Assessment of sorghum with varied lignin content for tar spot (Phyllachora sp.) resistance and agronomic traits

Abstract

Sorghum (Sorghum bicolor) has the potential to be developed and cultivated in Indonesia because it has a high tolerance for planting on marginal lands and a wide adaptation to dry areas and weather stress. Sorghum cultivation is constrained by pest and disease attacks, so apart from breeding sorghum plants, it is also necessary to select sorghum plant accessions that are resistant to disease infections. Tar spot disease caused by Phyllachora sp., and the potential to decrease production. A bioassay of tar spot disease resistance on nine varieties of sorghum plants with known lignin content was performed for this purpose. Planting took place from October 2021 until March 2022, and design of a sorghum plant resistance assay was a completely randomized block design (CRBD).  The tar spot disease scoring was conducted throughout plots using a 1–5 disease rating scale. The results of the bioassay of resistance of sorghum plants to tar spot disease in this study explain the response and relationship of lignin content between the resistance of sorghum plants against infection Phyllachora sp. infection through the value of disease severity and the value of the observed agronomic character reduction. The incidence of the tar spot disease in all genotypes was 100% from both the control and inoculation blocks. The reduction in disease severity was greatest (0.45) in the Pahat genotypes, which were known to have low lignin content. In the KS, 4183A, and SMM genotypes, which have high lignin content, the disease severity reduction value is relatively small. Lignin has a role in the mechanism of sorghum plant resistance to infection with the Phyllachora fungus that causes tar spot disease and also has a direct effect on the growth and productivity of sorghum plants.

Keywords:   Bioassay,  fungal pathogen,  plant defense, sorghum genotypes