Red Rot Disease Research Articles

Molecular Characterization and Pathogenicity of Colletotrichum falcatum Causing Red Rot on Sugarcane in Southern Florida

Red rot disease reduces sugarcane yield and impacts the sugar quality, posing an important threat to the sugarcane industry in Florida. Although Colletotrichum falcatum, the causal agent of red rot in Florida, was first reported in 1984 based on morphology, molecular and pathological data have remained limited, highlighting the critical need for comprehensive characterization. Thirteen isolates were obtained from three local sugarcane varieties in Belle Glade, Florida. Phylogenetic analyses of five genetic markers (ITS, ACT, TUB2, GAPDH, and CHS-1) confirmed all the strains as C. falcatum. In addition, the study documented the disease progression at the cellular level and assessed the pathogenicity of representative strains using the leaf sheath and whole-seedling inoculation methods. The varieties CP96-1252 and CP89-2143 showed greater host resistance. These findings represent the first report of C. falcatum causing red rot in southern Florida, offer valuable insights for/into red rot management, and provide a basis for future breeding programs to enhance sugarcane resistance to red rot disease.

Expression of Trichoderma spp. endochitinase gene improves red rot disease resistance in transgenic sugarcane.

Sugarcane (Saccharum spp.)is an economically useful crop grown globally for sugar, ethanol and biofuel production. The crop is vulnerable to fungus Colletotrichum falcatum known to cause red rot disease. The pathogen hydrolyses stalk parenchyma cells where sucrose is accumulated resulting in upto 75% losses in sugar recovery. In this study, transgenic sugarcane having resistance against red rot was developed by introducing Trichoderma spp. endochitinase following Agrobacterium mediated transformation. The transgene introduction and expression in genetically modified plants were verified through qRT-PCR revealing upto 6-fold enhancement in endochitinase expression than non-transgenic plants. Hyperspectral Imaging of transgenic plants displayed altered leaf reflectance spectra and vegetative indices that were positively correlated with ransgene expression. The bioassay with virulent pathotypes of C. falcatumCF08 and CF13 known for epiphytotic occurrence resulted in identification of resistant plant Chit 3-13.The plants with higher reflectance also displayed improved disease resistance, implying their early classification into resistant/susceptible. The losses in sucrose content were minimized (up to 4-fold) in inoculated resistant plant Chit 3-13 as compared to susceptible non-transgenic plant, and a fewer pathogen hyphae were detected in vascular cells of the former through optical microscopy. The electron micrographs confirmed sucrose-filled stalk parenchyma cells in Chit 3-13; in contrast, cells of non-transgenic inoculated plant were depleted of sucrose. The active sites involved in cleaving 1-4 β-glycoside bonds of N-acetyl-d-glucosaminein the pathogen hyphal walls were detected through endochitinase protein structural modelling. The transgenic sugarcane is an important source for in trogressingred rot resistance in plant breeding programs.

CoC 25–An early maturing high-yielding and red rot-resistant sugarcane variety suitable for the East Coast Zone of India

Aim: To develop early duration high-yielding sugarcane variety coupled with resistance or tolerant to major disease (red rot) and insect pests (borer complex). Methodology: CoC 25 was developed from two parents (Co 85002 and HR 83-144) and evaluated in station trials, state multi-location trials (five locations) and zonal varietal trials of AICRP (S) trials (IVT, AVT-I, AVT-II and AVT ratoon in five locations). Simultaneously, this clone was screened for major pest and diseases. Results: Based on the superiority performance of CoC 25 in cane yield (21.50% higher) and sugar yield (22.72% higher), it was observed in AICRP trials over the national check variety CoC 01061. Cane yield superiority was 12.75% compared to check variety observed in state multi-location trials. The CoC 25 was found moderately resistant (3.6%) to red rot disease and less susceptible to early shoot borer (9.42%) and inter-node borers. Interpretation: The results of this study revealed that CoC 25 is superior in terms of cane yield, CCS yield and resistance to red rot disease and it is less susceptible to borers. It was released by SVRC and notified for commercial cultivation in Tamil Nadu and Puducherry. Key words: Cane yield, CCS yield, Red rot resistance, Sugarcane

Quantitative detection of <i>Pythium porphyrae</i> and <i>Pythium chondricola</i> (Oomycota), the causative agents of red rot disease in <i>Pyropia farms</i> in China

Red rot disease is one of the notorious algal diseases that threaten the cultivation of <i>Pyropia</i> in China, and two <i>Pythium pathogens</i>, i.e., <i>Pythium porphyrae</i> and <i>P. chondricola</i>, have been reported as causative agents. To monitor the pathogens, a fluorescent quantitative polymerase chain reaction (PCR) method was developed to quantitatively detect their abundance. Using overlapping PCR and pathogen-specific primer pairs, two pathogen-specific fragments were concatenated to construct an internal standard plasmid, which was used for quantification. For zoospores of known numbers, the results showed that this method can detect as less as 100 and 10 zoospores mL<sup>-1</sup> in a 200 mL solution for <i>P. porphyrae</i> and <i>P. chondricola</i>, respectively. Using monthly collected seawater at 10 sites in Haizhou Bay, a typical aquaculture farm in China, a significantly higher temperature and a significantly lower salinity were determined in December 2021. <i>P. porphyrae</i> was determined to be more abundant than <i>P. chondricola</i>, though with similar temporal distribution patterns from December 2021 to February 2022. When a red rot disease occurred in December 2021, the two pathogens were significantly more abundant at two infected sub-sites than the uninfected sub-site within both seawater and sediment, though they were all significantly more enriched in sediment than in seawater. The present method provides the capability to quantify and compare the abundance of two pathogens and also has the potential to forecast the occurrence of red rot disease, which is of much significance in managing and controlling the disease.

Macroalgal Diseases: Exploring Biology, Pathogenesis, and Management Strategies

The global seaweed market is expected to reach USD 17.8 billion by 2032, fuelled by growing demand for sustainable and healthy food solutions and expanding applications in agriculture and aquaculture. However, this rapid growth poses significant challenges, particularly in managing diseases that often establish themselves in intensive macroalgal culture facilities. Red rot disease, Olpidiopsis, and green spot disease often affect marine macroalgae species of high commercial interest, as seen in Pyropia/Porphyra as has already happened for “ice-ice” malaise on Kappaphycus, causing huge economic losses. These diseases are caused by infectious agents that find their place in extreme environmental conditions, such as those characterized by sudden changes in temperature and pollution. Despite technological advances aimed at monitoring the well-being of cultivated seaweed, discrepancies between regions’ technological capabilities and species vulnerability exacerbate management difficulties. This review provides an overview of diseases prevalent among marine algae, their impact on aquaculture, and the effectiveness of currently adopted treatments. This study highlights the need to improve disease management strategies and highlights the importance of understanding host–pathogen interactions in order to mitigate future epidemics.

Evolution, identification, evaluation, and characterization of a stable salinity tolerant sugarcane variety CoG 7

From the fluff generated during 2005, after the preliminary experiments (2005–2007), a promising clone G2005047 has been identified. It showed moderate resistance to red rot (3.6 on a 9-scale scoring system), less susceptibility to shoot borer (13.25%) and internode borers (25.35%), and resistance to woolly aphid (0%). In the Advanced Yield Trials (2008–2011), it showed advantages over check for cane yield (CY) (11.79%), commercial cane sugar percent (CCSP) (0.35%), and sugar yield (SY) (20.33%). To ascertain its large-scale cultivation suitability, it has experimented under adaptive research trials (2012–2014) at farmers’ fields. It exhibited 18.04%, 1.27%, and 19.55% supremacy over the check Co 86032 for CY, CCSP, and SY respectively. The stability of G2005047 under salinity was ascertained through a multi-environment-based experiment (2015–2017). AMMI (Additive Main-effects and Multiplicative Interactions) and GGE (Genotype × Genotype-Environment interaction) biplots were utilized. ANOVA revealed that the genotypic variation exerted the most significant effect followed by genotype × environment interaction and environment. G2005047 had the highest mean values for yield and quality traits with minimal ASV (AMMI stability value) (2.38:CY; 0.57: CCSP; & 0.58:SY) indicating its good-yielding ability and stability. AMMI I, AMMI II, and GGE biplots confirmed the stability of G2005047. In the jaggery quality assessment trials (2018 and 2019), it yielded 37.1% increased jaggery over the check. Also, the clone G2005047, exhibited moderate resistance to red rot disease, less susceptibility to shoot borer (13.25%) and internode borer (25.35%), and resistance against sugarcane woolly aphid (SWA). Due to supremacy for yield, quality, better performance under salinized situations, and tolerance to disease and pests, the clone G2005047 was released as a variety CoG 7 in 2022.

The versatile plant probiotic bacterium Bacillus velezensis SF305 reduces red root rot disease severity in the rubber tree by degrading the mycelia of Ganoderma pseudoferreum1

Natural rubber is an indispensable material of strategic importance that has critical applications in industry and the military. However, the development of the natural rubber industry is impeded by the red root rot disease of rubber trees caused by Ganoderma pseudoferreum, which is one of the most devastating diseases in the rubber tree growing regions in China. To combat this disease, we screened the antifungal activity of 223 candidate bacterial strains against G. pseudoferreum, and found that Bacillus velezensis strain SF305 exhibited significant antifungal activity against G. pseudoferreum. B. velezensis SF305 had a nearly 70% efficacy against the red root rot disease of rubber trees with the therapeutic treatment (Tre), while it exhibited over 90% protection effectiveness with the preventive treatment (Pre). The underlying biocontrol mechanism revealed that B. velezensis SF305 could reduce the disease severity of red root rot by degrading the mycelia of G. pseudoferreum. An antiSMASH analysis revealed that B. velezensis SF305 contains 15 gene clusters related to secondary metabolite synthesis, 13 of which are conserved in species of B. velezensis, but surprisingly, B. velezensis SF305 possesses 2 unique secondary metabolite gene clusters. One is predicted to synthesize locillomycin, and the other is a novel nonribosomal peptides synthetase (NRPS) gene cluster. Genomic analysis showed that B. velezensis SF305 harbors genes involved in motility, chemotaxis, biofilm formation, stress resistance, volatile organic compounds (VOCs) and synthesis of the auxin indole-3-acetic acid (IAA), suggesting its plant growth-promoting rhizobacteria (PGPR) properties. B. velezensis SF305 can promote plant growth and efficiently antagonize some important phytopathogenic fungi and bacteria. This study indicates that B. velezensis SF305 is a versatile plant probiotic bacterium. To the best of our knowledge, this is the first time a B. velezensis strain has been reported as a promising biocontrol agent against the red root rot disease of rubber trees.

Isolation, Identification, and Biocontrol Mechanisms of Endophytic Burkholderia arboris DHR18 from Rubber Tree against Red Root Rot Disease.

Red root rot disease is a devastating fungal disease of rubber trees caused by Ganoderma pseudoferreum (Wakef). Biocontrols using beneficial microorganisms are safe and sustainable. We isolated a DHR18 endophytic bacterium from a healthy rubber tree to obtain a new efficient antagonistic bacterium for red root rot disease affecting rubber trees and evaluated the mechanism of action involved using a double culture assay, genome annotation analysis, and the ethyl acetate extraction method. The results revealed that the DHR18 strain inhibits G. pseudoferreum growth and has broad-spectrum antifungal activity by secreting cell wall hydrolases (proteases and chitinases), indole-3-acetic acid, and siderophores. Furthermore, it fixes nitrogen and is involved in biofilm formation and phosphate solubilisation, improving disease resistance and tree growth. The results showed that the antifungal substances secreted by DHR18 are mainly lipopeptides. Simultaneously, DHR18 enhanced the rubber tree resistance to G. pseudoferreum by increasing the activities of defence enzymes superoxide dismutase, phenylalanine ammonia lyase, peroxidase, catalase, and polyphenol oxidase. The results indicate that B. arboris DHR18 has biocontrol potential and could be used as a candidate strain for the control of red root rot disease in rubber trees.

First report of Fusarium andiyazi causing red rot disease on sugarcane in India

First report of Fusarium andiyazi causing red rot disease on sugarcane in India

Study on the Identification, Biological Characteristics, and Fungicide Sensitivity of the Causal Agent of Strawberry Red Core Root Rot

Strawberry red core root rot disease affects the growth and yield of strawberry (Fragaria ananassa Duch), which leads to economic losses in China. The study employed a tissue separation method to isolate and identify the causal agent responsible for strawberry red core root rot. This was achieved by the observation of its morphological characteristics, sequencing analyses, and pathogenicity tests. The sensitivity of five chemical fungicides against the two species of Fusarium was determined using the mycelial growth rate method, and the biological characteristics of the two species were examined. The pathogens were identified as Fusarium solani and Fusarium oxysporum. The optimal conditions for the mycelial growth of F. solani and F. oxysporum were determined to be potato sucrose agar at 25 °C and pH 6, and potato dextrose agar at 30 °C and pH 8, respectively, with a 24:24 light cycle. The most suitable carbon and nitrogen sources for the mycelial growth of F. solani were sucrose and sodium nitrate (NaNO3), while for F. oxysporum, they were glucose and peptone. A fungicide sensitivity test indicated that Prochloraz had a good inhibitory effect on the growth of F. solani and F. oxysporum with EC50 values of 0.088 mg L−1 and 0.162 mg. The growth inhibition effect of Azoxystrobin to F. solani and Carbendazim to F. oxysporum was not obvious. This study provides a theoretical basis for further research on strawberry red core root disease and its prevention.

Assessment and management of diverse isolates of Colletotrichum falcatum associated with red rot disease in sugarcane

Assessment and management of diverse isolates of Colletotrichum falcatum associated with red rot disease in sugarcane

A Novel Approach for Red Rot Disease Detection in Sugarcane Plants Using Transfer Learning Based VGG16 Model

Red rot in sugarcane is a devastating fungal disease caused by Colletotrichum falcatum. It leads to wilting, red discoloration, and yield losses, which can impact sugar production globally. Red rot hampers sugarcane production, causing yield reductions, and economic losses, and affecting the nation’s sugar industry demanding stringent disease management strategies. There is a need of a system that detects the red rot disease at an early stage before it spreads. Transfer learning enhances agricultural models, leveraging pre-trained data for improved crop predictions, resource optimization, and sustainability. In this article, we have proposed a transfer learning-based VGG16 model for the detection of red rot disease in sugarcane on a large dataset. The model achieves a remarkable 98.85% accuracy and an F1 score of 0.93 in early red rot detection in sugarcane. This work underscores the potency of leveraging re-trained models for crop disease identification, offering a promising avenue for proactive disease management. This research marks a substantial step towards enhancing crop yield and sustainability, presenting an accessible and impactful technological solution for early disease detection in sugarcane, ultimately benefiting agricultural practices.

Occurrence and field evaluation of promising sugarcane genotypes for resistance to midrib red rot disease in China

AbstractSugarcane midrib red rot caused by Colletotrichum falcatum is widespread in China. Standardizing the resistance evaluation methods and screening resistant varieties against this disease is crucial. C. falcatum was determined as the causal agent of midrib red rot by isolating and identifying pathogenic fungi from diseased leaves in Guangxi, China. A field trial of 237 sugarcane genotypes was conducted for three consecutive years to investigate disease incidence and indices for three experimental sites in Guangxi. The combined analysis of variance showed that disease incidence was significantly affected by genotype, year, location and their interactions. Cluster and discriminant analysis showed that 237 sugarcane genotypes were classified into five categories, including 20 as highly resistant, 82 as resistant, 71 as moderately susceptible, 46 as susceptible and 18 as highly susceptible. This study has enhanced our understanding of sugarcane resistance to midrib red rot, selected disease‐resistant parents and laid the foundation for developing elite disease‐resistant varieties.

Identification and Genetic Dissection of Resistance to Red Crown Rot Disease in a Diverse Soybean Germplasm Population.

Red crown rot (RCR) disease caused by Calonectria ilicicola negatively impacts soybean yield and quality. Unfortunately, the knowledge of the genetic architecture of RCR resistance in soybeans is limited. In this study, 299 diverse soybean accessions were used to explore their genetic diversity and resistance to RCR, and to mine for candidate genes via emergence rate (ER), survival rate (SR), and disease severity (DS) by a multi-locus random-SNP-effect mixed linear model of GWAS. All accessions had brown necrotic lesions on the primary root, with five genotypes identified as resistant. Nine single-nucleotide polymorphism (SNP) markers were detected to underlie RCR response (ER, SR, and DS). Two SNPs colocalized with at least two traits to form a haplotype block which possessed nine genes. Based on their annotation and the qRT-PCR, three genes, namely Glyma.08G074600, Glyma.08G074700, and Glyma.12G043600, are suggested to modulate soybean resistance to RCR. The findings from this study could serve as the foundation for breeding RCR-tolerant soybean varieties, and the candidate genes could be validated to deepen our understanding of soybean response to RCR.

Suppression of Sugarcane Red Rot Disease through Its Rhizospheric Mycoflora

Red rot disease of sugarcane is so devastating in nature that it has been referred to as “cancer of sugarcane”. The sugar industry in India suffered losses more than 500 million US dollars every year due to red rot. So, there is a need to look over the management and control of the disease. Biological control method is an alternative method of chemical pesticides which are an innovative, cost effective and eco-friendly approach. Soil samples were collected from sugarcane rhizosphere of four different varieties viz., CoPk 05191 and CoLk 94184 (resistant to red rot) and CoJ 64 and Co 1148 (susceptible to red rot) planted at ICAR-Indian Institute of Sugarcane Research, Lucknow experimental farm. The samples were subjected for the isolation of rhizospheric mycoflora on Potato Dextrose Agar media and antagonistic activities of the isolates were tested against red rot pathogens (Cf 07, Cf 08 and Cf 09). Isolates showing more than 50 % inhibition with all the three pathotypes (Cf 07, Cf 08 and Cf 09) were selected for further study. Among the twelve selected isolates used for field experiment for the management of red rot, isolate T16 was found to be highly effective. The suppression of red rot offered by rhizospheric isolates is probably due to induced systemic resistance in sugarcane plants or by the enzymatic action of metabolites produced by the rhizospheric mycoflora. The different levels of red rot infected seed cane viz., 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40% were treated with MHAT and planted along with healthy seed canes, infected seed canes, as a control to work out the losses caused by different level of red rot seed infection. The result revealed that a yield loss was recorded with the infected seed. The losses were directly proportionate with the level of red rot infected seed.

Yield, Quality and Disease Resistance of Sugarcane Clones: A Field Evaluation

Evaluation and identification of sugarcane clones for different maturity groups is of paramount importance in sugarcane cultivation to get higher recoveries in sugar mills. A field experiment was conducted to evaluate the performance of early maturing sugarcane clones for red rot resistance, cane yield, CCS yield, and their contributing traits in order to idendify the superior clones. Observation on germination per cent, number of tillers (x1000/ha), number of millable cane (x1000/ha), stalk length (cm), stalk diameter (cm), single cane weight (kg), cane yield (t/ha), brix per cent, sucrose (%), purity (%), extraction CCS (%), and sugar yield (t/ha). From the results, it could be concluded that the early maturing clone, CoC 15336, was found to be the best among the test clones for sucrose per cent and sugar yield with resistance to red rot disease. Another clone, CoC 15340, was the next-best entry, with higher cane yield, CCS yield, and sucrose percent compared to the better standards. As a result, clones CoC 15338 and CoC 15336 were identified as the best promising entries and could be forwarded for further yield evaluation trials for release as a new sugarcane variety suitable for East Coast Zone of India.

MAPK signaling pathway orchestrates and fine-tunes the pathogenicity of Colletotrichum falcatum

Colletotrichum falcatum is the causal organism of red rot, the most devastating disease of sugarcane. Mitogen-activated protein kinase (MAPK) signaling pathway plays pivotal role in coordinating the process of pathogenesis. We identified eighteen proteins implicated in MAPK signaling pathway in C. falcatum, through nanoLCMS/MS based proteomics approach. Twelve of these proteins were the part of core MAPK signaling pathway, whereas remaining proteins were indirectly implicated in MAPK signaling. Majority of these proteins had enhanced abundance in C. falcatum samples cultured with host sugarcane stalks. To validate the findings, core MAPK pathway genes (MAPKKK-NSY1, MAPK 17-MAPK17, MAPKKK 5-MAPKKK5, MAPK-HOG1B, MAPKKK-MCK1/STE11, MAPK-MST50/STE50, MAPKK-SEK1, MAPKK-MEK1/MST7/STE7, MAPKK-MKK2/STE7, MAPKKK-MST11/STE11, MAPK 5-MPK5, and MAPK-MPK-C) were analyzed by qPCR to confirm the real-time expression in C. falcatum samples cultured with host sugarcane stalks. The results of qPCR-based expression of genes were largely in agreement with the findings of proteomics. String association networks of MAPKK- MEK1/MST7/STE7, and MAPK- MPK-C revealed strong association with plenty of assorted proteins implicated in the process of pathogenesis/virulence. This is the novel and first large scale study of MAPK proteins in C. falcatum, responsible for red rot epidemics of sugarcane various countries. Key messageOur findings demonstrate the pivotal role of MAPK proteins in orchestrating the pathogenicity of Colletotrichum falcatum, responsible devastating red rot disease of sugarcane. SignificanceOur findings are novel and the first large scale study demonstrating the pivotal role of MAPK proteins in C. falcatum, responsible devastating red rot disease of sugarcane. The study will be useful for future researchers in terms of manipulating the fungal pathogenicity through genome editing.

Dry Rot Caused by the Complex Colletotrichum falcatum and Thielaviopsis paradoxa Emerges as a Key Stalk Disorder in Newly Expanded Sugarcane Plantations from Northwestern São Paulo, Brazil

Sugarcane dry rot emerged as an important stalk disorder in newly expanded plantations in northwestern São Paulo, Brazil, under the current no-burning fully mechanical harvest policy gradually implemented in the past 20 years. This emergence was probably due to a considerable increase in both pathogen inocula and insect pest populations in sugarcane crop residues kept in the field. In this study, we surveyed the incidence of three stalk-related disorders in commercial sugarcane fields in six municipalities in northwestern São Paulo and the corresponding yield losses. The three stalk-related disorders surveyed were as follows: the red rot disease caused by the fungal pathogen Colletotricum falcatum, the spittlebug-induced shoot stunting, and the stem dry rot, which is associated with the simultaneous infection of C. falcatum and Thielaviopsis paradoxa, the pineapple set rot pathogen. Red rot disease was detected in 88.2% of the fields surveyed, while the spittlebug-induced shoot stunting disorder and the internal stem dry rot were found in 97.1% of the fields. Stem dry rot had the highest incidence and resulted in the highest yield losses. Total sugarcane yield losses were estimated at 20.1%, with an average of 14.2 (±3.8) t·ha−1 per field. The multiple regression model constructed to determine which of the three stem-related disorders contributed the most to total yield losses was not significant. Subsequently, the performance analyses of single-variable polynomial regression models indicated that the simple linear model was the best fit in terms of independently predicting sugarcane yield losses based on each stem-related disorder. Positive and significant correlations were only detected between sugarcane yield losses in t·ha−1 and the incidence of red rot disease or leafhopper-induced shoot stunting. We concluded that the stalk’s internal dry rot, as a disease complex associated with both C. falcatum and T. paradoxa, was the most important disorder in sugarcane fields in the northwest region of São Paulo state. A sustainable pest management program is needed to reduce the impact of all three stalk-associated disorders on regional sugarcane production.

Genome-Wide Identification and Analysis of MYB Transcription Factors in Pyropia yezoensis.

MYB transcription factors are one of the largest transcription factor families in plants, and they regulate numerous biological processes. Red algae are an important taxonomic group and have important roles in economics and research. However, no comprehensive analysis of the MYB gene family in any red algae, including Pyropia yezoensis, has been conducted. To identify the MYB gene members of Py. yezoensis, and to investigate their family structural features and expression profile characteristics, a study was conducted. In this study, 3 R2R3-MYBs and 13 MYB-related members were identified in Py. yezoensis. Phylogenetic analysis indicated that most red algae MYB genes could be clustered with green plants or Glaucophyta MYB genes, inferring their ancient origins. Synteny analysis indicated that 13 and 5 PyMYB genes were orthologous to Pyropia haitanensis and Porphyra umbilicalis, respectively. Most Bangiaceae MYB genes contain several Gly-rich motifs, which may be the result of an adaptation to carbon limitations and maintenance of important regulatory functions. An expression profile analysis showed that PyMYB genes exhibited diverse expression profiles. However, the expression patterns of different members appeared to be diverse, and PyMYB5 was upregulated in response to dehydration, low temperature, and Pythium porphyrae infection. This is the first comprehensive study of the MYB gene family in Py. Yezoensis and it provides vital insights into the functional divergence of MYB genes.

Application and evaluation of probiotics against red rot disease in Pyropia

Biocontrol has been widely used in crop disease control, but rarely in algae. In this study, two Pseudoalteromonas piscicida strains (P3 and P6), which have an antagonistic effect on the growth of Pythium porphyrae, were used for the red rot disease control in Pyropia. The safety and antagonistic efficiency of P3 and P6 to Pyropia yezoensis thalli were tested by immersion. Results showed that thalli immersed with P3 or P6 grew normally without pathological changes. The inhibition effect of P3 and P6 against red rot disease was tested by experimental infection, and the disease spots were significantly inhibited in P3 and P6 treated groups, with inhibition rates of 42.81%–74.35% and 60.33%–91.11%, respectively. Additionally, the P6 treatment combined with air-drying was investigated to test the application in production. The infected Pyr. yezoensis thalli immersed with 107 CFU/mL P6 for 3 min and then air-dried for 1 h could significantly inhibit the development of red rot disease, with inhibition rates over 77.23%. These results indicate that P3 and P6 can inhibit Pyt. porphyrae infection in Pyr. yezoensis, and apply to control red rot disease combined with air-drying. Thus, this research provides an effective approach for the red rot disease control, and reveals new insights into algal disease prevention and biocontrol methods.