Potato (Solanum tuberosum L.) is the fourth major crop of the world after rice, wheat and maize. Potato is an important crop which holds promise for food to millions of people especially in developing countries. In Ethiopia, the yield per unit area of potato is very low compared to those of other countries. There are many factors that reduce the yield of the crop among which the diseases like late blight (Phytophthora infestans) and bacterial wilt (Ralstonia (Pseudomonas) solanacearum) which play an important role. Diseases such as late blight, early blight, fusarium wilt and black leg primarily affect the crop/foliage whereas diseases such as black scurf, wart, powdery scab and common scab disfigure the tubers and reduce their market value. Major fungal and bacterial diseases affecting potato crop are reviewed here with respect to their identification, symptoms on potato plants or tubers, nature of the pathogen involved, epidemiology, control measures etc. Management of these diseases is therefore very essential. Late blight of potato can be managed using the following management (control) strategies: use of biological control agents, use of resistant varieties, intercropping, use of certified disease-free seed, use of selective fungicides and cultural practices such as destruction of cull piles by freezing or deep burying, destruction of volunteer potato plants in nearby fields throughout the season, destruction (desiccate, disc or flail and desiccate) of infected plants to avoid spread, reduction of periods of leaf wetness and high humidity within the crop canopy by appropriately timing irrigation, application of a recommended fungicide spray program (the program should start prior to the arrival of the pathogen) and desiccation of vines prior to harvest.

Plant disease diagnosis is a form of hypothesis testing, where the hypothesis is simply the identity of the disease, and a good diagnostician goes through multiple iterations of the scientific method (seeking evidence through testing that supports or refutes the hypothesis that s/he generates). Identification of affected plants is one of the first steps in diagnosing a plant disease. Diagnosis is one of the most important aspects of a plant pathologist's training. Both scientific and common names of the plant should be noted. Without proper identification of the disease and the disease-causing agent, disease control measures can be a waste of time and money and can lead to further plant losses. Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll. Bacteria are prokaryotes. These are generally single-celled microorganisms whose genetic material (DNA) is not bound by a membrane and therefore is not organized into a nucleus. Our general objective was to acquaintance with Plant pathology laboratory materials & make disease diagnosis from field up to laboratory based on symptom and signs from different plant samples. All most all necro-tropic and bio-tropic fungi are grown on PDA agar, but bio-tropic fungi and bacterial diseases cannot grow on PDA agar. The best preferable method to diagnosis bio-tropic fungi is using direct leaf assay and blotting method on petri-dish. For bacterial disease identification we use NA agar. From this laboratory work I had concluded that those fungal and bacterial diseases need their niche to grow and well identified. It is very difficult to identify plant diseases based on sign and symptom. It is very imperative to diagnosis plant disease by collaborating both conventional (using sign and symptom) and molecular methods. It needs further work to identify rust diseases using race analysis up to f. species level.

Plant diseases have caused severe losses to humans in several ways. The goal of plant disease management is to reduce the economic and aesthetic damage caused by plant diseases. The main objective of this review was to understand about a gene pyramiding concepts with principles &application in disease management. Disease management procedures are frequently determined by disease forecasting or disease modeling rather than on either a calendar or prescription basis. Correct diagnosis of a disease is necessary to identify the pathogen, which is the real target of any disease management program. Improving disease resistance in crops is crucial for stable food production. Quantitative trait loci (QTLs), which usually have smaller individual effects than R-genes but confer broad-spectrum or non-race-specific resistance, can contribute to durable disease resistance (DR). Gene pyramiding holds greater prospects to attain durable resistance against biotic and abiotic stresses in crop. Agene pyramiding involves the use of several genes in a single cultivar to provide a wider base of disease resistance.