Status of sesame phyllody and its control methods in Yazd, Iran

Phyllody is one of the most important diseases of sesame in Iran. During 2008-10, to evaluate disease status, a survey was carried out in sesame fields in Yazd province. Occurrence of sesame phyllody was observed in all the sesame growing fields in Yazd, but whole infection of fields was observed in Rezvan Shahr (Ashkezar, Yazd province). On the basis of RFLP analysis sesame phyllody phytoplasma was identified as a member of peanut witches’ broom (16SrII) group. No differences were observed in plant heights of infected and healthy plants. Total seed yield was reduced by 55.07% in infected plants and 1,000 seed weight showed a 21.49% decrease in infected plants. Wrinkled seeds increased in diseased plants up to 56.07%. Results of variance analysis of control methods showed that sowing date and spraying have significant effects on infection. Mean comparison of infection percent with LSD tests showed that delay in sowing date reduced sesame phyllody up to 31%. Spraying with Confidor reduced disease incidence at the first and second sowing date by 18.8 and 7.8% respectively but no differences were observed in yields. Seed treatment with Gaucho has no effect on disease incidence. Collectively, sowing of sesame straight after wheat harvesting in May needed spraying to reduce disease incidence, but delay in the sowing date to July 5 can reduce disease incidence without any significant differences in seed yield. Delay in sowing date is dependent on weather and needs to be determined for each area