eChapters

ABSTRACT

Trichoderma spp. are important group of fungi which are mycoparasitic on several plant pathogenic fungi. Trichoderma spp. are, therefore, used as commercial biofungicides. Genetic manipulation through induced mutagenesis and molecular cloning are two important tools in improving the biocontrol potential of Trichoderma spp. In the present study, attempts were made to induce genetic variability in Trichoderma virens using UV- induced mutagenesis. In the process, a simple protocol was developed for obtaining high frequency mutations in Trichoderma virens. Using a UV-crosslinker, four stable mutants of T. virens have been developed, which are distinctly different from the wild type in appearance and in antagonism against Rhizoctonia solani and Sclerotium rolfsii. One of the mutants, designated as TI is very slow in growth, but sporulates densely, and retained its mycoparasitic potential against R. solani. Though all the mutants were able to antagonize R. solani, all of them were overgrown by the test pathogen S. rolfsii. These mutants could be used to identify genes involved in growth and conidiation in T. virens.

ABSTRACT

Soil samples from pepper growing tracts of six districts of Kerala viz., Ernakulam, Idukki, Kollam, Kottayam, Thrissur and Pathanamthitta were assessed for total microbial population. Thirty two fungi, 17 bacteria and three actinomycetes were isolated and studied for their antagonistic potential against the foot rot pathogen, Phytophthora capsici. All the 32 fungal isolates were found antagonistic to the pathogen and majority of them belonged to the genera Trichoderma, Aspergillus, Penicillium, Fusarium, Pythium, Cunninghamella and Rhizopus. Among these maximum inhibition was recorded by Trichoderma spp. which included T. pseudokoningii, T. longibrachiatum, T. polysporum and T. harzianum. The laboratory studies were followed by field trials laid out in farmers’ fields (newly planted pepper gardens) in six districts of Kerala. Effect of biocontrol agents in wilt incidence revealed that the two-time treatment of combined application of Trichoderma local isolate and potassium phosphate was superior in checking the foot rot incidence. The treatment, Trichoderma local isolate + Bordeaux mixture applied twice came in the second position. Data on biometric observations revealed a significant increase in the number of laterals in plots treated with Trichoderma local antagonist and potassium phosphate as compared to plots treated with Bordeaux mixture and copper oxychloride. Results of quality analysis of berries revealed that oleoresin content ranged from 6.98 - 11.84 per cent and piperine content from 3.61 - 5.92 per cent and the quality remain unchanged due to various treatments. The study has provided an ‘eco and health friendly’ biological control for the management of Phytophthora foot rot, the most devastating disease of pepper.

ABSTRACT

An in vitro evaluation was carried out to find out the efficiency of bacterial and fungal antagonists in checking the growth of pathogens of Kacholam. Out of the two methods tried to find out the effectiveness of Pseudomonas fluorescens against the two isolates of Ralstonia solanacearum, cross streaking produced lysis at the juncture and point inoculation produced clear inhibition zones. Among the two fungal antagonists tested Trichoderma viride was more efficient than Aspergillus niger because of its faster growth over the pathogen. However, both the antagonists showed complete overgrowth and dense sporulation on the area where the pathogen was streaked. To find out the efficacy of Pseudomonas fluorescens against leaf spot pathogens like Colletotrichum gloeosporioides and C. capsici, streaking on both sides yielded more than 50 per cent reduction in growth of both the fungal pathogens. The fungal antagonist T. viride showed a faster growth over pathogens than A. niger eventhough both recorded an antagonism index of 1500. Dense sporulation was seen over the pathogens in case of T. viride. The ability of fungal antagonists to produce volatiles and their effect on fungal pathogens were also assessed. It was noticed that the volatiles produced by T. viride was more effective than that of A. niger. Even though the extent of inhibition was less compared to direct action, this could also be one of the mechanisms of action of both the antagonists. The study revealed that all the three antagonists were effective against both bacterial and fungal pathogens and they could be utilized under field conditions.

ABSTRACT

The antagonistic organisms are known to bring out action on the pathogen by various mechanisms. Based on in vitro screening of epiphytic microbes from cocoa pod surface against Phytophthora palmivora, the incitant of pod rot of cocoa, a promising isolate of Trichoderma viride and two isolates of Pseudomonas fluorescens were selected. The mechanisms of antagonistic action of these selected epiphytic antagonists against P. palmivora were studied in comparison with the standard cultures of T. harzianum and P. fluorescens. The selected epiphytic fungal antagonist T. viride and standard culture of T. harzianum were found to be efficient parasites of P. palmivora. The hyphae of the pathogen were seen tightly held by coiling with hyphae of the fungal antagonists. The hyphae of the antagonists penetrated the host hyphae at several points and grew to its inner cavity. The fungal antagonists also caused disintegration of the pathogen hyphae, besides free intermingling, which resulted in malformation of host hyphae. The ability of the two epiphytic P. fluorescens isolates and standard culture of P. fluorescens in producing HCN and siderophores was assessed. It was found that these isolates produced HCN and siderophores in appreciable levels thereby suppressing the P. palmivora. Though, more than one mechanism may operate in suppressing the pathogen, the relative importance of a particular mechanism may vary with different conditions, which needed to be further investigated.

ABSTRACT

An In vitro study was conducted to evaluate the fungicidal efficiency of four selected fungal antagonists against leaf spot pathogens of ivy gourd by dual culture method. The antagonists evaluated were Trichoderma viride, Trichoderma harzianum, Aspergillus niger and Chaetomium globosum. The major leaf spot pathogens of ivy gourd used for the study were Cercospora cocciniae, Colletotrichum gloeosporioides and Alternaria alternata, causing severe infection on the foliage. Among the four antagonists tested, T. viride and T. harzianum were found to be the most effective recording the highest AI value of 1500 against all the three pathogens followed by A. niger. C. globosum was least inhibitory on C. gloeosporioides and A. alternata, but was effective against C. cocciniae. A complete overgrowth of the antagonists on all these pathogens were observed in the case of T. viride, T. harzianum and A.niger. C. globosum showed aversion to the hyphal growth of C. gloeosporioides and A. alternata, whereas in C. cocciniae, a homogenous growth was observed.

ABSTRACT

Interaction of cationic dye acridine orange with lipopolysaccharide (LPS) isolated from Rhizobium strains specific (IC59) and non-specific (TAL1000) to chickpea (Cicer arietinum.L L.) has been investigated by spectrophotometric measurements. The strain specific (IC59) lipopolysaccharide induced decrease in absorbance of the α-band of acridine orange at 490 nm and finally upon further addition of LPS /Dye ratio in the range of 30~60 giving rise to α-polymeric metachromatic band at 660 nm. In contrast the LPS from non-specific strain (TAL1000) induces a decrease in absorbance at the α-band till LPS / Dye ratios are 0~50. This suggest that the anionic changes of strain specific LPS is different from non-specific strain enabling formation of large acridine orange aggregate on the surface of specific strain.

ABSTRACT

Phytophthora pod rot (PPR) incited by Phytophthora palmivora is the most serious disease of cocoa, inflicting heavy crop losses. Since, antagonistic microbes are useful in ecofriendly management of plant diseases, the present study was undertaken to harness the potential of antagonistic epiphytic microflora isolated from cocoa pods for the management of PPR of cocoa. A quantitative estimation of the epiphytic microflora from pods collected from different locations of cocoa gardens of Thrissur district revealed more abundance of bacteria followed by fungi, actinomycetes and fluorescent pseudomonads. The in vitro antagonistic effect of 16 isolates of fungi, 22 isolates of bacteria, five isolates of actinomycetes and two isolates of fluorescent pseudomonads from pod surface against P. palmivora was carried out in comparison with standard cultures of Trichoderma harzianum and Pseudomonas fluorescens. The study revealed that all the epiphytic fungal and bacterial isolates including standard cultures of T. harzianum and P. fluorescens were antagonistic to P. palmivora in varying degrees. Based on the in vitro screening seven promising epiphytic fungal isolates and five bacterial isolates along with standard cultures of T. harzianum and P. fluorescens were evaluated for their efficiency in reducing the infection by P. palmivora on detached pods. The pathogen was inoculated on the pods one hour after application of antagonists. Observations taken 10 days after inoculation of the pathogen revealed that one isolate of T. viride and two isolates of P. fluorescens obtained from pod surface exerted more than 40 per cent efficiency over control in reducing the infection. The standard cultures of fungal and bacterial antagonists recorded 33-35 per cent efficiency. Hence, these efficient epiphytic and standard cultures could be utilized for the management of PPR of cocoa.

ABSTRACT

To study the antagonistic potential of rhizobacteria against the soil borne pathogen Rhizoctonia solani, soil bacteria were isolated from the rice fields of Agricultural Research Station, Mannuthy and screened against R. solani. Out of the 22 rhizosphere bacteria, 10 were found to be antagonistic to R. solani. Seven belonged to the genera Bacillus, Pseudomonas, Clostridium and Sporosarcina and the rest three being unidentified. The bacterial isolates viz., 2B, 4B, 19B (Bacillus sp.), 28B and 10B (Sporosarcina sp.) showed increase in inhibition on extending the period of incubation. Maximum inhibition was expressed by 2B on the third day of inoculation followed by 4B, 10B (Sporosarcina sp.), 7B (Bacillus sp.) and Pseudomonas fluorescens. The bacterial isolate 4B and 7B (Bacillus sp.) and 10B (Sporosarcina sp.) completely prevented the sclerotial production of R. solani whereas 1B (Clostridium sp.), 2B, 19B (Bacillus sp.) and P. fluorescens delayed the sclerotial production. Pot culture studies also confirmed the superiority of these rhizobacteria in controlling the infection by R. solani. The potentiality of these rhizobacterial antagonists can be exploited for the management of soil borne pathogens like R. solani.

ABSTRACT

Banana is one of the most accepted and versatile fruit crops across the globe and in Kerala, it is the most important economically profitable fruit crop grown, mainly by small and marginal farmers, providing a vital source of income. However, the productivity of this crop is very much reduced due to various diseases of which rhizome rot disease is an important one. In recent years, this disease has become a serious problem to the commercial cultivation of banana in southern states of India like Kerala, Karnataka, and Tamil Nadu.In Kerala the disease incidence is found to be nearly 30% and it will soon become cent percent if unnoticed since the disease is more seen in banana cultivated in paddy fields, and the area under the cultivation of banana in paddy fields in Kerala is rapidly increasing. The disease is caused by a gram negative bacterium, Erwinia carotovora. Developing an integrated management package involving biocontrol methods is the only remedy for managing the disease within the financial limits of the marginal farmers. With this intension a pot culture experiment was conducted to study the inhibitory effect of different biocontrol agents and botanicals in the incidence of the disease after testing their efficacy under in vitro cond itions. The results revealed that the biocont rol agent Pseudomonas flourescens (commercial preparation @ 7g /plant) was found to effective in managing the disease. The co- efficient of infection was found to be13.9% as against the control pot where it was 56.24%. With regard to the growth parameters also, the treatment with this biocontrol agent gave superior results. Thus it was proved that Pseudomonas flourescens (commercial preparation @ 7g /plant) could be successfully utilized in the integrated disease management making it cost effective.

ABSTRACT

Microbial antagonists not only reduce the soil borne disease, but also influence the growth of crop plants. In a study conducted for five years on the effect of microbial antagonists on damping off incidence and biometric characters of solanaceous seedlings, it was observed that seed treatment and soil application of Trichoderma viride, T. harzianum, Pseudomonas fluorescens, Azotobacter chroococcum reduced the damping off incidence considerably in brinjal, chilli and tomato. Application of these microbes also increased the per cent germination and promoted vigour of solanaceous seedlings as compared to control. Among the various antagonists, T. viride was the most effective one reducing the damping off diseases as well as promoting the growth of solanaceous vegetables.

ABSTRACT

Anursery experiment was conducted to study the effect of solarization, selected native antagonists viz., T. viride and T. longibrachiatum and the standard culture of T. harzianum for assesseing the growth enhancement and management of Phytophthora rot in black pepper nursery. The experiment was laid out at College of Horticulture with 20 different treatments and replicated thrice. The sprouting percentage of cuttings in different treatments was worked out at different intervals, which showed significant difference. In general, it was observed that the maximum sprouting percentage was noticed in treatments where solarized potting mixture and biocontrol agents were used. The population of soil microflora viz., fungi, bacteria and actinomycetes in different treatments were also estimated. The study indicated a fluctuation in the population of soil microbes in various treatments at different periods of observation. The observations on height and number of leaves of pepper cuttings in different treatments were recorded. It was noticed that cuttings raised in solarized potting mixture incorporated with native antagonists, especially T. viride, exerted a significant effect in increasing the height of cuttings. With regard to total number of leaves, it was also observed that addition of native antagonists in solarized potting mixture had a positive effect in increasing the leaf production. Thus, the effect of solarization enhanced the growth parameters in crop plants by making available the required nutrients. The increased growth response of plants by soil application of Trichoderma spp. may be due to the production of growth promoting substances by the antagonists. Thus, the nursery experiment revealed that, in general, soil solarization and incorporation of antagonists had a favourable effect in promoting the growth of pepper plants besides checking the Phytophthora rot in black pepper nursery.

ABSTRACT

Vesicular arbuscular mycorrhizal (VAM) fungi are known to improve the mineral nutrient and water status of the plants even under various abiotic stresses. During present investigations VAM fungus Glomus fasciculatum was used for developing mycorrhizal association with Sesbania sesban (L.) Merrill. In general mycorrhizal (M) plants exhibited better growth and development and showed significantly higher chlorophyll content, better PS II as well as PS I activities when compared to NM plants.

In general, both M and NM plants invariably showed reduced growth and development upon exposure to drought stress. However, the M plants could confront this abiotic stress more effectively than the NM plants. This was vindicated by the faster decline in the chlorophyll content and the photochemical activities in NM plants in comparison to the M plants upon exposure to drought stress. The higher photosynthetic efficiency of the M plants under drought stress indicate the presence of certain adaptive strategies in the form of osmotic adjustment operational in these plants through VAM association. The osmotic potential of the leaf cell sap in M plants was significantly lower than that of NM plants of Sesbania sesban, when exposed to either drought stress. The lower y of M plants as compared to NM plants under drought stress could be due to the accumulation of compatible solutes such as proline and sugars. A higher level of proline accumulation in the leaves of M plants than NM plants exposed to drought stress help them to counteract the adverse effects of stress better than NM plants.

ABSTRACT

Brinjal is an important solanaceous vegetable, which holds coveted position among the different vegetables. Developing hybrids with high yield and resistance to borer would be highly beneficial. The biochemical parameters are used to study the mechanism of resistance to pests and diseases. With this aim, the biochemical constituents were estimated in five intervarietal hybrids and their parents with susceptible variety. The study on biochemical basis of resistance to shoot and fruit borer showed that among the parents of intervarietal crosses, EP 65 had the highest level of peroxidase, polyphenol oxidase and total phenol content in both shoot and fruit and it also recorded high content of solasodine next to APAU Bagmathi. Among the hybrids, the cross EP 65 x Pusa Uttam had the highest level of peroxidase and polyphenol oxidase activity in both shoot and fruit and high level of total phenols and solasodine content next to EP 104 x APAU Bagmathi . The susceptible check (CO 2) registered the lowest value for all the biochemical constituents .The study revealed that the genotypes with high or moderate level of these biochemical constituents suffered less for shoot and fruit borer infestation.

The native gel electrophoretic study showed that for peroxidase enzyme, the intervarietal hybrids EP 65 x Pusa Uttam, EP 12 x MDU 1 and EP 104 x APAU Bagmathi and the susceptible variety CO 2 did not show difference in the induction of isoform (PO-1) and all were single and thick. For polyphenol oxidase (PPO), the intervarietal hybrids and the variety CO 2 showed single and strong band induction

The evaluation of genotypes based on biochemical constituents and isozyme studies revealed the superiority of the parents EP 65, APAU Bagmathi and MDU 1and the hybrids EP 65 x Pusa Uttam, EP 12 x MDU 1 and EP 104 x APAU Bagmathi. The identified hybrids with high yield and resistance to shoot and fruit borer could be exploited for commercial cultivation.

ABSTRACT

Bacterial wilt caused by Ralstonia solanacearum is the major constraint for cultivation of tomato in Kerala. Biocontrol of plant pathogens is becoming an important component of integrated disease management. Among the various antagonists tested against R. solanacearum of tomato, fungi were more effective than bacterial and actinomycetes organisms. Among them, Trichoderma virens, T. viride (Ozhalapathy and Vellanikkara) and T. pseudokoningii were the effective ones, recording the maximum antagonism index (AI) value of 6000 under in vitro condition. They inhibited the pathogen completely by the mechanism of both lysis and overgrowth. In pot culture study, T. viride and T. pseudokoningii and commercial Pseudomonas fluorescens gave maximum protection against wilt incidence. Under field condition, T. viride (Ozh), T. pseudokoningii and P. aeruginosa showed the lowest wilt incidence of 50.0, 58.3 and 58.3 respectively against cent per cent incidence in the control plot.

ABSTRACT

Chickpea is an important pulse crop of India and most suited to the use of rhizobia for its nitrogen requirement. Mesorhizobium ciceri which interact with the crop are poorly understood. Attempt has been made to select M. ciceri with several beneficial properties. Sixty four isolates of M. ciceri collected from the nodules of several chickpea varieties and mutant lines were screened for their growth properties on nitrogen free medium. Isolates MC59 and MC 18-7 showed normal growth and had ARA values at half level to that of Azotobacter. PCR amplification results suggested the presence of ACC deaminase gene sequence both in Azotobacter and M. ciceri. Invariably all isolates showed the presence of one plasmid in the range of 35 kb to 40 kb size.

ABSTRACT

Soft rot of ginger caused by the fungus Pythium aphanidermatum is a major disease affecting ginger cultivation. To combat invading pathogen in the event of infection plants are known to produce antimicrobial pathogenesis related proteins (PR proteins) prominent among which are antifungal hydrolases like glucanases and chitinases. Since Pythium lacks chitin in its cell wall, increase in level of glucanase in the plant may enhance the resistance of ginger to soft rot disease. Signal molecule like ethylene plays a prominent role in the defense response of plants. The present study was undertaken to investigate the role of ethylene in enhancing the level of glucanase in the ginger system. Detached leaves of Rio de Janeiro variety of ginger were used in different experiments. Leaves were treated with ethephon at different concentrations and different time intervals. Increase in the glucanase activity by ethephon treatment was quantified by enzyme assay using crude protein extract. Glucanase levels showed an initial increase with increasing concentration of ethephon but decreased at higher concentration (5 mg/ml). A longer exposure of detached leaves to ethephon (48 h) resulted in 3.7 fold increase in glucanase activity compared to control. The level of enhancement of the glucanase transcript also followed a similar trend as revealed by RT PCR analysis. Two acidic isoforms of glucanase were detected using native PAGE and their levels were found to be enhanced by treatment with ethephon. An increase in the levels of glucanase may contribute to the plant’s ability to resist infection by Pythium.

ABSTRACT

Studies on the impact of bio-fertilizers with levels of NPK on bulb yield, dry matter production, nutrient uptake and cost: benefit ratio in onion (cv. Bellary Red) were conducted in medium black soils during kharif and rabi seasons of 1999 and 2000 both under irrigated and rainfed conditions at the Agricultural Research Station, Hiriyur located under Central Dry Zone of Karnataka. The treatments were; T₁-Control, T₂-Azotobacter, T₃-Azotobacter+75% N+PK, T₄-Azotobacter +100%N+PK, T₅-Azospirillum, T₆-Azospirillum+75% N+PK, T₇-Azospirillum+100%N+PK, T₈-VAM, T₉-VAM 75% P+NK, T₁₀- VAM+100%P+NK, T₁₁ ? recommended NPK(125:50:125 kgha-1) and T₁₂-75% recommended NPK. The experiments were laid out in RBD in three replications.

The bio-fertilizers Azospirillum brasilence (500g ha-1) and Azotobacter vinelandii(500g ha-1) were applied to seedlings at transplanting separately by dipping the roots in the slurry for 15 minutes. The VAM fungi - Glomus mossae was applied to soil @ 1 kilogram per square meter area of nursery bed. The recommended dose of FYM @ 25 t ha-1 was applied to all the treatments as basal dose.

The results of the investigations revealed that the plants provided with Azospirillum + 100% N+PK (T₇) produced highest bulb yield (250.29;339.02;232.98 q/ha), highest total dry matter production (7053.96;8992.78;6287.03 kg/ha), maximum uptake of N, P a nd K ( 1 5 7 . 8 8 : 7 3 . 5 6 ; 7 0 . 4 6 N PK k g / ha ) , ( 2 0 6 . 8 6 : 9 6 . 2 5 : 9 1 . 1 0 N PK k g / ha ) , (131.81:50.25:71.24 NPK kg/ha) and also the maximum cost:benefit ratio of 4.00 (1:400), 5.42 (1:5.42), 3.94 (1:3.94) under irrigated condition during kharif and rabi seasons and under rainfed situation during kharif season respectively.

Thus, among all the treatments, application of Azospirillum + 100% N + PK (Azospirillum + 125:50:125 NPK kg/ha) was found to be most remunerative considering the nutrient uptake, bulb yield and total dry matter production and cost:benefit ratio, which gave the highest returns. This level can be followed for Bellary Red onion irrespective of seasons both under irrigated and rainfed conditions in the Central Dry Zone of Karnataka.

ABSTRACT

Phytophthora rot is the most destructive disease of black pepper nursery inflicting heavy crop losses. Considering the seriousness of the disease, the present study was undertaken to isolate and select the efficient antagonists from pepper nurseries raised in Government farms at Chelakkara, Pazhayannur, Mannuthy and Pananchery of Thrissur district. A quantitative estimation of the rhizosphere microflora from different nurseries revealed more abundance of soil bacteria followed by fungi and actinomycetes. Based on cultural characters of the rhizosphere microflora, 22 fungi, 20 bacteria and five actinomycetes were selected for further studies. Antagonistic action of soil microflora against Phytophthora capsici was studied by dual culture method in comparison with that of standard culture of T. harzianum. The study revealed that all fungal isolates and five bacterial isolates were antagonistic towards the pathogen with varying degrees. Among the fungal isolates, 13 isolates including T.harzianum recorded cent per cent inhibition of P.capsici. From among the fungal isolates that showed antagonistic reaction in dual culture, further selection of efficient ones was carried out based on the antagonistic index (AI). The isolate 22 F₂ (Trichoderma sp.) showed the maximum AI of 3000 followed by isolate 34 F₂ (Trichoderma sp.) and T. harzianum with an AI of 1500 each. The cultural and morphological characters of the efficient native isolates (22 F₂ and 34 F) were studied and were identified as Trichoderma longibrachiatum Rifai aggr. and Trichoderma viride Pers. ex S.F. Gray aggr. The three antagonists were found parasitic on P.capsici as evidenced by excessive coiling, penetration and disintegration of the hyphae and thereby these Trichoderma spp. used in the study is found to have effective parasitic effect on the pathogen in addition to some degree of antibiosis and these fungi could be utilised for the management of Phytophthora rot in black pepper nursery.

ABSTRACT

Biofertilizers can supplement the chemical nutrients and helps in reducing the production expenditure in agriculture. Crop biofertilization with microbial consortia is an important strategy to improve the physical, chemical and biological conditions of the soil. The facultative methylotrophs are capable of fixing atmospheric nitrogen, besides it produces phytohormones viz; IAA, GA and cytokinin, vitamin B₁₂, polysaccharides, PHB, and siderophores. The essential nutrients are considered as the most important, among the factors limiting growth and yield of the tomato crop. The application of adequate amount of fertilizers is a pre-requisite for exploiting the genetic potential of tomato variety. Therefore, efficient and economic use of the fertilizer with microbial consortia would help in decreasing the input costs for raising bumper crop.

More number of studies carried out on the effect of facultative methylotrophs in different parts of the world and in India. The results confirmed that the facultative methylotrophs have a greater importance in increasing the growth and yield of various crop plants. Keeping this in view an experiment was conducted to find out the interaction effect of facultative methylotrophs with other bioinoculants viz., Azospirillum, Azotobacter, PSB and VAM (by seedling dip method followed by PPFM phyllosphere spray) on yield of tomato var Ruchi. The results showed that the treatment with above microbial consortia (50.71 t/ha) was found to increase the yield of the tomato crop by 62.73 percent over uninoculated control (18.90 t/ha) and individual treatments.

ABSTRACT

Fruit rot and die back caused by Colletotrichum capsici is the destructive disease in chillies. The potential of Pseudomonas fluorescens for the management of fruit rot of chillies was evaluated under greenhouse and field conditions. Among the various strains of P. fluorescens tested in vitro, the strain Pf1 significantly inhibtied the mycelial growth of C. capsici. Combined application of talc-based powder formulation of P. fluorescens to seed (10 g/kg seed) and foliage (1 kg/ha) effectively controlled the fruit rot disease. Early and high induction of various defense compounds were observed due to P. fluorescens treatment.