Southern blight (Sclerotium rolfsii Sacc.) of cowpea: yield-loss estimates and sources of resistance

doi:10.1016/S0261-2194(01)00122-3

Crop Protection

Volume 21, Issue 5, June 2002, Pages 403-408

https://doi.org/10.1016/S0261-2194(01)00122-3 Get rights and content

Abstract

Replicated field studies were conducted over a three-year period to assess the yield-reducing potential of southern blight (Sclerotium rolfsii) on cowpea, and to evaluate the range of genetic variability in cowpea germplasm for resistance. Southern blight was shown to have a considerably greater impact on dry-seed yields than that suggested by a review of the published literature. The disease caused a dry-seed yield loss of 53.4% in one study, and losses approaching 50% were observed for some cultivars in a second study. Reduced pod numbers likely accounted for most of the reduced dry-seed yields. There is significant variability in cowpea germplasm for resistance to southern blight. Two cultivars, Brown Crowder and Carolina Cream, exhibited promising levels of resistance in two years of testing.

Section snippets

Materials and methods

The data reported here are from replicated field studies conducted at the US Vegetable Laboratory, Charleston, SC, during the years 1984, 1985, and 1986. Seeds of all cowpea accessions evaluated in these studies were produced by the authors prior to the initiation of specific studies and all seed lots exhibited high germination. The severity of southern blight symptoms in all of the studies was assessed by assigning each plant a subjective score for severity of wilting. Each plant in the 1984

Relationship between time of inoculation and dry-seed yield (1984 study)

An examination of the results of the early, medium, and late sclerotia inoculation treatments of the cultivar Pinkeye Purple Hull indicates that early inoculation with 20 sclerotia/plant, 35 days after planting, was the most effective timing for inoculation of cowpea plots (Table 1). This treatment caused a 53.4% reduction in seed yield from the uninoculated control, and an examination of the stem-lesion data suggests that most of the plants developed large stem lesions prior to harvest. The

Conclusions

The results of the studies reported here support the long-standing theory that southern blight is an important disease of cowpea. However, our data demonstrates that the impact of southern blight on cowpea seed yields can be considerably greater than that suggested by a review of the published literature. Reduced pod numbers likely accounted for most of the reduced seed yields. There is significant variability in the resistance of cowpea germplasm to southern blight. Two cultivars, Brown

References (9)

Aycock, R., 1966. Stem rot and other diseases caused by Sclerotium Rolfsii or the status of Rolfs’ fungus after 70...
W.M. Epps et al.
Physiology and parasitism of Sclerotium rolfsii
Phytopathology
(1951)
D.E. Hoffmaster et al.
The problem of dry rot caused by Macrophomina phaseoli (=Sclerotium bataticola)
Phytopathology
(1943)
S.F. Jenkins et al.
Problems and progress in integrated control of southern blight of vegetables
Plant Dis.
(1986)

There are more references available in the full text version of this article.

Cited by (28)

Morpho-molecular, cultural and pathological characterization of Athelia rolfsii causing southern blight disease on common bean
2023, Heliyon
Common bean (Phaseolus vulgaris), is a winter legume crop in Bangladesh and is considered an important vegetable with export potential. However, the production of common bean is severely affected by a newly reported soilborne fungal pathogen, Athelia rolfsii. This study aimed to characterize this new pathogen by morphological, molecular, cultural, and pathological analyses and determine the host range. The disease incidence in the affected field ranged between 6 and 13%. Initial disease symptoms were observed as brown sunken lesions at the point of infection and development of mycelia, followed by yellowing and quick wilting of the whole plant. A total of 10 fungal isolates were recovered from the infected plant samples, which were morphologically similar and produced white to brown mycelia and numerous brown sclerotia on the PDA medium. Two of them viz. BTCBSr3 and BTCBSr4 were used for the detailed study. Based on morphology and phylogenetic analyses of the sequenced data of internal transcribed spacer (ITS) and translation elongation factor 1 alpha (EF-1α), the pathogen was identified as A. rolfsii. Mycelial growth rate (3.6 cm/day) and fresh weight (107 mg) were higher in the PDA medium, whereas the number of sclerotia production (328/plate) was higher in OMA media. The isolates could grow in a wider range of incubation temperatures (15–35 °C) and media pH (3–9). In the cross-inoculation assay, both isolates were pathogenic on tomato, brinjal, and chickpea, but not on chili, soybean, and cowpea. This study has laid a foundation for further pathological research on the fungus in aid to develop an effective management practice against the pathogen.
Endophytic Alcaligenes faecalis mediated redesigning of host defense itinerary against Sclerotium rolfsii through induction of phenolics and antioxidant enzymes
2020, Biological Control
Endophytic microbes intricately modulate host defense pathways upon challenge with any form of environmental stress. In the current study, endophytic Alcaligenes faecalis treated okra plants were found to exhibit significant resistance to cell-lysis and disintegration upon infection with Sclerotium rolfsii. Apart from the morphological amendments, a systemic induction in phenolic content was observed in the endophyte treated hosts, such as that of gallic, cinnamic, synaptic, vanillic, ferulic, t-chlorogenic and gentisic acid as well as rutin, quercetin and kaempferol. Simultaneously, an upregulation of peroxidase (PO) and superoxide dismutase (SOD) was observed in the endophyte treated host leaf tissues along with significant lignification at the collar regions. Though similar number of isoforms of PO and SOD were observed in the endophyte treated plants and uninoculated control yet a higher intensity of the former suggests activation of defense pathways due to endophytic colonization. Thus this study may provide a thorough comprehension of the correlation among various defense pathways occurring simultaneously in planta upon endophyte treatment which particularly protect the host from S. rolfsii infection.
Quantitative polymerase chain reaction (Q-PCR) and fluorescent in situ hybridization (FISH) detection of soilborne pathogen Sclerotium rolfsii
2019, Applied Soil Ecology
Citation Excerpt :
Uninoculated pots were used with 6 uninfected grains as a control. Total of 20 inoculated and 40 uninoculated pots were assessed 8 weeks after inoculation for disease severity using a scale of 0–5 based on previously published disease scale (Fery and Dukes, 2002) with modifications, where 0 = no symptoms of basal stem lesions or wilting of leaves; 1 =< 20% of leaves wilted and/or 20% of basal stem with lesion; 2 = 20–40% of leaves wilted and/or 20–40% of basal stems with lesions; 3 = 40–60% of leaves wilted and/or 40–60% basal stem with lesions; 4 = 60–80% of leaves wilted and/or 60–80% of basal stem with lesions; and 5 => 80% of leaves wilted or dead plant (Wu et al., 2015). After completion of the greenhouse experiments, soil microbial DNA was extracted from 0.75 g soil samples using a PowerMax® Soil DNA Isolation Kit (Mo Bio Laboratories, Inc., Carlsbad, CA, USA) per supplier instructions.
Early detection of soilborne disease is essential for prediction of disease development and successful disease management. Traditional methods of monitoring soilborne diseases based on plant growth and symptoms did not take into account the presence and inoculum potential of pathogens in the soil, which generally delay the prevention of diseases. To detect and quantify soil populations of Sclerotium rolfsii, the causal agent of southern blight of tomatoes, quantitative polymerase chain reaction (Q-PCR) was used to measure the amount of soil general fungal and specific S. rolfsii DNA. Significantly higher amounts of total fungal and S. rolfsii DNA were detected in inoculated than in uninoculated soil in a greenhouse inoculation experiment. Fluorescent in situ hybridization (FISH) was successfully developed to detect the abundance of S. rolfsii through whole cell hybridization and was further applied for visual detection of the abundance of S. rolfsii in the soil samples of greenhouse inoculation experiment. Natural abundance of S. rolfsii in soil with a DNA amount of 0.06 pg µl⁻¹ DNA extraction, which was equivalent to 8 pg g⁻¹ soil, was successfully detected. The hybridization signal detected in soil for S. rolfsii had a great correlation with the amount of infested DNA levels of S. rolfsii. Molecular detection and quantification of soilborne pathogens in plant roots and in the soil could provide valuable information to predict disease development and apply management practices for soilborne diseases.
Biocontrol of Rhizoctonia solani and Sclerotium rolfsii on tomato by delivering antagonistic bacteria through a drip irrigation system
2010, Crop Protection
Citation Excerpt :
After 24 h the tomato plants were inoculated by spraying on the stem zone, including the wound, as well as on the entire pot-soil surface, with 200 μL of fungal (R. solani and S. rolfsii) biomass. Disease severity was periodically assessed using an empirical key of 5 disease classes: 1 (no stem lesion), 2 (small stem lesion: <25% of the stem circumference), 3 (moderate stem lesion: 26–50% of the stem circumference), 4 (large stem lesion: >51% of the stem circumference), and 5 (dead plant: stem completely girdled) (Fery and Dukes, 2002). The experiment was conducted twice and the data of repeated experiments were pooled before performing statistical analysis.
In a 2-year assessment carried out on tomato crops of Central and Southern Italy, a high incidence of Rhizoctonia solani and Sclerotium rolfsii was found. These fungal pathogens attack horticultural crops and are responsible for severe crown and stem rot. Because of technical, economical and environmental issues their chemical control is an arduous task. To find alternative and eco-compatible control methods, the effectiveness of two new antagonistic bacterial isolates (Burkholderia cepacia, T1A-2B, and Pseudomonas sp., T4B-2A), previously selected from suppressive organic amendments, were tested on tomato plants grown under both growth chamber and field conditions. The potential antagonists were compared with two commercial biofungicides, based on Bacillus subtilis (BSF4) and Trichoderma asperellum (TV1), and four synthetic fungicides (tolclofos-methyl, azoxystrobin, fosetyl-Al and fosetyl-Al + propamocarb). In 2-year field experiments carried out on tomato plants, the biocontrol bacteria as well as the other treatments were applied to the soil, proximal to the plant crowns and main roots, by means of an effective and specific system of drip irrigation. In all the experiments the novel selected biocontrol bacteria significantly reduced both incidence and severity of the diseases caused by S. rolfsii or R. solani, with results demonstrating effectiveness equal to TV1, better than BSF4 and comparable with the synthetic fungicides, except for tolclofos-methyl which was the most effective treatment. In field experiments, carried out for two consecutive years, isolate T1A-2B reduced up to 58.33% and up to 63.8% the severity of the diseases caused by S. rolfsii and R. solani respectively; whereas isolate T4B-2A gave reduction of S. rolfsii and R. solani diseases severity up to 73.2% and up to 62.7%, respectively.
This investigation provided insight for the development of novel antagonistic bacterial isolates and, particularly, a suitable method for a more efficient antagonist's distribution in the field in order to better control fungal crown and root rot of horticultural crops.
Pathogenic diversity of Sclerotium rolfsii isolates from Mexico, and potential control of southern blight through solarization and organic amendments
2006, Crop Protection
Pathogenic diversity and cultural control of Sclerotium rolfsii are two fields of knowledge not well understood. In this work, two onion isolates of S. rolfsii from the States of Morelos and Guanajuato, Mexico were inoculated to 51 plant species and disease severity levels were determined. Subsequently, 12 out of 51 plant species were selected for the determination of pathogenic reaction to 20 isolates of S. rolfsii from different regions of Mexico. Onion isolates from Morelos and Guanajuato produced variable levels of disease severity for half of the plants tested. Five plant species were susceptible or highly susceptible to all isolates. The remaining plants tested showed differential reactions to individual isolates, ranging from highly resistant to highly susceptible. Three organic soil amendments alone or combined with solarization were tested for control of S. rolfsii on microplots containing onion seedlings in naturally infested soil. A combination of solarization and incorporation of Parthenium hysterophorus into soil was effective in reducing damage and sclerotial numbers of S. rolfsii. However, the amendment alone was associated with increased damage and high sclerotial populations.
The soil-borne fungal pathogen Athelia rolfsii: past, present, and future concern in legumes
2023, Folia Microbiologica

View all citing articles on Scopus

View full text

Article preview

Crop Protection

Abstract

Section snippets

Materials and methods

Relationship between time of inoculation and dry-seed yield (1984 study)

Conclusions

References (9)

Physiology and parasitism of Sclerotium rolfsii

Phytopathology

The problem of dry rot caused by Macrophomina phaseoli (=Sclerotium bataticola)

Phytopathology

Problems and progress in integrated control of southern blight of vegetables

Plant Dis.

Cited by (28)

Morpho-molecular, cultural and pathological characterization of Athelia rolfsii causing southern blight disease on common bean

Endophytic Alcaligenes faecalis mediated redesigning of host defense itinerary against Sclerotium rolfsii through induction of phenolics and antioxidant enzymes

Quantitative polymerase chain reaction (Q-PCR) and fluorescent in situ hybridization (FISH) detection of soilborne pathogen Sclerotium rolfsii

Biocontrol of Rhizoctonia solani and Sclerotium rolfsii on tomato by delivering antagonistic bacteria through a drip irrigation system

Pathogenic diversity of Sclerotium rolfsii isolates from Mexico, and potential control of southern blight through solarization and organic amendments

The soil-borne fungal pathogen Athelia rolfsii: past, present, and future concern in legumes