Abstract
1. The leaf blotch of sesame (Sesamum indicum DC.) caused by Helmin-thosporium sesamum SACC. affects seedlings, leaves, petioles, stems and pods.
2. Conidiophores of the fungus are darkish olive, measuring 105.0-337.5μ (average 194.0μ) in length by 5.0-10.0μ (average 7.11μ) in width, being provided with 2-9 (average 4.30) septa. Conidia are darkish brown, curved to one side or rarely straight, 27.5-267.5μ (average 102.9μ) by 5.0-17.5 (average 15.03μ), with 3-20 (average 8.77) septa.
3. The causal fungus grows readily on various culture media. The inoculation experiments proved the pathogenicity of the present oraganism on sesame plants. The presence of any wound on the plant is not always necessary for its infection.
4. The optimum temperature for growth of the fungus lies between 27 and 30°C, the maximum and minimum being about 37° and below 12°C respectively. Incubating at 54° for 5 minutes, the conidia in suspension were completely killed.
5. The size, shape and number of septa of conidia varies with temperatures during culture. The conidia measured in average 100.20 and 88.70μ in length, and 10.66 and 10.46μ in width at 23° and 37°C respectively.
6. The fungus was able to grow in solutions presenting pH value of 4.0 to 7.0, while it seemed to be most favoured in pH 6.2. It was noted that pH value of the liquid media inoculated with this fungus changed gradually towards 7.
7. The pathogenes are often carried in the seeds. For disinfection of such contaminated seeds, hot water treatment has been proved to be effective.
