Maximum Colony Growth Research Articles

In‐vitro and in‐vivo assessment of biological control potential of nematode symbiont Xenorhabdus nematophila against Pseudomonas syringae, the causative agent of angular leaf spot of cucumber

AbstractBacterial diseases cause colossal losses in vegetable crops and are considered major limiting factors for the commercial production of vegetables around the globe. Among bacterial diseases, angular leaf spot of cucumber caused by Pseudomonas syringae is one of the most economically important diseases that cause substantial economic loss to the cucumber crop. In this study, the in‐vitro and in‐vivo effects of different strains (X1–X15) of the nematode symbiotic bacterium Xenorhabdus nematophila was determined on the growth of P. syringae in different selected media (TB, SB, SOB, SOC, YT and LB) and at different pH levels (6.5, 7.5 and 8.5) and on the incidence of angular leaf spot disease on potted cucumber plants. According to the results, maximum growth inhibition of P. syringe (25 mm) was observed in the case of strain X12, followed by strains X10 (23 mm), X8 (21 mm) and X6 (20 mm), while maximum colony growth was observed in the control. Moreover, this P. syringae growth inhibition by the X12 strain of X. nematophila was significantly maximum in SB medium and at pH 7.5. Results of the in‐vivo experiment with potted plants showed a maximum incidence (90%) of angular leaf spot disease in control plants, while a minimum disease incidence (15%) was observed for the plants treated with two times dilution of X. nematophila culture, followed by ten times (23%) and fifty times (35%). The overall results of this study demonstrate the inhibitory effect of X. nematophila on the growth and incidence of P. syringae and underscore its putative role in the biological management of plant pathogenic bacteria.

Management of Stemphylium Blight of Garlic (Allium sativum) by Botanicals

Stemphylium blight is an economically important disease of garlic causing significant reduction in crop yield. Usually, the management tactics relies on the use of synthetic chemicals. So, in this context, an eco-friendly approach was followed by using botanicals for controlling the disease. The antifungal effects of aqueous extracts were tested under in vitro and in vivo conditions. The fungitoxic activity of these botanicals was compared with the standard check (mancozeb 75 WP). The maximum colony growth inhibition was shown by mancozeb (62.4%), neem oil (43.3%) followed by neem extract (28.8%), aak (23.8%) and lantana (22.9%). The maximum spore germination inhibition was shown by mancozeb (56.6%), neem oil (40.2%) followed by neem extract (24.7%) and lantana (19.9%). The lowest disease severity was recorded in plants sprayed with mancozeb 75WP (14.8%) followed by the neem oil (34.8%) under in vivo conditions. The study revealed that neem oil can be a good candidate for managing this disease for avoiding the harmful effects of synthetic chemicals.

Modelling the effect of temperature and water activity on the growth rate of Aspergillus flavus and aflatoxin production in peanut meal extract agar

Aspergillus flavus is the predominant species that produce aflatoxins in stored peanuts under favourable conditions. This study aimed to describe the growth and aflatoxin production by two A. flavus strains isolated from imported raw peanuts and to model the effects of temperature and aw on their colony growth rate as a function of temperature and aw in Peanut Meal Extract Agar (PMEA). A full factorial design with seven aw levels (0.85–0.98 aw) and five temperature levels (20–40 °C) was used to investigate the growth and aflatoxin production. Colony diameter was measured daily for 28 days while AFB1 and total aflatoxin were determined on day 3, 7, 14, and 21. The maximum colony growth rate, μmax (mm/day) was estimated by using the primary model of Baranyi, and the μmax was then fitted to the secondary model; second-order polynomial and linear Arrhenius-Davey to describe the colony growth rate as a function of temperature and aw. The results indicated that both strains failed to grow at temperature of 20 °C with aw <0.94 and aw of 0.85 for all temperatures except 30 °C. The highest growth rate was observed at 30 °C, with 0.98 aw for both strains. The analysis of variance showed a significant effect of strain, temperature, and aw on the fungal growth and aflatoxin production (p < 0.05). Furthermore, both secondary models were in good agreement with the observed μmax. However, the polynomial model was found to be a better predictor of the experimental data. A similar pattern was observed in aflatoxin production but in a narrower range of temperature (25–35 °C) and aw (0.92–0.98 aw). The highest production of aflatoxins was observed on day 21 at 30 °C with the aw level of 0.98 for both strains. Overall, the current findings may help in improving the mycotoxin management and intervention strategies in peanuts, especially during storage.

EVALUATION OF DIFFERENT ESSENTIAL OILS AND BIO CONTROL AGENTS AGAINST ALTERNARIA ALTERNATA THE CAUSAL AGENT OF FRUIT ROT OF JUJUBE

This study was carried out on the evaluation of different essential oils and biocontrol agents against Alternaria alternata the causal agent of fruit rot. For the pathogenicity test against A. alternata was performed through cut and injection inoculation methods. The antifungal potential of different essential oils like turpentine, laung, neem and castus root was carried out at different doses i.e. 5, 10 and 15% by food poisoned method to find out the effective and suitable oil for the growth inhibition of A. alternata and evaluate the effect of some biocontrol agents on growth inhibition of A. alternata. The findings of this investigation stated that cut method of inoculation showed higher percentage (2.60) of rotting as compared to injection method of inoculation (2.35). Minimum colony growth of A. alternata (31.60, 21.25 and 15.16%) was examined under Laung oil at the dosage of 5, 10 and 15% followed by Neem oil (42.60, 31.60 and 21.30%), respectively. Maximum colony growth of A. alternata (62.71, 52.40 and 41.75%) was observed under Castus root oil at the dosage of 5, 10 and 15%. Zero growth of target pathogen was examined under Turpentine at 5, 10 and 15%. Under control the A. alternata showed (90 mm) colony growth. Minimum linear colony growth of A. alternata was observed for Hypoxylon Sp1 (50.31%), followed by Neurospora spp. (52.97%), Lasiodiplodia theobromae (54.7%), Chactomium subaffine (57.07%) and Fusarium sp. (65.4%). Maximum mycelial colony growth (90%) was recorded in control. Based on present investigation, Similarly, for controlling the linear colony growth of A. alternata under in vitro conditions Turpentine oil ranked 1st, Laung oil ranked 2nd, Neem oil ranked 3rd, Castus root oil ranked 4th.

Preliminary and Biochemical Characterization of Bacterial Strains Isolated from Ramie Cane Soils

For the present study a total of 18 bacterial isolates were isolated from Ramie canes soils. Preliminary characteristics like colony characteristics and substrate concentrations were studied for the microorganisms. Physicochemical factors affecting the bacterial growth. The three seasons winter, summer and rainy seasons were also affected the growth of the bacteria. Various substrates like starch peptone, xylan peptone, Glycerol, Aspargine, glucose nitrate agar, carboxymethyl cellulose agar and pectin peptone agar media were studied. Maximum colony growth was recorded in pectin peptone agar media. Cream white, orange, red, yellow, lemon yellow and watery white colonies were recorded. The size of the bacterial strains was recorded in 1-55 mm in diameter. All the strains were entire lobed, convex having smooth and rough surface. of the 18 strains 11 were gram positive rods and the remaining strains were negative rods. Among the 18 strains, we were selected six strains for further studies like effect of seasons on growth and amino acid infilteration of bacteria. Maximum growth was recorded in winter season with 85.0 colony count in the presence of CCLS strain. There are 10 amino acids were introduced into the bacteria, with maximum growth was WCES bacterial strain. The results of this study reveal that the soil microflora associated with the ramie cane soils. These bacterial strains were used in the process of decortication and degumming.

Isolation and characterization of Macrophomina phaseolina isolates prevailing in Sindh, Pakistan

Macrophomina phaseolina (Tassi) Goid is economically important fungal pathogen with wide host range. In this study we found morphological and phenotypical variation among isolates of the fungus infecting sunflower crop in Sindh province of Pakistan. Thirty two M. phaseolina isolates were obtained from infected plant samples of sunflower collected from different ten districts viz., Badin, Thatta, Hyderabad, Tando Muhammad Khan, Shaheed Benazirabad, Mirpurkhas, Sanghar, Dadu, Sukkur and Khairpur. Significant variation in characteristics was noticed among collected isolates. They were usually black, blackish-gray, grayish-black and gray in colony color. Generally three growths pattern; dense, feathery and restricted were seem. Among them dense was most common (50.0%) followed by feathery (34.36%) and restricted (15.64%). Maximum colony growth (90.0%) and minimum (65.0%) was recorded after 7 days of inoculation on medium. Feathery growth was generally fast and restricted growth was slow. Maximum average linear colony growth (13 mm) and minimum (9 mm) growth was noted. Isolates showed significantly varied sizes of microsclerotia. Maximum sclerotia size (124.0 µm) was obtained from fields of Badin while, minimum size of microsclerotia (83.0 µm) from sunflower fields of Sukkur. Microsclerotia from dense growth pattern were black and big in size and small microsclerotia from gray growth pattern. Keywords: Charcoal rot; Isolates and Characterization; Macrophomina phaseolina; Sunflower http://dx.doi.org/10.19045/bspab.2018.700152

In-vitro efficacy of bio-control agent and essential oils against leaf blight of chickpea caused by Alternaria alternata

Alternaria leaf blight is one of the most destructive foliar diseases of chickpea in different countries including Pakistan and has caused huge losses ranging from 5 to 100% around the world. This study was carried out to check the in-vitro effectiveness and sustainability of a bio-control agent Trichoderma viride and some essential oils like Castor, Jasmine, Clove, Sesame, Neem, Coconut, Henna, Black seed, and Mint oil at different doses of 1%, 2%, 4%, and 6% by food poisoned method against the mycelial colony growth inhibition of A. alternata which causes leaf blight in chickpea. The results indicate that maximum germination (80%) was recorded in control, (63%) under soil infestation and a minimum germination of (60%) was recorded in seed infestation. Maximum shoot weight (0.5630 g) in control, (0.2751 g) under soil infestation and (0.2064 g) in seed infestation. Maximum root weight (0.5937 g) in control, (0.4359 g) under soil infestation method, and (0.4102 g) in seed infestation method. Maximum shoot length (20.00 cm) in control, (10.23 cm) under soil infestation method and (7.053 cm) in seed infestation method. Maximum root length (7.19 cm) in control, (4.80 cm) under soil infestation method and (4.80 cm) in seed infestation. Bio-control agent Trichoderma viride showed (74.44%) growth inhibition compared to control (1.00%) growth inhibition of A. alternata. Maximum colony growth inhibition of A. alternata was (80.00%) Sesame, Coconut (77.04%), Henna (72.59%), Mint (66.07%), Black seed (71.85%), Jasmine (64.07%), Clove (70.74%), Neem (73.33%), Castor (58.89%) and minimum of (1.00%) was recorded in control. The results of this study will be very helpful for researchers and farming community for better management of this destructive disease of chickpea.

Antifungal exploitation of fungicides against Fusarium oxysporum f. sp. capsici causing Fusarium wilt of chilli pepper in Pakistan.

The research was conducted to evaluate in-vitro efficacy of numerous fungicides against Fusarium oxysporum f. sp. capsici. In present research, six treatments (T) viz. Carbendazim, Benomyl, Topsin-M, Difenoconazole, Nativo, and Alliete along with control, various concentrations (C), days (D), and their interactions, i.e., (T × C), (T × D), (C × D), and (T × C × D) were exploited in a laboratory through food poison technique. Alliete expressed maximum colony growth (1.93cm) as compared to all other fungicides with respect to control. Interaction between treatments and concentration (T × C) exhibited maximum colony growth of all treatments (Carbendazim, Benomyl, Topsin-M, Difenoconazole, Nativo, and Alliete), i.e., 0.87, 1.23, 1.73, 2.20, 2.53, and 2.93cm at 300ppm as compared to 500 and 700ppm concentrations, respectively. Similar trend was also observed concerning interaction between (fungicides × days) and (tested concentrations × days). Results of the present study revealed that among tested fungicides, Carbendazim at 700ppm expressed significant reduction in fungal growth.

Optimisation of Fungal Inoculum for Inoculation of Gyrinops walla for Inducing Agarwood Formation

Various fungi including Aspergillus and Fusarium induce agarwood resin formation as a selfdefense mechanism in Gyrinops walla, a tree belongs to the family Thymelaeaceae. Since artificial fungal inoculation induces to form agarwood, there is a growing need for potential fungal inocula to promote the formation of agarwood resin in G. walla. The aim of the study was to determine the optimum inoculum densities of Aspergillus sp. and Fusarium sp. which can act as inducing agents of agarwood resin formation in G. walla. Cultural conditions for optimum growth, sporulation, germination, and inoculum density and incubation period of selected two species of Aspergillus and Fusarium were examined. The radial growth of the fungal colony on different culture media (PDA, YEGA, MEA and CDA) was measured to determine the suitable medium for the growth. Sporulation on different media was examined at different time intervals after incubation at room temperature. Percentage of spore germination was determined using freshly prepared spore suspension in water and in potato dextrose broth by counting the germinated spores. Optimum spore density for the germination was measured examining five different spore densities ranging from 103 ml-1 to 107 ml-1. The pH of the suitable medium and wood of the live stem (aqueous wood extract) of the tree was measured. Both Aspergillus sp. and Fusarium sp. showed maximum colony growth on PDA medium. However, the colony growth and the sporulation were much faster in Aspergillus than in Fusarium on this medium. The pH of the live stem of the tree was recorded as 6.08 which is approximately equal to the pH of PDA medium 6.22. The highest spore germination for Aspergillus was at the density of spores 105 ml-1 while Fusarium at 107 ml-1. Both fungal species reached the highest percentage of spore germination after 12 hours of incubation. Results reveal that the spore densities of 105 ml-1 and 107 ml-1 of water are optimum inoculum densities for Aspergillus and Fusarium respectively. The recorded optimum inoculum densities of Aspergillus and Fusarium can be recommended as potential inocula for inducement of agarwood in G.walla. Keywords: Aspergillus, Fusarium, Gyrinops walla, Agarwood, Inoculum density, Sporulation

Morphological and Molecular Variability of Rhizoctonia solani Isolates Causing Banded Leaf and Sheath Blight in Maize

Twenty seven isolates of Rhizoctonia solani causing Banded Leaf and Sheath Blight in maize were collected from different maize varieties and one from rice grown in various regions of Telengana State, India for easy breeding task. The isolates were analysed for their morphological and genetic characterization. The hyphal width varied from 5.00 (RS2, RS20) to 7.97 μm (RS10) of rice isolate (7.34 μm). The isolates RS7, RS 8, RS9 (Karimnagar), RS10, RS11, RS12 (Khammam) RS16 (Krishna) and RS26 (Kurnool) and one rice isolate RS28 produced barrel shaped monilioid cells. The clamp connection was present only in RS1 isolate from Pragnyapur mandal of Medak district. The three isolates RS16, RS17, RS18 from Krishna district and rice isolate RS28 recorded maximum colony growth of 90.00 mm within 48 h of incubation. The colour of most isolates varied from light grey to brown while the rice isolate showed a typical yellowish brown shade. The sclerotial number per 5.00 mm culture disc of test isolates ranged from between (7.00) to (17.67). Their size varied between 0.21 μm (RS 24) and 1.57 μm (RS11). The rice isolate RS28 recorded highest (19.00) sclerotial count compared to that of maize isolates. Sclerotial colour in all isolates except for RS 24 was yellowish brown to dark reddish brown whereas the rice isolate was dark yellowish brown. Molecular characterization of the test isolates using RAPD markers with UPGMA exhibited two major clusters with 66 to 90% genetic similarity. Art ic le History

Modelling the effect of water activity and temperature on growth rate and aflatoxin production by two isolates of Aspergillus flavus on paddy

This study was conducted to characterize the growth of and aflatoxin production by Aspergillus flavus on paddy and to develop kinetic models describing the growth rate as a function of water activity (a(w)) and temperature. The growth of A. flavus on paddy and aflatoxin production were studied following a full factorial design with seven a(w) levels within the range of 0·82-0·99 and seven temperatures between 10 and 43°C. The growth of the fungi, expressed as colony diameter (mm), was measured daily, and the aflatoxins were analysed using HPLC with a fluorescence detector. The maximum colony growth rates of both isolates were estimated by fitting the primary model of Baranyi to growth data. Three potentially suitable secondary models, Rosso, polynomial and Davey, were assessed for their ability to describe the radial growth rate as a function of temperature and a(w). Both strains failed to grow at the marginal temperatures (10 and 43°C), regardless of the a(w) studied, and at the a(w) level of 0·82, regardless of temperature. Despite that the predictions of all studied models showed good agreement with the observed growth rates, Davey model proved to be the best predictor of the experimental data. The cardinal parameters as estimated by Rosso model were comparable to those reported in previous studies. Toxins were detected in the range of 0·86-0·99 a(w) with optimal a(w) of 0·98 and optimal temperature in the range of 25-30°C. The influences of a(w) and temperature on the growth of A. flavus and aflatoxin production were successfully characterized, and the models developed were found to be capable of providing good, related estimates of the growth rates. The results of this study could be effectively implemented in minimizing the risk of aflatoxin contamination of the paddy at postharvest.

Predictive modelling of temperature and water activity (solutes) on the in vitro radial growth of Botrytis cinerea Pers

The objective of this work was to develop validated models predicting the ‘in vitro’ effect of a w and temperature on the radial growth of Botrytis cinerea. The growth rate ( g, mm d − 1 ) of B. cinerea was calculated at three incubation temperatures (25 °C, 15 °C, 5 °C) and six water activities (ranging from 0.995 to 0.890). The water activity was adjusted with glucose, NaCl, glycerol, or sorbitol. Statistical analysis showed a significant effect of temperature, solute, a w, and their two- and three-way interactions on the growth rate. No growth was observed at a w = 0.93 in the presence of NaCl or at 0.89 in the presence of a non-ionic solute. The maximum colony growth rate decreased when the incubation temperature and water activity was lowered. Secondary models, relating the colony growth rate with a w or a w and temperature were developed. Optimum a w values for growth ranged from 0.981 to 0.987 in glycerol-, sorbitol-, or glucose-modified medium and were close to 1 in NaCl-modified medium. A quadratic polynomial equation was used to describe the combined effects of temperature and a w on g (mm d − 1 ) in the presence of each solute. The highest and lowest radial growth rates were observed in models based on glucose and NaCl respectively, whatever the incubation temperature. All models prove to be good predictors of the growth rates of B. cinerea within the limits of experiments. The quadratic polynomial equation has bias factors of 0.957, 1.036, 0.950, and 0.860 and accuracy factors of 1.089, 1.070, 1.120 and 1.260 in media supplemented with glucose, NaCl, glycerol and sorbitol respectively. The results from modelling confirm the general finding that a w has a greater influence on fungal growth than temperature.

Growth modelling of heat-resistant fungi: the effect of water activity

Growth of three strains of heat-resistant fungi, Byssochlamys fulva, Neosartorya fischeri and Talaromyces avellaneus, was studied at 25°C at eight or nine water activities ( a w) adjusted with sucrose between 0.995 and 0.85. The flexible growth model of Baranyi describing the change in colony diameter (mm) with respect to time was first fitted to measured growth data and from the fitted curves the maximum colony growth rates were estimated. These values were fitted with respect to a w to predict colony growth rates at any a w within the range tested. Optimum a w values of 0.986, 0.985, and 0.990 for growth, and maximum colony growth rates of 12.6, 13.2 and 20.2 mm d −1, respectively, were calculated. The time to reach a colony diameter of 3 mm and the optimum a w for each strain were also calculated. The results can be applied to the prevention of spoilage of canned fruit or juices and other heat processed fruit based products.

Predicting fungal growth: the effect of water activity on Aspergillus flavus and related species

Growth of four species belonging to Aspergillus Section Flavi (A. flavus, A. oryzae, A. parasiticus and A. nomius) was syudied at 30°C at ten water activities (a w) between 0.995 and 0.810 adjusted with equal mixtures of glucose and fructose. Colony diameters were measured at intervals and plotted against time. A flexible growth model describing the change in colony diameter (mm) with respect to time was first fitted to the measured growth data and from the fitted curves the maximum colony growth rates were calculated. These values were then fitted with respect to a w to predict colony growth rates at any a w within the range tested. The optimum a w for each species and time to reach a colony diameter of 3 mm were also calculated.

Ecology of Pectinatella magnifica (Bryozoa) in an Alabama Oxbow Lake: Colony Growth and Association with Algae

Colonies of the bryozoan Pectinatella magnifica commonly occur on submersed substrata in an oxbow lake (Touson Lake) in the floodplain of the Black Warrior River, Alabama. Seasonal growth patterns, substratum preference, and potential effects of bryozoan colonies on algal assemblages attached to artificial and natural substrata were determined. Colony growth on artificial substrata (pine sticks) and natural ones (dead cypress twigs and aquatic plants) was monitored at biweekly intervals from the appearance of bryozoans during early autumn to the loss of colonies from substrata in late December. Maximum colony growth occurred during late September and early October. Some colonies reached up to 65 cm in length and 10 cm in diameter. Colonies showed no preference among the substrata examined, but young colonies always developed first on the shaded side of the substratum. The presence of bryozoan colonies affected the composition of attached algae. Blue-green algae (90%) dominated on surfaces enclosed by the colonies and also within the gelatinous colony matrix, whereas surfaces uncolonized by Bryozoa developed mixed communities of diatoms (78%), blue-green algae (12%), and green algae (11%).

The effects of sodium saccharin with and without N-methyl- N-nitrosourea co-treatment on anchorage-independent growth of human diploid fibroblasts

In order to examine the effects of sodium saccharin on in vitro cell transformation, neonatal human diploid fibroblasts were treated with various levels of the compound during specific phases of a synchronized cell cycle, then subcultured for a suitable expression period, and assayed for anchorage-independent growth in soft agar. The dose-relatedness and cell-cycle-dependency of the effects were determined both in cells treated with sodium saccharin and in cells co-treated with saccharin and the direct-acting carcinogen N-methyl- N-nitrosourea (MNU). Cell treatment with saccharin at ng/ml levels for 10 hr following release from a metabolic block (G 1 phase), with or without MNU treatment (70 μg/ml) at 10 hr, was an effective transforming regimen. Continuous saccharin treatment for 12 days (from the end of the synchronized cell cycle until seeding into soft agar) was often as effective as G 1 exposure, but treatment during the metabolic block or during S-phase and mitosis was always less effective. The dose-relatedness of the effects was similar both for saccharin-induced transformation at ng/ml treatment levels, and for co-transformation with MNU. Maximum colony growth (>100/50,000 seeded cells) was observed at a concentration of 50 ng/ml, and a variable, but decreased, response was seen at higher and lower exposures. MNU co-treatment served to maintain the transformation response at higher (μg/ml) saccharin levels at which saccharin alone was not effective. Thus, sodium saccharin demonstrated significant transforming activity over a wide dose range, both when used alone, and in combination with MNU.

Physiological studies on Alternaria porri and Stemphylium vesicarium causing purple blotch complex in onion

Effect of different culture media, pH levels and natural substrates on mycelial growth and sporulation of Alternaria porri and Stemphylium vesicarium, incitants of purple blotch complex of onion was investigated. Maximum colony growth of A. porri and S. vesicarium was recorded on oat meal agar and Richard’s agar while, oat meal agar and V8 juice agar recorded the maximum sporulation, respectively. Similarly, pH 5.0 and 6.0 on potato dextrose agar (PDA) recorded the maximum colony growth of A. porri and S. vesicarium, respectively. None of the pH levels on PDA supported the sporulation of A. porri while maximum sporulation of S. vesicarium was recorded on pH 5.0. Onion seed stalks and garlic leaves were found to be the most suitable natural substrates for mass multiplication of A. porri and S. vesicarium, respectively. The present findings are useful for preparation of inoculums required for resistance breeding and fungicidal evaluation against purple blotch complex.