The ability of Streptomyces spp. to inhibit the growth of Alternaria sp. isolated from leaf spot disease in lettuce.

Abstract

Lettuce is a widely popular crop nowadays due to its ease of cultivation, fast growth, and high nutritional value. However, as a leafy vegetable, lettuce is highly susceptible to plant diseases, especially during the rainy season or in areas with high humidity. These conditions often lead to outbreaks of various diseases, such as leaf spot caused by Alternaria sp., which can severely damage the crop, resulting in reduced quality and yield. To control such diseases, most farmers commonly use chemical treatments because they are convenient and fast-acting. However, effective chemical control requires continuous use over a long period, which may lead to chemical residue accumulation in the produce, as well as negative impacts on farmers, consumers, and the environment. Therefore, this study aimed to evaluate the effectiveness of 11 isolates of Streptomyces spp. in inhibiting the growth of Alternaria sp. isolated from leaf spot disease in lettuce. The dual culture test was conducted on Potato Dextrose Agar (PDA) medium. The results showed that Streptomyces spp. were able to inhibit the growth of Alternaria sp. with inhibition percentages ranging from 46.77% to 57.49%. The isolate with the highest inhibition efficiency was 2CRA05, with an average inhibition percentage of 57.49%, followed by isolates 2CRA01, 2CRF04, 2CRA08, 2CRA04, 2CRA02, SNP3-9C04, KSCB01, KSCB02, KSAB25 and KSDL03 with average inhibition percentages of 56.74%, 55.80%, 54.74%, 54.33%, 53.08%, 49.63%, 49.05%, 47.94%, 47.05%, and 46.77%, respectively.