The mass spectral analysis of some chemical elements’ content in the flag leaves of wheat (Triticum aestivum L.) isogenic lines with different resistance to brown rust

The wheat resistance to diseases, including the leaf rust pathogen, is the essential factor contributing to yield preservation. The Thatcher lines with Lr -genes are widely used in the assessment of differential interaction between resistance and virulence genes of a host plant and the pathogen. The aim of this work was a quantitative analysis of chemical element composition of flag leaves in 29 Thatcher isogenic lines with various genes for resistance to wheat leaf rust, Tc Lr28, Tc Lr29, Tc Lr24, Tc Lr47, Tc Lr18, Tc Lr19, Tc Lr36, Tc Lr3ka, Tc Lr3bg, Tc Lr16, Tc Lr17, Tc Lr44, Tc Lr1, Tc Lr2b, Tc Lr2c, Tc Lr3a, Tc Lr10, Tc Lr11, Tc Lr14a, Tc Lr20, Tc Lr33, Tc Lr26, Tc LrB (juvenile resistance); Tc Lr35, Tc Lr12, Tc Lr21, Tc Lr48 (age-related resistance); Tc Lr46, Tc Lr34 (partial resistance genes). The content of twenty-one chemical elements, including heavy, light metals, and metalloids (Na, Mg, Al, К, Са, Cr, Mn, Fe, Co, Cu, Ni, Zn, Se, Mo, Ba, Pb, Sb, As, Cd, Be, Ag) in leaves of the isogenic lines was identified by mass spectrometry analysis. For quantitative analysis, leaves without visual symptoms of wheat leaf rust were collected. The disease development according to the R.F. Peterson’s scale, pustule number on flag leaves, pustule area according to the ellipse area formula, and reaction type according to the scale of E.B. Mains and H.C. Jackson have been considered as parameters of the pathogenesis caused by the wheat leaf rust agent. The wide range of the parameters enabled us to use various statistical methods and to improve the accuracy of the differences identified. On the highly resistant lines protected by the Lr -genes of juvenile resistance, Lr24, Lr28, Lr29, Lr47, the signs of brown rust have not been revealed. The lines Tc Lr18, Tc Lr19 and Tc Lr36 were moderately resistant to the disease whereas the lines Tc Lr3ka, Tc Lr3bg, Tc Lr12, Tc Lr16, Tc Lr17, Tc Lr44, and Tc Lr46 were moderately susceptible. The high susceptibility to the wheat brown rust was found for Tc Lr1, Tc Lr2b, Tc Lr2c, Tc Lr3a, Tc Lr10, Tc Lr11, Tc Lr14a, Tc Lr20, Tc Lr33, Tc Lr26, and Tc LrB. In the leaves of highly resistant isogenic lines with juvenile resistance and no symptoms, there was significantly less amount of heavy metals (Ni, Ag, Cr, Fe, Co, and Cd) and also K as compared to that in the lines with high susceptibility to the disease. The brown rust intensity decreased with the increase of the selenium content in the flag leaves. The lines bearing juvenile resistance Lr -genes showed a fewer reliable correlations between the chemical elements accumulation in the flag leaves and the greater affection by the leaf rust pathogen compared to the lines with genes of age-related resistance. It was found that the flag leaf levels of Al, Cr, Co, Sb, K in the lines with Lr -genes of juvenile resistance and Al, Fe, Ni, Zn in the lines with genes Lr1, Lr10, Lr21, Lr3a, Lr24 significantly correlate with leaf rust manifestations. The leaf rust severity intensified significantly as the coefficients of Al, K, CR, Fe, Co, Ni, Sb, and Cd biological accumulation in the flag leaves increased. The line with Lr34 gene, encoding a wheat protein similar to ABC transporters, differs from the other lines in lower biological accumulation coefficients for some toxic elements when compared to the lines which express plant NBS-LRR proteins. These findings can be helpful in spring soft wheat screening when breeding cultivars adapted to the environment conditions of the north-western regions of Russia.