Effect of plant age on sesame infection by Alternaria leaf spot

Abstract

The effect of plant growth of sesame (Sesamum indicum L.) on development of seed infection by Alternaria leaf spot, and seed infection by Alternaria sesami, was monitored in plants of sesame accession SPS SIK 110. Increase in percentage of leaf area blighted and percent defoliated fitted the Gompertz model more closely than the logistic model. Rates of increase in diseased leaf area and defoliation as well as areas under disease curves (AUDPC) varied among the five plant ages. Plant ages with larger AUDPC generally had faster rates of disease progress. Sesame plants inoculated at 8 and 12 weeks of age were most susceptible to the disease; plants inoculated at 4 weeks exhibited the least susceptibility. Seed infection as determined by oat meal agar plate method was highest in plants inoculated at 8 and 10 weeks and least in plants inoculated at 4, 6 and 12 weeks.