Detection of the PR-1 Resistance Gene and SSR-Based Genetic Diversity Analysis of S2 Lines in Local South Sulawesi and Introduced Maize

Abstract

Maize cultivation in Indonesia faces significant challenges, particularly the prevalence of downy mildew. Plants infected by Peronosclerospora spp., the causal agents of this disease, increase the expression of pathogenesis-related (PR-1) proteins as an induced defense mechanism. Developing superior varieties through breeding programs requires robust germplasm management to maintain broad genetic diversity. Therefore, utilizing biomolecular methods to detect resistance genes and analyze genetic diversity is a strategic approach for maize genetic improvement. This study aimed to evaluate the basal expression of the PR-1 gene associated with downy mildew resistance and analyze the genetic diversity of S2 lines derived from local South Sulawesi maize (Sinjai and Tana Toraja) and introduced maize (National Varieties and CIMMYT). Of the 30 lines used, consisting of 5 lines from local Sinjai maize, 15 lines from local Tana Toraja maize, and 10 lines of introduced maize, all were detected to have the PR-1 gene. Meanwhile, the genetic diversity analysis using 15 pairs of SSR primers from 10 chromosomal loci spread across corn obtained an average number of alleles of 10.27 alleles/locus and an average polymorphism information content (PIC) value of 0.76 (very informative). Cluster analysis shows a similarity coefficient value ranging from 0.68 to 0.96, with two main clusters at a similarity coefficient of 0.68. Cluster I consists of 27 lines, and Cluster II consists of 3 lines. The greatest genetic distance is possessed by the lines LK1 and BK5. The presence of the PR-1 gene and the high genetic diversity observed in the S2 lines represent promising genetic materials for developing maize varieties with durable resistance to downy mildew.