Mitochondrial Genome Resource of Phomopsis longicolla, a Fungus Causing Phomopsis Seed Decay in Soybean

Phomopsis seed decay is one of the most devastating seed diseases reducing soybean seed quality worldwide. This disease is caused primarily by a seed-borne fungus, Phomopsis longicolla (syn. Diaporthe longicolla). As part of a genome sequencing project for P. longicolla, we present the mitochondrial genome resource of the isolate MSPL 10-6, one of the most aggressive field isolates. The circular mitochondrial genome is 53,646 bp long with GC content of 34.27%, and it encodes 14 common protein genes, 23 tRNA and two rRNA genes, and 10 introns. Forty-five SNPs and InDels also were identified during comparative analyses with another isolate. The mitochondrial genome sequence provides a useful resource for developing molecular markers for pathogen detection and for improvement of control strategies for the disease. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Evaluation of Commercial Soybean Cultivars for Reaction to Phomopsis Seed Decay

Phomopsis seed decay (PSD), caused by Phomopsis longicolla (syn. Diaporthe longicolla), is an economically important soybean disease causing poor seed quality. Planting resistant cultivars is one of the most effective means to control PSD. In this study, 16 commercially available maturity groups IV and V soybean cultivars, including two previously identified PSD-resistant and two PSD-susceptible checks, were evaluated for seed infection by P. longicolla in inoculated and noninoculated plots, and harvested promptly or with a 2-week delay in harvest. The test was conducted at Stoneville, Mississippi, in 2012 and 2013. Seed infection by P. longicolla ranged from 0.5 to 76%, and seed germination ranged from 18 to 97%. One MG IV cultivar (Morsoy R2 491) and five MG V cultivars (Progeny 5650, Progeny 5706, Asgrow 5606, Asgrow 5831, and Dyna-Gro33C59) had significantly (P ≤ 0.05) lower percent seed infected by P. longicolla than their respective susceptible checks and other cultivars in the same tests. Information obtained from this study will be useful for soybean growers and breeders for selection of cultivars for planting or breeding and future genetic studies in the development of cultivars with improved resistance to PSD.

Evaluation of Diverse Soybean Germplasm for Resistance to Phomopsis Seed Decay

Phomopsis seed decay (PSD), caused primarily by the fungal pathogen Phomopsis longicolla, is one of the most important diseases reducing seed quality and yield of soybean. Few cultivars have been identified as resistant. To identify new sources of resistance to PSD, 135 soybean germplasm accessions, originating from 28 countries, were field screened in Arkansas, Mississippi, and Missouri in 2009. Based on seed assays of natural field infection by P. longicolla in 2009, 42 lines, including the most resistant and susceptible lines, were reevaluated in the field in 2010, 2011, and 2012 with P. longicolla-inoculated and noninoculated treatments. Six maturity group (MG) III (PI 189891, PI 398697, PI 417361, PI 504481, PI 504488, and PI 88490), four MG IV (PI 158765, PI 235335, PI 346308, and PI 416779), and five MG V (PI 381659, PI 381668, PI 407749, PI 417567, and PI 476920) lines had significantly lower percent seed infection by P. longicolla than the susceptible checks and other lines in the same test (P ≤ 0.05). They appeared to have some levels of resistance to PSD. These new sources of PSD resistance can be used in developing soybean breeding lines or cultivars with resistance to PSD, and for genetic mapping of PSD resistance genes.

Identification of Diaporthe longicolla on Dry Edible Pea, Dry Edible Bean, and Soybean in North Dakota

North Dakota soybean production has expanded geographically, and possible short rotations with dry edible bean and pea raise concerns of pathogens (such as Diaporthe longicolla, cause of Phomopsis seed decay and stem disease of soybean) developing overlapping host ranges. To the best of our knowledge, this is the first report of D. longicolla causing stem disease on dry edible beans and dry edible peas, and stem disease on soybean in North Dakota. Its impact on dry edible beans and dry edible peas is uncertain. Accepted for publication 16 February 2015. Published 15 April 2015.