The diseases are severely affected multibillion-dollar agriculture industry by plant pathogens including fungi, bacteria, and viruses. Many of the diseases in plants have similar signs and symptoms, making it difficult to diagnose the specific problem pathogen. Incorrect diagnosis leads to the delay of treatment and excessive use of pre and post-harvest chemicals. Proper identification of damage, defects, diseases, and disorders is the first step in solving the issue and producing quality crops. There are many methods for diagnosing pathogens on plants. Traditional methods include symptoms, morphology, and microscopy identification. These have been followed by nucleic acid detection and onsite detection techniques. Many of these methods allow for rapid diagnosis, some even within the field without much expertise. There are several methods that have great potentials, such as high-throughput sequencing and remote sensing. The utilization of these techniques for disease diagnosis allows for faster and accurate disease diagnosis and a reduction in damage and cost of control. Understanding each of these techniques can allow researchers to select which method is best suited for their pathogen of interest.

Solanum tuberosum L. (Solanaceae) known as potatoes is a globally important crop plant producing high yields of nutritionally valuable food in the form of tubers.Rhizoctonia solani AG3-PT, teleomorph Thanatephorus cucumeris, is a polyphagous necrotrophic plant pathogen of the Basidiomycete order is an important fungal pathogen of potato (Solanum tuberosum L.) world-wide. Host resistant sources are the most recommenced, durable and environmentally friendly method for managing disease. Three resistant and three susceptible potato genotypes out of 92 potato genotypes screened for resistance against R. solani AG3-PT under field conditions were subjected to bio-genetic assays using PR-5, Glub2, pcht28, PR-1b, ERF4, PAL1, PIN2 and LOX1 genes and ef1α as a housekeeping gene; and antioxidant enzymes including peroxidase (POX), superoxide dismutase (SOD), polyphenol oxidase (PPO), catalase (CAT) and phenylalanine ammonia-lyase (PAL1) analysis. Resistance and susceptibility of the selected potato genotypes were confirmed under greenhouse conditions. Biomass parameters in susceptible genotypes decreased significantly compared to resistant genotypes. Gene expression and enzyme activities increased in resistant potato genotypes inoculated with Rhizoctonia solani AG3-PT compared to susceptible and controls, non-inoculated genotypes. Changes in expression levels of genes increased the highest in pcht28 (8.41 fold), followed by PR-1b (6), ERF4 (5) and PR-5 (5). Antioxidant enzymes activities were increased the highest in SOD (10 fold), followed by PAL1 (4), PPO (3) and POX (3). Identification and production of potato cultivars resistant to R. solani will be possible based on changes in biomass, gene expression level and enzyme production rate.