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Deployed resistance to common blight is not a drag

 

Many crops may rely upon wild germplasm and related species to provide novel genes for improving disease resistance. Such genes are transferred from the exotic sources into commercial lines using backcross breeding, recurrent selection, or other means. Such resistance genes, when introduced into a commercial background, often result in reduced yield and quality, due to linkage drag effects.

Common bacterial blight is a severe seed-borne disease that limits dry bean production worldwide. The genes conferring the highest levels of resistance to common blight in dry bean derive from tepary bean, a related cultivated species from the tertiary gene pool. 

In an article recently published in Crop Science, researchers documented the effect that two well-known tepary-derived genes for quantitative resistance (QTL) to bacterial blight had on yield and quality traits when transferred into a popular commercial dry bean cultivar. Six backcrosses to the recurrent commercial parent were used to incorporate the genes. Advanced backcross inbred lines with and without the genes were compared across five environments. One gene had a slightly negative impact on canning quality. But the genes protected yield in diseased plots as expected, and even more importantly did not drag down yield nor seed size in clean plots. 

This work provides another example of novel genes from exotic sources having enormous importance in breeding disease resistant cultivars for current and future generations.

Read the full open access article in Crop Science