Rotting Potato Tubers Research Articles

Metabarcoding Approach for Evaluation of Bacterial Diversity in Soft Rotting Potato Tubers and Corresponding Geocaulospheres

Metabarcoding Approach for Evaluation of Bacterial Diversity in Soft Rotting Potato Tubers and Corresponding Geocaulospheres

Ralstonia solanacearum as a potato pathogen in Serbia: Characterization of strains and influence on peroxidase activity in tubers

AbstractSince 2011, the outbreaks of brown rot caused by Ralstonia solanacearum race 3, biovar 2, phylotype IIB‐1 (R3/B2/PIIB‐1) have significantly compromised potato production in Serbia. During 6 years of monitoring (2013–2018) among 3,524 potato tuber samples, 344 were found positive for brown rot disease. R. solanacearum R3/B2/PIIB‐1 was isolated from seven cultivars among 12 monitored, and in five localities among 17 monitored. Cultivar Lady Claire was found to have the highest disease frequency (31.98%). A total of 78 isolates were identified by R. solanacearum‐specific primer pairs (PS‐1/PS‐2 and OLI‐1/Y‐2), as well as the following tests: restriction fragment length polymorphism analysis, biovar determination, immunofluorescence, biochemical analysis, and pathogenicity. The genetic composition of 36 selected isolates assessed using multilocus sequence analysis with seven genes (adk, gapA, gdhA, gyrB, ppsA, hrpB, and fliC) showed that all isolates originating from Serbian potato were homogeneous. By using the TCS algorithm of concatenated sequences to get insight into the phylogeography of isolates and other R. solanacearum strains deposited in the NCBI database, we showed that their origin is undetermined. Peroxidase (POD) activity was measured in brown rotted potato tubers. A positive correlation was found between POD activity and disease severity rated on the analysed tubers. In general, POD activity increased by 2–22 times in vascular necrotic tissues compared to non‐necrotic ones, and depended on disease severity but not on cultivar. Native polyacrylamide gel electrophoresis analysis of POD profiles resulted in a total of 10 distinct POD isoforms, of which PODs 3–5 were highly intensified in response to R. solanacearum.

English

Studies were conducted in the Department of Plant Pathology, College of Agriculture, Orissa University of Agriculture and Technology, Odisha, India in 2010-2011 on serological detection methods for identification of bacterial pathogens associated with rotted potato tubers. One hundred and two rotten potato tubers of KufriJyoti variety were collected from freshly harvested lot of All India Co-ordinated Potato Improvement Project, Orissa University of Agriculture and Technology. Tubers were cut into two equal halves and categorized into 6 groups, on the basis of internal symptoms exhibited, that is, (A) cut tubers showing brownish discolouration along the vascular region, (B) cut tubers showing brownish discolouration along the vascular region with soft rotten cavities filled with whitish ooze, (C) cut tubers showing brownish blackish discolouration along the vascular region and soft rotten tissues extending towards centre, (D) cut tubers showing soft rotten tissues extending towards centre without brownish discolouration, (E) cut tubers showing soft rotten tissues extending towards centre with brownish black discolouration, (F) cut tubers showing dry tissues with cavities surrounded by soft tissues. The association of two bacterial species was assayed following tube agglutination test using the known antiserum for each bacterium, Ralstonia solanacearum and Pectobacterium carotovorum. It was revealed that R. solanacearum could be associated exclusively with 54.10% of diseased tubers with symptom Category–A. No other bacteria could be detected from the rest of the samples belonging to the said category. Similarly, exclusive association of P. carotovorum could be detected in 87.50% of the rotten tubers with symptom Category–D. In the symptom categories B, C, E and F, both test bacteria were found to be associated either singly or as mixture. Least bacterial infection due to P. carotovorum (12.5%) was observed in symptom Category–F. It is a very quick detection method which can reveal the percentage of bacterial pathogen association after two hours of testing. Key words: Rotten potato tubers, bacteria, bacterial pathogen, serological detection, Ralstonia solanacearum, Pectobacterium carotovorum.

Mixed rots of potato tubers in Ukraine

The pathogens involved in rotting potato tubers at harvest or in store have been identified in the forest and forest‐steppe zones of Ukraine. Fusarium spp., Phytophthora infestons, Erwinia carotovora and Ditylenchus destructor are the most important.

Sambutoxin, a new mycotoxin produced by toxic Fusarium isolates obtained from rotted potato tubers.

Ninety-nine isolates of Fusarium species were obtained from rotted potato tubers from various parts of Korea. Of these isolates, 80 were identified as Fusarium oxysporum, F. solani, or F. sambucinum. The isolates of these species were grown on autoclaved wheat grains and examined for toxicity in a rat-feeding test. A total of 8 of 57 F. oxysporum isolates, 3 of 14 F. solani isolates, and 5 of 9 F. sambucinum isolates caused the death of the rats. Of the 16 toxic isolates, 1 isolate of F. oxysporum produced a substantial amount of moniliformin, which could account for its toxicity. None of the other 15 isolates produced trichothecenes, moniliformin, fusarochromanone, fumonisin B1, or wortmannin. F. sambucinum PZF-4 produced an unknown toxin in wheat culture. This new toxin, given the trivial name sambutoxin, caused toxic effects in rats, including body weight loss, feed refusal, hemorrhage in the stomach and intestines, and, finally, death when rats were fed diets supplemented with 0.05 and 0.1% sambutoxin. The toxin was also toxic to chicken embryos, and the 50% lethal concentration was 29.6 micrograms per egg. Sambutoxin formed as white crystals that turned purple when combined with reagents such as sulfuric acid and p-anisaldehyde. It exhibited a green color immediately after treatment with potassium ferricyanide-ferric chloride. Its UV spectrum had absorption maxima at 213, 233, and 254 nm, and its infrared spectrum showed an amide group at 1,650 and 1,560 cm-1 and a hydroxy group at 3,185 cm-1. Mass spectrometry showed that the molecular weight of the toxin was 453 and the molecular formula was C28H39NO4.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic Nitrate Respiration by Erwinia carotovora subsp. atroseptica during Potato Tuber Invasion

The in planta induction of anaerobic nitrate respiration by Erwinia carotovora subsp. atroseptica in relation to the in situ oxygen status in soft rotting potato tubers has been investigated. In vitro experiments have shown that nitrate was required for the induction of respiratory nitrate reductase activity in E. carotovora. In addition, oxygen was found to repress this activity. Expression of respiratory nitrate reductase was found in E. carotovora cells extracted from soft rotting potato tuber tissue. However, the rate of nitrite production in these cells was approximately 70-fold lower than the rate recorded in fully induced anaerobic cultures. Oxygen measurements in soft rotting potato tubers indicated that the invading bacteria encounter the lowest oxygen concentration at the interphase between healthy and macerated tissue. Consequently, growth of bacteria present in this specific zone will be stimulated by nitrate which is present in sufficient amounts in tuber tissue. A high nitrate content of the tuber will most likely facilitate the proliferation of E. carotovora in the tuber tissue.

Luminescence-based detection of Erwinia carotovora associated with rotting potato tubers.

A luminescence-based marker system has been used to follow rotting of potato tubers by Erwinia carotovora. The early stages of infection could be detected by visual observation of areas of luminescence developing from the point of inoculation. During later stages luminescence was limited to peripheral regions and to central regions where the structure of the potato was destroyed. Luminometry demonstrated reduction in aerobic activity of infecting cells due to oxygen limitation. The system enables rapid and sensitive detection of active marked populations and distinction between aerobic and fermentative activity.

Formation of fusarenone X, nivalenol, zearalenone, alpha-trans-zearalenol, beta-trans-zearalenol, and fusarin C by Fusarium crookwellense.

Fusarium crookwellense KF748 (NRRL A-28100) (isolated from dry rotted potato tubers in Central Poland) produced six mycotoxins on both rice and corn substrates at 25 degrees C. The metabolites detected were zearalenone, alpha-trans-zearalenol, beta-trans-zearalenol, fusarin C, and the trichothecenes fusarenone X and nivalenol. This is the first report of formation of alpha-trans-zearalenol, beta-trans-zearalenol, fusarenone X, and nivalenol by F. crookwellense.

ToxigenicFusarium species isolated from rotted potato tubers

Fusariumsambucinum(F. trichothecioides),F. avenaceum andF. crookwellense, were the species most frequently isolated from lots of potato tubers imported to Southern Italy in 1985. Isolates of these species were tested for the production of zearalenone, zearalenols, trichothecenes and moniliformin, on three solid media (autoclaved kernels of maize or rice, and fresh potato tubers), incubated at different conditions. The toxigenic potential of the isolates was expressed only on rice and maize, while they were non capable to produce toxins on fresh potato under any conditions. In particular,F. crookwellense produced zearalenone and/or zearalenols (diastereomeric mixture) on maize, andF. avenaceum produced moniliformin both on maize and on rice; while no toxins were produced byF. sambucinum.

Physiological and pathological characteristics of Erwinia chrysanthemi isolates from potato tubers

Nine isolates of Erwinia chrysanthemi from rotting potato tubers were compared with six type or reference strains of this species. Phenotypic properties of the potato isolates closely agreed with those of Erw. chrysanthemi pv. zeae and with the characteristics proposed for Dickey's infrasubspecific subdivision IV (1979) and Samson & Nassan‐Agha's biovar 3 (1978), where Zea mays was among the most common host species. Pathogenicity tests on 20 ornamental and agricultural species showed only Cyclamen sp. and Z. mays to be susceptible. In Ouchterlony double diffusion tests, antisera to whole live cells of one potato strain reacted with four of the six pathovars of Erw. chrysanthemi. Tuber isolates did not produce blackleg symptoms in inoculated stems. The rationale of intensive pathogenicity testing is discussed.

Metabolites from microbially infected potato. Part 1. Structure of phytuberin.

Phytuberin (1) was obtained from bacterially rotted potato tubers and shown to be a novel tricyclic sesquiterpene acetate. Two heterocyclic rings, a dihydrofuran ring which was hydrated under acid conditions to give the lactol (6) and readily oxidised to the γ-lactone (8), and a relatively inert tetrahydrofuran ring, were shown to be present. N.m.r. studies, including the use of lanthanide shift reagents, established an overall constitution for phytuberin {8-(1-acetoxy-1-methylethyl)-5,5a,6,7,8,9-tetrahydro-3a,5a-dimethyl-3aH-furo[3,2-c]isobenzofuran} and showed that the third ring was a cyclohexane held rigidly in a chair conformation by the two fused heterocyclic rings. Catalytic hydrogenation of phytuberin provided a dihydro-derivative (2) which was used in an independent X-ray crystallo-graphic structure determination.

Bunonema (Rhodolaimus) Estonicum N. Sp. - Eine Faulende Kartoffelknollen Bewohnende Neue Nematodenart

Bunonema (Rhodolaimus) estonicum n. sp., from rotting potato tubers in Estonia is described. The new species is nearest to B. (Rh.) poligraphi (Fuchs, 1930) Sachs, 1949, but differs in having a more complex system of tubercles. The rows of warts terminate anteriorly and posteriorly in individual tubercles. The tubercles are held together by a delicate membrane. The posterior two to five tubercles on the anterior part of the body (transition tubercles) are not paired but are alternately placed. The cuticle has regular transverse rows of tiny dots, which are coarser between the rows of warts. The new species is saprobic and not, like B. poligraphi, associated with bark beetles. This is the first record of the subgenus Rhodolaimus in USSR.

On the nomenclature and identity of the coliform soft-rot bacteria

Summary Pathogenicity and biochemical tests were carried out with twenty-eight strains of coliform soft-rot bacteria, mainly isolated from rotting potato tubers, in an attempt to clarify the nomenclature of the group. The Separation of the two species Bacterium carotovorum and B. phytophthorum on differences in pathogenicity and fermentation reactions is shown to be unsatisfactory. B. carotovorum, B. phytophthorum and B. aroideae are considered to be strains of a single species, which should be called Bacterium carotovorum (Jones) Lehmann & Neumann.

OCCURRENCE OF BACILLUS POLYMYXA (PRAZ.) MIG. IN ALBERTA SOILS WITH SPECIAL REFERENCE TO ITS PATHOGENICITY ON POTATO TUBERS

The spore-forming bacterium, Bacillus polymyxa, was found to occur widely in Alberta soils. All isolates obtained from the soil, together with several from other sources, proved capable of rotting potato tubers when introduced through wounds under conditions of abundant moisture and high temperature.In these studies pure cultures of Bacillus polymyxa rotted potato slices at temperatures from 20 °C. to 45 °C. and whole tubers at temperatures from 30 °C. to 45 °C. but caused no damage below the minimum temperatures mentioned.Though potato tubers and other vegetables that are formed in the soil probably often come in contact with Bacillus polymyxa, they are not likely to be rotted by it except when temperature and other factors are favourable. In general, soil temperatures in the field in Alberta are not conducive to the decay of potatoes by this organism, but those near the soil surface may on occasion reach favourable levels. The fact that B. polymyxa can be isolated quite frequently from rotted stored potatoes indicates that it is of some importance as a cause of decay in harvested potatoes. If, however, recommended storage temperatures are maintained in the storage quarters no damage from this organism should occur there.