Gray leaf spot (GLS) caused by some Cercospora species is a devastating
maize disease. The cultivation of GLS-resistant hybrids is the most
efficient way to control this disease. However, GLS resistance is a
quantitatively inherited trait. Researchers led by Mingliang Xu of China
Agricultural University now aim to map and characterize the quantitative
trait loci (QTLs) for GLS resistance.

A major GLS resistance QTL, qRgls2, was previously detected in the
centromere of chromosome 5. By using advanced backcross populations from the
cross of the resistant and a susceptible line, a recombinant-derived progeny
testing was done to fine map qRgls2. The region of qRgls2 was narrowed
further, flanked by markers G346 and DD11.

The qRgls2 gene showed additive effects and significantly increased the
resistance across multiple generations. A total of 15 genes were predicted
in the mapped region. It is assumed that qRgls2 could be widely used to
improve maize resistance to GLS.

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