Impact of Temperature and Rainfall Change on Epidemics caused by Plant viruses

Plant virus diseases are one of the limiting factors to crop productivity by diminishing the quantity, quality and responsible for significant economic losses worldwide. The Epidemic of plant virus diseases is the result of interactions between virus, host plant, vector, and environmental factors. Changes in host plants and insect vector dynamics that result from temperature and rainfall change could have an influence on the spread of plant viruses. The rising of temperature and heat stress increase the susceptibility of host plants to virus infection and accelerates the fitness of viruses to cause disease. The increasing temperature also changes insect vector population dynamics by accelerating insect phenology, causing earlier and prolonged colonization because it makes appropriate environmental conditions for the insect vectors. Insect populations of most virus vectors build up more rapidly in areas with high temperatures and high relative humidity and decline at low temperature. In addition, the rising temperatures can increase the efficiency of virus transmission from infected to healthy plants by insect vectors. An increasing frequency of heavy rainfall events is likely to slow the virus prevalence and incidence by washing insect vectors, thus reducing vector density. Flooding within annual crop growing period enhances the subsequent growth of weed and volunteer crop plant which act as reservoirs of insect vectors and the viruses, and its occurrence outside growing seasons increases subsequent growth of such reservoirs. Keywords: Host plant; Vectors; Virus epidemics DOI: 10.7176/JNSR/12-3-05 Publication date: February 28th 202

Review on Maize Chlorotic Mottle Virus: Distribution, Host Range, Transmission Mechanisms and Management Options

Plant virus diseases are serious constraints to the productivity and profitability of a wide range of crops. Epidemics of existing plant virus diseases and the emergence of novel virus diseases have become a serious threat to subsistence and commercial agriculture. The knowledge of virus transmission and its survival helps to understand how the disease transmits from infected plant to healthy, where it reserved, and this will lead to identify the most important variables and focus efforts to develop sustainable management strategies. Maize chlorotic mottle virus (MCMV) is transmitted from location to location, and from plant to plant through various mechanisms (mechanically, seed, insect vectors, and soil) and many kinds of wild grass and cultivated crops, maize residue are used as its reservoirs. Different weed species and cultivated plants used as alternate hosts, and soil and seed transmissibility of MCMV are epidemiologically important and contribute to maintaining virus inoculum available in the absence of maize in the field and increase the chances of continuing its survival. Integrated disease management approach, regular field monitoring, assessment of virus symptoms, and rouging-out diseased plants are recommended to prevent further spread by insect vectors. Apart from this, because the disease is still widespread in various countries, intensive MCMV recruitment, combined with integrated disease management, requires ongoing practice in countries where MCMV is prevalent and in those countries that have not yet reported MCMV. Keywords: Integrated management; Insect vector; plant residue; Soil transmission; Zea mays DOI: 10.7176/JNSR/13-5-02 Publication date:March 31st 202

Occurrence, Distribution, Economic Importance and Management of Maize Chlorotic Mottle Virus: A Review

Plant virus diseases are serious constraints to the production and productivity of a wide range of crops among which maize chlorotic mottle virus (MCMV) is a serious problem in maize production and productivity. The virus is primarily originated in South America (Peru) and later distributed into many countries of all the continents except Australia and Antarctica. It is transmitted from location to location, and from plant to plant mechanically, through seed, insect vectors, and/or soil. The virus has many host ranges of agricultural crops (Maize, Sorghum, Sugarcane and Finger millet) and wild species (Dinebra retroflexa, Setaria verticillata, Cyperus assimilis, Digitaria ternta and  Oplismenus hirtellus). MCMV alone causes 10-15% crop loss and up to 100% loss when it co-infects maize plants with other maize viruses such as maize dwarf mosaic virus, Sugar cane mosaic virus or Wheat streak mosaic virus. No any single disease control measure alone is effective in controlling the MCMV. However, an integrated virus disease management options (the use of disease-resistant crop varieties, proper field sanitation, removal of infection sources, use of virus-free seeds and chemical pesticides to indirectly control insect vectors) play a critical role in controlling the virus. Since the current status of the disease is wide spreading and on increasing trend, intensive MCMV employment, combined with integrated disease management, requires ongoing practice in countries where the virus is prevalent and in those countries that have not yet reported MCMV. Keywords: Integrated management; Insect vector; plant residue; Soil transmission; Zea mays DOI: 10.7176/ALST/87-03 Publication date: April 30th 202

Maize Chlorotic Mottle Virus: Distribution, Alternative Hosts, Transmission Mechanisms and Management Options

Plant virus diseases are serious constraints to the productivity and profitability of a wide range of crops. Epidemics of existing plant virus diseases and the emergence of novel virus diseases have become a serious threat to subsistence and commercial agriculture. The knowledge of virus transmission and its survival helps to understand how the disease transmits from infected plant to healthy, where it reserved, and this will lead to identify the most important variables and focus efforts to develop sustainable management strategies. Maize chlorotic mottle virus (MCMV) is transmitted from location to location, and from plant to plant through various mechanisms (mechanically, seed, insect vectors, and soil) and many wild types of grass and cultivated crops, MCMV infected maize residue are used as its reservoirs. Different weed species and cultivated plants used as alternate hosts, and soil and seed transmissibility of MCMV are epidemiologically important and contribute to maintaining virus inoculum available in the absence of maize in the field and increase the chances of continuing its survival. Integrated disease management approach, regular field monitoring, assessment of virus symptoms, and rouging-out diseased plants are recommended to prevent further spread by insect vectors. Apart from this, because the disease is still widespread in various countries, intensive MCMV recruitment, combined with integrated disease management, requires ongoing practice in countries where MCMV is prevalent and in those countries that have not yet reported MCMV. Keywords: Integrated management; Insect vector; plant residue; Soil transmission; Zea mays DOI: 10.7176/JBAH/11-19-04 Publication date:October 31st 202

Plant Viruses Detection and Diagnosis Based on Polymerase Chain Reaction Techniques: Review

Plant virus diseases result in the loss of billions of dollars annually by limiting plant production quantity and quality in the world. Among different strategies adapted for plant virus disease management, proper diagnosis and detection are the most important and essential strategies for the development of appropriate control measures. The current advanced techniques developed for the detection of plant viruses provided the chance to take practical managemental actions timely. Nowadays one of the most advanced diagnosis methods, polymerase chain reaction (PCR) is used extensively for the detection and identification of plant viruses. PCR is the advanced method that allows the specific amplification and hence detection of target DNA sequences from a mixture of nucleic acid extract in which specific amplification of targeted fragments of a single or a few copies of source DNA material is achieved within a few hours. The PCR method copies each piece of DNA fragments through all the cycles that leading to an exponential doubling of copies over time. Several modifications of PCR methods have been developed to boost the effectiveness of the method in diagnostic settings based on their applications. Reverse transcriptase PCR, immunocapture PCR, Multiplex PCR, co-operational PCR, and real-time PCR are the common and widely used types of PCR variants. Keywords: Detection techniques; PCR; Plant virus DOI: 10.7176/ALST/86-02 Publication date:March 31st 202

Maize Lethal Necrosis Disease in Ethiopia: A Newly Emerging Threat to Maize Production

The occurrence of maize lethal necrosis (MLN) disease in Ethiopia was first reported in 2014. Thereafter, consecutive surveys were carried out in all majormaize growing areas across the country to understand the levels of distribution and incidence as well as potential alternate hosts of the disease.  Symptomatology was used to determine the incidence and level of damage caused by MLN at the field level. Samples of maize plants and alternative  grass hosts showing MLN symptoms were collected in all areas surveyed. Viruses associated with the symptoms were diagnosed in the laboratory using  Enzyme-Linked Immunosorbent Assay (ELISA), Lateral Flow Assay (LFA), Real Time-Polymerase Chain Reaction (RT-PCR), Multiplex RT-PCR, and RT-PCR  using porous ceramic cube. The results showed a wider distribution of MLN in Ethiopia with incidence levels reaching as high as 100% in some areas.  Maize planted during the off-season were found to be severely affected by MLN as compared to the main season crop. In addition to maize, MLN viruses  were found to infect various grass species indicating the presence of alternate hosts. This study confirmed seed transmission of MLN disease, but  variable rates of transmission were observed that needs to be studied further. Considering the current rate of MLN disease distribution in Ethiopia,  necessary management strategies should be devised and implemented before the disease causes significant damage to maize production.&nbsp

Advanced and Commonly Used Serological Techniques for Detection and Diagnosis of Plant Virus: Review

Plant diseases caused by viruses are the most menace to sustainable agriculture, leading to numerous billion dollars in losses annually. Proper and accurate detection of plant viruses is always the key to developing appropriate solutions to manage the economic losses caused by them. Advances in technology have simplified the tools available to detect and diagnose viruses at a time when control measures should be used. Currently, nucleic acid and serological based diagnostic methods are widely used for plant viral identifications. Serological techniques which based on antibody and antigen reaction is broadly used for the detection of plant viruses because of its simplicity, adaptability and sensitivity. A large number of advanced serological tests are available such as enzyme-linked immunosorbent assay (ELISA), dot immunobinding assay, tissue blotting immunoassay and Lateral flow assay. Various ELISA varieties such as double-antibody sandwich- ELISA, triple-antibody sandwich-ELISA, and antigen-coated-ELISA are widely used in the detection and testing of plant viruses. Dot immunobinding assay performed on a nitrocellulose that the plant extracts are spotted onto a membrane while tissue blotting immunoassay is an easy method that the crude sap from plants is directly blotted and used for detection through immunology. Lateral flow assay is the latest and the only serological method used for the detection of viruses without the aid of laboratory and skilled personnel. It is an onsite and quick assay that can be performed by anyone and suitable for the detection of viruses that occur in high concentrations in plants. Keywords: Antibody, Antigen, ELISA, Plant virus, Detection, Serology DOI: 10.7176/ALST/91-02 Publication date: January 31st 202

Economical and Epidemiological Consequences of Seed Transmitted Plant Viruses. Review

Plant virus diseases greatly influence man’s economy by reducing the yield and quality of plant products. About one-quarter of the known plant viruses are transmitted through the seed. Seed transmission of plant viruses is an important means for the introduction of plant viruses into new localities where they may become established, spread rapidly, and can cause epidemics in the presence of suitable vectors and host species. Viruses may persist in seed for long periods so that commercial distribution of a seed-borne virus over long distances may occur. The location of the virus in seed determines the transmissibility of viruses through seed. The virus is considered to be externally seed transmitted when it is outside the functional seed and internally seed transmitted when it is within the tissue of the seed. Seed infection by the virus is epidemiologically important for the reason that it is the primary source of inoculums and forms the starting point for the initiation of the disease. Avoidance of virus inoculum from infected seeds; chemical seed disinfection, implementing the cultural practices like field sanitation, rouging, and crop rotation can reduce the virus disease incidence. The role of quarantines, resistant cultivars, healthy seed production, and certification schemes for healthy seed production are also critical measures for seed transmitted virus management. Keywords: Inoculum source; Management; Plant virus; Seed transmission DOI: 10.7176/RHSS/12-7-03 Publication date: April 30th 202

Economic Impact and Management of Plant Viral Disease: Review

Plant viral diseases in food crops pose a serious constraint to the productivity and profitability of a wide range of crops that affecting food production globally and cause enormous economic losses. Plant virus infections are emerging from time to time as major concerns in improving agricultural productivity. Rapidly-expanding global climatic change creates favorable conditions for development and increased spread of plant virus diseases due to direct or indirect impacts on population dynamics of virus-transmitting insect vectors. Plant virus disease management is the selection and use of appropriate technologies and practices to suppress disease to a tolerable level. Plant virus diseases are basically difficult to manage directly by use of chemical pesticides; however, integrated management methods which include cultural practices such as removal of infection sources, field sanitation, removal of alternative hosts, use of healthy seed (virus free seeds); chemical pesticides to control insect vectors indirectly through seed treatment and foliar spray are the most possible management measures of plant viral diseases. Keywords: Avoidance; Host resistance; Plant virus; Prevention DOI: 10.7176/JESD/13-5-01 Publication date:March 31st 202

Review on Seed Transmitted Plant Viruses: Economical and Epidemiological Consequences

Plant virus diseases greatly influence man’s economy by reducing the yield and quality of plant products. About one-quarter of the known plant viruses are transmitted through the seed. Seed transmission of plant viruses is an important means for the introduction of plant viruses into new localities where they may become established, spread rapidly, and can cause epidemics in the presence of suitable vectors and host species. Viruses may persist in seed for long periods so that commercial distribution of a seed-borne virus over long distances may occur. The location of the virus in seed determines the transmissibility of viruses through seed. The virus is considered to be externally seed transmitted when it is outside the functional seed and internally seed transmitted when it is within the tissue of the seed. Seed infection by the virus is epidemiologically important for the reason that it is the primary source of inoculums and forms the starting point for the initiation of the disease. Avoidance of virus inoculum from infected seeds; chemical seed disinfection, implementing the cultural practices like field sanitation, rouging, and crop rotation can reduce the virus disease incidence. The role of quarantines, resistant cultivars, healthy seed production, and certification schemes for healthy seed production are also critical measures for seed transmitted virus management. Keywords: Inoculum source; Management; Plant virus; Seed transmission DOI: 10.7176/ALST/93-02 Publication date: April 30th 202