Effects of Pyramiding Genes for Partial Resistance to Leaf Rust (Puccinia recondita)
in Wheat (Triticum aestivum)

Indira Galit, Daniel Cristina, Alina-Gabriela Turcu, Matilda Ciucă, 
Cristina Mihaela Marinciu, Gabriela Șerban, Nicolae N. Săulescu

National Agricultural Research and Development Institute Fundulea

Keywords: wheat, leaf rust, Puccinia recondita, partial resistance, Lr genes, gene pyramiding, marker-assisted selection.

Abstract: Wheat, one of the most widely grown crop globally and in Romania, is affected by numerous diseases, among which leaf rust, caused by the pathogen Puccinia recondita, is one of the most frequent and can lead to yield losses of up to 40%.
Genetic resistance is the most convenient way, both economically and ecologically, to reduce the impact of this disease, and many strong resistance genes, offering complete protection against leaf rust, are available. However, experience has shown that the pathogen can rapidly develop new races virulent to such resistance genes, if they are deployed on large areas, making this genetic protection against leaf rust short lived. Partial resistance genes, usually manifested only at adult stage, proved to offer a more durable but incomplete protection. Pyramiding such genes in one wheat genotype, was suggested and has been used in several breeding programs, to ensure adequate and long-term resistance.
In this study molecular markers associated with genes Lr34, Lr37, Lr46 and Lr68 were used to identify genotypes carrying one to four of these resistance genes. The genotypes were tested at NARDI Fundulea, under artificial inoculation with a mixture of races prevalent in the area, during 2023 to 2025. Percentage of leaf area affected by rust was visually estimated. Averaged over three years and several genotypes carrying the same number of Lr genes, entries carrying one gene reduced the attack from 66.7% in susceptible genotypes to 20.0%, while entries cumulating two Lr genes showed 7.1% attack. In entries cumulating 3 or 4 Lr genes no leaf rust attack was observed. Presence of the Lr46 gene alone reduced the attack from 66.7% to 26.7%. Adding to it the genes Lr68 or Lr37 further reduced the attack to 7.8% and 4.4%, respectively, while adding both Lr37 and Lr34 provided complete protection against leaf rust.
These results, consistent with international studies and adapted support as we routinely use marker assisted selection to increase the frequency of partial resistance genes in the breeding program and to attempt pyramiding these genes for more complete and durable genetic protection.