Rot Of Potato Tubers Research Articles

First Report of Fusarium nirenbergiae Causing Rot of Potato in China.

Potato (Solanum tuberosum L.) is the third largest food crop globally following rice and wheat, which is consumed by more than 1 billion people worldwide (FAO 2024). In October 2022, tuber rot of potato (cv. Chuanyu-50) was observed in three adjacent indoor storage areas (about 1000 m2 per area) in Sichuan, China (103°10' E, 30°54' N), with an average incidence rate of 12%. Symptoms included tuber shrinkage, rot, and brown flesh. White hyphae were visible on the surface of the severely decayed tubers. Fifteen diseased tubers were collected from three areas (five per area). They were rinsed with sterile water and cut into pieces (3-5 mm thick, two pieces per tuber) at the boundary of the symptomatic area. The pieces were surface sterilized in 75% ethanol for 1 min, rinsed five times with sterile water, placed on potato dextrose agar (PDA), and incubated at 27°C in the dark. After 7 days, 24 of 30 isolates generated white to pale pink aerial hyphae on PDA. Macroconidia on carnation leaf agar were falcate, hyaline, one to five septate, and averaged 22 to 50 μm in length. Microconidia were hyaline, 0-1-septate, ellipsoidal to falcate, and smooth- and thin-walled. Chlamydospores were globose to subglobose, and 4-6 µm in diameter. These characteristics align with the description of Fusarium (Leslie and Summerell 2006; Lombard et al. 2019). Sequences of the translation elongation factor 1 alpha (TEF1-α) (O'Donnell et al. 1998), internal transcribed spacer (ITS) (Badotti et al. 2017), and RNA polymerase II second largest subunit (RPB2, primers 5F2/7CR) (Liu et al. 1999 ) from three representative isolates DR-1, DR-5 and DR-6 were amplified, sequenced and deposited in GenBank (TEF1-α: PP795695, PP795696, and PP795697; ITS: PP794584, PP794585, and PP794586; RPB2: PP998061, PP998062, and PP998063). Polyphasic identification of the TEF1-α, ITS, and RPB2 sequences from the DR-1 showed 99.84%, 100%, and 99.54% similarity with sequences of F. nirenbergiae strain CBS 130301 (NRRL 26374) (GenBank nos. MH485017, MH865885, and MH484926) in the FUSARIOID-ID database, respectively. Phylogenetic analysis of the concatenated TEF1-α and RPB2 sequences using the maximum likelihood method assigned these isolates to the F. nirenbergiae clade. Pathogenicity tests were conducted on potato tubers (cv. Chuanyu-50). The epidermis of each tuber was slightly wounded using a sterile blade. Conidial suspension (1×106 conidia/ml; approximately 10 μl per tuber) of the isolate DR-1 was point-inoculated into the wounded tubers. Twenty tubers were inoculated with the DR-1 conidial suspension, while five noninoculated potato tubers injected with sterilized water as controls. Meanwhile, another isolate DR-5 was also point-inoculated into tubers in the same manner. After inoculation, the potato tubers were kept in a moist chamber at 25°C. All inoculated tubers rotted and turned brown with white hyphae after 15 days, and the necrotic area ranged from 40% to 60% in the inoculated tubers. However, the controls remained healthy. The pathogen was reisolated from the inoculated tissues but not from the control tubers. All pathogens reisolated from 10 inoculated tubers were F. nirenbergiae, and the identity was confirmed as described above. The experiments were repeated three times with similar results. To our knowledge, this is the first report of F. nirenbergiae causing rot of potato in China. These results will contribute to developing control strategies for F. nirenbergiae-induced potato disease.

Effect of Temperature, Relative Humidity, and Incubation Time on the Mycotoxin Production by Fusarium spp. Responsible for Dry Rot in Potato Tubers.

Potato is the fourth most consumed crop in the world. More than half of the crop is stored for three to nine months at cold temperatures (3-10 °C) for the fresh and seed market. One of the main causes of fresh potato waste in the retail supply chain is the processing of fungal and bacterial rots during storage. Dry rot is a fungal disease that mainly affects the potato crop during storage and is responsible for 1% of tuber losses in the UK. It is produced by Fusarium spp., such as Fusarium sambucinum and F. oxysporum, which can lead to the accumulation of mycotoxins in the potato tuber. Little is known about the impact of environmental factors on the accumulation of mycotoxins in potato tubers. Understanding the ecophysiology of these fungi is key to mitigating their occurrence under commercial storage conditions. Therefore, this work aimed to elucidate the effect of three different temperatures (5, 10, and 15 °C) and two different water activities (aw; 0.97, 0.99) on the ecophysiology and mycotoxin accumulation of F. sambucinum and F. oxysporum in a potato-based semi-synthetic medium. The mycotoxin accumulation was then studied in vivo, in potato tubers cultivated under organic farming conditions, stored for 40 days at 8.5 °C. Results showed that higher temperatures and aw enhanced fungal growth, lag time, and mycotoxin accumulation in vitro. Growth rate was 2 and 3.6 times higher when the temperature increased from 5 to 10 and 15 °C, respectively. Six different mycotoxins (T-2, HT-2, diacetoxyscirpenol, 15-acetoxyscirpenol, neosolaniol, and beauvericin) were detected in vitro and in vivo. T-2 was the most abundant mycotoxin detected in vitro, observing 106 ng of T-2/g media after 21 days of incubation at 10 °C and 0.99 aw. Due to the long period of time that potato tubers spend in storage, the fluctuations of environmental factors, such as temperature and relative humidity, could promote the development of fungal rot, as well as mycotoxin accumulation. This could result in important food and economic losses for the potato market and a threat to food safety.

Laboratory Efficacy of Essential Oils Against Pectobacterium carotovorum Subsp. carotovorum and Pectobacterium atrosepticum Causing Soft Rot of Potato Tubers

AbstractThe antibacterial activity of essential oils (EOs) from Carum carvi, Cinnamomum zeylanicum, Cuminum cyminum, Eugenia caryophyllus, Foeniculum vulgare, Melaleuca alternifolia, Mentha × piperita, Origanum vulgare, Rosmarinus officinalis and Thymus vulgaris was tested against Pectobacterium carotovorum subsp. carotovorum (Pcc) and Pectobacterium atrosepticum (Pa), which cause soft rot of potato tubers. In disc diffusion, minimum inhibitory concentration and minimum bactericidal concentration (MBC) tests, cinnamon EO was found to be most effective against both bacteria. The inhibition zones ranged from 20.46 to 29.58 mm for a concentration of 100 μL/mL. The minimum inhibitory concentration was 0.5 μL/mL, and MBC was between 0.5 and 5 μL/mL. The higher sensitivity of bacteria was manifested in clove (Pcc and Pa), mint (Pcc), oregano (Pa) and thyme (Pa) EOs. Rosemary EO was the least effective. The results of the in vivo test were not entirely consistent with those of the in vitro tests. The most significant antibacterial effect was achieved with mint EO. The treatment of potato tuber discs with mint EO at a concentration of 3 μL/mL for Pcc and 3–10 μL/mL for Pa was 100% effective. The efficacy of the essential oils of caraway (5–10 μL/mL), thyme (10 μL/mL) and oregano (5 μL/mL) also ranged from 95.7 to 99.7%. Based on the results of the in vivo test, it may be recommended that mint EO and potentially caraway, oregano and thyme EOs be further tested for pickling potato tubers against bacteria of the genus Pectobacterium.

Isolation and Characterization of Pathogenic Mold Causing Potato Tuber Rot Disease

The potato plant (Solanum tuberosum L.) is a perennial crop that contains high amounts of carbohydrates, minerals, and vitamins in its tubers, making it a carbohydrate-rich alternative food to rice or corn. One of the diseases that often appear on potato plants is potato rot caused by pathogenic molds. This study aims to isolate and characterize pathogenic fungi that cause blight on potato tubers based on Koch's Postulates. Potato pathogenic molds were isolated from potato tubers that had been rotted, then the molds were grown on PDA and purified twice. The purified isolates were then inoculated onto 30 healthy potato tubers and incubated for 7 days. Healthy potato tubers experienced the same symptoms as potato tuber rot. The isolated pathogenic fungi were then characterized so that the pathogenic fungi of Phytophthora infestans were obtained. In this study, Koch's Postulate method was successfully applied to isolate and characterize the pathogenic fungi that cause potato tuber rot. The pathogenic fungi caused a potato tuber rot disease incidence value of 100% with a disease severity value of 60.7%. The two factors that determine the disease incidence and disease severity values are internal factors (genes and traits of the pathogen) and external factors (environment).

Identification and Pathogenicity of Fusarium Fungi Associated with Dry Rot of Potato Tubers.

Dry rot of potato tubers is a harmful disease caused by species of the Fusarium genus. Studies on the composition and features of Fusarium spp. that cause the disease in Russia are limited. Thirty-one Fusarium strains belonging to the F. sambucinum species complex (FSAMSC) and F. solani species complex (FSSC) were accurately identified using multilocus phylogenetic analysis of the tef and rpb2 loci, and their physiological characteristics were studied in detail. As a result, 21 strains of F. sambucinum s. str. and 1 strain of F. venenatum within the FSAMSC were identified. Among the analyzed strains within the FSSC, one strain of F. mori, four strains of F. noneumartii, and two strains of both F. stercicola and F. vanettenii species were identified. This is the first record of F. mori on potato as a novel host plant, and the first detection of F. noneumartii and F. stercicola species in Russia. The clear optimal temperature for the growth of the strains belonging to FSAMSC was noted to be 25 °C, with a growth rate of 11.6-15.0 mm/day, whereas, for the strains belonging to FSSC, the optimal temperature range was between 25 and 30 °C, with a growth rate of 5.5-14.1 mm/day. The distinctive ability of F. sambucinum strains to grow at 5 °C has been demonstrated. All analyzed Fusarium strains were pathogenic to potato cv. Gala and caused extensive damage of the tuber tissue at an incubation temperature of 23 °C for one month. Among the fungi belonging to the FSAMSC, the F. sambucinum strains were more aggressive and caused 23.9 ± 2.2 mm of necrosis in the tubers on average compared to the F. venenatum strain-17.7 ± 1.2 mm. Among the fungi belonging to the FSSC, the F. noneumartii strains were the most aggressive and caused 32.2 ± 0.8 mm of necrosis on average. The aggressiveness of the F. mori, F. stercicola, and especially the F. vanettenii strains was significantly lower: the average sizes of damage were 17.5 ± 0.5 mm, 17.2 ± 0.2 mm, and 12.5 ± 1.7 mm, respectively. At an incubation temperature of 5 °C, only the F. sambucinum strains caused tuber necroses in the range of 6.7 ± 0.5-15.9 ± 0.8 mm.

Impact of green synthesized zinc oxide nanoparticles for treating dry rot in potato tubers

Potato (Solanum tuberosum) crops have experienced a 22% reduction due to attacks from microbial pathogens and pests. Dry rot disease occurred from risks in El-Minya governorate, Egypt, where potato is the major cultivated crop. Potato cultivar ‘Cara’ samples were collected from the markets of six regions in El-Minya for isolation. They were also tested for the application of biosynthesized zinc oxide nanoparticles (ZnONPs) for disease management. The ability of Exserohilum rostratum to synthesize ZnONPs was documented via UV-visible, X-ray diffraction, Fourier transform infrared spectrum, and transmission and scanning electron microscopy. Spherical shape and crystallite small size (51.0 ± 3.0 nm) were attributed to the created ZnONPs. The ZnONPs were applied in the bio-control of the causative agent (Fusarium nygamai) of dry rot disease and large economic loss of potato cv. ‘Cara’ productivity. The mycosynthesized ZnONPs by E. rostratum at 100 μg/ mL (3 mM) showed antifungal activity against F. nygamai with higher reducing value of mycelium growth diameter 2.0 ± 0.14 cm compared to Revanol 50%, traditional product with a diameter of 3.85 ± 0.10 cm. Overall, ZnONPs are an excellent agent that can be applied to repress the most common fungal disease of potato.

Antifungal Activity of Some Inorganic Salts on the Development of Fusarium spp., Causal Agents of Potato Tuber Dry Rot

Potato dry rot caused by Fusarium spp. is one of the main fungal diseases hampering the production and marketing of potato tubers in Cameroon. This study was carried out in order to improve the health status of potato tubers and their preservation. To achieve this objective, Fusarium spp. were isolated on the Potato Dextrose Agar (PDA) culture medium and identified on the basis of morphological and microscopic characteristics using reference documents. Antifungal activity of six inorganic salts was evaluated in vitro on the development of Fusarium spp. and on potato tubers artificially infected with these fungal species. The results showed that all the inorganic salts had a depressant effect on the development of Fusarium spp. Copper sulfate inhibited at 100%, the radial growth and sporulation of Fusarium spp. at all concentrations. Sodium metabisulfite and sodium carbonate inhibited at 100%, the growth and sporulation of all fungal species from a concentration of 6.4 mg/ml. No lesions were observed on inoculated potato tubers when they were treated with copper sulfate. These results suggest the implementation of a strategy to control dry rot of potato tubers through the use of inorganic salts, in order to reduce the losses caused by Fusarium spp.

Fusarium sambucinum: causing dry tuber rot of potatoes

Among the 140 isolates collected from symptomatic potato tubers in four different European regions of Russia in 2021–2022, as many as 37.8 % isolates were identified as Fusarium sambucinum. Randomly selected isolates (n=19) of F. sambucinum were identified with DNA sequence data of the TEF locus and morphological characteristics on nutrient media. The growth rate of strains on potato-sucrose agar was assessed in the temperature range of 5–35 °C. The temperature optimum for growth of all strains was set at 25 °C, the average growth rate of strains was 13.68 ± 0.67 mm/day. The upper critical temperature completely arresting growth of strains was 35 °C, while at the temperature of 5 °C the strains were still able to grow at an average rate of 0.85 ± 0.27 mm/day. Fusarium sambucinum strains were characterized by their ability to produce symptoms of rot in potato tubers after inoculation and further incubation at 5 and 23 °C. Most strains caused extensive necrosis at the higher temperature, but there were strains whose aggressiveness was not affected by temperature. There is no clearly defined relationship between the origin of F. sambucinum strains and their aggressiveness.

First Report of Pectobacterium parvum Causing Diseases on Potato in Inner Mongolia, China.

Soft rot enterobacterial plant pathogens Pectobacterium spp. and Dickeya spp. have caused devastating blackleg, aerial stem rot, and soft rot of potato tubers (Charkowski 2018). In August 2021, potato plants (cv. Xisen6# or Maiken1) with blackleg or aerial stem rot symptoms were observed in two commercial fields in Xinghe County, Ulanqab City, Inner Mongolia Autonomous Region, China. The plants were wilted, and the crown stem showed gradual degradation and browning. The disease incidence was around 3 to 7% and 20 to 25% in Xinghe Zhangyou Village (33 ha) and Bianjia Village (7 ha), respectively. Pathogens were isolated on crystal violet pectate agar (CVP) plates (Ge et al. 2018). Briefly, symptomatic stem tissues were surface sterilized in 75% ethanol, ground, then serial dilutions were cultured on CVP plates (Handique et al. 2022). The plates were incubated at 28oC for 2 days. Pure colonies of Pectobacterium spp. were obtained from the pits of CVP plates and sequenced for identification using the universal 16S rRNA gene primers 27F/1492R (Monciardini et al. 2002). Results of the comparison of 16S sequences against NCBI GenBank showed 100% sequence identity to P. parvum FN20211T (CP087392.1) type strain for the three colonies designated as ZRIMU1006 (1542/1542 bp), ZRIMU1019 (1542/1542 bp), and ZRIMU1020 (1542/1542 bp). Sequences were deposited under accession numbers OP941529, OP941525, OP941526, respectively. Additionally, six housekeeping gene sequences were used to confirm identification at the species level and were uploaded to GenBank: fusA (OP793177, OP793171, OP793172), gapA (OP793221, OP793216, OP793217), gyrB (OP793265, OP793259, OP793260), infB (OP793310, OP793304, OP793305), pgi (OP793355, OP793349, OP793350), and rplB (OP793400, OP793394, OP793395). Phylogenetic trees constructed using the MEGA X program of concatenated sequences of the housekeeping genes sequences show that the three isolates grouped with P. parvam FN20211T, confirming that they are P. parvam. Pathogenicity tests for stem rot were done by injecting a bacterial suspension into potato seedlings (cv. Favorita) grown from seed tubers. The tubers were planted in perlite potting mix and 3 weeks after emergence, a 100 μl bacterial suspension (105 CFU/ml) or sterile phosphate-buffered solution was injected at the stem base. The bacterial injection experiment was performed twice in a greenhouse with five plants inoculated per bacterial strain. Plants were covered with plastic bags to maintain 100% humidity at 25°C for 2 days. Seven days after inoculation, the inoculated area of the seedlings had rotted or turned black, while the controls remained symptomless. Symptomatic tissues from each strain were processed as above and placed on CVP plates to reisolate the Pectobacterium spp. 16S rRNA sequence analysis confirmed the bacteria to be similar in sequence to the inoculated strains, thus completing Koch's postulates. Soft rot development was performed by adding bacterial suspension (100 μl, 105 CFU/ml) on tuber slices. The infected tubers rotted, while the controls were symptomless. The vacuum infiltration method on tuber that is used to test pathogens for blackleg did not result in the development of blackleg symptoms. Briefly, five tubers were inoculated with the pathogen by vacuum infiltration and planted in potting mix. The plants showed wilting after emergence, but no blackleg symptoms were observed. Recently, multiple new Pectobacterium species including P. parmentieri, P. polaris, and P. punjabense, were identified to cause potato disease in different provinces of China (Cao et al. 2021; Handique et al. 2022). In China, P. parvum was first isolated from Brassica, and in the year 2022, it was reported to cause aerial stem-rot on potato in Hebei province in China (Wang et al. 2022). Inner Mongolia is a major potato-seed-producing province and the incidence of new strains of Pectobacterium in the province causing aerial stem rot and soft rot of tuber might cause a reduction in seed production. This report will draw attention to the management of P. parvum by the seed-producing companies in Inner Mongolia which distributes the seed throughout China.

Effect of postharvest management on the microbial quality of potato (Solanum tuberosum L.) tubers

Abstract This experiment was conducted to appraise the role of the curing phytohormone treatment and storage method in the postharvest microbial decay of ware potatoes during storage. The study was designed as a Split-Split-Plot Design (SSPD) in which the curing period was placed in the main plot, and the storage method and the phytohormone were put in subplot and sub-sub-plot respectively. Each treatment was replicated three times to form a 4 × 3 × 3 factorial experiment. Each treatment consisted of 20 potato tubers out of which decayed samples were counted for the calculation of percentage rot loss and identification of the causal agent, which was done fortnightly until the end of the storage period of 12 weeks. Temperature, relative humidity, and wind velocity were monitored weekly. All data collected were subjected to analysis of variance (ANOVA) using the GenStat Discovery Edition statistical software package. Means that exhibited significant difference were separated using Duncan’s Multiple Range Test (DMTR) at p = 0.05 level of significance. The results of the analysis showed that the phytohormone levels had highly significant influence (p ≤ 0.01) on percentage rot loss. Although there was a significant interaction between the curing periods and phytohormone concentration, storage conditions (p ≤ 0.05) were observed throughout the storage period of 2–8 weeks. Fusarium solani, Rhizopus oryzae, and Aspergillus niger were implicated in the rotting of potato tubers.

First identification of potato tuber rot caused by Penicillium solitum, its silver nanoparticles synthesis, characterization and use against harmful pathogens.

Potato is one of the highly consumed vegetable crop grown in different regions across Pakistan that is affected by fungal diseases. The current research was conducted to identify fungal pathogen causing mold-like disease of potato in Khyber Pakhtunkhwa (KP), Pakistan. For molecular identification and characterization of the fungal disease; potato tuber samples were collected followed by culturing on potato dextrose agar (PDA). Based on morphological features, the pathogen was identified as a Penicillium species. This result was obtained in 45 different isolates from potato tubers. Molecular identification was done using β-tubulin primers and ITS5 sequencing of 13 different isolates that releveled 98% homology with BLAST (GenBank accession no. KX958076) as Penicillium solitum (GenBank accession nos. ON307317; ON307475 and ON310801). Phylogenetic tree was constructed that showed Penicillium solitum prevalence along with Penicillium polonicum and Penicillium citrinum on potato tubers. Based on this, Penicillium solitum based silver nanoparticles (Ag NPs) were synthesized and characterized using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and field emission scanning electron microscopy (FE SEM). UV-analysis showed a characteristic peak at 410 nm confirming synthesis of Penicillium solitum based Ag NPs. This was further confirmed by XRD followed by EDX and SEM that showed face cubic crystal structure with Ag as major constituent of 18 nm formed spherical Ag NPs. FTIR showed band stretching of O-H, N-O and C-H of biological origin. Similarly, Penicillium solitum based Ag NPs presented strong anti-bacterial and anti-fungal activity at 0.5 level of significance LSD. According to our knowledge, this is the first report of Penicillium solitum identification in Pakistan, its Ag NPs synthesis and characterization to be used against pathogens of agricultural significance.

In Vitro Evaluation on Resistance of Phytopythium vexans (NG Isolate) Cultured from Sublethal Concentration against Several Fungicides

Phytopythium vexans isolated from potatoes rhizospher in Ngablak, Magelang, Central Java was reported having a potency to cause potato tuber rot in in vitro test. Some fungicides had been intensively applied in this area to control potato late blight even using sublethal dose. This study investigated resistance response of the pathogen against several fungicides which were Mancozeb, Dimethomorph, mixture of Mancozeb and Mefenoxam, and mixture of Oxathiapiprolin and Famoxadone. The experiment was conducted to observe the sensitivity response of pathogen against those fungicide and the experiment repeated with one of the isolates which growth in sublethal concentration to observe the resistance response. Both experiment data was analyzed by Probit Analysis. On sentivity test, data showed that P. vexans were insensitive against Dimethomorph, but it was sensitive against Mancozeb, mixture of Mancozeb and Mefenoxam, as well as mixture of Oxathiapiprolin and Famoxadone. On Mancozeb treatment, mycelia were inhibited 100% at the sugested concentration. However, at the sublethal concentration the mycelial collony grew abnormally. Pathogen isolate from the sublethal concentration were used as material for the resistance response study. The effect of the sublethal application of Mancozeb to P. vexans caused resistance to Mancozeb itself and cross resistance against Dimetomorph and mixture of Oxathiapiprolin and Famoxadone. It was proven by higher value of predicted EC50 and EC95 on the second experiment compared to the predicted EC50 and EC95 from the first one. The resistant P. vexans isolate was able to produce sporangium and chlamydospore.

Bacteriophages as a Strategy to Protect Potato Tubers against Dickeya dianthicola and Pectobacterium carotovorum Soft Rot.

The protective effect of bacteriophage suspensions (Ds3CZ + Ds20CZ and PcCB7V + PcCB251) on phytopathogenic bacteria causing soft rot of potato tubers, namely Dickeya dianthicola (D50, D200) and Pectobacterium carotovorum (P87, P224), was observed in ex vivo and in vitro experiments. Ex vivo tests were performed (with air access) on potato slices, on cylindrical cuts from the center of the tubers, and directly in whole potato tubers. In vitro experiments were carried out in a liquid medium using RTS-8 bioreactors, where bacterial growth was monitored as optical density. In particular, the inhibitory effects of phages were confirmed in experiments on potato slices, where suppression of rot development was evident at first glance. Phage treatment against selected bacteria positively affected potato hardness. Hardness of samples treated with bacteria only was statistically significantly reduced (p < 0.05 for D50 and p < 0.001 for D200 and P87). Ex vivo experiments confirmed significant inhibition of P87 symptom development, partial inhibition of D200 and D50 in phage-treated tubers, and no effect was observed for P224. The inhibitory effect of phages against bacteria was not observed in the in vitro experiment.

Trichocladium solani sp. nov.-A New Pathogen on Potato Tubers Causing Yellow Rot.

A new species, Trichocladium solani, was isolated from potato (Solanum tuberosum L.) tubers from Russia. The species has no observed teleomorph and is characterized morphologically by non-specific Acremonium-like conidia on single phialides and chains of swollen chlamydospores. Phylogenetic analysis placed the new species in a monophyletic clade inside the Trichocladium lineage with a high level of support from a multi-locus analysis of three gene regions: ITS, tub2, and rpb2. ITS is found to be insufficient for species delimitation and is not recommended for identification purposes in screening studies. T. solani is pathogenic to potato tubers and causes lesions that look similar to symptoms of Fusarium dry rot infection but with yellowish or greenish tint in the necrotized area. The disease has been named "yellow rot of potato tubers".

Control of dry rot and resistance induction in potato tubers against Fusarium sambucinum using red onion peel extract

The efficacy of red onion peel methanol extract to prevent dry rot in potato tubers caused by Fusarium sambucinum was investigated. At 20 mg mL−1, the methanol extract caused a great decrease in the fungal growth and spore germination by 86.3 %, and 91.2 %, respectively. Also, the dry rot control efficacy in potato slices inoculated with F. sambucinum reached 91.8 % at the same concentration. The treatment with methanol extract significantly increased the total phenolics to 0.31 g kg−1 compared with the control (0.19 g kg−1) in potato slices on the fourth day of the storage period as well as the increase in the level of total flavonoids. The relative leakage rate was 46.3 % in treated potato tuber slices compared to the control by 76.5 % and MDA content was much lower in slices treated compared with control slices during four days of storage. The methanol extract enhanced the activity of phenylalanine ammonia-lyase (PAL), polyphenoloxidase (PPO), catalase (CAT), and peroxidase (POD) in potato slices throughout the experiment. The major compounds in the methanol extract were the flavonoids rutin, quercetin triglucoside, ferulic acid, quercetin diglucoside, quercetin monoglucoside, isorhamnetin glucoside, quercetin, kaempferol, and isorhamnetin using HPLC-UV/DAD, QTOF, and NMR spectra (1H NMR, APT, HSQC, COSY, HMBC, and NOESY).

Fungi associated with sweet potato tuber rot at CSIR - PGRRI, Bunso, Eastern Region, Ghana

Rotten sweet potato root tuber samples were collected from a barn and experimental field of the CSIR - Plant Genetic Resources Research Institute (PGRRI), Bunso. Isolation and identification of the fungi associated with the samples were carried out at the Plant Pathology Laboratory of the same institute. In all, six fungal species belonging to four genera, namely Fusarium solani, Sclerotium rolfsii, Lasiodiplodia theobromae, Aspergillus ochraceus, Aspergillus flavus and Aspergillus niger were isolated from the samples from both the barn and the experimental field of CSIR - PGRRI. Fusarium solani and Aspergillus niger were frequently isolated from the sweet potato tuber samples from both the field and the barn. Pathogenicity tests carried out using the six fungal isolates on fresh and healthy sweet potato tubers showed that all the six fungi isolated were pathogenic in causing rot of sweet potato tubers with Lasiodiplodia theobromae being the most virulent.

Utilization of the antagonistic yeast, Wickerhamomyces anomalus, combined with UV-C to manage postharvest rot of potato tubers caused by Alternaria tenuissima

Postharvest rot of potato tubers caused by fungal pathogens is the main cause of significant economic losses, while also raising potential food safety issues. Integrated disease management, utilizing bio-safe and eco-friendly methods, represents a sustainable strategy for reducing postharvest losses in crops, including potato. In the current study, the application of the antagonistic yeast, Wickerhamomyces anomalus, combined with a UV-C treatment was evaluated for the management of postharvest Alternaria rot of potato tubers, caused by Alternaria tenuissima. Both W. anomalus and UV-C as individual treatments reduced the size of A. tenuissima infections on potato tubers, relative to the control, while the combined treatment of W. anomalus and UV-C exhibited the highest level of inhibition. W. anomalus or UV-C alone, and especially when used in combination, induced the expression of defense-related genes, including polyphenol oxidase, peroxidase, and β-1,3-glucanase, and also increased the level of flavonoids and lignin in potato tubers. Our findings indicate that the mechanism of action by which UV-C enhances the biocontrol effect of W. anomalus against postharvest Alternaria rot includes the activation of defense-related response in potato tubers. The integration of biocontrol agents and physical treatments (e.g., UV-C) represents an effective, eco-friendly hurdle technology for managing postharvest rot in potato.

Bactericidal activity of some plant essential oils against Ralstonia solanacearum infection

Potato plants and their tubers in Egypt are affected by one of the most renowned soil-borne pathogen, Ralstonia solanacearum, that caused brown rot in potato tubers and wilt in plants. There is no efficient therapeutic bactericide so; control of bacterial wilt is very rough.The study investigated three different concentrations of seven essential plant oils under in vitro and in vivo conditions as a result of their effects on Ralstonia solanacearum growth and their possibility use as potato seed pieces dressing for controlling bacterial wilt disease incidence. In vitro, anise oil at the three tested different concentrations (0.04, 0.07, and 0.14% vol/vol) was the most effective one inhibiting the growth of T4 and W9 isolates of Ralstonia solanacearum then pursued by thyme, lemongrass, and clove oils. On the other hand, rocket oil at the tested concentration was the least effective one followed by fennel oil. However, wheat germ oil was not completely effective. In vivo, experiment revealed that anise oil at the three concentrations significantly reduced disease incidence and severity in sponta and hermes potato cultivars and their effect was associated with increase of peroxidase, polyphenoloxidase, phenols and the foliar fresh weight of treated plants as well as the weight of tubers/plant followed by thyme and lemongrass oils compared to the infected untreated control.Morphological differences in bacterial cell structure have been observed using a transmission electron microscope (TEM). Anise oil at higher concentration caused of cell wall rupture and degraded cellular components.

Field asymmetric ion mobility spectrometry for pre-symptomatic rot detection in stored Ranger Russet and Russet Burbank potatoes

This study was aimed at early detection and rot progression monitoring in stored potatoes using a portable field asymmetric ion mobility spectrometry (FAIMS) system. Tuber samples of Ranger Russet (RR) and Russet Burbank (RB) cultivars were inoculated with Pectobacterium carotovorumsubsp.carotovorum (causes soft rot) and sterile water (control). The samples were stored in jars either at room temperature (25 °C with 30 % relative humidity [RH]) or reduced temperature (4 °C with 95 % RH). Volatile headspace from samples was scanned with FAIMS at regular intervals up to 14 days for room temperature and 31 days for reduced temperature storages. Infection symptoms were detected for higher ion current pertinent to headspace of inoculated samples compared to the controls of both the cultivars. Such discrimination was evident at FAIMS compensation voltage (CV)-dispersion field (DF) ranges of −1.70–1.31 V and 38–90 % for room temperature and −1.58–1.31 V and 36–92 % for reduced temperature storages. The rot was detected as early as one day after inoculation (DAI) under room temperature and five DAI under reduced temperature storages. The ion currents were affected by the storage temperature and humidity, and associated interaction with the DAI and cultivar (F7,712 = 21.6–31.4, p < 0.001). The FAIMS responses of control and inoculated tubers were also classified by the Naïve Bayes and Random Forest algorithms at accuracies in the ranges of 70–90 % and 75–100 %, respectively. Overall, a portable and tunable FAIMS system was found suitable for high throughput early detection of soft rot in potato tubers. Future studies need to revalidate the FAIMS system in commercial storage facilities for timely rot detection and initiation of potential remedial measures.

Impact of Fusarium dry rot on physicochemical attributes of potato tubers during postharvest storage

Fusarium is a major spoilage fungus of potato tubers during post-harvest storage. The dry rot disease caused by Fusarium species severely affects the harvested potatoes and impose a critical loss to processing industries and consumers. In our experiment, we investigated the occurrence of Fusarium sambucinum (FS) and Fusarium oxysporum (FO) as major storage fungus causing Fusarium dry rot in potato tubers. Further, we performed morpho-molecular identification of both the fungi and confirmed their pathogenicity on potato tuber during storage. We evaluated the susceptibility parameters and quality attributes during infection in two popular cultivars namely ‘Kufri Pukhraj’ (table purpose) and ‘Kufri Chipsona 3’ (processing purpose). Out of two cultivars, ‘Kufri Pukhraj’ was shown to have greater susceptibility as compared to ‘Kufri Chipsona 3’ in terms of lesion diameter, fungus penetration and rot volume during periodic observation of 20, 40 and 60 d of storage. FS was highly aggressive as compared to FO. However, a mixed inoculum of Fusarium species caused higher damage irrespective of cultivars. The physicochemical analysis revealed that fungus infection (individual or mixed inoculum) leads to a reduction in starch and amylose content in both the cultivars after 60 d of storage. Moreover, amylopectin, reducing sugars, sucrose and total soluble sugar content were increased in response to fungal infection in both cultivars. Pearson correlation analysis indicated that lesion diameter and rot volume was negatively correlated (R < -0.80) with starch and amylose content. However, amylopectin, reducing sugar, sucrose and total soluble sugar was positively correlated with susceptibility parameters. This study highlights the impact of storage fungus infection on the nutritional quality parameters of potato tubers which is a critical concern for consumers and processing industries.