Bacterial Wilt Disease Incidence Research Articles

Short Communication: Peanut introduced germplasm response against Ralstonia bacterial wilt disease

Nugrahaeni N, Rahayu M. 2017. Short Communication: Peanut introduced germplasm response against Ralstonia bacterial wilt disease. Nusantara Bioscience 9: 138-140. Peanut germplasm introduction is a means to increase genetic variability within the germplasm collection. However, its utilization is frequently hampered by its susceptibility to bacterial wilt disease, the main disease in peanut cultivation in Indonesia. The aim of the present study was to assess peanut introduced germplasm response against Ralstonia bacterial wilt disease. One hundred and fifty peanuts introduced germplasm were planted on the bacterial wilt endemic area in Pati, Central Java, Indonesia. Pre-planted isolation revealed that the bacterial population in the soil was considered high, i.e. 2.6x106 cfu.g-1. The trial was laid out in RCBD, replicated two times. Each accession was planted in two rows of 4-m length with 40 cm x 10 cm plant spacing. The crop received a basal dose of Phonska at 300 kg.ha-1 and SP36 at 100 kg. ha-1. Observations were made on bacterial wilt disease incidence and agronomic traits. Research result showed that the introduced germplasm was highly variable in their responses to the wilt disease with wilt incidence ranging from 0% to 100%. Twenty-three accessions, out of 150, were resistant to the disease. Those resistant accessions showed good agronomic characters and gave dry pod yield in the range of 1.56-4.5 t.ha-1. This results indicated that introduced germplasm could be used in increasing variability of bacterial wilt resistant gene source as well as in increasing yield potential in developing new peanut improved cultivars.

Cendawan Endofit yang Potensial Meningkatkan Ketahanan Cabai Merah terhadap Penyakit Layu Bakteri

Ralstonia solanacearum has been known to cause bacterial wilt disease on chili pepper. Despite many reports on the potential use of endophytic fungi to induce plant resistance, its utilization to suppress bacterial wilt disease of chili has not been widely reported. The aims of this research was to screen potential endophytic fungi that may increase chili resistance against bacterial wilt disease. Selection of endophytic fungi was done using in vivo and antibiosis test. Strains of fungi were considered the most potent in suppressing the development of bacterial wilt in chilli were identified. Ten out of 62 isolates of endophytic fungi gave the highest suppression on chilli’s bacterial wilt disease. Most strains of endophytic fungi were able to suppress the development of bacterial wilt disease, but not always positively correlated to the vegetative and generative growth of chilli. Based on the level of disease intensity and the growth of plants were obtained three strains of endophytic fungi that considered potentially suppress the incidence of bacterial wilt disease. The three isolates was identified as Fusarium solani f.sp. phaseoli (AC-2.13 and AC-4.4) and Trichoderma asperellum (AC-3.18) using morphology and molecular characters. Although all three selected isolates were able to suppress bacterial wilt disease in this study, but application of F. solani f.sp. phaseoli should be considered in practical use since it is generally known as the causal agent of root rot disease of beans

Significant relationship between soil bacterial community structure and incidence of bacterial wilt disease under continuous cropping system

Soil bacteria are very important in biogeochemical cycles and play significant role in soil-borne disease suppression. Although continuous cropping is responsible for soil-borne disease enrichment, its effect on tobacco plant health and how soil bacterial communities change are yet to be elucidated. In this study, soil bacterial communities across tobacco continuous cropping time-series fields were investigated through high-throughput sequencing of 16S ribosomal RNA genes. The results showed that long-term continuous cropping could significantly alter soil microbial communities. Bacterial diversity indices and evenness indices decreased over the monoculture span and obvious variations for community structures across the three time-scale tobacco fields were detected. Compared with the first year, the abundances of Arthrobacter and Lysobacter showed a significant decrease. Besides, the abundance of the pathogen Ralstonia spp. accumulated over the monoculture span and was significantly correlated with tobacco bacterial wilt disease rate. Moreover, Pearson's correlation demonstrated that the abundance of Arthrobacter and Lysobacter, which are considered to be beneficial bacteria had significant negative correlation with tobacco bacterial wilt disease. Therefore, after long-term continuous cropping, tobacco bacterial wilt disease could be ascribed to the alteration of the composition as well as the structure of the soil microbial community.

Altering Transplantation Time to Avoid Periods of High Temperature Can Efficiently Reduce Bacterial Wilt Disease Incidence with Tomato.

Tomato bacterial wilt caused by Ralstonia solanacearum bacterium is a severe problem in Southern China, where relatively high environmental temperatures commonly prevails during the crop seasons. Previous research has indicated that bacterial wilt disease incidence generally increases during the warm months of summer leading to reduced tomato yield. Moreover, the efficacy of bio-organic fertilizers (BOFs)–organic compost fortified with pathogen-suppressive bacteria—is often lost during the periods of high environmental temperatures. Here we studied if the disease incidence could be reduced and the BOF performance enhanced by simply preponing and postponing the traditional seedling transplantation times to avoid tomato plant development during periods of high environmental temperature. To this end, a continuous, two-year field experiment was conducted to evaluate the performance of BOF in two traditional (late-spring [LS] and early-autumn [EA]) and two alternative (early-spring [ES] and late-autumn [LA]) crop seasons. We found that changing the transplantation times reduced the mean disease incidence from 33.9% (LS) and 54.7% (EA) to 11.1% (ES) and 7.1% (LA), respectively. Reduction in disease incidence correlated with the reduction in R. Solanacearum pathogen density in the tomato plant rhizosphere and stem base. Applying BOF during alternative transplantation treatments improved biocontrol efficiency from 43.4% (LS) and 3.1% (EA) to 67.4% (ES) and 64.8% (LA). On average, the mean maximum air temperatures were positively correlated with the disease incidence, and negatively correlated with the BOF biocontrol efficacy over the crop seasons. Crucially, even though preponing the transplantation time reduced the tomato yield in general, it was still economically more profitable compared to LS season due to reduced crop losses and relatively higher market prices. Preponing and postponing traditional tomato transplantation times to cooler periods could thus offer simple but effective way to control R. solanacearum disease outbreaks.

Bahasa Indonesia

One of the factors affected production of tomato is the incidence of bacterial wilt disease caused by Ralstonia solanacearum . An alternative control to manage the disease which is environmentally friendly is the use of biocontrol agents. Application of endophytic bacteria ( Staphylococcus epidermidis BC4) and plant growth promoting rhizobacteria ( Pseudomonas fluorescens RH4003 and Bacillus subtilis AB89) as biocontrol of tomato bacterial wilt was expected to be an alternative method. The objective of this study is to evaluate the interaction among endophytic bacteria and PGPR to suppress the development of bacterial wilt disease ( R. solanacearum ) and promoting the growth of tomato. Bacterial treatment which caused the highest suppression on disease incidence was single application of P. fluorescens RH4003. Disease index caused by S. epidermidis BC4 and P. fluorescens RH4003 applied individually was up to 41.18 dan 45.88%, respectively. Interaction between the endophytic bacteria and both of the PGPRs were antagonistic.

Evaluation of rhizosphere bacteria and derived bio-organic fertilizers as potential biocontrol agents against bacterial wilt (Ralstonia solanacearum) of potato

Potato bacterial wilt (Ralstonia solanacearum) is a soil-borne disease that affects the potato plant (Solanum tuberosum) worldwide and causes serious economic losses in southern China. The objective of this study is to study the effect of bacterial antagonists and bio-organic fertilizers on potato bacterial wilt and rhizosphere soil microbial population. In the present study, pot and field experiments were conducted to evaluate the LH23 (Bacillus amyloliquefaciens) and LH36 (Bacillus subtilis) strains and their derived bio-organic fertilizers (BIO23 and BIO36) as potential biocontrol agents against potato bacterial wilt. BIO23 and BIO36 decreased the incidence of bacterial wilt disease and increased potato yields. In pot experiments, the disease incidence of BIO23 and BIO36 was 8.9 % and 11.1 % respectively, much lower than the control (57.7 %). The biocontrol efficiency of BIO23 was 84.6 %, which was the most successful treatment and BIO36 was the second with a biocontrol efficiency of 80.8 %. The increased percentages of potato yields when compared with the control were 63.5 % (BIO23), 64.7 % (BIO36) 34.8 % (LH23), 33.6 % (LH36) and 20.7 % (OF). The counts of antagonists, bacteria and actinobacteria in the rhizosphere soil were significantly increased in BIO23 and BIO36 treatments, whereas the counts of R. solanacearum and fungi in the soil in the both treatments decreased. In field experiments, 70 days after treatment, the biocontrol efficacies of BIO23 and BIO36 treatments were 92.0 % and 84.0 %, and the yield increases of BIO23 and BIO36 treatments were 42.3 % and 28.8 %, respectively, when compared with the organic fertilizer treatment. In addition, the changes in the microbial populations were the same as those observed in the greenhouse experiment. Potato bacterial wilt could be well controlled by the application bio-organic fertilizer containing a specific antagonist, mainly through the alternation of soil microbial community

Applications of Bacillus subtilis and Trichoderma spp. for controlling the potato brown rot in field

Possibilities of biological control of brown rot disease caused by Ralstonia solanacearum were investigated in a greenhouse and in a naturally infested commercial potato field. Three biocontrol agents (BCAs) namely Bacillus subtilis, Trichoderma album and Trichoderma hamatum, isolated from commercial potato field and identified in the Department of Plant Pathology, National Research Centre in Egypt. In the greenhouse experiment, B. subtilis as seed tuber treatment significantly reduced the bacterial wilt disease incidence in potato cvs. Diamante and Spounta, followed by T. hamatum and T. album compared with the controls. Three field experiments were carried out as follows: (i) the first experiment during the winter of 2006/2007 seasons, (ii) the second during the summer of the 2007 season, and (iii) the third during the winter of 2007/2008 seasons. The BCA treatments improved the vegetative growth parameters such as plant height, stem number/pit and leaf number/plant compared with the control plants. The treatments also enhanced the average tuber weight and tuber yield/plant. Field application of the BCAs as tuber and/or soil treatments significantly reduced the brown rot incidence and bacterial wilt severity. In the first experiment, the BCA treatments reduced the brown rot incidence in potato cv. Diamante from 15.3 to 21.3% compared with 21.9% in the untreated plants. In the second experiment, the percentage of bacterial wilt severity (BWS) in treated potato cv. Nicola was in the range 18.0–22.0% 60 days after planting compared with 38.0% in the control plants. The percentage disease control was in the range 42.1–52.6%. The brown rot incidence (BRI) was in the range 21.2–46.3% as tuber treatment and 18.9–29.1% as soil treatment in treated potato plants compared with a disease incidence of 60% in the control plants. In the third experiment, the BWS was less than 8% in treated potato cv. Diamante, compared with 16% in control plants 60 days after planting. T. hamatum completely protected the potato tubers against brown rot, than T. album and B. subtilis as well as the control. The BCA as soil treatments were more effective than tuber treatments for decreasing the BRI in potato and enhancing the growth and tuber yield parameters. This study revealed that B. subtilis, T. hamatum and T. album are promising as BCAs which are effective under field conditions for controlling potato brown rot.

Indirect costs of a nontarget pathogen mitigate the direct benefits of a virus-resistant transgene in wild Cucurbita

Virus-resistant transgenic squash are grown throughout the United States and much of Mexico and it is likely that the virus-resistant transgene (VRT) has been introduced to wild populations repeatedly. The evolutionary fate of any resistance gene in wild populations and its environmental impacts depend upon trade-offs between the costs and benefits of the resistance gene. In a 3-year field study using a wild gourd and transgenic and nontransgenic introgressives, we measured the effects of the transgene on fitness, on herbivory by cucumber beetles, on the incidence of mosaic viruses, and on the incidence of bacterial wilt disease (a fatal disease vectored by cucumber beetles). In each year, the first incidence of zucchini yellow mosaic virus occurred in mid-July and spread rapidly through the susceptible plants. We found that the transgenic plants had greater reproduction through both male and female function than the susceptible plants, indicating that the VRT has a direct fitness benefit for wild gourds under the conditions of our study. Moreover, the VRT had no effect on resistance to cucumber beetles or the incidence of wilt disease before the spread of the virus. However, as the virus spread through the fields, the cucumber beetles became increasingly concentrated upon the healthy (mostly transgenic) plants, which increased exposure to and the incidence of wilt disease on the transgenic plants. This indirect cost of the VRT (mediated by a nontarget herbivore and pathogen) mitigated the overall beneficial effect of the VRT on fitness.

Control of Bacterial Wilt Disease of Tomato Through Integrated Crop Management Strategies

Tomato cultivation is severely affected by bacterial wilt disease caused by the soilborne pathogen Ralstonia solanacearum (previously known as Pseudomonas solanacearum Smith). Effects of rotation of tomato (Lycopersicon esculentum Mill.) with other crops on soil populations of R. solanacearum and on bacterial wilt disease incidence of tomato were evaluated in the field. Monocropped Cassava (Manihot esculenta Crantz), Mucuna puriens L., Crotalaria juncea L., and intercrops of Cassava/Crotalaria, Cassava/Mucuna, and a natural grass mix (control) were rotated with the tomato cvs. Mira, Ronita, Roma VFN, and Ibadan Local. Monocropped Mucuna significantly reduced soil population of R. solanacearum by the end of the rotation period, whereas the natural grass rotation had the highest population of the pathogen. Other crops with the exception of monocropped cassava also reduced the pathogen soil population. The incidence of wilt was delayed in cvs. Mira, Roma VFN, and Ronita compared to ‘Ibadan Local’, but all were 80% or more infected after 8 weeks.

Winter Cover Crops Reduce Bacterial Wilt of Flue-cured Tobacco

Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease for tobacco farmers in the southeastern USA. The lack of suitable land for crop rotation and increased area of production on farms has resulted in shorter rotations, and increased losses due to bacterial wilt. Cover crops are rarely grown immediately before a tobacco crop because soil fumigation for nematode control necessitates early destruction of the cover crop. The microbial activity associated with growing winter cover crops may alter populations of R. solanacearum. This field study evaluated vetch, canola, or rye winter cover crops for suppression of bacterial wilt. Averaged over two tobacco crops, vetch preceding tobacco reduced bacterial wilt disease incidence 33% and increased crop yield and value (37% and 41%, respectively) when compared to a winter fallow. A two-year rotation involving both winter cover and summer rotation crops also showed that winter cover crops increased yields and reduced disease incidence when used following a nonsusceptible summer crop. Soybean rotation followed by a vetch winter cover reduced disease incidence 73% and increased yields 132% when compared to tobacco without a summer soybean rotation and with a bare winter fallow. Data suggest that losses to bacterial wilt can be reduced significantly with use of a vetch winter cover. Accepted for publication 14 February 2007. Published 22 May 2007.

Influence of Methyl Bromide Fumigation on Microbe-induced Resistance in Cucumber

Field experiments were conducted to evaluate growth promotion and induced systemic disease resistance (ISR) in cucumber mediated by plant growth-promoting rhizobacteria (PGPR) with and without methyl bromide soil fumigation. In both fumigated and nonfumigated plots, numbers of cucumber beetles, Acalymma vittata (F.), and the incidence of bacterial wilt disease, caused by the beetle-transmitted pathogen Erwinia tracheiphila , were significantly lower with PGPR treatment compared with the nonbacterized control. However, in PGPR-treated plots, the incidence of bacterial wilt was more than 2-fold lower in the nonfumigated treatments compared with fumigated treatments, indicating that the level of PGPR-mediated ISR was greater without methyl bromide fumigation than with methyl bromide. Cucumber plant growth at 21 days after planting was greater in fumigated plots than in nonfumigated plots; however, plant height values in the nonfumigated, PGPR treatments and the fumigated, PGPR treatments were equivalent. This suggests that PGPR treatment compensated for delayed plant growth that often occurs in nonfumigated soil. These results indicate that, in cucumber production systems, withdrawal of methyl bromide will not negatively impact PGPRmediated ISR, and also that PGPR may have potential as an alternative to methyl bromide fumigation.

Integration of Soil Solarization and Biological Control with a Fluorescent Pseudomonas Sp. for Controlling Bacterial Wilt Ralstonia solanacearum (E. F. Smith) Yabuuchi et al. of Ginger

Soil solarization after irrigation, 45 days prior to planting, is found to be effective in reducing bacterial wilt disease incidence in a wilt sick field in Wayanad district of Kerala (16.02 % compared to 21.10 % in control). The maximum mean difference in temperature taken at 14.00 h. was 12.2° C in plots mulched after irrigation. Significant reduction in the soil microbial population was observed during solarization. Seed treatment with Pseudomonas fluorescens strain EM 85 along with solarization decreased the wilt incidence to 7.42 per cent and increased the yield to 29.42 U ha compared to 19.51 t/ha in control. Soil amendment with neem cake before solarization provide no additional advantage in controlling the disease.

Imidacloprid Effects on Acalymma vittata (Coleoptera: Chrysomelidae) and Bacterial Wilt in Cantaloupe

The systemic nitroguanidine insecticide imidacloprid was investigated in cantaloupes, Cucumis melo L. variety reticulatus, for management of Acalymma vittata (F.) and bacterial wilt caused by Erwinia tracheiphila (E. F. Smith) Holland that is vectored by this beetle. The influence of management strategies using imidacloprid upon plant growth and development, beetle population dynamics, and bacterial wilt disease incidence and severity was evaluated. Application of imidacloprid to seedlings at higher doses caused short-term marginal leaf necrosis, and biomass of seedlings was reduced in an approximately linear pattern with increasing dose on a log scale up to 0.01 g (AI) per plant. Application to seedlings at doses low enough to avoid any phytoxicity resulted in adult A. vittata mortality rates that declined exponentially with time. Exponential decay models of bioassay data suggested ≍11d of 100%adult mortality was achieved with low rates applied to seedlings before transplanting. Applications to seedlings delayed adult immigration, and the combination of seedling application and limited foliar sprays resulted in significant increases in yield. Addition of imidacloprid at low rates to seedlings combined with 2 foliar sprays, or application to seedlings combined with an application through drip irrigation and 2 foliar sprays, was not effective in reducing the proportion of cantaloupe plants that showed bacterial wilt symptoms but did significantly reduce severity of the disease. The results suggest that low rates of imidacloprid applied before or near the time of transplanting, at times combined with few foliar sprays, could dramatically improve crop productivity via influence upon both a herbivore and a plant pathogen vectored by the herbivore.