Influence of crop combinations and soil factors on diversity and association of arbuscular mycorrhizal fungi in arecanut based cropping systems

Arbuscular mycorrhizal (AM) species diversity and extent of association were investigated in arecanut based cropping systemsdiffering in crop combinations. The study was carried out in farmers’ fields under acidic soil conditions at three locations representinglow land (Maneikkara), midland (Cheruvanjeri) and high land (Nedumpoyil) regions of Kannur district in Kerala. The croppingsystems in Maneikkara, Cheruvanjeri and Nedumpoyil had arecanut-banana, arecanut-banana-black pepper and arecanut-bananablackpepper-cardamom as component crops. AM spore load and root colonization differed significantly in arecanut in the threecropping systems. Highest spore load was recorded in Maneikkara followed by that in Nedumpoyil and Cheruvanjeri regions.Crops which formed components of the cropping system differed in root colonization levels, with banana recording the highestlevel, followed by arecanut, black pepper and cardamom. Colonization pattern was Paris type in all crops, but varied with respectto predominance of arbuscules in arecanut and vesicles in banana. Arecanut-black pepper-banana system at Cheruvanjeri inmidland was superior with respect to species diversity and species richness as evidenced by Shannon–Weiner index (Hs), Simpson’sindex of diversity (Ds) and species richness index. Arecanut-banana cropping system in Maneikkara in low land had low level ofspecies diversity and species richness, indicating the combined influence of crop combinations and soil factors such as N and P onAM diversity and distribution. Rhizophagus fasciculatus, Funneliformis geosporum, F. mosseae, Glomus macrocarpum,G. aggregatum, G. multicaule, G. glomerulatum and Acaulospora bireticulata were the AMF species identified from the arecanutcropping systems. F. geosporum was the most abundant (29-50%) species in the cropping system. The relative occurrence andabundance of AM species varied significantly with respect to the crops and locations

Antagonistic activity of coconut rhizospheric and endophytic Bacillus spp. against Ganoderma applanatum and Thielaviopsis paradoxa

A screening study was carried out to detect the antagonistic potential of Bacillus spp. against Ganoderma applanatum and Thielaviopsis paradoxa, fungal pathogens of coconut. A total of 327 heat resistant, endospore producing bacilli were isolated from the rhizospheric soil and roots of coconut growing in Kerala, Tamil Nadu, Karnataka, Andhra Pradesh and Maharashtra. All the isolates were tested for antifungal activity against G. applanatum and T. paradoxa by dual cultural technique on nutrient agar medium. The zone of inhibition was measured and percentage of inhibition was calculated. More than 90 % of the rhizospheric and root endophytic isolates were found to effectively inhibit the mycelial growth of G. applanatum, with a maximum inhibition zone of 12 mm and percentage inhibition ranging from 44 to 91. About 86 % of the isolates inhibited the mycelial growth of T. paradoxa, with a maximum inhibition zone of 14 mm and percentage inhibition ranging from 42 to 93. Further tests of potent antagonists revealed that more than one mode of mechanisms like production of chitinase, siderophores, HCN, antibiotics, ammonia, β-1,3- glucanase and salicylic acid may be involved in the antagonistic activities. The results of this study revealed 13 Bacillus spp. having potential for use as biocontrol agents against G. applanatum and T. paradoxa, fungal pathogens of coconut

Isolation and identification of spore associated bacteria (SAB) from Glomus and Gigaspora spp. in coconut and arecanut based cropping systems

Arbuscular mycorrhizal symbiosis is exhibited by 80% of the terrestrial plants. The spores of arbuscular mycorrhizal fungi (AMF) form a unique microhabitat for the colonization by many species of bacteria. The present study was undertaken to isolate and identify spore associated bacteria (SAB) and evaluate their functional role in AMF-host interactions with respect to germination of spores. Coconut and arecanut based cropping systems under organic management practices in farmer’s field in Kasaragod district, Kerala and high density multi species cropping system (HDMSCS), CPCRI farm were selected for the study. The results revealed that AMF spore load of a particular cropping system increase with the number of intercrops. Spore associated bacteria (SAB) were isolated from the cytoplasm of surface sterilized spores of Glomus and Gigaspora spp. Identification based on BIOLOG and 16S rRNA sequencing revealed the presence of bacteria - Citrobacter amalonaticus, Staphylococcus arlettae, Bacillus subtilis, Bacillus amyloliquefaciens, in association with spores of Glomus spp. Corynebacterium coyleae, Bacillus cereus and Bacillus subtilis were found to be associated with Gigaspora spp. In vitro studies to determine the germination potential in spores showed the maximum results with Bacillus cereus GiPHD1 and Citrobacter amalonaticus GLNCB1 with 40% increase over control

In vitro antagonism of rhizospheric fluorescent pseudomonads of coconut against Ganoderma applanatum and Thielaviopsis paradoxa, fungal pathogens of coconut

A total of 156 fluorescent pseudomonads were tested for antagonistic activity towards G. applanatum and T. paradoxa in a dual-plate assay on King’s B agar plates. Eight percent of the total fluorescent pseudomonads showed antagonism towards G. applanatum (inhibition ranging from 39% to 73%) and 16% of the isolates inhibited T. paradoxa in the range of 20% - 76%. Moreover, eight percent of the fluorescent pseudomonads significantly inhibited both pathogens tested. They were found to possess some important biocontrol traits such as HCN, siderophores, ammonia and antibiotics. Among them fluorescent Pseudomonas spp. KiSF 17 and KiSF 16 exhibited strong antagonistic activity. They were identified as P. aeruginosa by Biolog® GEN III microplate identification system and confirmed by 16S rDNA sequencing. The present studies revealed the survival of useful bacterial antagonists in the rhizosphere of coconut palm, which have the potential to be used as a biocontrol agent

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Microbiome selection could spur next-generation plant breeding strategies

Plants, though sessile, have developed a unique strategy to counter biotic and abiotic stresses by symbiotically co-evolving with microorganisms and tapping into their genome for this purpose. Soil is the bank of microbial diversity from which a plant selectively sources its microbiome to suit its needs. Besides soil, seeds, which carry the genetic blueprint of plants during trans-generational propagation, are home to diverse microbiota that acts as the principal source of microbial inoculum in crop cultivation. Overall, a plant is ensconced both on the outside and inside with a diverse assemblage of microbiota. Together, the plant genome and the genes of the microbiota that the plant harbours in different plant tissues i.e the ‘plant microbiome’, form the holobiome which is now considered as unit of selection: ‘the holobiont’. The ‘plant microbiome’ not only helps plants to remain fit but also offers critical genetic variability, hitherto, not employed in the breeding strategy by plant breeders, who traditionally have exploited the genetic variability of the host for developing high yielding or disease tolerant or drought resistant varieties. This fresh knowledge of the microbiome, particularly of the rhizosphere, offering genetic variability to plants, opens up new horizons for breeding that could usher in cultivation of next-generation crops depending less on inorganic inputs, resistant to insect pest and diseases and resilient to climatic perturbations. We surmise, from ever increasing evidences, that plants and their microbial symbionts need to be co-propagated as life-long partners in future strategies for plant breeding

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Not AvailableThe process to recycle lignin-rich coconut leaves, pro-duced in abundance from coconut gardens, to vermi-compost, using a local isolate of Eudrilus sp. is an important value-addition technology from ICAR-Central Plantation Crops Research Institute helping coconut farmers and entrepreneurs to enhance their economic returns. Vermicompost is produced in ce-ment tanks and at the end of the composting period, earthworms are hand-sorted from the mature and partially composted materials by employed workers. The scarcity of labour for earthworm sorting and non-availability of earthworms at the required time for further vermicomposting had become an impediment in sustained production of vermicompost leading to abandonment of the technology by many adopters. To overcome this situation, a simple push–pull/pull–pull strategy was developed for harvesting the earth-worms, wherein freshly ground mustard solution was used as repellant (push agent) and cow dung (with or without bagasse/banana wastes) was used as an attractant (‘pull’ agent). The strategy is simple, efficient and saves on labour, eliminates drudgery, reduces production cost and time. It will pave way for sustained adoption of vermicomposting technology by coconut farmers and entrepreneurs.Not Availabl

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Not Available“No plant is an island too…” Plants, though sessile, have developed a unique strategy to counter biotic and abiotic stresses by symbiotically co-evolving with microorganisms and tapping into their genome for this purpose. Soil is the bank of microbial diversity from which a plant selectively sources its microbiome to suit its needs. Besides soil, seeds, which carry the genetic blueprint of plants during trans-generational propagation, are home to diverse microbiota that acts as the principal source of microbial inoculum in crop cultivation. Overall, a plant is ensconced both on the outside and inside with a diverse assemblage of microbiota. Together, the plant genome and the genes of the microbiota that the plant harbors in different plant tissues, i.e., the ‘plant microbiome,’ form the holobiome which is now considered as unit of selection: ‘the holobiont.’ The ‘plant microbiome’ not only helps plants to remain fit but also offers critical genetic variability, hitherto, not employed in the breeding strategy by plant breeders, who traditionally have exploited the genetic variability of the host for developing high yielding or disease tolerant or drought resistant varieties. This fresh knowledge of the microbiome, particularly of the rhizosphere, offering genetic variability to plants, opens up new horizons for breeding that could usher in cultivation of next-generation crops depending less on inorganic inputs, resistant to insect pest and diseases and resilient to climatic perturbations. We surmise, from ever increasing evidences, that plants and their microbial symbionts need to be co-propagated as life-long partners in future strategies for plant breeding. In this perspective, we propose bottom–up approach to co-propagate the co-evolved, the plant along with the target microbiome, through – (i) reciprocal soil transplantation method, or (ii) artificial ecosystem selection method of synthetic microbiome inocula, or (iii) by exploration of microRNA transfer method – for realizing this next-generation plant breeding approach. Our aim, thus, is to bring closer the information accrued through the advanced nucleotide sequencing and bioinformatics in conjunction with conventional culture-dependent isolation method for practical application in plant breeding and overall agriculture.Not Availabl

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Not AvailableAmong the low external input resources, vermicompost is one the major components of organic farming practices for sustaining soil health, fertility and crop productivity. Vermicompost production is a process that can recycle many of the agricultural refuse into wealth. Many crop residues are now a days being converted to vermicompost. Coconut and arecanut palms are two important plantation crops widely grown in southern India and other states. Put together, about 2.4 million ha is under cultivation for these two palms in India. These plantation crops have the character of generating voluminous quantities of biomass residues that are difficult to decompose naturally because of high lignin contents. Using the earthworms, Eudrilus sp., Eudrilus eugeniae and Eisenia fetida, adapted to converting the difficult-to-decompose coconut and arecanut leaves, a unique vermicomposting technology for these palm wastes have been developed at ICAR- CPCRI. As a side-product, vermiwash can also be produced from this technology which can act as liquid organicfertilizer and used in fertigation. In this review, we highlight the production process, field studies and their role in organic farming of the plantation crops.Not Availabl

Mechanism of plant growth promotion by rhizobacteria

856-862Plant growth results from interaction of roots and shoots with the environment. The environment for roots is the soil or planting medium which provide structural support as well as water and nutrients to the plant. Roots also support the growth and functions of a complex of microorganisms that can have a profound effect on the growth and survival of plants. These microorganisms constitute rhizosphere microflora and can be categorized as deleterious, beneficial, or neutral with respect to root/plant health. Beneficial interactions between roots and microbes do occur in rhizosphere and can be enhanced. Increased plant growth and crop yield can be obtained upon inoculating seeds or roots with certain specific root-colonizing bacteria- ‘plant growth promoting rhizobacteria’. In this review, we discuss the mechanisms by which plant growth promoting rhizobacteria may stimulate plant growth