مطالعه علل زوال درختان گيلاس در منطقه لاريجان آمل

Study on the causal agents of sweet cherry trees decline in Larijan-Amol area

Some soil-borne fungi are caused root rot pathogen and decline of Sweet cherry in Larijan region of Amol. In this investigation samples were infected roots tissue of Sweet cherry and for determining physical and chemical characteristics of soil region , five profiles of soil were studied. The results showed that pathogens are related to two species of fungus . Fungus of Rosellinia necatrix was formed from grey calary and thick mycelium ampoule-like at septum region. Also. fungus produced coremium and one cell conidia on dead tissue. This fungus was more frequent than others. Other fungus is Arnmillaria me/lea produced yellowish-orange colonies on the media, and simple mycelia with clamp connection at septum area. Fungus telemorph as honey-coloured mushroom is formed as a group on crown of same trees in autumn. In same isolates fungus that was isolated from crown of trees identified as Fusarium lateritium. This fungus produced white colony which then becomes orange with curved macroconidia by three to seven cells. Results of soil analysis indicated that soil in this area has texture with clay-loam to clay and high moisture. Reaction of soil pH showed the level of neutral to weak alkaline. Ratio of CIN was in balance and this type of soil was evaluated as poor nitrogen level_ But, from point of various elements, phosphorus, sodium, calcium and magnesiaum were in high level and suitable. With attention to high level of pi! and nitrogen reductions in soil. trees are highly under environmental stress so that field condition is prepared for disease development.