Abstract
Simple SummaryWheat leaf rust is one of the most significant diseases worldwide, incited by a parasitic fungus which infects leaves, affecting grain yield. This pathogen is spread by the wind over large areas through microscopic spores. This huge number of spores favors the selection of virulent forms; therefore, there is a continuous need for new resistance genes to control this disease without fungicides. These resistant genes are naturally found in resistant wheat varieties and can be introduced by standard crosses. In this work, seven resistant genes were introduced into several commercial susceptible varieties. The selection of resistance genes was assisted by DNA markers that are close to these genes on the chromosome. Additionally, the selection of desirable traits from the commercial variety was also assisted by DNA markers to accelerate the process. In field testing, the varieties developed here were resistant to leaf rust, and suitable for commercial use.Leaf rust is one of the most significant diseases of wheat worldwide. In Argentina, it is one of the main reasons for variety replacement that becomes susceptible after large-scale use. Some varieties showed durable resistance to this disease, including Buck Manantial and Sinvalocho MA. RILs (Recombinant Inbred Lines) were developed for each of these varieties and used in genetics studies to identify components of resistance, both in greenhouse inoculations using leaf rust races, and in field evaluations under natural population infections. In Buck Manantial, the APR gene LrBMP1 was associated with resistance in field tests. In crosses involving Sinvalocho MA, four genes were previously identified and associated with resistance in field testing: APR (Adult Plant Resistance) gene LrSV1, the APR genetic system LrSV2 + LrcSV2 and the ASR (All Stage Resistance) gene LrG6. Using backcrosses, LrBMP1 was introgressed in four commercial susceptible varieties and LrSV1, LrSV2 + LrcSV2 and LrG6 were simultaneously introgressed in three susceptible commercial varieties. The use of molecular markers for recurrent parent background selection allowed us to select resistant lines with more than 80% similarity to commercial varieties. Additionally, progress towards positional cloning of the genetic system LrSV2 + LrcSV2 for leaf rust APR is reported.
Highlights
World wheat production in the last five years was over 700 million tons
Three selected races from the collection stored at the Instituto de Genética “Ewald A
Four recombinants were found between Lr16 and LrBMP1, indicating a genetic distance of 1.7 cM (Chi2 independence test p < 0.0001)
Summary
World wheat production in the last five years was over 700 million tons. This cereal has become one of the most important sources of food for humans, providing energy, fiber and essential nutrients, and to a lesser extent for animal nutrition. In Argentina, wheat annual production was around 15–20 million tons (last five years), reaching a value of more than USD 3000 million per year, according to current wheat prices on the world market. Concerning wheat fungal diseases, rusts cause important yield losses. The three wheat rusts: stem rust, leaf rust and yellow rust, are incited by different species of Puccinia, impacting on wheat yield according to environmental conditions and resistant genes present in cultivated varieties.
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