Loci controlling partial resistance to rice blast do not show marked QTL × environment interaction when plant nitrogen status alters disease severity

Summary

This study examined whether quantitative trait loci conferring partial resistance to rice blast (Magnaporthe grisea) remain effective under different nitrogen regimes, using a mapping population of 100 Bala × Azucena rice lines grown at two nitrogen levels. Although high nitrogen application increased disease severity primarily through increased lesion numbers and elevated plant nitrogen concentration by 66%, most resistance loci were stable across nitrogen treatments; only one major QTL on chromosome 12 showed significant nitrogen-dependent reduction in efficacy. The findings suggest that blast resistance genes retain general effectiveness despite nitrogen-induced increases in overall disease susceptibility.

Regional applicability

The study was conducted with international rice germplasm and uses model crop genetics methodology applicable to temperate cereal breeding programmes. Whilst rice is not a primary UK crop, the findings on nutrient-disease interactions and QTL stability principles are transferable to resistance breeding in wheat and barley under UK nitrogen management practices.

Key measures

Disease severity, lesion number and size, plant nitrogen and carbon concentrations, QTL detection and QTL × treatment interaction

Outcomes reported

The study identified nine quantitative trait loci (QTL) controlling partial resistance to rice blast across two nitrogen treatment levels, and assessed the stability of resistance loci under altered plant nitrogen status. Only one QTL showed significant nitrogen × environment interaction, indicating that most blast resistance loci remain effective regardless of nitrogen application.

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