The role of activated charcoal in plant tissue culture.

Characterizing microbial communities associated with disease-suppressive soil is an important first step toward understanding the potential of microbiota to protect crops against plant pathogens. In the present study, we compared microbial communities in suppressive- and conducive-soils associated with Fusarium wilt disease in a vanilla long-term continuous cropping system. Suppressive soil was associated with higher fungal diversity and lower bacterial diversity. The fungal phyla Zygomycota and Basidiomycota, and the bacterial phyla Acidobacteria, Verrucomicrobia, Actinobacteria and Firmicutes were strongly enriched in the suppressive soil. Notably, suppressive soil was dominated by the fungal genus Mortierella, accounting for 37% of the total fungal sequences. The hyper-dominance of Mortierella spp. in suppressive soil suggests that this taxon may serve as an indicator and enhancer of Fusarium wilt disease suppression in vanilla. In addition, Molecular Ecological Network analysis revealed that fungal communities were more connected and showed more co-occurrence relationships in the suppressive versus conducive soils. Our results indicate that fungal communities may be important in the development of soil suppressiveness against vanilla Fusarium wilt disease.

Distinct roles for soil fungal and bacterial communities associated with the suppression of vanilla Fusarium wilt disease

In the present study, soil bacterial and fungal communities across vanilla continuous cropping time-series fields were assessed through deep pyrosequencing of 16S ribosomal RNA (rRNA) genes and internal transcribed spacer (ITS) regions. The results demonstrated that the long-term monoculture of vanilla significantly altered soil microbial communities. Soil fungal diversity index increased with consecutive cropping years, whereas soil bacterial diversity was relatively stable. Bray-Curtis dissimilarity cluster and UniFrac-weighted principal coordinate analysis (PCoA) revealed that monoculture time was the major determinant for fungal community structure, but not for bacterial community structure. The relative abundances (RAs) of the Firmicutes, Actinobacteria, Bacteroidetes, and Basidiomycota phyla were depleted along the years of vanilla monoculture. Pearson correlations at the phyla level demonstrated that Actinobacteria, Armatimonadetes, Bacteroidetes, Verrucomicrobia, and Firmicutes had significant negative correlations with vanilla disease index (DI), while no significant correlation for fungal phyla was observed. In addition, the amount of the pathogen Fusarium oxysporum accumulated with increasing years and was significantly positively correlated with vanilla DI. By contrast, the abundance of beneficial bacteria, including Bradyrhizobium and Bacillus, significantly decreased over time. In sum, soil weakness and vanilla stem wilt disease after long-term continuous cropping can be attributed to the alteration of the soil microbial community membership and structure, i.e., the reduction of the beneficial microbes and the accumulation of the fungal pathogen.

Different Continuous Cropping Spans Significantly Affect Microbial Community Membership and Structure in a Vanilla-Grown Soil as Revealed by Deep Pyrosequencing

Fusarium wilt disease is a growing problem in agriculture systems. Application of bio-fertilizers containing beneficial microbes represents a promising disease control strategy. However, the mechanisms underlying disease suppression remain elusive. Here, in order to assess the importance of direct antagonism and modified soil microbiota on suppression of Fusarium wilt disease, we conducted a pot experiment with chemical, organic and biologically enhanced fertilizers, we tracked the impact of those fertilizer amendments on disease incidence, and measured the pathogen density and changes in soil microbiota. Alterations in bacterial abundance and community structure after bio-fertilizers application were determined to be key factors in constraining the pathogen, Fusarium oxysporum. In particular, bio-fertilizer application increased the abundance of indigenous microbial groups with reported antifungal activity, such as Lysobacter spp., which could play a keystone role in controlling this pathogen. The microbes introduced in the bio-fertilizer treatments (e.g. Bacillus and Trichoderma spp.) induced suppressiveness via alteration of the soil microbiome rather than direct pathogen inhibition. These results contrast with the commonly held paradigm of disease suppression using beneficial microbes and open up new perspectives for the promotion of soil health. In addition to seeking antagonistic microbes based on their direct inhibitory activity, disease suppression may also be achieved by introducing keystone species that reshape soil microbiome structure and function.

Bio-fertilizer application induces soil suppressiveness against Fusarium wilt disease by reshaping the soil microbiome

To investigate the chemical composition and insecticidal activity of the essential oils of certain Chinese medicinal herbs and spices, the essential oils were extracted from the stem barks, leaves, and fruits of Cinnamomum camphora (L.) Presl, which were found to possess strong fumigant toxicity against Tribolium castaneum and Lasioderma serricorne adults. The essential oils of the plants were extracted by the method of steam distillation using a Clavenger apparatus. Their composition was determined by gas chromatography/mass spectrometric (GC-MS) analyses (HP-5MS column), and their insecticidal activity was measured by seal-spaced fumigation. D-camphor (51.3%), 1,8-cineole (4.3%), and α-terpineol (3.8%), while D-camphor (28.1%), linalool (22.9%), and 1,8-cineole (5.3%) were the main constituents of its fruits. The essential oils of the C. camphora all showed fumigant and contact toxicity. Other compounds exhibited various levels of bioactivities. The results indicate that the essential oils of C. camphora and its individual compounds can be considered a natural resource for the two stored-product insect management.

https://www.mdpi.com/1422-0067/17/11/1836/pdf

The Chemical Composition of Essential Oils from Cinnamomum camphora and Their Insecticidal Activity against the Stored Product Pests

Multiple shoots were induced from shoot tips and nodal segments of a 12-year-old tree of Cinnamomum camphora on Woody Plant Medium (WPM) supplemented with BA and kinetin. The nodal segments from the in vitro developed plantlets could be induced again to produce a large number of harvestable shoots. Harvested shoots were rooted in vitro in WPM supplemented with activated charcoal (AC) and IBA. The plantlets were transferred to thermocol cups after which they were replanted into polybags and then to field. These plants survived with over 90% success under field conditions and exhibited vigorous growth. This system could be utilized for large-scale multiplication of C. camphora by tissue culture.

Micropropagation of camphor tree ( Cinnamomum camphora )

Vanilla is naturally distributed in Mexico and parts of Central America and the history of origin of cultivated vanilla suggests that the entire stock outside Mexico may be from a single genetic source. In the present study, RAPD polymorphism was used to estimate the level of genetic diversity and interrelationships among different collections of Vanilla planifolia Andr., and few related species, including both leafy and leafless types such as V. tahitensis J.W.Moore, V. andamanica, Rolfe, V. pilifera Holtt., and V. aphylla Blume. Studies revealed that there are very limited variation within collections of V. planifolia, indicative of its narrow genetic base, and of the related species we tested, V. tahitensis is nearest to V. planifolia. The species studied are diverse and have a similarity ranging from 1.2 to 57.3 %. Of the sampled taxa, V. andamanica is the most divergent and there is also reasonable variability within its collections, indicating the possibility of natural seed set. A total of 82 polymorphic bands expressed in the RAPD profiles were used to generate a genetic distance matrix, which was then used in cluster analysis. Specific groupings were revealed by the cluster analysis whereby the leafless forms (V. aphylla, V. pilifera and the new species) and V. andamanica formed separate clusters. This is the first report of species interrelationship studies, including both cultivated and wild vanilla species.

Genetic variations and interrelationships in Vanilla planifolia and few related species as expressed by RAPD polymorphism

Celastrus paniculatus Willd, a vulnerable important woody liana with high medicinal value and limited reproductive capacity has been over exploited due to its demand in the pharmaceutical industry. In the present study, an efficient micropropagation protocol was developed from nodal explants on Murashige and Skoog and woody plant medium. The effect of various strengths of WP and MS medium (total, half strength) and different concentrations of plant growth regulators including cytokinins [6-benzylaminopurine (BAP) and Kinetin) and auxins (α-naphthaleneacetic acid (NAA) and (IBA) indole-3-butyric acid] on proliferation and rooting was investigated. C. paniculatus shoots showed maximum proliferation in WP medium supplemented with BAP (0.5 mg l-1). Best rooting frequency and higher root number and length were attained in medium fortified with NAA in combination with 0.2% activated charcoal. Seventy percent of the plantlets were successfully acclimatized to ex vitro conditions, exhibiting normal development. These plantlets can be used to replenish the declining populations in the wild. Molecular profiling of the in vitro developed plantlets was done using RAPD to confirm their genetic uniformity.

D. Minoo

Papers

Micropropagation of camphor tree ( Cinnamomum camphora )

Genetic variations and interrelationships in Vanilla planifolia and few related species as expressed by RAPD polymorphism

In vitro propagation and genetic fidelity analysis of Celastrus paniculatus Willd – a vulnerable high trade medicinal woody liana of Western Ghats