Cotton seed borne disease in Golestan Province in Northern Iran

Abstract

Abstract. In order to effect of seed mycroflora to incidence of seedling diseases and verticillium wilt, five thousands of cotton seed were collected from five categories (nucleus, super elite, elite, maternal and certified seed) of Sahel cultivar. Seed were delinted with sulfuric acid and treated by sodium hypochlorite 0.5%.Coat and embryo of seeds separated and placed on Potato Dexterous Agar and Alcol Agar medium and incubated at 18 – 24 0c . After 5 – 15 days fungi that grew on were isolated and diagnosed. Sand (less than 2mm) were collected on sea coast and sterilized for 30 minutes at 30 0c for three times and transfer on flower pot. Fuzzy and delinted seeds and embryo (each 400 number) planted inside them and placed at 17 – 25 0c on green house. Percent of seedling diseases and seed rot after 15 days and vertcillium wilt after 60 days were counted. The results showed that on 63% of coat of seed,43% of embryo that cultured on PDA, fungi were grew on. Frequency of species, Rhizoctonia solani, Aspergillus flavus, Alternaria macrospora &A.alternata and Fusarium spp. , on coat seeds were 13.3,0,25 andv21.4 and on embryo of seeds were 0,4,32.14 and 33.3 respectively. Percent of healthy seedling, diseased seedling and seed rot that planted on sterilized sand in delinted seeds were 75.5, 3.76 and 12, in fuzzy seeds 67.25, 18.25 and 14.5 and in embryo 74.75, 2.75 and 20.5 respectively. Aspergillus flavus (6.6%), Alternaria macrospora &A.alternata (66.6%) and Fusarium spp.(26.6%) were isolated and diagnosed on diseased seedling and rotted seed . Verticillium dahliae the casual agent of wilt have not on fungi that isolated and symptom of wilt was not found on plant that planted on flower pot after 60 days.