Incidence Of Black Scurf Research Articles

Influence of soil parameters and planting depth on black scurf development in Potato

Solanum tuberosum is an important vegetable crop worldwide. Among various diseases, black scurf disease caused by Rhizoctonia solani Kuhnh as emerged as a major problem and is known to cause qualitative and quantitative losses in potato.The management of R. solani causing black scurf is complex due to its soilborne nature and high level of survival and poses a challenge for the eco-friendly management of the disease. The existing fungicides control measures are neither economical nor environment friendly; therefore sustainable effective disease management strategy is required. Available information on management of black scurf (R. solani) disease is scanty. The present investigation was carried out in the Agricultural Research farm (Vegetable Science), Guru Kashi University, Talwandi Sabo during rabi seasons, 2021-22 and 2022- 23.The ‘Kufri Pukhraj’ infected potato tubers were planted during 15th November in both respective years under field conditions with three replications at different depth of planting (soil depth: 15, 20 and 25 cm). Results revealed that per cent disease incidence and severity increased with increase in depth of planting during both the years. Black scurf incidence and severity showed a positive correlation with morning soil temperature and soil moisture whereas, a negative correlation with evening soil temperature (STe). The optimization in depth of planting can be a good eco-friendly and economic alternative for the management of black scurf of potato.

Effects of different rotation cropping systems on potato yield, rhizosphere microbial community and soil biochemical properties.

Continuous potato cropping systems cause yield reduction, soil-borne disease aggravation, and soil degradation, but crop rotation can alleviate these negative effects. However, there are limited studies on the relationships between microbial community and other soil biochemical properties of continuous potato cropping at both pre-planting and harvest in North China. A 4-year study was conducted to explore the effects of different rotation system on soil biochemical properties, microbial community at pre-planting and harvest, and potato yield, tuber number and black scurf incidence at harvest in 2020 and 2021, which included 4 treatments vis. potato-potato-potato-potato (PC), potato-oat-faba bean-potato (PR), oat-faba bean-potato-oat (O), and faba bean-potato-oat-faba bean (B). The results showed that soil biochemical properties and microbial community among all treatments showed no significant difference at pre-planting after a long cold winter generally. At harvest, PC reduced tuber yield and number and significantly increased black scurf incidence relative to potato rotation systems. PC also reduced soil enzyme activities, the content of soil nutrients, and fungal community diversity, and increased bacterial community diversity compared with the other treatments, insignificantly when compared with PR. Relative abundance of microorganisms related to the degradation of organic residues, soil nitrogen cycling, and disease suppression, such as the genera Devosia, Aeromicrobium, Paraphoma, and Papiliotrema, were significantly higher in O or B than in PC and PR, while microorganisms related to disease infection such as the genera Pseudomonas, Colletotrichum, Plectosphaerella, Fusarium, and Verticillium exhibited increased in PC and PR. Principal Coordinates Analysis (PCoA) showed that there were significant differences in the microbial community structure of PC and PR at harvest compared with that of O and B. Redundancy analysis (RDA) revealed that soil available potassium (AK), acid phosphatase (ACP), available phosphorus (AP), sucrase (SUC) and pH were the dominant factors that significantly affected bacterial and fungal community structure. Partial least squares structural equation model indicated rotation system had significant negative effect on fungal community. It was concluded that growing oat or faba bean after potato can increase soil beneficial microorganisms and maintain the ecosystem healthy, thus reducing the incidence of tuber black scurf and increasing potato yield.

Factors associated with soils suppressive to black scurf of potato caused by Rhizoctonia solani

Soils in which disease fails to develop despite pathogen presence are considered disease-suppressive. They offer sustainable, effective protection to plants against infection by soil-borne pathogens. Naturally disease-suppressive soils have been reported for diseases of a diverse range of agricultural crops worldwide yet the underlying mechanisms of disease suppression are still not completely understood. Two large greenhouse experiments, conducted during 2017/18 (Year 1) and 2018/19 (Year 2), determined that soils naturally suppressive to stem canker and black scurf of potato (caused by Rhizoctonia solani) are present in vegetable-arable cropping soils of the Auckland and Waikato regions of New Zealand. Soil was pre-treated with heat prior to inoculation with R. solani and compared with untreated and uninoculated controls to ascertain if stem canker and black scurf suppression was ‘general’, or ‘specific’ (i.e. transferable; possibly involving specific microorganisms). Rhizoctonia solani inoculation was also combined with transfer of one part test soil to nine parts of a known disease-conducive soil. Abiotic factors such as soil texture and organic matter content influenced black scurf incidence and severity. Soil microorganisms were also involved in disease suppression since black scurf incidence and severity markedly increased when they were eliminated or reduced by soil heat pre-treatment. Microbial profiling of the soils through sequencing revealed that taxa of geographically close soils of the same type had similar fungal and bacterial community structure and diversity even though they differed in their capacity to suppress black scurf. These results suggest that although the soil microbiome as a whole, was mainly responsible for soil disease suppressiveness, certain bacterial genera or species may play a role in black scurf suppression.

EFFICACY OF SOME BIOCONTROL ORGANISMS, ANIMAL MANURES AND FUNGICIDES ON CONTROLLING OF POTATO BLACK SCURF AND STEM CANKER DISEASE

In the last few years, stem canker and black scurf disease caused by Rhizoctonia solani Kuhn (teleomorph Thanathephorus cucumeris [Frank] Donk) are among different diseases important attacked potato crop under the Egyptian climate conditions. Eight fungal isolates were isolated from diseased plants representing different localities in different governorates i.e. El-Kassasen (Ismailia Gov.), Kafer El-zayat (Gharbia Gov.), El-Katatba (Minofya Gov.), Housh-Essa (Behera Gov.), El-Badrashen (Giza Gov.), Behdal (Minia Gov.), Dairoot (Assiut Gov.) and Shandaweel (Sohag Gov.). The obtained isolates differed in their culture color, number and size of sclerotia. Isolates which isolated from El-Kassasen, Kafer El-zayat, El-Khatatba, El-Badrashen and Behdal, were belonging to AG-3 anastomosis group. Under greenhouse conditions this isolates were tested for their pathogenicity to potato (Lady-Roseta cv.), during summer growing season 2015 and gave high rates of infection to potato plants. In this manner, the isolate which obtained from El-Badrashen (Giza Gov) was the highest aggressive one and causing the highest percentage of stem canker and black scurf. In separate experiments under greenhouse conditions, a number of biocontrol organisms,animal manure extracts and fungicides were evaluated alone in their efficacy to reduce the infection of potato stem canker and black scurf diseases.With regard to bioagents test, Trichoderma harzianum at concentrate 2.0% improving percentages of eyes germination and reduce dead sprouts of potato and decrease of stem canker and black scurf incidence, compared with Bacillus subtilis and algae treatments. While, animal manure test, Pigeons extract at concentrate 2.0%, gave the highest effect on reducing of stem canker and black scurf incidence compared to Chicken extract. In fungicides experiment, Rizolex (Tolchlophos-methyl) when used before soil inoculation give the best effect in reducing of non-germinated eye, dead sprouts and incidence of stem canker and black scurf compared to Monceren (Pencycuron). On the other hand, the effect of different treatments on the content of potato plants of phenols and oxidative enzymes were studied. In this respect T. harzianum, gave the highest content of phenols and activities of oxidative enzymes Peroxidase (PO) and Polyphenoloxidase (PPO).

Cultivar Effects on the Interaction between Free-Living Plant-Parasitic Nematodes and the Fungal Pathogen Rhizoctonia solani in Potato

Crop damage is associated with infection by plant pathogens but can also arise through abiotic factors. However, the plant pathogens are involved in biotic interactions with other plant pathogens, and these interactions may differ depending of the cultivar of the crop. Here, the interaction between the fungus Rhizoctonia solani (AG3) and free-living plant-parasitic nematodes was investigated in a pot experiment with different potato cultivars. No synergistic interaction between R. solani and plant-parasitic nematodes was found, instead there was an effect of treatment with lower tuber yield when nematodes occurred alone. There were differences among the cultivars regarding incidence of black scurf, dry weight of stems and tubers, and there was interactive effects between treatment and cultivar regarding dry weight of stolons and roots. Therefore, results concerning incidence and damage of R. solani and/or plant-parasitic nematodes found for one cultivar may not be applicable to other cultivars.

Potato seed dressing with Pseudomonas aeruginosa strain RZ9 enhances yield and reduces black scurf

A rhizospheric strain RZ9 of Pseudomonas aeruginosa was assessed for in-vitro growth inhibition of Rhizoctonia solani and effectiveness to control black scurf on potatoes ( Solanum tuberosum L.) of the cultivars Spunta and Nicola, in greenhouse and field experiments. The strain RZ9 inhibited R. solani mycelial growth by more than 60% and completely inhibited the germination of sclerotia from infested potato tubers in in-vitro tests. In greenhouse assays, seed potato treatment with RZ9 cell suspension increased stem length, decreased the relative weight of infected potato tubers (by 67%), and increased the potato yield (by 16%) compared to pathogen-inoculated plants for both potato cultivars. In field trials conducted on sandy soils during 2012 and 2013, strain RZ9 reduced black scurf incidence and increased potato yield by an average of 5.3 t ha -1 for ′Spunta′ and 5 t ha -1 for ′Nicola′. This study showed that the selected strain of P. aeruginosa is an efficient bacterium for enhancing yield and reducing black scurf of field-grown potatoes.

Effects of High Glucosinolate Mustard on Red Potato Yield and Skin Quality

Yield and disease resistance are important components influencing potato growers’ variety selection. Potato appearance, nutritional content, and specific culinary uses often affect consumer selection. A 3-year study was conducted to investigate how red potato (Solanum tuberosum L.) yield and skin quality were affected by variety and previous crop and specifically if red potato varieties would benefit from a plowed-down high-glucosinolate mustard (HGM; Brassica spp.) cover crop. The three previous crops were barley (Hordeum vulgare L.), canola (Brassica napus L.), and HGM. Each season six red varieties were planted, and yield and skin quality were evaluated. Two red varieties were planted consistently across three growing seasons, and three were similar across two growing seasons. Potatoes were harvested, washed, graded, weighed, and rated for skin surface quality. Potato yields were influenced by variety and year (due to variable environmental conditions), but the previous crop only influenced yield in the wettest year, when potato yield increased by 19%, probably from the N released from the HGM biomass. For varieties grown across similar environments, HGM cover crops resulted in a 52% lower incidence of black scurf. Thus, HGM green manures can be used to reduce soilborne pathogens.

Survival of Sclerotia of Rhizoctonia solani AG3PT and Effect of Soil‐Borne Inoculum Density on Disease Development on Potato

AbstractSclerotia produced by a single isolate of Rhizoctonia solani AG3PT were buried in small plot experiments to investigate the effects of sclerotial production method, soil type and burial depth on sclerotial viability in field soil. The factor with the greatest effect on sclerotial viability, defined as the percentage of sclerotia germinating on agar following retrieval, in all experiments was the duration of burial. After 18 months, on average across all experiments, 20% of retrieved sclerotia were viable. A comparison between sclerotia produced in vitro on malt yeast extract agar and in vivo using micropropagated tubers in field soil found no significant differences between the two production methods on sclerotial viability. Burial in field soil at 20‐cm depth was found to significantly reduce sclerotial viability to 50% compared to 60% at 5 cm. In two pot experiments, amending the growing medium and soil with increasing inoculum densities of R. solani was found to increase stem number, stem canker and black scurf severity regardless of whether this soil‐borne inoculum was derived from mycelium or sclerotia. Black scurf incidence and severity were assessed 30–32 days posthaulm destruction and found to be similar for a range of sclerotial soil‐borne inoculum densities (1.0 × 10−1 g/kg d.w. soil to 6 × 10−3 g/kg d.w. soil). The significance of these findings in relation to pathogen survival, detection in soil and disease development is discussed.

Evaluation of potato clones for resistance to stem canker and tuber black scurf in field studies following artificial inoculation with Rhizoctonia solani AG-3 in Maine*

Potato clones were evaluated for resistance to Rhizoctonia stem canker, stolon lesion and black scurf in field experiments during the 1997 and 1998 growing seasons. Seed pieces were inoculated with Rhizoctonia solani Anastomosis group 3 (AG-3) by dipping them in a slurry or suspension of inoculum. Uninoculated controls were also planted. Seed emergence was assessed beginning at two weeks after planting. After 60 days, incidence and severity (%) of stem and stolon cankers were assessed. The numbers of root and stolon lesions were also quantified. At harvest, the incidence of black scurf on tuber yield and numbers were also determined. Significant differences in emergence of potato seed pieces (%) were detected between inoculated and control treatments and the incidence of stem and root cankers differed among clones in both years. The incidence and severity of stem cankers and the numbers of stem and root lesions were not significantly correlated with the black scurf incidence on tubers. These studies suggest that various symptom types incited by Rhizoctonia can be important epidemiological factors in disease development.

Biological and chemical control and their combined use to control different stages of the Rhizoctonia disease complex on potato through the growing season

Abstract Rhizoctonia solani causes stem canker and black scurf diseases on potato and negatively affects the yield in all potato‐growing areas. While seed‐borne infection can be efficiently controlled by dressing with fungicides, few means of effective control are available against soil‐borne infection. In this study, commercially available antagonistic fungi and bacteria, and the combination of antagonistic Trichoderma harzianum and seed dressing with flutolanil, were tested for their efficacy in the control of soil‐borne infection of R. solani in the field. Combined use of flutolanil and T. harzianum was found feasible because even the highest tested concentration of flutolanil [13.0 μg active ingredient (a.i.) mL−1] had little effect on the growth of T. harzianuminvitro, whereas over 100‐fold lower concentrations (0.1 μg a.i. mL−1) were sufficient to strongly inhibit the growth of R. solani (EC50 0.045 ± 0.0068 μg a.i. mL−1). The variables under focus in plants inoculated with R. solani were the relative stem lesion index; sprout/stem number; stolon number, weight and incidence of symptoms on stolons; total yield and the yield of marketable sized tubers, and incidence of black scurf on the marketable‐sized tubers. Flutolanil and its combined application with T. harzianum reduced the damage to sprouts and severity of stem canker at the early stages of growth (up to 30 days postplanting). Towards the end of the growing season, T. harzianum was required to reduce disease severity. When applied in‐furrow alone or in combination with flutolanil‐dressed seed potatoes, T. harzianum increased the proportion of marketable‐sized tubers in yield from 35% to 60% and decreased the incidence of black scurf on progeny tubers from 31% to 11%, which was not achieved using flutolanil alone. The number and weight of stolons and the yield of plants remained lower in the inoculated plants than un‐inoculated control plants regardless of the method of control used. The other two antagonists tested, Streptomyces griseoviridis and Gliocladium catenulatum, showed no consistent control of R. solani. Taken together, the results suggest that combining the application of the antagonist T. harzianum with seed dressing with flutolanil may provide the best protection of the potato crop against damage caused by R. solani throughout the growing season.

Infection of potato by Rhizoctonia solani: effect of anastomosis group

Glasshouse and field experiments showed that the pathogenicity and disease type on potato varied between different anastomosis groups (AGs) of Rhizoctonia solani. For example, severe stem and stolon disease developed in plants inoculated with a single isolate of AG3PT and AG5. Severe root disease was observed with single isolates of AG8 and to a lesser extent AG3PT, but rarely with single isolates of the other AGs tested. In both field and glasshouse experiments the AG2‐1 isolate (X81) produced only small lesions (<5 mm). However, this was not representative of two other AG2‐1 isolates. When AG2‐1 isolates of the three different rDNA IGS1 types were tested in a glasshouse trial, one caused more severe stem and stolon infection than AG3PT. In the field experiment, the yield of tubers, by weight, was significantly less (P < 0·05) in all inoculated plants than for uninoculated (control) plants. Yield losses were greatest and tuber numbers smallest in plots inoculated with an AG8 isolate, suggesting that root infection is important in determining quantitative yield loss. The incidence of black scurf was greatest in the progeny tubers in plots inoculated with AG3PT (83·9%), whereas only very small amounts of black scurf developed on tubers from plants infected with AG2‐1 (510 bp) or AG5 isolates. This is supported by laboratory tests, where isolates of AG3PT produced significantly more sclerotia on potato dextrose agar than isolates of AGs 2‐1, 4, 5 and 8.

The effect of autumn ridging and inter-row subsoiling on potato tuber yield and quality on a sandy soil in Denmark

Autumn ridging is a modified version of the ridge tillage system. Instead of setting up ridges during the growing season, they are established in autumn and left for the winter. Previous studies have documented positive effects of autumn ridging on potato yield and we hypothesized that subsoiling could enhance these effects. To determine the effect of autumn ridging and inter-row subsoiling on potato yield and quality a field experiment was conducted on sandy soil from 2001 to 2003. Autumn ridging resulted in an average total and marketable tuber yield of 25.6 and 9.2 t ha −1, which was not significantly different from the average total and marketable yield of 25.6 and 8.9 t ha −1 with ploughing. However, autumn ridging significantly reduced the incidence of black scurf from 2.5% to 2.2%. Inter-row subsoiling in the growing season significantly increased marketable potato tuber yield from 8.4 to 9.6 t ha −1 and reduced the occurrence of malformed potatoes from 9.3% to 7.5%, irrespective of tillage treatment and irrigation level. There was no significant interaction between autumn ridging and subsoiling. The beneficial effect of subsoiling on marketable yield was driven by a 48.5% increase in the dry year of 2001. Subsoiling reduced the incidence of common scab from 7.8% to 6.9% when irrigation was reduced. It is concluded that at least three factors may modify the effects of subsoiling: Soil water status in the growing season, precipitation immediately before and after the subsoiling operation, and crop growth stage at the time of subsoiling.

The Influence of the Inoculum Source of Rhizoctonia solani on Development of Black Scurf on Potato

Abstract Rhizoctonia solani, the causal agent of stem canker and black scurf on potato, survives as sclerotia on tubers, in soil and in plant residues. The objective of the present study was to evaluate the importance of inoculum source on disease development. Disease‐free minitubers and seed tubers contaminated with low levels of R. solani were planted in fumigated or artificially inoculated growth mixture in greenhouse experiments. Black scurf incidence and severity were significantly higher when the inoculum was present in both seed tubers and soil, compared with either of them separately. The severity of disease symptoms on the subterranean parts of the plant also were significantly higher in plots where both seed tubers and soil were contaminated, compared with plots where the inoculum source was either the seed tubers or the soil. Thus, both major sources of inoculum, seed tubers and soil, are important in disease development. However, when both sources are present, black scurf incidence and severity are increased, leading to economical damage to tuber yield and quality. Additional results from field trials support these findings. Disease incidence and severity on daughter tubers were correlated with levels of contamination in seed tubers and soil. When seed tubers and soil were heavily infested, the levels of black scurf incidence and severity on daughter tubers were very high; when seed tuber and soil infestation were very low, black scurf incidence and severity on progeny were also lower. Disease levels were reduced by in‐furrow fungicide treatment, but were less effective when the initial levels of the fungus on the seed tubers and in the soil were high.

Early‐Season Applications of Sulfur Fertilizers Increase Potato Yield and Reduce Tuber Defects

Sulfur recommendations are based on avoiding deficiency. Since S may have additional effects, the objective was to determine whether S fertilizers increase yield and reduce tuber defects. Potato (Solanum tuberosum L.) cultivar Atlantic was treated with wettable sulfur (WS), ammonium sulfate (AS), and ammonium thiosulfate (TS) at 0, 28, 56, 84, and 112 kg S ha−1 applied at planting [in‐furrow (IF)], 11 d later [pre‐emergence (PE)], 11 d after emergence [postemergence (PT)], and at tuber initiation (TI). Separate trials were conducted for each fertilizer and application. Ammonium nitrate and urea were added to AS and TS to equalize N. Yield of U.S. “A” potato was increased 11 to 34% by fertilizers at S rates greater than 56 kg ha−1 at IF, PT, and by AS and WS at TI. These fertilizers applied IF and at TI reduced the incidence of common scab (Streptomyces scabies) on tubers. When applied PT, AS and TS reduced common scab; WS did not. The incidence of black scurf (Rhizoctonia solani) on tubers was reduced when AS and TS were applied PT but not when applied IF and at TI. Pre‐emergence application had no effect. Other tuber characteristics, e.g., specific gravity and vascular discoloration, were unaffected. Plant growth was inhibited by TS applied after emergence but recovered. Yield was increased by S at 56 kg ha−1 applied IF, PT, and at TI except for TS applied at TI. Common scab and black scurf were reduced depending on application timing and fertilizer.

Biological control of black scurf on potato under organic management

Field experiments showed that Trichoderma harzianum, nonpathogenic Rhizoctonia (np-R) and cattle manure compost amendment (CMC-H) applied in furrow could reduce black scurf incidence in organically grown potatoes. Incorporation of T. harzianum applied to the soil surface had a relatively small effect compared to the in-furrow treatment. Application of two isolates of nonpathogenic-binucleate Rhizoctonia (RS 521 and RU 56-8-AG-P) also significantly reduced the incidence of infected tubers in field experiments. Although treatments significantly reduced disease incidence and severity, total yield was unaffected. For the first time the efficiency of T. harzianum and np-R in reducing the incidence of black scurf on daughter tubers was demonstrated using naturally infested soil and contaminated seed tubers.

Effects of seed size, planting density and planting pattern on the severity of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes

SummaryThe effects of different seed sizes, planting densities and planting patterns on the transmission of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes were examined in five field experiments with cv. Estima in 1991–93.In all experiments, silver scurf was more severe with increase in seed size and planting density. At high planting density, silver scurf was less severe from a square planting pattern than from planting in wide rows. The incidence of black scurf also tended to increase with increase in seed size and was increased markedly high planting density.

Effect of haulm destruction supplemented by cutting off roots on the incidence of black scurf and skin damage, flexibility of harvest period and yield of seed potatoes in field experiments

In field experiments, supplementing chemical haulm destruction (CHD) with cutting off roots resulted in a lower incidence of black scurf and skin damage (ripping off the skin) at harvest date than CHD alone. The lower susceptibility to skin damage at harvest allowed harvesting to beging on an earlier date, when only a few sclerotia ofRhizoctonia solani had developed. Furthermore, black scurf often developed more slowly after haulm destruction if roots had been severed and this enabled harvesting to be postponed.

Post-harvest development of Rhizoctonia solani and its penetration of potato tubers in Northern Ireland

The incidence of black scurf and the number of sclerotia per tuber on progeny tubers increased significantly up to 4 weeks following haulm destruction. On tubers harvested 1, 4 and 8 weeks after haulm destruction and stored at 5, 10 or 15°C under low or high relative humidity, the incidence of black scurf and the number of sclerotia per tuber increased. The increase was least at 5° under low relative humidity. R. solani penetrates the periderm of tuber tissue intercellularly but does not spread beyond the phellogen, which collapses in advance of hyphal penetration. Infection through lenticels or common scab (Streptomyces scabies) lesions resulted in deeper penetration.