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Evaluation of soybean breeding lines for resistance to Phomopsis seed decay: Results of 2014, 2015, and 2016 field trials in Stoneville, Mississippi


<div>Soybean [<em>Glycine max</em> (L.) Merr.] is one of the most important crops in the world. Phomopsis seed decay (PSD) is a soybean seed disease that causes poor seed quality. This disease is caused primarily by a fungal pathogen, <em>Phomopsis longicolla</em> (syn. <em>Diaporthe longicolla</em>). Planting PSD-resistant soybean cultivars is the most effective means to control PSD. In this study, breeding lines were developed from three crosses between PSD-resistant and high germination parents (DS25-1 x PI 424324B; DS25-1 x PI 417274; DS34-1 x PI 424324B) and from one cross between two PSD-resistant parents (PI 80837 x SS93-6181). Results from seed plating assays of 122 breeding lines from field trails in 2014, 2015, and 2016 showed that the range of percent seed infection by <em>P. longicolla</em> among all lines tested was from 0 to 52%. Fourteen breeding lines were completely free of PSD based on seed plating assays in 2014, 2015, and 2016 using F5, F6, and F7 seed, respectively. The mean germinations of the 14 lines were 95.5% and 92.9% in the tests in 2015 and 2016, respectively. Breeding lines with resistance to PSD and high-germination were entered into multi-year yield tests in 2017 and the most resistant lines will be selected for future use in developing PSD-resistant soybean cultivars.</div>