Maize (Zea mays L.), one of the most widely consumed crops globally, faces significant threats from the fungal pathogen Macrophomina phaseolina (Mp), which can cause devastating yield losses. Recent research published on March 6, 2025, sheds light on genetic markers associated with resistance to this pathogen, promising new avenues for breeding more resilient maize varieties.
The study involved 120 maize genotypes evaluated for their phenotypic responses to Mp under controlled conditions. Results revealed troubling averages, with disease scores indicating susceptibility among much of the tested population. "The average disease score was calculated as 4.2," highlighting the challenges posed by this pathogen, which can lead to losses exceeding 33% of crop yields.
Among the genotypes assessed, 12 were classified as resistant, 43 as moderately resistant or tolerant, 48 as moderately susceptible, and 17 as highly susceptible. These assessments formed the foundation for conducting genome-wide association studies (GWAS) which successfully identified seven significant SNP markers across four chromosomes linked to disease resistance.
Using Diversity Array Technology (DArT), researchers filtered through 79,166 initial single nucleotide polymorphisms (SNPs) to retain 37,470 high-quality markers for their analysis. The population structure analysis divided the maize genotypes based on genetic attributes, allowing for more precise association mapping.
The GWAS, carried out with the MLM (Q + K) model, aimed to reduce false positives by assessing both population structure and genetic linkages. Among the notable findings, SNP6999, situated on chromosome 2, was identified as having the strongest association with resistance, boasting a -log10P value of 3.70, followed closely by SNP12080 and SNP34600 on chromosome 8.
Candidate gene analysis revealed 33 distinct genes situated within 100,000 base pairs of the identified SNPs, each contributing to disease resistance mechanisms through roles such as cell wall synthesis and phytohormone signaling. This significant genetic insight is pivotal for breeding programs, as the markers can facilitate the development of maize varieties resistant to Mp.
The study reports high heritability for the resistance trait, with broad sense heritability calculated at 0.80. This finding indicates a strong genetic basis for the observed resistance and enhances the reliability of using these markers for breeding innovative maize cultivars.
Current methods to control Mp, such as chemical fungicides and irrigation, have proven inadequate and environmentally detrimental, underscoring the urgency of developing resistant cultivars. This research paves the way for marker-assisted selection, enabling faster breeding processes and promoting sustainable agricultural practices.
With its global significance—especially considering Turkey's substantial maize production, estimated at 8.5 million tons annually—the need for effective solutions against Mp is pressing. The identification of these molecular markers not only reinforces the genetic foundation for resistance but also promises to safeguard maize production against one of its deadliest foes, contributing to enhanced food security worldwide.
To conclude, the findings from this study highlight the importance of investing in genetic research to address agricultural challenges posed by pests and diseases. The newly identified SNP markers associated with resistance to Macrophomina phaseolina represent a step forward, providing valuable tools for breeding more resilient maize varieties for future global food demands.