Tuber Surface Research Articles

Morphological and molecular characterization of cubios (Tropaeolum tuberosum Ruiz & Pavón) collected in two municipalities in Boyaca - Colombia

In this study, we aimed to determine the extent of genetic variation among cubios (Tropaeolum tuberosum) in a diversity micro-center in the department of Boyacá, Colombia, with morphological and ISSR (Inter Simple Sequence Repeats) molecular markers. Twenty-five cubio morphotypes were collected across different farms within the municipalities of Belén and Ventaquemada in Boyacá and were sown for subsequent morphological and molecular characterizations. Tuber features were evaluated according to descriptors of the International Potato Center, namely predominant tuber surface color, secondary tuber surface color, secondary tuber surface color distribution, predominant tuber pulp color, secondary tuber pulp color, distribution of secondary tuber pulp color, tuber shape, and depth of tuber eyes. Molecular variation was assessed via eight ISSR primers. Morphological and molecular characterizations allowed us to identify 25 cubio morphotypes with significant genetic variation in the study area. This finding is likely attributed to mechanisms maintaining genetic variability, such as naturally occurring crosses between morphotypes modulated by environmental conditions and local agricultural practices, including seed exchange and a preference for given morphotypes.

A machine learning system to identify progress level of dry rot disease in potato tuber based on digital thermal image processing

This study proposed a quick and reliable thermography-based method for detection of healthy potato tubers from those with dry rot disease and also determination of the level of disease development. The dry rot development inside potato tubers was classified based on the Wiersema Criteria, grade 0 to 3. The tubers were heated at 60 and 90 °C, and then thermal images were taken 10, 25, 40, and 70 s after heating. The surface temperature of the tubers was measured to select the best treatment for thermography, and the treatment with the highest thermal difference in each class was selected. The results of variance analysis of tuber surface temperature showed that tuber surface temperature was significantly different due to the severity of disease development inside the tuber. Total of 25 thermal images were prepared for each class, and then Otsu’s threshold method was employed to remove the background. Their histograms were extracted from the red, green, and blue surfaces, and, finally, six features were extracted from each histogram. Moreover, the co-occurrence matrix was extracted at four angles from the gray level images and five features were extracted from each co-occurrence matrix. Totally, each thermograph was described by 38 features. These features were used to implement the artificial neural networks and the support vector machine in order to classify and diagnose the severity of the disease. The results showed that the sensitivity of the models in the diagnosis of healthy tubers was 96 and 100%, respectively. The overall accuracy of the models in detecting the severity of tuber tissue destruction was 93 and 97%, respectively. The proposed methodology as an accurate, nondestructive, fast, and applicable system reduces the potato loss by rapid detection of the disease of the tubers.

Polyploid QTL-seq revealed multiple QTLs controlling steamed tuber texture and starch gelatinization temperature in sweetpotato.

Sweetpotato (Ipomoea batatas) includes diverse cultivars with flesh textures ranging from dry to moist. Moist-fleshed cultivars often contain starch with a lower gelatinization temperature (GT). To elucidate the genetic determinants of flesh texture and starch GT, we conducted a QTL analysis using F1 progenies obtained from a cross between dry-fleshed and moist-fleshed cultivars, 'Benikomachi' (BK) and 'Amahazuki' (AH), by using an updated polyploid QTL-seq pipeline. Flesh texture was assessed based on the wet area ratio (WAR) observed on the cut surface of steamed tubers, as progenies with dry and moist flesh exhibited low and high WAR values, respectively, demonstrating a strong correlation. Three QTLs were found to regulate the WAR. Notably, two AH-derived alleles at 4.30 Mb on Itr_chr05 and 21.01 Mb on Itr_chr07, along with a BK-derived allele at 2.89 Mb on Itr_chr15, were associated with increased WAR. Starch GT, which displayed no correlation with either flesh texture or WAR, was distinctly influenced by two QTLs: a GT-increasing BK-derived allele at 1.74 Mb on Itr_chr05 and a GT-decreasing AH-derived allele at 30.16 Mb on Itr_chr12. Consequently, we developed DNA markers linked to WAR, offering a promising avenue for the targeted breeding of sweetpotato with the desired flesh textures.

First Report of Penicillium cellarum Causing Rot Disease on Dioscorea polystachya in China.

Dioscorea polystachya (Chinese yam) is a kind of medicine and food homologous crop, the tubers as its main production organ, with high potassium, low fiber, high protein and rich nutrition characteristics. In 2022, at the Chinese herbal medicine planting experimental site in Anguo, Baoding City, Hebei Province, China, we found the symptoms of Chinese yam decay during the storage, with an incidence of 15%~25%. The diseased part of Chinese yam tuber rots expands from the outside to the inside and sags, with a brown or dark brown discoloration, and the surface covered with a thick grayish green mold. The diseased tissue was first rinsed with clean water to remove dirts from the surface. Thereafter, 3 to 4 mm Chinese yam pieces were picked from rotting edge with a sterilized forceps, sterilized with 75% alcohol for 30 s followed by 0.1% mercuric chloride solution for 1min, and then rinsed three times with sterile water. The sterilized pieces were cultured on potato dextrose agar (PDA). One isolated fungus was obtained, and conidia were observed after incubation for 5 days at 26°C. Pure cultures were isolated by single-spore isolation. Conidia were single spore, round or oval, colorless. Conidiophores produce several rounds of symmetric or asymmetric small stems after multiple branches, which were shaped like brooms. The length and width of 100 conidia were measured, and size ranged from 3 to 4×3 to 4 μm. On the basis of morphological characteristics, the isolate was identified as Penicillium spp. (Uy et al. 2022). To further assess the identity of isolated species, the genomic DNA of the fungal isolate (SYRF1) was extracted by CTAB protocol. The ribosomal DNA internal transcribed spacer (ITS) region and the ribosomal large subunit (LSU) were amplified and sequenced with primers ITS1/4, LR5/LROR respectively (White et al. 1990, Xu et al. 2010). The obtained ITS-rDNA region and LSU sequences (GenBank accession OQ707937 and OQ704185) of the isolate were more than 99% identity to the corresponding sequences of Penicillium cellarum in GenBank (KM249068 and MG714818). Phylogenetic results based on a maximum-likelihood analysis revealed that SYRF1 was grouped with P. cellarum. To determine the pathogenicity of the isolated fungi, tests were carried out by aseptic inoculation of fresh and healthy tubers. Before the experiment, the healthy tubers were washed, surface disinfected and dried. The tubers were then wounded with sterile inoculation needles, and the conidium-bearing hyphal discs (5 mm) were inoculated on the surface of the wounded tubers and covered with wet sterile cotton. Three tubers were inoculated repeatedly each time as the experimental group.Inoculate sterile PDA with three tubers as the control group. Each tuber was inoculated with four mycelium disks, and the pathogenicity test was repeated four times. The inoculated tubers were incubated at 26°C for 14 days with sterile PDA as control. After ten days, the inoculated points showed symptoms similar to those of the initial infection, whereas controls remained symptomless. The reisolated fungus matched SYRF1 based on morphological and sequence analyses, thereby fulfilling Koch's postulates. To the best of our knowledge, this is the first report of Penicillium cellarum as causative agent of postharvest rot of Chinese yam tubers in China. This finding will help inform the prevention and management of postharvest diseases of Chinese yam tubers.

УРОЖАЙНОСТЬ И КАЧЕСТВО КАРТОФЕЛЯ В ЗАВИСИМОСТИ ОТ ПЛОЩАДИ ПИТАНИЯ

The relationship between the yield per unit area and the size of the feeding area is expressed by a parabolic curve. This curve is also characteristic of the action of many other agrotechnical factors – fertilizer application rates, when their influence is studied against the constant background of other conditions that determine the yield. The article examines and identifies different areas of nutrition of potato varieties with a plant density of thousand/ha. It was revealed that the Luck variety had the highest productivity of potatoes with different feeding area schemes, at 70x35 cm the yield was 154 kg/ha, and at 70x25 cm – 194 kg/ha. The yield of the Romano variety was less – 149-183 kg/ha. With a feeding area of 70x35 cm, the marketability of the Romano variety was the highest – 90.4%, the starch content was 11.8%, and the Luck variety had a slightly lower marketability and amounted to 88.3%, the starch content was 12.4% higher than that of the Romano variety. The marketability of tubers is determined by the signs, with the smell and taste characteristic of this botanical variety, healthy, ungrown, whole, dry. The minimum size of tubers for round-oval potatoes is 30 cm, for an elongated shape – 25 mm. The content of tubers of smaller sizes is allowed no more than 5%, with growths, growths that have turned green on an area of more than 2 cm2, but not more than ¼ of the tuber surface - no more than 2%. The content of tubers affected by wet, dry, ring rot and late blight is not allowed. Variants of the experiment with different planting schemes, the marketability of potato tubers in the Romano variety was 86.3-89.5%, and in the Udacha variety it was less than 84.5-86.9%. The starch content was high in the Udacha variety 11.1-11.9%, and in the Romano variety it was slightly less and amounted to 10.8-11.4%.

Aqueous Ozone Efficacy for Inactivation of Foodborne Pathogens on Vegetables Used in Raw Meat-Based Diets for Companion Animals

The present study evaluates the efficacy of a batch wash ozone sanitation system (BWOSS) and spray wash ozone sanitation system (SWOSS) against Listeria monocytogenes (two strains) and Salmonella enterica subsp. enterica (three serovars) inoculated on the surface of carrots, sweet potatoes, and butternut squash, commonly used in raw meat-based diets (RMBDs) marketed for companion animals such as dogs and cats. Produce either remained at room temperature for 2 h or were frozen at −20°C and then tempered overnight at 4°C to mimic the preprocessing steps of a raw pet food processing operation (‘freeze-temper’) prior to ozone treatment. Two ozone concentrations (0 and 5 ppm) were applied for either 20 s or 60 s for BWOSS and 20 s for SWOSS. Based on an ANOVA, BWOSS data showed no significant difference (P > 0.05) in microbial reduction between 0 and 5 ppm ozone concentration across all treatment durations for each produce type. BWOSS resulted in mean microbial reductions of up to 1.56 log CFU/mL depending on the treatment time and produce type. SWOSS data were analyzed using a generalized linear model with Quasipoisson errors. Freeze-tempered produce treated with SWOSS had a higher bacterial log reduction at 5 ppm ozone compared to 0 ppm ozone (P = 0.0013) whereas room temperature produce treated with SWOSS did not show any significant difference in microbial reduction between ozone concentrations. The potential to mitigate microbial cross-contamination was also investigated during SWOSS treatment. The results indicate that 5 ppm ozone decreased pathogens in the rinsate and proximal surfaces by 0.63–1.66 log CFU/mL greater than no ozone depending on the pathogen and sample. Overall, data from this study indicate that SWOSS would be more effective compared to BWOSS in reducing the microbial load present on the surface of root tubers and squash subjected to freezing and thawing and has the potential to mitigate cross-contamination within RMDB manufacturing environments.

First Report of Mucor Rot Caused by Mucor circinelloides on Gastrodia elata in China.

Gastrodia elata Blume is used as a traditional Chinese herbal medicine and is widely planted throughout China (Zhu et al. 2019). From September to October 2022, G. elata tuberous rot occurred in 47 households in Yiliang County, Zhaotong City (27°39' N, 104°16' E), Yunnan Province, China, within a major G. elata production area covering 776 ha, with an incidence rate of 10 to 15%. Symptoms manifested as black and brown lesions on the tuber surface, which were concave, soft, foul-smelling, and surrounded by grayish-brown tissue . Three infected G. elata were randomly collected from each household, placed in transparent plastic bags, and pathogen isolation was conducted in a laboratory. Infected G. elata tubers were surface-sterilized with 0.5% NaOCl for 2 min, rinsed five times with sterile water, and dried. Symptomatic tissues from the margin between necrotic and healthy tissues were cut into 5 × 5 mm pieces, placed onto potato dextrose agar (PDA), and incubated at 28 ºC in the dark for 3 days. Hyphal tips of fungi growing from the samples were transferred onto new PDA plates and incubated until they produced conidia. Five fungal isolates (Charliezhao 417, 418, 419, 420, and 421) with the same morphological characteristics were obtained from the samples. Colonies tended to be yellow or light grey, and produced sporangiospores that were sub-globose, ellipsoid, or irregular, measuring 4.0 to 9.7 × 2.5 to 4.6 μm (n = 50). The morphological characteristics of the isolates resembled Mucor circinelloides (Wagner et al. 2020). Genomic DNA of two representative isolates (Charliezhao 417 and 418) was extracted using the DN14 cetyltrimethylammonium bromide rapid plant genome extraction kit (Aidlab Biotechnologies Co., Ltd, Beijing). The ITS and RPB1 genes were amplified by polymerase chain reaction using the primers ITS1/ITS4 (White et al. 1990) and Af/Cf (Matheny et al. 2002), respectively. All sequences were deposited in GenBank (accession no. OQ612709, OR028949 for ITS, OQ621439, OR033135 for RPB1). A BLASTN homology search with the ITS nucleotide sequences showed that they had 99.5 to 99.2% identity with M. circinelloides isolate KR056083 (603/606 bp) and isolate KJ588204 (617/622 bp), respectively; and the RPB1 sequences had 99.89% to 99.75% identity to isolates KJ588206 (874/875 bp) and isolate KJ588206 (803/805 bp), respectively. To complete Koch's postulates, five mature, healthy G. elata tubers were surface disinfected with 1% NaClO solution for 1 min, rinsed with sterile water, and dried at 25℃ for 30 min. A conidial suspension (106 spores/ml) collected from two isolates (Charliezhao 417 and 418) was sprayed onto G. elata tubers, and the control treated with distilled water. All G. elata tubers were incubated at 25 ºC with 80% relative humidity. The experiment had five replicates. After 7 days of incubation, there were obvious brown spots on inoculated tubers; no symptoms were observed on the controls. The pathogen was re-isolated from all inoculated G. elata tubers and confirmed as M. circinelloides by morphological and molecular analyses, completing Koch's postulates. This is the first report of M. circinelloides causing G. elata mucor rot in China. The tubers of G. elate are often employed in the treatment of headaches, convulsions and neurodegenerative disorders (Manavalan et al. 2012). Thus, the declining yield of G. elate due to persistent obstacles related to continuous cropping and diseases poses a potential threat to the development of the G. elate industry.

IDENTIFICATION OF MORPHOLOGY AND RELATIONSHIPS OF PORANG PLANTS (AMORPHOPHALLUS MUELLERI BLUME) IN KUMPEH ULU DISTRICT, MUARO JAMBI REGENCY

Porang (Amorphophallus muelleri Blume) is a group of tuber plants that are useful as food and medicine so that they have bright prospects for development. In Jambi Province, especially in Muaro Jambi Regency, porang plants are found growing wild among duku trees. This study aims to determine the morphological character of porang plants and to determine the level of diversity and kinship of porang plants found in Kumpeh Ulu District, Muaro Jambi Regency. The research was carried out from August to September 2021, in 18 villages located in the Kumpeh Ulu District. The research was conducted using a non-experimental descriptive method with proportionate stratified random sampling, and the sample was measured quantitatively and qualitatively. The morphological identification of porang plants from 18 villages in Kumpeh Ulu District showed similarities in bulbil shape, bulbil surface colour, bulbil surface texture, bulbil flesh colour, leaf shape and petiole colour. However, there were differences in leaf colour, tuber flesh colour, tuber surface texture and tuber shape.

Yield of seed potatoes and rhizoctonia infestation of tubers depending on the application of different treatment methods

Aim. Study the effect of Rise P® biological product, pesticide Celest Top, fungicide Quadrison on the growth, development, productivity and infestation of seed potato tubers with rhizoctonia. Methods. Field, measuring, weight, statistical. Results. Scientific studies have established the effectiveness of Rise P® biological product (Bacillus amyloliquefaciens (strain IT45)), pesticide Celest Top, fungicide Quadris for seed potatoes growing. The yield of seed potato of Skarbnytsia variety of superelite class in the variant with the treatment of planting material with Rise P® (450 g/t) increased by 3.3 t/ha or 8.9%. The combination of treatment of tubers with Rise P® and pesticide Celeste Top (0.7 l/t) contributed to an increase in potato yield relative to the control variant by 3.7 t/ha (9.9%), relative to the variant with the application of the pesticide of chemical origin – Celest Top, an increase in yield by 1.8 t/ha or 4.8% was observed. Application of Celest Top + Quadris (3.0 l/ha) provided an increase in yield to the control variant by 2.5 t/ha (6.7%). The treatment with tank mixtures of Celest Top + Rise P® + Quadris resulted in a yield increase of 4.0 t/ha (10.8%) compared to the control variant. Conclusions. The application of Rise P® biological product contributed to the growth of the overall yield and productivity of the basic seed potatoes of Skarbnytsia variety and reduction of tuber damage by rhizoctonia. Treatment of potato planting material with Rise P® biological product at the application rate of 450 g/t provided 4.3% of weakly affected tubers and 1.3% of tubers with a surface covering more than 10%, with infestation on the control variant without treatment of tubers with weak damage 14.0% and with a strong damage – 6.7%, which meets the norms of national legislation – “Methodological requirements in the field of seed production to preserve the varietal and sowing qualities of seed potatoes”, the order of the Ministry of Agrarian Policy and Food of Ukraine of July 12, 2019 No. 384. The permissible degree of tuber infection by Rhizoctonia (for tuber surface infestation over 10%) is 5.0%.

Tare Soil Alters the Composition of the Developing Potato Rhizosphere Microbiome

Understanding the factors influencing microbial community composition in the rhizosphere is an important step toward managing the microbiomes of globally important crops such as potato ( Solanum tuberosum). Potato is vegetatively propagated and seed tubers are planted with tare soil, or soil adhering to the tuber surface, from their field of origin. Bulk soil is known to influence rhizosphere microbiome composition but whether tare soil additionally contributes to compositional variation is not known. We tested this hypothesis in a greenhouse experiment where tare soil was removed (or remained intact for controls) prior to planting in either soil from a potato field or soil from a previously uncultivated area next the potato field. We used internal transcribed spacer and 16S metabarcoding to characterize the fungal and bacterial rhizosphere communities of plants grown from the experimental seed tubers. We found that tare soil influenced rhizosphere microbial composition, more strongly for fungi than bacteria. As expected, bulk soil origin explained the greatest amount of variation in the rhizosphere microbiome overall but we found no evidence that the impact of tare soil on microbial community composition differed between bulk soil origins. However, the magnitude of the tare soil effect did depend, in part, on seed tuber origin. Our findings reveal that tare soil explains a significant, though modest, amount of variation in rhizosphere composition, and sets the stage for future work addressing functional consequences for plant health and productivity.

First report of Geotrichum candidum causing rubbery rot of potato (Solanum tuberosum) in Michigan.

In April 2018, rotted 'Lamoka' tubers were received from a commercial storage facility (<1% incidence) in St. Joseph County, Michigan by the MSU Potato & Sugar Beet Pathology and Plant & Pest Diagnostics programs. Dense circular colonies of white fungal-like growth were observed on the surface of the tubers, and internal tissues were watery and spongy with gray to brown discoloration (Supplemental Figure 1). Tubers had a strong, sweet alcoholic odor. External and internal tuber tissues were surface disinfested in 0.825% sodium hypochlorite for 1 min, rinsed twice in sterile distilled water, blotted on sterile filter paper, and placed onto 1.5% (w/v) water agar (WA). After 3 days at 21-24°C and ambient light conditions, septate, branched mycelia and hyaline, cylindrical, single-celled conidia 5.2-8.9 µm x 3.6-5.2 µm (n=20 arthrospores) were observed singly or in chains (Supplemental Figure 2A&B). On potato dextrose agar (PDA), colonies were white, circular, and dense (Supplemental Figure 2C). These observations matched morphological descriptions of Geotrichum candidum (Carmichael 1957). No Pythium or Phytophthora spp. were detected. A mono-conidial isolate of the fungus was obtained and maintained on PDA. DNA was extracted from mycelia using a DNeasy plant mini kit (QIAGEN). Fragments of the internal transcribed spacer (ITS) and 18S ribosomal RNA gene regions were amplified using primers ITS1F/4 primers and NS3/8, respectively (White et al. 1990). Purified PCR products (QIAquick PCR purification kit, QIAGEN) were submitted for Sanger sequencing at the Genomics Research Technology Support Facility (East Lansing, MI). The ITS1F/4 and NS3/8 consensus sequences (OP142324 and OP153873) aligned with GenBank accessions of G. candidum KY103456.1 (100% identity) and JF262193.1 (99.75% identity), respectively. Healthy 'Lamoka' tubers were rinsed with tap water, surface disinfested in 0.825% sodium hypochlorite for 15 min, rinsed twice in sterile distilled water, and blotted dry on sterile paper towel. Ten tubers were inoculated by placing 10-mm diameter fully colonized agar plugs, excised from the margin of a 9-day-old PDA culture, onto the surface of each tuber (Duellman et al. 2021). Ten tubers were mock-inoculated using sterile PDA. Tubers were placed in a moist chamber and incubated in the dark at room temperature. After nine days, inoculated tubers exhibited white colony growth on tuber surfaces and an alcoholic scent was present. After 27 days, internal tissues were rubbery, but no discoloration was observed. No rubbery rot symptoms were observed on the control tubers. Samples were excised 1 cm laterally from and vertically beneath the inoculation site. Tissues were surface disinfested as described above and plated on 1.5% WA. After 9 days, a Geotrichum sp. identical to the original isolate was confirmed in 50% of samples from inoculated tubers. No Geotrichum sp. were detected from mock-inoculated tubers. Since 2018, G. candidum has been confirmed in commercial storages in three counties in the Lower Peninsula (incidences up to 1-2%). Geotrichum candidum was recently reported causing rubbery rot of potato in Idaho (Duellman et al. 2021); however, to our knowledge this is the first report of rubbery rot in Michigan. Despite increasing detection frequencies, incidences remain low and spread in storage appears limited. Seed decay leading to stand loss (incidence 1-3%) was observed after planting infected lots, which should be avoided or minimized.

Diversity of bacterial community in Jerusalem artichoke (Helianthus tuberosus L.) during storage is associated with the genotype and carbohydrates.

Jerusalem artichoke (JA) is a fructan-accumulating crop that has gained popularity in recent years. The objective of the present study was to determine the dynamics of the JA-microbiome during storage. The microbial population on the surface of the JA tuber was determined by next-generation sequencing of 16S rRNA amplicons. Subsequently, the changes in carbohydrate and degree of polymerization of fructan in tubers during storage were measured. Among different genotypes of JA varieties, intergeneric differences were observed in the diversity and abundance of bacterial communities distributed on the surface of tubers. Additionally, bacterial diversity was significantly higher in storage-tolerant varieties relative to the storage-intolerant varieties. Redundancy analysis (RDA) and the correlation matrix indicated a relationship between changes in the carbohydrates and microbial community succession during tuber storage. The tuber decay rate correlated positively with the degree of polymerization of fructan. Moreover, Dysgonomonas and Acinetobacter in perishable varieties correlated significantly with the decay rate. Therefore, the bacteria associated with the decay rate may be involved in the degradation of the degree of polymerization of fructan. Furthermore, Serratia showed a significant positive correlation with inulin during storage but a negative correlation with the decay rate, suggesting its antagonistic role against pathogenic bacteria on the surface of JA tubers. However, the above correlation was not observed in the storage-tolerant varieties. Functional annotation analysis revealed that storage-tolerant JA varieties maintain tuber quality through enrichment of biocontrol bacteria, including Flavobacterium, Sphingobacterium, and Staphylococcus to resist pathogens. These results suggested that crop genotype and the structural composition of carbohydrates may result in differential selective enrichment effects of microbial communities on the surface of JA varieties. In this study, the relationship between microbial community succession and changes in tuber carbohydrates during JA storage was revealed for the first time through the combination of high-throughput sequencing, high-performance liquid chromatography (HPLC), and high-performance ion-exchange chromatography (HPIC). Overall, the findings of this study are expected to provide new insights into the dynamics of microbial-crop interactions during storage.

Device for waterless cleaning of root crops

Existing devices for waterless cleaning do not provide essential quality due to low efficiency either because of significant tubers damage. Device for waterless cleaning of root crops is developed in Omsky SAU which relates to the agricultural machine-building industry in particular to devices for dry cleaning of tubers from the soil, grassy impurities and haulm before sale preparation as well as for feeding preparation in technological lines of feed mills. High quality cleaning from the soil is achieved by the spiral line of pile arrangement which provides the uniform movement of the processing material heap and prevents tubers unloading due to various pile length that increases the speed of tubers rotation and provides more frequent tuber surface contact with working tools due to spring-loaded bottom providing required compression degree of processing tubers to the brush roll at the expense of dust collector that allows to get rid of small impurities during the technological process and prevents from resetting on tuber surface. Usage of this device allows to reach high quality of cleaning under low degree of damage.

The influence of pre-plant potato treatment on plant development

The improvement of pre-plant treatment is possible on the basis of hot and cold mist of biopreparations. The device to treat seed tubers consists of a box made of thin metal or plywood on a loader conveyor with a rubber shutter to ensure the tightness of the treating area. Mist treatment occurs when the oncoming movement of tubers, ensuring fine droplets. Hot mist of biopreparations promotes heating of the surfaces of tubers by 1-2° C, accelerating physiological processes in them. The analysis of plant development has established that the best result is achieved by treating potato seed tubers of “Lily” variety with hot mist of biopreparations, and the highest efficiency is obtained from biopreparation Potassium humate. The value of the vegetative activity index in plants treated with hot mist of Potassium humate is 18 % higher in comparison with plants in the control plot not treated with biopreparations. The height of the stems of potato plants is 7.3 % higher in those treated with hot mist of Potassium humate than those treated with cold mist of the same preparation. In comparison with plants in the control plot, it is 75.1 % more. The number of leaves on potato bushes when treated with hot mist of Potassium humate is 13.1 % higher in comparison with those treated with cold mist of the same preparation and by 18.9 % in comparison with the values in the control plot. Studies have shown that the treatment with the mist of biopreparations helps to accelerate the development of plants, and treating with hot mist increases the physiological activity of tubers.

Streptomyces rhizophilus Causes Potato Common Scab Disease.

Common scab (CS) caused by Streptomyces spp. is a significant soilborne potato disease that results in tremendous economic losses globally. Identification of CS-associated species of the genus Streptomyces can enhance understanding of the genetic variation of these bacterial species and is necessary for the control of this epidemic disease. The present study isolated Streptomyces strain 6-2-1(1) from scabby potatoes in Keshan County, Heilongjiang Province, China. PCR analysis confirmed that the strain harbored the characteristic Streptomyces pathogenicity island (PAI) genes (txtA, txtAB, nec1, and tomA). Pathogenicity assays proved that the strain caused typical scab lesions on potato tuber surfaces and necrosis on radish seedlings and potato slices. Subsequently, the strain was systemically characterized at morphological, physiological, biochemical, and phylogenetic levels. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 6-2-1(1) shared 99.86% sequence similarity with Streptomyces rhizophilus JR-41T, isolated initially from bamboo in rhizospheric soil in Korea. PCR amplification followed by Sanger sequencing of the 16S rRNA gene of 164 scabby potato samples collected in Heilongjiang Province from 2019 to 2020 demonstrated that approximately 2% of the tested samples were infected with S. rhizophilus. Taken together, these results demonstrate that S. rhizophilus is capable of causing potato CS disease and may pose a potential challenge to potato production in Heilongjiang Province of China.

Physical and mechanical properties of cassava (Manihot esculenta Crantz) cultivars: Implications for the design of mechanical peeling machines

AbstractThe data on physical and mechanical properties of short and long‐duration cassava cultivars are limited to design an efficient continuous type peeling machine for small‐scale processing. Short duration cultivars included Sree Jaya, Sree Vijaya, and Sree Swarna, as well as long duration cultivars included M‐4, Sree Athulya, Sree Suvarna, H‐226, Sree Raksha, Sree Pavithra, and Sree Vishakam, were investigated. The moisture content, girth, proximal diameter, middle diameter, cylindricity, and tuber surface taper angle were the highest for long‐duration cultivar H‐226. The maximum length was observed in the short‐duration cultivar Sree Swarna. The periderm thickness was the highest for Sree Suvarna, whereas the highest proximal cortex thickness, middle cortex thickness, and distal cortex thickness were observed in Sree Athulya, Sree Vijaya, and M‐4 cultivar, respectively. The highest bulk density, true density, and porosity were observed in the long‐duration cultivars; Sree Raksha, Sree Athulya, and Sree Suvarna, respectively. The highest hardness, shear force, and rupture force were recorded for cassava peelings in the cultivar Sree Athulya. Similarly for cassava flesh, the highest hardness, shear force, and rupture forces were recorded in the Sree Suvarna cultivar. A strong positive correlation for true density with bulk density and proximal diameter and moisture content with cylindricity and middle‐end diameter was found from the multivariate correlation analysis. Statistical analysis showed that the reported physical and mechanical properties of the cultivars were highly significant (p &lt;.01).Practical ApplicationsEngineering properties such as physical and mechanical properties are important for designing machines, storage structures, and processes. Cassava tuber peeling by the manual method is time‐consuming, labor‐intensive, and has a low capacity. Thus, the design of a peeling machine for small‐scale processing becomes important. The physical and mechanical characteristics of cassava flesh and peelings are critical design considerations for developing peeling machines for small‐scale processing. The physical and mechanical properties investigated here would provide technical and scientific data for designing continuous shearing type cassava peeling machine units such as tuber feeder length, peeling knife selection, peeling knife angle, and adjustable spring with required tension for holding rotary type peeling knife.

Gradient Cleaning Method of Potato Based on Multi-Step Operation of Dry-Cleaning and Wet Cleaning

In view of the poor effectiveness of existing potato cleaning methods in China and reflecting the findings of a research analysis of basic sizes and types of impurities on potato tubers, a gradient cleaning method for potato based on a multi-step dry-cleaning and wet cleaning operation was proposed. The method mainly consists of dry-cleaning and wet cleaning. The dry-cleaning stage, which combines vibration and brushing, could effectively remove impurities such as residual rhizomes, peeled potato skin, and large pieces of soil and crushed stone from the surface of potato tubers. The wet cleaning stage adopts the gradient cleaning method of pre-cleaning, rough cleaning and fine cleaning, which could further remove soil and crushed stone attached to the surface and hidden in the sprout eyes of potato tubers. The optimal parameter combination for the gradient cleaning method was determined as follows. The potato feeding amount was 3 t/h, the speed of the rubber chain rod mechanism was 25 r/min, the speed of the first and third brush roller was 40 r/min, the speed of the second and fourth brush roller was 56 r/min, the moving speed of the immersion mechanism conveying net chain was 0.04 m/s, the speed of the brush roller in the high pressure spray and brush roller combination mechanism was 40 r/min, the ultrasonic power was 1200 W, the ultrasonic frequency was 33 kHz, the bubble intensity was 300 L/min, and the moving speed of the conveying net chain in the ultrasonic and bubble combination mechanism was 0.05 m/s. Taking the impurity removal rate and damage rate of potato tuber as the test indexes, a potato cleaning performance test was carried out under the optimal parameters combination. The results showed that the average impurity removal rate and damage rate of potato tubers were 99.05% and 2.48%, respectively. Additionally, the operational performance fully met the requirements for potato cleaning. This study provides a new method for potato cleaning in China and can also provide a reference for cleaning other root and tuber crops.

Co-Inoculation of Organic Potato with Fungi and Bacteria at High Disease Severity of Rhizoctonia solani and Streptomyces spp. Increases Beneficial Effects.

Rhizobacteria-based technologies may constitute a viable option for biological fertilization and crop protection. The effects of two microbial inoculants (1) PPS: Pseudomonas protegens, P. jessenii and Stenotrophomonas maltophilia biocontrol bacterium strains and (2) TPB: Trichoderma atroviride, Pseudomonas putida, and Bacillus subtilis fungi, bacteria biocontrol, and biofertilizer combinations were examined on potato (Solanum tuberosum L. var. Demon) in three consecutive years in irrigated organic conditions. The number of tubers showing symptoms of Streptomyces sp. and Rhizoctonia sp. was recorded. The severity of symptoms was evaluated based on the damaged tuber surface. There was a large annual variability in both the symptoms caused by soil-borne pathogens, and the effect of bio-inoculants. In the first and second year, with a stronger Rhizoctonia and Streptomyces spp. incidence, the bacterial and fungal combination of TPB inoculums with both the potential plant nutrition and biocontrol ability of the strains seemed to have a better efficiency to control the diseases. This tendency was not supported in the third year, and this may be attributed to the relatively high natural precipitation. Further studies are required to investigate the agronomic benefits of these inoculants and to tailor their application to the soil microbial characteristics and weather conditions.

The results of ecological testing of early and mid-season potato varieties in the Komi Republic

Search and introduction of new potato varieties that can be recommended for cultivation in soil and climatic conditions of the Komi Republic are especially important against the background of the average yield in the region of 12.1 t/ha, that is 6.7 t/ha lower than the average in Russia. In 2019-2020 on the basis of the A. V. Zhuravsky Institute of Agrobiotechnology of the Federal Research Center of the Komi Scientific Center of the Ural Branch of the Russian Academy of Sciences, there were tested potato varieties of the early maturing group – Armada, Meteor, Gulliver, Taifun and Krepysh (standard) and the mid-season group – Varyag, Vympel, Krasa Meshchery, Kumach, Fritella, Vychegodskii and Zyryanets (standard). From the early maturing group, the varieties Armada and Gulliver have been selected as giving a consistently high yield, which exceeded the standard by 6.8-7.1 t/ha on average for two years. Among mid-season varieties no one reliably exceeded the standard variety Zyryanets in terms of yield productivity. The highest yield and marketability was noted for the Fritella variety – 30.5 t/ha and 97 %. All the varieties under study, except for Vychegodskii, showed an average resistance of the tops to late blight damage. Moderate early blight damage of the tops (up to 20 % of the leaf surface) was noted in three varieties – Meteor, Taifun and Vychegodski. The following varieties showed high resistance to common scab - Vympel (no damage), Zyryanets (few lesions) and Gulliver (up to 10 % of tuber surface damage). In all studied varieties the potato tubers were not affected by late blight during both years of research. For cultivation, the agricultural producers of the Komi Republic should use the varieties Armada (29.7 t/ha), Gulliver (28.1 t/ha), Vympel (29.2 t/ha), Fritella (30.5 t/ha), which have good resistance to phytopathogens and high quality of tubers.

Habituation to thaxtomin A increases resistance to common scab in 'Russet Burbank' potato.

Common scab is a potato disease characterized by the formation of scab-like lesions on the surface of potato tubers. The actinobacterium Streptomyces scabiei is the main causal agent of common scab. During infection, this bacterium synthesizes the phytotoxin thaxtomin A which is essential for the production of disease symptoms. While thaxtomin A can activate an atypical programmed cell death in plant cell suspensions, it is possible to gradually habituate plant cells to thaxtomin A to provide resistance to lethal phytotoxin concentrations. Potato ‘Russet Burbank’ calli were habituated to thaxtomin A to regenerate the somaclone RB9 that produced tubers more resistant to common scab than those obtained from the original cultivar. Compared to the Russet Burbank cultivar, somaclone RB9 generated up to 22% more marketable tubers with an infected tuber area below the 5% threshold. Enhanced resistance was maintained over at least two years of cultivation in the field. However, average size of tubers was significantly reduced in somaclone RB9 compared to the parent cultivar. Small RB9 tubers had a thicker phellem than Russet Burbank tubers, which may contribute to improving resistance to common scab. These results show that thaxtomin A-habituation in potato is efficient to produce somaclones with increased and durable resistance to common scab.