User:Minick molly

Host

Phoma terrestris is a fungus that infects a wide host range, with the disease called Pink Root. Phoma terrestris is known for its negative effect on onion crops. The other crops that this fungus infects in the onion family include garlic, potatoes, and shallot. The other crops not included in the onion family that this disease infects are cantaloupe, carrot, cauliflower, cucumber, eggplant, lima bean, muskmelon, pea, pepper, spinach, squash, sweet potato, tomato, corn, sorghum, cereals, many grass types, millets, cowpeas, field cress, common flax, and tepary bean.

Symptoms

If a plant is infected with this disease, it may show symptoms of wilting and seedling death. Another symptom is a change in root color; the roots will turn pink in color. After the roots, have turned pink, the roots will likely begin to shrivel. After shriveling occurs, the roots become a very dark red color. Once the roots become red, they will turn to an even darker color, black, and will die. Most plants however, will not die, rather they will become stunted. If an onion is infected, the bulbs feel soft to the touch, underdeveloped, and smaller than a non diseased onion, caused by the toll that the disease takes on the onion's roots.

Disease cycle

Pycnidia serve as Phoma terrestris's survival structure. The pycnidia produce conidia, which infect younger roots and get into the cortical tissue, where they continue to grow. New pycnidia are produced in the cortical tissue, and when the plants die, even more pycnidia are produced, which then produce more conidia, and the disease cycle repeats. Therefore, asexual reproduction takes place. This disease does not cause a systemic infection because it does not infect the basal plate or scales, even though it can travel through the roots. Phoma terrestris can survive in the soil for a very long time. So once the cycle begins, the disease can occur year after year unless management for this disease is conducted. The pathogen overwinters in the soil and plant debris, and then becomes favorable when temperatures are warmer, around 75 to 82 degrees Fahrenheit. This disease becomes more prevalent during the warmer months of the year.

Environment

Phoma terrestris can survive in a wide range of soil temperatures, but prefers them to be warmer, (75 to 82 degrees Fahrenheit), it also prefers soils that are not sufficient in organic matter. Though the disease can survive in a wide range of pH’s, it prefers a pH as close to 6.5 as possible. This disease is more likely to be prevalent in areas of soil that are not drained well, and higher in moisture. If a plant is damaged by other diseases, insects, or physical features, the plant may have a higher chance of being affected by the disease. The disease can also be spread via tools, cross drainage of water between fields, human transfer, or any other way of soil transport.