Purple Seed Stain Research Articles

Cercospora leaf blight and purple seed stain of soybean: A permanent challenge

AbstractCercospora leaf blight (CLB) and purple seed stain (PSS) are major diseases of soybean responsible for significant yield loss. These diseases are caused by Cercospora species, such as C. kikuchii and C. cf. flagellaris, among the main species. These pathogens overwinter in infested debris and infected seed. Due to the combination of no‐till farming, monoculture in large soybean cultivation areas and climate changes, these diseases have become serious and prevalent. At present, in addition to the practice of monoculture soybean cultivation, there is a lack of soybean varieties with genetic resistance to these diseases. As a result, the application of fungicides becomes an essential tool for effectively managing this pathosystem. However, in the main soybean‐producing countries, resistance to quinone outside inhibitors and benzimidazole fungicides has already been studied and documented. Furthermore, Cercospora spp. are believed to be naturally insensitive to succinate dehydrogenase inhibitors. Consequently, there is a growing interest in innovative and integrated tools for managing crop diseases. These new approaches include the use of biofungicides, biostimulants and plant defence inducers. Research testing new management tools in a complementary and integrated approach involves a short‐term challenge to improve CLB/PSS management in the field. This review provides comprehensive details on the taxonomy, identification and genetic diversity of the pathogen, its disease symptoms and host range. Additionally, it outlines epidemiological aspects, fungicide resistance and the latest advancements in tools and technologies, aiming to guide future research and strategies to address the escalating threat to soybean crops globally.

Phytochemical profiling of soybean genotypes using GC-MS and UHPLC-DAD/MS.

Soybean is one of the most economically important crops worldwide. However, soybean yield can be substantially decreased by many diseases. Soybean genotypes could have different reactions to pathogen infection. As a first step toward investigating the biochemical basis of soybean resistance and susceptibility to disease, phytochemicals in the seeds of 52 soybean genotypes previously reported to have different reactions to diseases of soybean rust (SBR), Phomopsis seed decay (PSD), and purple seed stain (PSS) were analyzed. Using GC-MS, a total of 46 compounds were tentatively identified which included 11 chemical groups. Among those, the major group was esters, followed by carboxylic acid, ketone, and sugar moieties. Compounds having reported antioxidant, anti-microbial, and anti-inflammatory activities were also identified. UHPLC-DAD/MS analysis indicated that there were five major isoflavone components presented in the samples, including daidzin, glycitin, genistin, malonyldaidzin, and malonylglycitin. Isoflavones have been reported to play an important role in defense from plant pathogens. Although there was variance in the isoflavone content among soybean genotypes, those with the SBR resistance Rpp6 gene (PI 567102B, PI 567104B, PI 567129) consistently exhibited the highest concentrations of daidzin, glycitin, genistin, and malonyldaidzin. The SBR resistant genotype, PI 230970 (Rpp2) had the greatest amount of genistin. The SBR resistant genotype, PI 200456 (Rpp5) resistant genotype uniquely contained glycitein, a compound that was absent in the other 51 genotypes examined. A PSD-resistant genotype PI 424324B had nearly four times the amount of stigmasterol as PI 556625, which was susceptible to SBR, PSD, and PSS in our previous tests. Results of this study provide useful information for further investigation of the biochemical basis of soybean resistance to diseases. The results may also aid in selection of soybean lines for breeding for resistance to soybean rust and other diseases.

Effect of Mancozeb Application Timing and Frequency on the Control Efficacy of Purple Seed Stain of Soybean Caused by Cercospora kikuchii

Effect of Mancozeb Application Timing and Frequency on the Control Efficacy of Purple Seed Stain of Soybean Caused by <i>Cercospora kikuchii</i>

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

AbstractCercospora species cause cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean. Because there are few resistant soybean varieties available, CLB/PSS management relies heavily upon fungicide applications. Sensitivity of 62 Argentinian Cercospora isolates to demethylation inhibitor (DMI), methyl benzimidazole carbamate (MBC), quinone outside inhibitor (QoI), succinate dehydrogenase inhibitor (SDHI) fungicides, and mancozeb was determined in this study. All isolates were sensitive to difenoconazole, epoxiconazole, prothioconazole, tebuconazole, and cyproconazole (EC50 values ranged from 0.006 to 2.4 µg/ml). In contrast, 51% of the tested isolates were sensitive (EC50 values ranged from 0.003 to 0.2 µg/ml), and 49% were highly resistant (EC50 &gt; 100 µg/ml) to carbendazim. Interestingly, all isolates were completely resistant to azoxystrobin, trifloxystrobin, and pyraclostrobin, and insensitive to boscalid, fluxapyroxad, and pydiflumetofen (EC50 &gt; 100 µg/ml). The G143A mutation was detected in 82% (53) of the QoI‐resistant isolates and the E198A mutation in 97% (31) of the carbendazim‐resistant isolates. No apparent resistance mutations were detected in the succinate dehydrogenase genes (subunits sdhB, sdhC, and sdhD). Mancozeb completely inhibited mycelial growth of the isolates evaluated at a concentration of 100 µg/ml. All Argentinian Cercospora isolates were sensitive to the DMI fungicides tested, but we report for the first time resistance to QoI and MBC fungicides. Mechanism(s) other than fungicide target‐site modification may be responsible for resistance of Cercospora to QoI and MBC fungicides. Moreover, based on our results and on the recent introduction of SDHI fungicides on soybean in Argentina, Cercospora species causing CLB/PSS are insensitive (naturally resistant) to SDHI fungicides. Insensitivity must be confirmed under field conditions.

Effects of Purple Seed Stain on Seed Quality and Composition in Soybean.

Purple seed stain disease, caused by (Cercospora kukuchii), is a major concern in soybean (Glycine max (L.)) in Mississippi, USA, due to its effects on seed quality, reducing soybean seed grade and potential market price at elevators. Therefore, investigating the effects of purple seed stain (PSS) on seed quality (germination and vigor) and seed composition (nutrition) is critical. The objective of this study was to investigate the effects of PSS on seed harvest index, seed germination, seed vigor, and seed composition components (protein, oil, fatty acids, and sugars). A field experiment was initiated in 2019 in Stoneville, MS, at the Delta Research and Extension Center (DREC) on a Commerce silt loam soil (fine-silty, mixed, superactive, nonacid, thermic Fluventic Epiaquepts). Soybean variety Credenz 4748 LL was used. The results showed that infected (symptomatic) seed had a 5.5% greater Seed Index (based on 100 seed weight) when compared to non-infected (non-symptomatic, as control) seed. Non-infected seed had greater percent germination and seedling vigor when compared to infected seed. Germination was 30.9% greater and vigor was 58.3% greater in non-infected seed. Also, the results showed that infected seed with PSS had higher protein content and some amino acids. No changes in total oil and fatty acids. Sucrose and stachyose were lower in infected seed than in non-infected seed. The research showed that PSS impacted seed health and seed quality (germination and vigor) and seed composition (protein, sugars, and some amino acids). Purple stained seed should be avoided when planting and should be managed properly as low germination is a potential risk. Planting population should be adjusted accordingly due to lack of germination and vigor if PSS is present. This research help growers for purple seed management, and scientists to further understand the potential negative impact on seed quality and nutrition. Further research is needed before conclusive recommendations are made.

Evaluation of soybean genotypes for reaction to natural field infection by Cercospora species causing purple seed stain.

Purple seed stain (PSS) of soybean (Glycine max (L.) Merr.) is a prevalent seed disease. It results in poor seed quality and reduced seed lot market grade, and thus undermines value of soybean worldwide. The objectives of this research were to evaluate the reaction of selected soybean genotypes collected from 15 countries representing maturity groups (MGs) III, IV, and V to PSS, and to identify new sources of resistance to PSS based on three years of evaluation of natural field infection by Cercospora spp. in the Mississippi Delta of the U. S. In this study, 42 soybean genotypes were evaluated in 2010, 2011, and 2012. Seventeen lines including six MG III (PI 88490, PI 504488, PI 417361, PI 548298, PI 437482, and PI 578486), seven MG IV (PI 404173, PI 346308, PI 355070, PI 416779, PI 80479, PI 346307, and PI 264555), and four MG V (PI 417567, PI 417420, PI 381659, and PI 407749) genotypes had significantly lower percent seed infection by Cercospora spp. than the susceptible checks and other genotypes evaluated (P ≤ 0.05). These genotypes of soybean can be used in developing soybean cultivars or germplasm lines with resistance to PSS and for genetic mapping of PSS resistance genes. In addition, among these 17 lines with different levels of resistance to PSS, nine soybean genotypes (PI 417361, PI 504488, PI 88490, PI 346308, PI 416779, PI 417567, PI 381659, PI 417567, and PI 407749) were previously reported as resistant to Phomopsis seed decay. Therefore, they could be useful in breeding programs to develop soybean cultivars with improved resistance to both seed diseases.

Multi-host species of Cercospora are associated with Cercospora leaf blight and purple seed stain of soybean

Many Cercospora spp. are multi-host pathogens. The versatility of Cercospora newly associated with Cercospora leaf blight (CLB) and purple seed stain (PSS) in soybean seems to have been historically underestimated. Herein, we assembled multilocus sequence data (seven nuclear gene regions) with sequences from 36 fungal isolates sampled from non-soybean host species from Brazil (15 species) and United States (six species), in addition to 13 isolates from soybean. Phylogenetic tools explored relationships among isolates of Cercospora obtained from either soybeans or non-soybean hosts. Cercosporin production was determined to confirm whether the isolates belong to cercosporin-producing species of Cercospora. Among the five genealogical lineages, Lineage 1 showed C. kikuchii as the only member; this species is known to infect only soybean. The remaining four lineages were multi-host Cercospora which infected soybean along with ornamental and weed species. Genealogical placements were unrelated to host association and isolates clustered according to geography. Multi-host species of cercosporin-producing Cercospora are associated with CLB and PSS of soybean.

Control of Purple Seed Stain of Soybean Using Remote-Controlled Multi-Rotor

Control of Purple Seed Stain of Soybean Using Remote-Controlled Multi-Rotor

Cercospora cf. flagellaris and Cercospora cf. sigesbeckiae Are Associated with Cercospora Leaf Blight and Purple Seed Stain on Soybean in North America.

Cercospora kikuchii has long been considered the causal agent of Cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean, but a recent study found C. cf. flagellaris associated with CLB and PSS in Arkansas (United States) and Argentina. Here, we provide a broader perspective on the distribution of C. cf. flagellaris on soybean and alternate hosts within the United States (Arkansas, Louisiana, Mississippi, Missouri, and Kansas). We used a multilocus phylogenetic approach with data from actin, calmodulin, translation elongation factor 1-α, histone 3, the internal transcribed spacer region of rDNA and the mating-type locus to determine that two species, C. cf. flagellaris (200 of 205 isolates) and C. cf. sigesbeckiae (five of 205 isolates), are associated with CLB and PSS in the United States. In our phylogenetic analyses, species-level lineages were generally well-supported, though deeper-level evolutionary relationships remained unresolved, indicating that these genes do not possess sufficient phylogenetic signal to resolve the evolutionary history of Cercospora. We also investigated the potential for sexual reproduction in C. cf. flagellaris in Louisiana by determining the frequency of MAT1-1/MAT1-2 mating-type idiomorphs within the Louisiana population of C. cf. flagellaris. Though the MAT 1-2 idiomorph was significantly more common in our collection, the presence of both mating types suggests the potential for sexual reproduction exists.

Optimal Timing of Fungicide Spray against Purple Seed Stain in Soybean Caused by Cercospora kikuchii in Hokkaido

Optimal Timing of Fungicide Spray against Purple Seed Stain in Soybean Caused by <i>Cercospora kikuchii </i>in Hokkaido

More Cercospora Species Infect Soybeans across the Americas than Meets the Eye.

Diseases of soybean caused by Cercospora spp. are endemic throughout the world’s soybean production regions. Species diversity in the genus Cercospora has been underestimated due to overdependence on morphological characteristics, symptoms, and host associations. Currently, only two species (Cercospora kikuchii and C. sojina) are recognized to infect soybean; C. kikuchii causes Cercospora leaf blight (CLB) and purple seed stain (PSS), whereas C. sojina causes frogeye leaf spot. To assess cryptic speciation among pathogens causing CLB and PSS, phylogenetic and phylogeographic analyses were performed with isolates from the top three soybean producing countries (USA, Brazil, and Argentina; collectively accounting for ~80% of global production). Eight nuclear genes and one mitochondrial gene were partially sequenced and analyzed. Additionally, amino acid substitutions conferring fungicide resistance were surveyed, and the production of cercosporin (a polyketide toxin produced by many Cercospora spp.) was assessed. From these analyses, the long-held assumption of C. kikuchii as the single causal agent of CLB and PSS was rejected experimentally. Four cercosporin-producing lineages were uncovered with origins (about 1 Mya) predicted to predate agriculture. Some of the Cercospora spp. newly associated with CLB and PSS appear to represent undescribed species; others were not previously reported to infect soybeans. Lineage 1, which contained the ex-type strain of C. kikuchii, was monophyletic and occurred in Argentina and Brazil. In contrast, lineages 2 and 3 were polyphyletic and contained wide-host range species complexes. Lineage 4 was monophyletic, thrived in Argentina and the USA, and included the generalist Cercospora cf. flagellaris. Interlineage recombination was detected, along with a high frequency of mutations linked to fungicide resistance in lineages 2 and 3. These findings point to cryptic Cercospora species as underappreciated global considerations for soybean production and phytosanitary vigilance, and urge a reassessment of host-specificity as a diagnostic tool for Cercospora.

Screening a Diverse Soybean Germplasm Collection for Reaction to Purple Seed Stain Caused by Cercospora kikuchii.

Purple seed stain (PSS), caused by Cercospora kikuchii, is a prevalent soybean disease that causes latent seed infection, seed decay, purple seed discoloration, and overall quality deterioration. The objective of this research was to screen soybean accessions from the United States Department of Agriculture germplasm collection for resistance to PSS. In total, 123 plant introductions (PI) from 28 different countries, representing maturity groups (MG) III, IV, and V, were screened. Incidence of Cercospora leaf blight (% CLB), visual PSS (% PSS), and seed infected by C. kikuchii (% C. kikuchii) in harvested seed were determined. In 2007, % C. kikuchii was 2 to 51% for MG III, 2 to 35% for MG IV, and 0 to 33% for MG V. In 2008, % C. kikuchii was 0 to 45% for MG III, 1 to 71% for MG IV, and 0 to 15% for MG V. In total, four and ten PI from MG III and IV, respectively, were identified as resistant to PSS in both years. Highly positive correlations were found for inoculated versus noninoculated treatments and for % PSS versus % C. kikuchii infection. The PSS-resistant PI identified in this study will be valuable to breeders in developing resistant cultivars.

Inheritance of and molecular markers for purple seed stain resistance in soybean

Purple seed stain (PSS), caused by Cercospora kikuchii, is a disease that causes seed quality deterioration in soybean. Breeding for genetic resistance is a cost-efficient and practical way to control the disease. The objectives of this research were to investigate the inheritance of resistance to PSS and identify SSR markers tightly linked to the major resistance gene Rpss1. Two populations were developed by crossing a PSS resistant line, PI 80837, to PSS susceptible lines AP 350 and MO/PSD-0259. F2:5 lines from each cross were grown at Kibler, AR in a randomized complete block design with three replications. Each plot was harvested and seed samples were taken to evaluate the percentages of visual PSS (% PSS) and C. kikuchii infection (% C. kikuchii). Ranges, LSMeans, and confidence intervals of the parents were used to classify resistant and susceptible reactions in the F2:5 lines for the two variables evaluated. Sixteen SSR markers in a 17.1 cM region on chromosome (Chr.) 18 were used to screen the parents and both F2:5 populations. Significant differences in % PSS and % C. kikuchii were observed for the parents and both F2:5 populations. For the two variables evaluated, both populations showed a good fit to a ratio of 15:1 (resistant: susceptible), indicating two dominant gene action. One chromosomal region in the vicinity of Satt115 and Satt340 on Chr. 18 was determined to be associated with the resistance gene Rpss1 in both populations. These results confirm the presence of a major resistance gene, Rpss1, in PI 80837 and also indicate an additional putative gene for PSS resistance.

Effects of tillage, cultivar and fungicide on Phomopsis longicolla and Cercospora kukuchii in soybean

It has become a standard practice for farmers to use a no-till production system where crop residues are left on the soil surface rather than incorporated into the soil. This practice helps reduce soil erosion, conserve energy, increase soil moisture, and reduce erosion. However, many plant pathogens survive in the previous year's crop residue, increasing disease risk in reduced-tillage systems. The effect of tillage on seed borne diseases has not been objectively evaluated in side by side comparisons of till and no-till culture. We evaluated the impact of tillage and foliar fungicide on percent seed infection by Phomopsis Seed Decay (PSD) and Purple Seed Stain (PSS) over 4 years at the Milan Research and Education Center, Milan, TN. Analysis of variance indicated there was no significant difference (P≤0.05) in PSD and PSS infection due to tillage. However, there was a significant interaction between fungicide and tillage where fungicide significantly reduced PSD in tilled but not in no-till plots. On the contrary, PSS increased in both tilled and no-till plots with fungicide application. These results suggest that fungicide programs under both till and no-till systems may alter the level of severity of these two seed borne diseases and may require further research to minimize the risk.

Effective Application of Chemical Controlling Soybean Purple Seed Stain Fugus Resistant to Thiophanate-Methyl

Effective Application of Chemical Controlling Soybean Purple Seed Stain Fugus Resistant to Thiophanate-Methyl

Genetic Mapping of Resistance to Purple Seed Stain in PI 80837 Soybean

Purple seed stain (PSS) of soybean caused by Cercospora kikuchii is an important disease that reduces market grade and can affect seed germination and vigor. A single dominant gene was shown to confer PSS resistance in PI 80837. The objective of this research was to map the PSS resistance gene in PI 80837 using simple sequence repeat (SSR) markers. A cross was made between the PSS-susceptible cultivar Agripro 350 (AP 350) and PI 80837. The F2 population and parents were grown in the field, and the resistance or susceptibility of individual plants was determined by assaying the seed for infection by C. kikuchii. DNA of parent and F2 plants was extracted for SSR analysis and mapping. Segregation ratios for seed infection and for SSR markers showed that a single dominant gene conditions resistance to PSS in PI 80837. The candidate resistance gene was mapped between Sat_308 (6.6 cM) and Satt594 (11.6 cM) on molecular linkage group G. These markers may be useful in marker-assisted selection for utilizing PSS resistance from PI 80837 in a breeding program.

Inheritance of Resistance to Purple Seed Stain Caused by Cercospora kikuchii in PI 80837 Soybean

Purple seed stain (PSS) of soybean [Glycine max (L.) Merr.], caused by Cercospora kikuchii (T. Matsu. &amp; Tomoyasu) Gardner, is favored by high moisture and warm temperatures during early pod development. PSS can significantly reduce seed and grain quality. Characterizing genetic resistance to PSS would be valuable in the development of resistant lines and varieties. PI 80837 has a high level of resistance to PSS and also good resistance to Phomopsis seed decay (PSD) caused primarily by Phomopsis longicolla Hobbs. Resistance to PSD in PI 80837 is conferred by a single dominant gene. The research reported here genetically characterizes PSS resistance in PI 80837 and examines if genes for PSS and PSD resistances are linked. Crosses were made between PI 80837 and ‘Agripro 350’ (AP 350) (susceptible to PSS and PSD), PI 91113 (susceptible to PSS and PSD), and line MO/PSD‐0259 (susceptible to PSS but resistant to PSD). Populations and lines were grown in the field and C. kikuchii infection was assayed by plating seed. Cercospora seed infection of F1 plants from reciprocal crosses of AP 350 × PI 80837 was not significantly different from that of PI 80837, indicating that resistance is under nuclear control. Segregation data from each of four F2 populations fit a single dominant gene model for resistance. Data from F2:3 lines of AP 350 × PI 80837 and PI 80837 × MO/PSD‐0259 fit the model for a single dominant gene for PSS resistance. A linkage test for reaction to Cercospora and Phomopsis seed infection in F2:3 lines of AP 350 × PI 80837 showed that the genes for PSS and PSD resistances in PI 80837 are not linked.

Effect of Pod Development Stage, Temperature, and Pod Wetness Duration on the Incidence of Purple Seed Stain of Soybeans

The incidence of soybean seed infected by Cercospora kikuchii was influenced by temperature, length of pod wetness period, and developmental stage of the soybean pods at the time of inoculation. The statistical significance was determined using logistic regression. Infected seeds were observed when small pods (<0.5 cm in length) and large pods (0.5-2.0 cm in length) were inoculated with a conidial suspension. No infection was observed when flowers in full bloom or postbloom (desiccated petals) stages were inoculated (...)

A Method for Evaluating the Effectiveness of Seed Disinfectant against Purple Seed Stain of Soybean

A Method for Evaluating the Effectiveness of Seed Disinfectant against Purple Seed Stain of Soybean

Synchronization of Soybean Maturity by Picking off Flowers and Its Application for Selection of Resistant Varieties to Purple Seed Stain

Synchronization of Soybean Maturity by Picking off Flowers and Its Application for Selection of Resistant Varieties to Purple Seed Stain