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Subject: Agricultural Microbiology × Author: KAU × End date: 2015 × Start date: 2015 ×
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    ThesisItemOpen Access
    Functional diversity of beneficial microorganisms from the rhizosphere of black pepper in Wayanad
    (Department of agricultural microbiology, College of Horticulture,Vellanikkara, 2015) Athira, P S; KAU; Girija, D
    Black pepper (Piper nigrum L.) is a perennial, woody and flowering climber belonging to family Piperaceae. It is one of the important spice crops which provides major source of income and employment for rural households in Kerala. Wayanad dominated in pepper farming in the state about 20 years ago. Annual production of pepper was 40,000 tonnes in the mid-1980s, which comprised about half of India’s total pepper production. But recently, the production has declined drastically due to the infestation of pests and diseases. Foot rot caused by Phytophthora capsici and yellowing of black pepper are the major diseases devastating most of the plantations in Wayanad. However, some of the plants in the disease affected areas remain healthy which could be due to inherent activity of native rhizosphere microflora. The present study focused on assessing the functional diversity of beneficial microorganisms which could possibly be exploited for the benefit of plant growth. Four healthy gardens, four gardens each affected by foot rot and yellowing were selected for sample collection. Rhizosphere soil samples were collected from five healthy vines in each garden. Population of beneficial microbes in the rhizosphere soils of healthy and disease affected gardens were compared. In general, rhizosphere soil from healthy gardens recorded higher population of bacteria, fungi, phosphate solubilizers and fluorescent pseudomonads. A total of 207 isolates (including 112 bacteria, 32 actinomycetes and 63 fungi) were purified and maintained to study their plant growth promoting and antagonistic activities. Maximum IAA production (292.50 μg ml-1) was recorded by HPLBC-6 followed by HABC-3 (46.43 μg ml-1). The isolate HPLPSB-3 was the most efficient P solubiliser (162.7 μg ml-1) followed by HPLF-5 (161.3 μg ml-1). The isolate YPTN- 3 fixed maximum amount of nitrogen (46.92 mg of N g-1 of sucrose) followed by HVKN-6 (32.62 mg of N g-1 of sucrose). From the invitroexperiment, two most promising isolates each of IAA producers, phosphate solubilizers and nitrogen fixers were selected for preliminary screening for growth promotion on blackpepper cuttings. The isolate HPLPSB-3 (P solubiliser) recorded maximum sprouting, vine length, number of leaves, number of roots and roots fresh weight underinplanta screening for plant growth promotion. However, maximum root length was observed in HPLBC-6 (IAA producer). All the isolates were screened in vitro for their antagonistic activity against foot rot pathogen Phytophthora capsici. Among the bacteria, isolate HPLPSB-6 recorded maximum inhibition (69.27 %) of the pathogen. Among the actinomycetes, HVZACT-1 recorded maximum mycelial inhibiton of 66.66 %. Among the fungal isolates screened, maximum inhibition (75.17 %) was recorded by the isolate FPRF-3. The three most promising PGPM selected from preliminary in planta screening and three antagonists from in vitro screening were further tested for their efficiency in controlling foot rot disease in blackpepper nursery. Minimum disease incidence (6.23%) and severity (4.00 %) were observed in isolate FPRF-3. This was followed by actinomycete HVZACT-1 with disease incidence of 13.20 % and severity of 8.00 %. Maximum disease incidence and severity were observed in control with pathogen alone. In addition to biocontrol activity, FPRF-3 also improved plant growth parameters such as length of vine, number of leaves and roots. The selected growth promoting isolates HPLPSB-3, HPLBC-6 and YPTN-3 were identified as Acinetobacter grimontii, Providencia sp. and Paenibacillus sp. The three selected antagonists HPLPSB-6, HVZACT-1 and FPRF-3 were identified as Paenibacillus polymyxa, Streptomyces termitum and Trichoderma viride respectively. Based on in planta evaluation, Acinetobacter grimontii was considered as the best PGPM and Trichoderma viridethe most promosing antagonist against P. capsici. These isolates could be further exploited for improving the growth and managing foot rot disease, after validation under field conditions. The compatibility of PGPM with antagonists and chemical fungicides may also be evaluated.This is the first report of antagonistic activity of the actinomycete S. termitum against P. capsici causing foot rot disease in blackpepper.
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    ThesisItemOpen Access
    Evaluation of bioinoculant consortia for organic cultivation of ginger
    (Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2015) Haritha, T R; KAU; Surendra Gopal, K
    Ginger is one of the major spice crops of Kerala. Several constraints hinder its production and the major one is its succeptibility to various diseases. This has led to the use of high doses of chemical pesticides. Ginger is also a highly nutrient exhausting crop, which demands use of high doses of fertilizers. Although, chemical fertilizers and pesticides are highly effective, their continuous use has led to many environmental problems. Alternative approaches are therefore needed to minimize the use of chemical fertilizers and agrochemicals, since ginger is directly consumed. Emphasis should be given for the organic cultivation of ginger. The role of bioinoculants assumes special significance in this context. The magnitude of plant growth promoting activities is reported to be better in the case of consortia or mixed cultures than single strain. Therefore, bioinoculants formulation consisting of biofertilizer and biocontrol agent would be a novel technology which will provide nutrients as well as manage diseases. The literature on the use of consortia of biofertilizers and biocontrol agents are scanty. Hence, a study was undertaken on “Evaluation of bioinoculant consortia for organic cultivation of ginger’’ with an objective to evaluate and find a suitable consortia of bioinoculants for ginger cultivation. Azospirillum lipoferum, phosphate solubilizing bacteria (PSB), potash solubilizing bacteria (KSB), Pseudomonas fluorescens and Trichoderma viride cultures of KAU were used for the study. When tested for their compatibility with each other, it was found that Azospirillum lipoferum, PSB, KSB, Pseudomonas fluorescens were mutually compatible with each other. However, Pseudomonas fluorescens and Trichoderma viride were incompatible. Based on the compatibility test, consortia consisting of biofertilizers alone and biofertilizer + biocontrol agents were selected for the field evaluation. The consortia KAU-AZO +KAU- PSB + KAU-KSB, KAU-AZO + KAU-PSB + KAU-KSB + KAU-PF and KAU-AZO + KAU-PSB + KAU-KSB + KAU-TV were selected. These consortia were compared with individual bioinoculants, vii PGPR Mix I, PGPR Mix II, Organic adhoc package (KAU, 2009) and POP recommendation (KAU, 2011). Based on the overall biometric and yield parameters, T11 (Organic adhoc package, KAU, 2009) was found to be best among all the treatments evaluated. Among the consortia, days taken for germination was minimum (17.33) in the case of T6 (KAU-AZO+KAU-PSB+ KAU-KSB) while both T7 (KAUAZO+ KAU-PSB+ KAU-KSB +KAU-PF) and T8 (KAU-AZO+KAU-PSB+ KAUKSB +KAU-TV) recorded the highest per cent (91.67) germination. Plant height, number of tillers, and yield were maximum in T8 (KAU-AZO+KAU-PSB+ KAUKSB +KAU-TV). With regard to disease and pest incidence, T8 (KAU-AZO + KAU-PSB + KAU-KSB + KAU-TV) recorded minimum per cent rhizome rot (5.23%) incidence. However, T7 (KAU-AZO+KAU-PSB+ KAU-KSB +KAU-PF) recorded the minimum per cent incidence (5.21) of Rhizoctonia leaf blight and shoot-borer (4.17 %). The T6 treatment (KAU-AZO+KAU-PSB+ KAU-KSB) was the least succeptible (6.25 %) to rhizome maggots. At the time of harvest, T7 (KAU-AZO+KAU-PSB+KAU-KSB +KAU-PF) and T8 (KAU-AZO+KAU-PSB+ KAU-KSB +KAU-TV) recorded the lowest pH (5.30) and T8 (KAU-AZO + KAU-PSB+ KAU-KSB+ KAU-TV) registered highest available nitrogen (188.68 kg/ha) among the consortia. However, highest organic carbon (1.55 %) and available phosphorus (37.44 kg/ha) was recorded in T7 (KAU-AZO+KAU-PSB+KAU-KSB+ KAU-PF). All the consortial treatments were on par with each other with respect to available potassium content in soil. Population of inoculated individual and consortial isolates in soil indicated a decreasing trend till the time of harvest. The population decreased from 108 cfu/ml to 104 cfu/ml in the case of bacteria and 106 to 10 3 cfu/ml in the case of fungus. The Benefit:Cost ratio was maximum (1.65) in the case of T8 (KAU-AZO + KAU-PSB + KAU-KSB + KAU-TV). viii The present studies clearly indicated that consortia inoculated plants performed better than the individual isolates. The consortia of bioinoculants treated plants were on par, but T8 (KAU-AZO + KAU-PSB + KAU-KSB + KAUTV) was the most promising treatment among the consortia. Therefore, it can be concluded that bioinoculant consortia consisting of bioagents for nutrient fixation /solubilization (N, P, K) and fungicidal effect would be a novel technology in present-day agriculture.
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    ThesisItemOpen Access
    Utilization of free living diazotrophic bacteria from Wayanad as a biofertilizer
    (College of Horticulture, Vellanikkara, 2015) Fathima, Shaheena K M; KAU; Girija, D
    Agriculture is heavily dependent on the use of chemical fertilizers. However, excessive and unbalanced use of these inputs may lead to environmentalpollution and health hazards. Biofertilizers are biological fertilizers which play a key role in maintaining productivityand sustainability of soil, thereby protecting the environment. Hence, a study was undertaken to isolate, screen and evaluate free living diazotrophic bacteria to develop an efficient biofertilizer. Rhizosphere soils and plant samples were collected from ten healthy black pepper gardens of different locations of Wayanad district. A total of 43 free living diazotrophic bacteria were isolated on three different N-free media (Jensen’s agar, Beijerinckia agar and Ashby’s agar). Maximum population of nitrogen fixers was obtained on Jensen’s agar. Twenty predominant isolates were selected, including eleven isolates from rhizosphere soil and nine isolates from phylloplane, based on their growth characteristics on N-free media for further evaluation. Twenty selected isolates were screened under in vitro condition for growth, nitrogen fixation and acid tolerance. As pH was lowered from 7.0 to 5.0, a reduction in growth and nitrogen fixation was observed. However, among the isolates, two from the rhizosphere (NKdS and NPS-1) and two from phylloplane (NKPV-2 and NPPV) performed better. Twenty selected isolates were screened in vitro for plant growth promoting activities like production of IAA, HCN, siderophore and ammonia.The antagonistic activity of all the twenty isolates was tested against three soil borne plant pathogens Fusarium oxysporum, Rhizoctonia solaniand Ralstonia solanacearum. Isolates NkdS, NPPV and NKS-1 were found to exhibit antagonistic activityagainst Rhizoctonia solani.Six isolatesinhibited the growth ofRalstonia solanacearum. None of the isolatesrecorded antagonistic activity against Fusarium oxysporum. Four most promising diazotrophs including, two rhizosphere isolates (NKdS and NPS-1) and two phylloplane isolates (NPPV and NKPV-2) were selectedfor in xxx planta evaluation, based on nitrogen fixation ability, tolerance to acidic pHand PGPR activities. 16S rDNA sequence analysis was carried out and promising isolates were identified asMicrobacterium sp. (NKdS and NPPV); Cellulosimicrobium sp. (NPS-1) and Brevundimonas sp. (NKPV-2). In planta evaluation was carried out with tomato as the test crop. These isolates were applied alone, in combination with 75% N and with 75% N + 50% FYM. Diazotrophs were inoculated as seed treatment, seedling dip and soil/foliar application. Seeds treated withKAU Azotobacter formulation triggered faster germination compared to all other treatments. However, after 7 days of sowing, maximum number of seedling emergence (90.24%) was recorded in seeds treated with Cellulosimicrobium sp. Plant height, number of leaves, fresh weight and volume of root, fresh weight and dry weight of plants,yield per plant, average fruit weight and number of fruits were observed to be maximum in treatment T12 (Microbacterium sp.+ 75% N + 50% FYM). T11 (Cellulosimicrobium sp. +75% N + 50% FYM) recorded maximum girth of stem, leaf area and minimum days to flowering. Total nitrogen content of index leaf and plant was maximum in T12 (Microbacterium sp. + 75% N + 50% FYM). The same treatment recorded maximum nitrogen content in soil at 60DAS. At harvest, T11 (Cellulosimicrobium sp. + 75% N + 50% FYM) recorded highest nitrogen content in soil. Population build up of bioinoculants in soil was higher in presence of FYM.Endophytic colonization was higher in root, in case of soil application of bioinoculants and higher in leaves, in case of foliar spray. The study revealed that novel, free living diazotrophic bacteria like Microbacterium and Cellulosimicrobium could be exploited as biofertilizer formeeting 25% of the nitrogen requirement. Results also indicated the importance of application of organic manure along with the isolates, for their best performance