Theses

Browse

Search Results

Now showing 1 - 5 of 5

Open Access
Identification of graft transmissible resistant factors and development of si RNA mediated resistance in cassava against cassava mosaic geminivirus
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Asha, B Nair; KAU; Umamaheswaran, K
The present study entitled ‘Identification of graft transmissible resistant factors and development of siRNA mediated resistance in Cassava against Cassava mosaic virus’ was carried out during the period 2012-2017 at the Department of Plant Pathology, College of Agriculture, Vellayani. The study was carried out with the objective of identification of transferability of resistance factor from resistant cassava, Sree Padmanabha to susceptible, Vellayani Hraswa by grafting and to develop siRNA mediated technology for the development of cassava plant resistant to Cassava mosaic geminivirus. Grafting experiments were conducted using resistant Sree Padmanabha as root stock and susceptible Vellayani Hraswa as scion. Symptoms like leaf mosaic, chlorotic spots, reduction in leaflet size and stunting of plants were noticed in susceptible variety. Virus concentration was found to be less in grafted plants. Grafting experiments showed the expression of an extra protein by SDS-PAGE and Coomassie staining in grafted plants which is around 38 kDa. Molecular weight of the new protein revealed the presence of extracellular protein in grafted samples. The extra proteins found in the grafted plants are assumed to be transferred from Sree Padmanabha to Vellayani Hraswa by the process of grafting. The study also involved the development of an intron hairpin RNA vector against replicase gene of SriLankan cassava mosaic virus and introduction of this construct into embryogenic cells via Agrobacterium mediated transformation. A protocol for somatic embryogenesis in cassava variety, Vellayani Hraswa was developed by using immature leaf lobes as explants. The young leaf lobes from tissue culture plantlets produced through meristem culture was used for embryogenic callus formation. Cremish white calli was initiated in Murashige and Skooge (MS) medium supplemented with picloram 12 mg L-1 in dark. For embryogenesis, the calli were transferred to MS medium supplemented with BA 2µM and NAA 1µM which resulted in the production of glassy elongated somatic embryos. The germinated cotyledonary embryos were then regenerated into plantlets by culturing in MS medium supplemented with BA 1mg L-1. Effort was taken to construct an intron hairpin RNA vector and the gene targeted for silencing was the replicase gene of SriLankan cassava mosaic virus (SLCMV). Total DNA was extracted from virus infected plants and the whole replicase gene was isolated using gene specific primers. Sequencing of the whole gene was done. BLAST analysis showed 98% similarity to replicase gene of various isolates of SLCMV. The sequence was then subjected to miRNA target prediction and restriction mapping to select suitable region for the construct. Based on this information, a fragment of 397 bp towards the 5’ end was amplified by designing a set of primers with anchored restriction sites. The primers anchored with Xho and Kpn 1sites were used for the amplification of sense strand and the primers anchored with Xba and Cla 1sites were used for amplification of antisense strand. Selected region was amplified to form sense and anti-sense fragments and cloned to pTZ57R/T cloning vector. Inserts were then released from pTZ57R/T using the corresponding restriction enzymes. The sense and anti-sense fragments were then integrated in the primary vector pHANNIBAL on either side of the pdk intron which facilitated the formation of intron hairpin RNA construct. The intron hairpin RNA construct in pHANNIBAL contained CaMV35S promoter, sense strand, pdk intron, antisense strand and OCS terminator in the order with Not 1 restriction sites. After confirmation of integration by restriction digestion, the Not1 fragment with sense and anti-sense strand were released from pHANNIBAL and ligated to the digested Not1 site in the lacZ gene of binary vector pART27 containing antibiotic resistant marker nptII and spec. the binary vector was confirmed for the presence of insert by transferring to DH5α cells and colony selection by blue white screening. Plasmid DNA isolated from transformed colonies grown on Luria agar medium supplemented with 100 mg L -1 spectinomycin were confirmed for the presence of insert. After confirmation of insert in the binary vector, it was transformed to Agrobacterium tumefaciens strain LBA4404 via freeze thaw method. Transformed colonies were selected on kanamycin selection medium at 100 mg L -1 and confirmed for the presence of binary vector and ihpRNA insert using nptII primers and primer for sense and antisense strands by PCR reaction. Cotyledons excised from the somatic embryos were transformed with LBA4404 having pART 27 by co-cultivation and the transformed embryos were selected with antibiotic pressure (Kanamycin 100 mg L-1). DNA was isolated from the transformed somatic embryos and confirmed for the presence of insert using forward primer of sense fragment and reverse primer of antisense fragments. Transformed embryos were subjected to regeneration.
Open Access
Molecular characterization of virus causing infectious chlorosis disease of banana
(Department of Plant Pathology, College of Horticulture Vellanikkara, 2017) Ahamed Mujtaba, V; KAU; Anita Cherian, K
The experiment entitled “Nutrient management in strawberry (Fragaria x ananassa Duch.)” was undertaken at Regional Agricultural Research Station, Ambalavayal, Wayanad during the year 2016-17. Performance of strawberry variety Winter Dawn was evaluated under nine treatments and a control in the open field viz., FYM 10 t ha-1 + NPK 50:20:50 kg ha-1 (T1); FYM 10 t ha-1 + NPK 75:30:75 kg ha-1 (T2 ); FYM 10 t ha-1 + NPK 100:40:100 kg ha-1 (T3); FYM 20 t ha-1 + NPK 50:30:100 kg ha-1 (T4); FYM 20 t ha-1 + NPK 75:40:50 kg ha-1 (T5); FYM 20 t ha-1 + NPK 100:20:75 kg ha-1 (T6); FYM 30 t ha-1 + NPK 50:40:75 kg ha-1 (T7); FYM 30 t ha-1 + NPK 75:20:100 kg ha-1 (T8); FYM 30 t ha-1 + NPK 100:30:50 kg ha-1 (T9) and an absolute control (T10), without any nutrient application. All the treatments were on par and superior over the control (T10) in case of plant height. In case of plant spread, T2, T3, T5, T6, T7, T8 and T9 were on par and superior over the control while T1 and T4 were on par with each other but differs with other treatments. All the treatments except T2 were on par and superior over the control with respect to number of leaves per plant. Application of treatments had no significant effect on days to first flowering. In case of number of flowers and clusters per plant, T1, T2, T3, T5, T6, T7, T8 and T9 were on par and superior over the control while T4 was on par with the control (T10). Days to first harvest was minimum in T6, T7, T8 and T9 which were on par while all other treatments were on par with the control (T10).In case of number of fruits and yield per plant, T7 (FYM 30 t ha-1 + NPK 50:40:75 kg ha-1) and T8 (FYM 30 t ha-1 + NPK 75:20:100 kg ha-1) were on par and superior over other treatments including T1, T2, T3, T4, T5, T6 and T9 which were on par and superior over the control. Average fruit weight recorded under T3, T5, T6, T7, T8 and T9 were on par which was followed by T2 on par with T4 and T1. Days to final harvest was not found to be influenced by the application of different treatments. Biochemical characters of fruits viz., TSS, acidity and TSS/acidity ratio were not having any significant effect due to the application of treatments. In case of total sugars, T3, T7, T8 and T9 were having the highest content and were on par which was followed by T5 on par with T1, T2, T4, T6 and T10. The overall sensory score was highest in T7 followed by T8. Application of different treatments had no significant effect on the shelf life of strawberry fruits. N, P, K and Ca content in the plant were not significantly affected by any treatment while Mg content was found to be on par in all treatments and superior over the control. Soil analysis after the harvest of the crop revealed that the values for soil EC, available P, K, Mg and S were found to be elevated while soil pH, organic carbon and available Ca content were found to be at lower levels than the initial values before planting. It was concluded that among different nutrient combinations evaluated, T7 (FYM 30 t ha-1 + NPK 50:40:75 kg ha-1) with a BC ratio of 3.06 can be recommended for further optimization and refinement.
Open Access
Enhancement of systemic resistance to soil borne pathogens of ginger by enriched spent mushroom substrate of pleurotus sajor-caju
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Remya, J S; KAU; Beena, S
Spent mushroom substrate (SMS) is the composted organic material retained after a crop of mushroom. The world mushroom industry needs to discard more than 50 million tons of SMS every year. The latest research throw light on the efficient use of SMS for the disease management of crop plants. A preliminary study on the use of SMS of Pleurotus spp. as mulch for the management of rhizome rot complex disease of ginger under pot culture condition was carried out in the Department of Plant Pathology, College of Horticulture, Vellanikkara. In this study, among the various SMS used, the paddy straw SMS of P. sajor-caju as mulch recorded the highest biometric characters and least disease incidence compared to control. Hence this project was proposed as the continuation of the above study to evaluate the efficacy of enriched SMS of P. sajor-caju in enhancing growth and systemic resistance for the management of soil borne pathogens of ginger under field conditions. SMS of P. sajor-caju was produced during three different periods viz., March-April, June-July and November-December (2013) at six different locations of Kerala viz., College of Horticulture, Vellanikkara (Thrissur dist.), farmer’s field at Kodakara (Thrissur dist.), Perinjanam (Thrissur dist.), Krishnagiri (Wayanad dist.), Mananthavady (Wayanad dist.) and College of Agriculture, Vellayani (Thiruvananthapuram dist.). Enumeration of microflora of these SMS was carried out and a total of 47 fungal and 45 bacterial isolates were obtained. The antagonistic efficiency of these isolates were evaluated against the five pathogens viz., Pythium aphanidermatum, Fusarium oxysporum, Rhizoctonia solani, Sclerotium rolfsii and Ralstonia solanacearum under in vitro conditions. All the isolates from SMS showed antagonistic property against one or the other soil borne pathogens, with varying degree of inhibition. Mutual compatibility between the most efficient fungal and bacterial antagonists was evaluated to develop an effective microbial consortium for enriching the SMS and could be used against the soil borne diseases of ginger. Biosoftening efficiency of selected fungal and bacterial antagonists on SMS was evaluated. Two separate experiments were carried out with the selected antagonists effective against fungal and bacterial pathogens. For each experiment, five fungal antagonists, five bacterial antagonists and three compatible pairs were selected based on the in vitro evaluation of antagonistic efficiency and mutual compatibility studies. SMS was enriched separately with different antagonists and standardized the period for biosoftening of SMS as mulch for ginger cultivation. A period of 15 days was selected as most suitable for biosoftening the SMS as mulch with optimum antagonistic fungal and bacterial population. Wide range of C:N ratio was recorded by the SMS enriched with each antagonists. By considering the C:N ratio along with external appearance, the treatments having C:N ratio of 30:1 to 45:1 were selected, since it was the most suitable stage to be used as mulch in ginger. The effectiveness of biosoftened SMS against rhizome rot and bacterial wilt diseases of ginger was evaluated in two pot culture experiments. Three fungal and bacterial antagonists each and one compatible pair of antagonists which were selected based on the in vitro evaluation of antagonistic and biosoftening property were used for enriching the SMS. After enrichment, the SMS were kept for 15 days for biosoftening and were applied as mulch in the experiments. Observations on germination percentage and other growth parameters viz., number of tillers/plant, number of leaves/tiller and height of tillers were recorded at one month intervals from two months after planting (MAP). Challenge inoculation of pathogens was done at 45 days after germination and per cent disease incidence was recorded at 7 and 14 days after inoculation (DAI). In the experiment for the management of P. aphanidermatum, the lowest disease incidence was observed in T7 (SMS softened with P1F1+ M1F2) on 14th day after inoculation (DAI). This treatment also recorded the highest number of tillers, number of leaves/ tiller and height of tillers and rhizome yield. In the experiment for the management of R. solanacearum, the treatment T2 (SMS softened with T1F2) was found to be the most efficient one, which recorded the least disease incidence at 14 DAI, whereas the highest values for biometric characters and rhizome yield were recorded by T7 (SMS softened with K1B1 + T2B1). The activity of phenol and defense related enzymes such as peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were estimated by spectroscopy, before challenge inoculation with pathogen and at one, three and five days after the challenge inoculation. For estimation, leaf samples were collected separately from the pot culture experiments I and II for the management of P. aphanidermatum and R. solanacearum respectively. The treatments which recorded less disease incidence in both the pot culture experiments exhibited the highest activity of defense related enzymes and phenol. The highest activity of defense related enzymes and phenol was recorded at 5 DAI. Thus the present study showed that in addition to direct antagonism and plant growth promotion, induction of defense related enzymes was also contributed by SMS to enhance resistance against invasion of soil borne pathogens of ginger. Field evaluation of the selected treatments from pot culture experiments showed the lowest disease incidence in the treatment T2 (SMS softened with T1F2) followed by T5 (SMS softened with P1F1+M1F2). Statistically these were on par with each other. The treatment T5 (SMS softened with P1F1+M1F2) recorded the highest germination percentage, number of tillers, number of leaves/tiller and rhizome yield also. Analysis of primary nutrients viz., nitrogen, phosphorus and potassium in SMS, plant and soil from field experiment was conducted. Among these, SMS softened with P1F1+M1F2 recorded the highest percentage of N, P and K. This treatment recorded the highest nutrient content in ginger rhizome and soil also. Attempts were also made to identify the fungal and bacterial antagonists selected for field experiment. Based on the cultural and morphological characters, the fungal antagonists viz., Kr1F4, T1F2, P1F1 and M1F2 were tentatively identified as Trichoderma viride (Pers.), T. viride (Pers.), T. koningii (Oudem.) and T. harzianum (Rifai) respectively. The identification got confirmed from National Centre for Fungal Taxonomy (NCFT), New Delhi. The bacterial antagonists selected for field experiment were also identified based on cultural, morphological, biochemical and 16s rRNA sequence analysis. The three bacterial antagonists P3B2, T2B1 and K1B1 were identified as Bacillus safensis, B. methylotrophicus and Burkholderia gladioli respectively. Spent mushroom substrate is rich in microflora and these microflora exert antagonistic activities against soil borne pathogens. It stimulates the natural defense system in plants, provide necessary nutrients for plant growth and also improve soil physical condition. From field evaluation it was found that the SMS softened with T. viride recorded the lowest disease incidence and which enhanced systemic resistance to soil borne pathogens of ginger by defense related enzymes and phenol. The results were on par with the SMS softened with consortium of antagonists, T. koningii and T. harzianum (P1F1+M1F2). The highest rhizome yield and other growth parameters were also contributed by the SMS softened with T. koningii and T. harzianum. The content of nitrogen, phosphorus and potassium were also recorded the highest in this SMS. So from the present study it can be concluded that the SMS softened with T. koningii and T. harzianum can be used as mulch in ginger which was found equally effective to induce systemic resistance against soil borne pathogens and to enhance growth parameters and rhizome yield.
Open Access
Characterization and exploitation of jelly mushrooms (auricularia spp./ Tremella spp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Priya, R U; KAU; Geetha, D
The present study entitled “Characterization and exploitation of jelly mushrooms (Auricularia spp./ Tremella spp.)” was carried out in College of Agriculture, Vellayani during 2014-2017, with the objective of standardization of techniques for production of jelly mushrooms (Auricularia spp./ Tremella spp.) in agricultural wastes and to study their morphological, physiological and cultural characteristics as well as nutritional and organoleptic qualities. Survey was conducted in ten different locations of Thiruvananthapuram and Kollam districts of Kerala during 2014-2016. Sporocarps of Auricularia spp. and Tremella spp. were collected from tree stumps, predominantly Mango, Coconut, Drumstick, Teak wood and Rubber. All the mushrooms collected from all the locations were gregarious in nature and lignicolous in habitat. Morphological studies of jelly mushrooms showed that the sporocarps were light brown to dark brown in colour with incurved margin, ear shaped, soft and velvety in texture and devoid of stipe. The internal stratification of hyphae showed eight different zonations. Basidiospores were hyaline, oval and sub cylindrical to cylindrical shaped. Two fast growing isolates selected based on the time taken for complete mycelial growth and nature of mycelial growth, designated as A1 and A2 were sent to Directorate of Mushroom Research, Solan for identification. These were identified as Auricularia polytricha (Mont.) Sacc. (Accession number of A1 was DMRO-825 and A2, DMRO-826). The maximum mycelial growth was recorded on malt extract agar medium and a temperature of 250C, pH 7 and light conditions were found favourable for mycelial growth. Evaluation of different substrates for spawn production revealed that paddy grain was the best substrate followed by sorghum. Rubber sawdust spawn recorded maximum keeping quality. Malt extract broth was found to be the best for submerged culture production of both A1 and A2. Evaluation of different substrates for mushroom production revealed that rubber sawdust was the best substrate for cultivation which recorded maximum Biological Efficiency (BE) of 14.8% for A1 and 12.2% for A2. The minimum time for spawn run was taken by paddy straw and the maximum was taken by neopeat. Major insect pests observed were Megaselia sp., Seira sp. and Staphylinus sp. The competitor moulds observed were Coprinus sp, Aspergillus spp., Penicillium sp. and Trichoderma sp. Among the different amendments, wheat bran (2.0 and 4.0 %) and groundnut cake (2.0%) were found to be the best for enhancing the growth parameters whereas, rice bran (2.0% and 4.0%) was the best for increasing yield parameters. Analysis for the proximate constituents in A. polytricha (A1 and A2) revealed that it contained appreciable amount of carbohydrate (47.1 and 48.8%), protein (18.06 and 20.75%), polyphenols (9.53 and μg), fibre (17.69 and 15.49%), total anti oxidants (116 and 74μg), β carotene (0.178 and 0.150 μg) and the energy value was 251.49 and 264 respectively. Sensory evaluation of mushroom products made from A. polytricha (A1 and A2) indicated that mushroom tomato sauce scored maximum for overall acceptability. Under refrigeration (40C) in perforated poly propylene covers mushrooms could be kept fresh for three days. Indoor cultivation of both A1 and A2 showed significant results for growth parameters as well as yield parameters compared to outdoor cultivation. Comparative performance of A. polytricha with two ruling mushrooms of Kerala namely oyster mushroom (Pleurotus florida (Mont.) Singer.) and milky mushroom (Calocybe gambosa (Fr.) Donk.) indicated that oyster mushroom took minimum days for spawn run, pinhead formation and first flush compared to milky mushroom and A. polytricha. Milky mushroom recorded highest BE (66.1%) compared to others. Studies on medicinal activities of A. polytricha indicated that it possessed anticancerous activities for cervical, colon and liver cancer cell lines and higher activity was recorded in 100 μg/ml concentration. Based on the results of present investigation, A. polytricha can be cultivated successfully in tropical areas on locally available materials. Paddy grain was the most suitable substrate for spawn production and Rubber sawdust amended with 2% rice bran, the most suitable growing medium. Mushrooms possessed significant nutritional and medicinal activities. The findings of the above investigations recommend the adoption of a suitable cultivation package for jelly mushrooms (A. polytricha), a highly prized mushroom.
Open Access
Enhancing bio - efficacy of Trichoderma spp. for the management of soil borne fungal pathogens
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Hima, V M; KAU; Beena, S
A study on ‘Enhancing bioefficacy of Trichoderma spp. for the management of soil borne fungal pathogens’ was carried out in the Department of Plant Pathology, College of Horticulture, Vellanikkara, during the period 2011- 2016. Soil borne fungal pathogens are the major threat to the farmers for the cultivation of the crops. Estimate showed that 37 per cent of the crop loss was due to pests of which 12 per cent was due to pathogens (Radheshyam et al., 2012). Eventhough, there are various mechanisms including chemicals for the management of soil borne diseases, biocontrol approach is getting wide acceptance because of its broad spectrum activity and eco friendly nature. The ascomycetous fungus, Trichoderma spp. based bio control products share 60 per cent of all fungal based products in the global market. Taking the high potentiality of this fungus in the management of soil borne fungal pathogens, the present study was conducted. Purposive sample surveys were conducted in Kerala state and collected 51 rhizosphere soil samples from different locations of northern, central and southern zones of Kerala including Wayanad. A total of 128 isolates of Trichoderma spp. were isolated from the collected soil samples and were named as Tr 1 to Tr 128. The estimation on soil pH revealed that the occurrence of Trichoderma spp. was more in the pH range of 5.5 - 6.5. Six important soil borne fungal pathogens viz., Pythium aphanidermatum, Phytophthora capsici, Fusarium oxysporum f. sp. cubense, Sclerotium rolfsii, Ganoderma lucidum and Rhizoctonia solani were isolated from the diseased specimens of ginger, pepper, banana, pepper, coconut, rice respectively and were selected to study the antagonistic activity. After preliminary screening and dual culture experiments 20 isolates of Trichoderma spp. showed antagonistic efficiency against all the six pathogens were selected. The antagonistic efficiency of native Trichoderma isolates was compared with that of reference biocontrol agents T. viride and T. harzianum released from KAU. All the isolates, except Tr 2 and Tr 109, recorded cellulase activity of 0.5 to 1.0. Based on the above characters, 12 native isolates of Trichoderma spp., Tr 9, Tr 48, Tr 52 and Tr 76 from northern zone, Tr 2, Tr 14, Tr 43 and Tr 86 from central zone and Tr 34, Tr 41, Tr 97 and Tr 109 from southern zone, were selected for the evaluation of their antagonistic efficiency and the plant growth promoting efficiency under pot culture experiment, where ginger was taken as the test crop and P. aphanidermatum as the test pathogen. In the pot experiment, all the treatments recorded > 72 per cent of germination on 1 MAP. After absolute control, plants treated with Tr 43 showed highest number of tillers/plant, height of the plant and the number of leaves/tiller with records of 45, 19.25cm and 6.72 respectively. Compared to control plants, the least incidence of disease was noticed in the treatment Tr 76 (40.12%) which was followed by Tr 43 (32.33%). Out of 12 Trichoderma isolates, five isolates named Tr 43, Tr 76, Tr 9, Tr 41 and Tr 48, expressed better plant growth promotion and disease suppression activity in the pot culture experiment were selected for further study. The compatibility study of these five isolates with the selected fungicides and insecticides revealed that all the isolates tested were found incompatible with fungicides, carbendazim (0.1%), Bordeaux mixture (1%) and the insecticide quinalphos (0.05%). Only the isolate, Tr 9 was found compatible with the fungicide, mancozeb (0.3%). None of the isolates was inhibited by the insecticide, flubendiamide (0.01%). The field evaluation of these isolates was carried out by taking ginger as test crop and P. aphanidermatum as test pathogen. One month after planting, > 69 per cent of germination was noticed in all the treatments. The treatment Tr 43 recorded highest number of tillers of 8.71. The maximum height of tiller (34.02 cm) and number of leaves (8.82) were recorded by the treatment Tr 9. The least incidence of disease over control was recorded by Tr 9 (27.87 %). Among the five isolates, two isolates (Tr 9 and Tr 43) which showed highest bio-efficacy were selected for strain improvement by mutation and protoplast fusion technics. The parental cultures, Tr 9 and Tr 43 were morphologically characterized and were identified from ITCC (Indian Type Culture Collection) IARI, New Delhi as Trichoderma sp. and T. asperellum respectively (I. D No. 9778.15 and 9782.15). The molecular characterization (RAPD and ITS - PCR) of these isolates was carried out and were identified and confirmed as T. erinaceum and T. asperellum respectively. The mutation of parental cultures Tr 9 (T. erinaceum) and Tr 43 (T. asperellum) conducted by the combination of treatment with UV rays and sodium nitrate, yielded 97 isolates. Preliminary screening of these isolates with the pathogen, S. rolfsii resulted in the selection of three out of 23 mutants of Tr 9 and six out of 74 mutants of Tr 43. The protoplast fusion of Tr 9 and Tr 43 was carried out by using glucanex as lytic enzyme and poly ethylene glycol as fusagent. Out of 15, five fusant isolates were selected after the preliminary screening with S. rolfsii. The antagonistic efficiency of the selected nine mutants and five fusants were further evaluated with soil borne fungal pathogens, Pythium aphanidermatum, Phytophthora capsici, Fusarium oxysporum f. sp. cubense, Sclerotium rolfsii and Rhizoctonia solani. The two mutants, M40M3 and K80M13 and the two fusants, F2 and F4 which showed better antagonism than their parents and the KAU reference cultures, were further evaluated under the pot and field experiments.In the pot culture experiment, the treatment with the mutant K80M13 exhibited better plant growth by recording 91.67 per cent of germination, 30.17 tillers/plant, 36.63 cm height of tiller and 8.9 leaves /tiller. The least incidence of rhizome rot (27 %) was noticed in the plants treated with K80M13 with a maximum yield of 616.67 g/plant. The estimation of total phenols and defense related enzymes viz., peroxidase (PO), poly phenol oxidase (PPO), and phenyl alanine ammonia lyase (PAL) revealed that there was significant increase in the production of defense molecules among the treatments. The highest content of PO, PAL and total phenol was recorded in the plants treated with mutant K80M13 showed 5.93 min-1 and 29.46 nmol trans cinnamic acid and 9.88 μg per g of fresh tissue respectively. The highest content of PPO was observed in plants treated with the fusant F2 (0.12) which was closely followed by that of mutant isolate K80M13 (0.1). The mutant, K80M13 showed better biometric characters of plants in the field condition. It recorded 90.63 per cent of germination, 39.6 tillers/plant, 36.73 cm height of tiller and 11.45 leaves/tiller. Among all the treatments, K80M13 recorded lowest disease incidence of 13 per cent. The maximum record of yield (3.7 Kg/bed) was also noticed in the treatment K80M13. The morphological and molecular characterization of the mutants (M40M3 and K80M13) and the fusants (F2 and F4) was conducted. The results revealed that the sequences of M40M3 and F2 showed significant homology to genes of T. erinaceum and that of K80M13 and F4 showed homology to genes of T. asperellum. The studies revealed that, the mutants M40M3 (T. erinaceum) and K80M13 (T. asperellum); the fusants F2 (T. erinaceum) and F4 (T. asperellum) and their parents Tr 9 (T. erinaceum) and Tr 43 (T. asperellum) were the promising candidates with significant disease suppression and increased plant growth. Among them, the mutant K80M13 which was identified as Trichoderma asperellum recorded maximum disease suppression (45.83%) and highest yield (43.97%) compared to the reference culture of KAU under field condition. This improved mutant Trichoderma asperellum can be released as an efficient biocontrol agent in future after conducting multi-locational trials and toxicological studies.

Theses

Browse

Thesis Type

Type

Author

Date

Subject

Search Results