LF strip for 5 min. The conservative detection limit was as low as 10 pg DNA under optimized conditions. Furthermore, the diagnostic results obtained by SVBV-LF-RPA on-site for detection of suspected samples were consistent with those obtained by polymerase chain reaction (PCR), achieving the aim of highly sensitive on-site rapid diagnosis of most isolated SVBV strains. The system was successfully applied and validated for on-site detection of SVBV in the production of strawberry virus-free seedlings in Shanghai, demonstrating its suitability for on-site diagnosis of SVBV and high potential for application to SVBV detection nationwide.
Visser, B.Terefe, T.Pretorius, Z. A.Boshoff, W. H. P....
10页
查看更多>>摘要：Cultivated barley (Hordeum vulgare) is an important winter cereal in South Africa (SA), ranked second after wheat. Leaf rust, caused by Puccinia hordei Otth. (Ph), is one of the most common diseases affecting grain yield and quality of barley. In this study, isolates of Ph were pathotyped using differential cultivars and lines with designated Rph-resistance genes, as well as a set of Bowman introgression lines (BW) containing resistance genes Rph1 to Rph15. Single pustule isolates derived from recently collected field isolates, typed as Ph race UVPh7235, showed increased virulence to Rph3 when compared with previously described races from SA. Discrepancies in phenotypic responses were recorded between standard differential lines carrying Rph2 , Rph6 and Rph9 and the corresponding BW lines. Results for barley cultivars with designated sources of adult plant resistance revealed low seedling infection types (ITs) for Baronesse (Rph20 + Rph24) to all Ph isolates and for Lenka (Rph20 + Rph23 + Rph24) to isolates of Ph races UVPh3231 and UVPh7231. The barley cultivars Agulhas and Cristalia showed low seedling ITs and moderate to high levels of adult plant resistance under field and greenhouse conditions, respectively. Genotyping of 48 Ph isolates with 20 microsatellite markers revealed five closely related genetic lineages with low gene diversity and allelic richness levels. While STRUCTURE analysis revealed three clusters, no clear division of the isolates into the clusters was evident, as the isolates were admixed for all three. Linkage disequilibrium analysis, as well as higher HO versus HE values, supported the hypothesis that the South African Ph population is clonal, consisting of a single genetic lineage.
查看更多>>摘要：Early blight (EB) caused by Alternaria solani is one of the most important tomato diseases in Kenya and farmers predominantly rely on synthetic fungicides to control it. However, there have been many complaints from farmers about the declining control efficacy of many fungicides used. In this study, 96 A. solani isolates, collected from tomato fields in 3 counties of Kenya (Kirinyaga, Kajiado and Kiambu), were assessed in vitro for sensitivity to two commonly used fungicides; Azoxystrobin and Difenoconazole, at varying concentrations. Isolates were considered resistant to the fungicide whenever their Percent Mycelial Growth Inhibition (MGI) at manufacturer's recommended dosage was below 50% and sensitive if above 50%. Although Difenoconazole resistance was not detected at the tested concentrations, majority of the isolates (64%) were resistant to Azoxystrobin. To determine the genetic basis of this Azoxystrobin resistance, DNA was extracted from all isolates, the Cyt b gene amplified and analyzed for resistance-associated mutations, at positions 129, 137 and 143. Results indicated that two mutations were present in the isolates. The F129L mutation was present in all Azoxystrobin resistant isolates plus 10 sensitive ones with MGI values close to the discriminatory threshold (MGI 50%). The G143S mutation was detected in 26 isolates (27%) but did not have a significant effect on sensitivity of isolates to Azoxystrobin. These findings indicate that Kenya's A. solani populations are developing resistance to some fungicides by mutation and provide justification for deployment of anti-resistance strategies, to ensure more effective management of tomato early blight.
Kiniec, AgnieszkaPieczul, KatarzynaPiszczek, Jacek
6页
查看更多>>摘要：Long-term and intensive use of fungicides may lead to fungal resistance to active ingredients, even with different modes of action. In Poland, Cercospora leaf spot (CLS), the most remarkable disease of sugar beet, is mainly controlled with benzimidazoles (MBC), triazoles (DMI), and strobilurins (QoI). A constant monitoring of the emergence and the development of resistant fungal strains is required by the limited number of active ingredients. On the basis of RFLP analysis application, the aim of the study was to determine and monitor simultaneous appearing of C. beticola strains with E198A and G143A mutations. Mutation E198A in the beta-tubulin gene is the main reason for MBC-resistance. Whereas mutation G143A in the cytochrome b is responsible for QoIresistance. Most of the 414 tested C. beticola isolates (90%) were able to grow (growth inhibition percentage<50%) on the medium amended with 1 mu g/ml thiophanate-methyl, and 34% of the isolates on the medium amended with 1 mu g/ml azoxystrobin. Based on the PCR-RFLP analysis both mutations were detected in 44% of the tested isolates. The current study is the pioneer detection of multiple resistances to MBC and QoI fungicides in C. beticola in Poland and the European Union. The presence of multiple resistant isolates in the population of pathogens is adverse and this phenomenon requires thorough monitoring and registration of new active ingredients, allowing effective control of CLS.
查看更多>>摘要：Cassava mosaic disease (CMD) is the main threat to cassava (Manihot esculenta Crantz) production in Benin. This study was conducted to assess CMD incidence, disease severity, and adult whitefly (Bemisia tabaci) populations in 11 regions of Benin. A total of 180 cassava fields across the country were assessed during June-December 2020 following the harmonized protocol of the Central and West African Virus Epidemiology program. Based on symptoms observation, CMD was present in all surveyed fields in Oueme and Alibori regions. The highest disease incidence levels were observed in Malanville (100%), Kpomasse (86.67%), Kandi and Zagnanado (both 81.67%), Segbanan (80%), and Avrankou (76.67%) districts. The highest mean severity scores were in Couffo (3.68), Mono (3.63), and Atlantique (3.33) regions, while the lowest was in Alibori (2.37). Adult whitefly populations (mean number/plant) were highest in Couffo (15.88) and Mono (13.00) regions and lowest in Donga (0.06). Significant relationships were found between CMD severity and whitefly abundance (P = 0.0010) but there was no significant relationship between whitefly numbers and CMD incidence (P = 0.0577). These findings indicate that CMD has expanded its range across Benin. They also provide a basis for designing a response strategy for the control of cassava virus diseases such as CMD.
NSTL
Elsevier