Effects of Plant Growth-promoting Rhizobacteria on Physiological Characteristics and Inorganic Elements in Paris polyphylla var. yunnanensis / 中国实验方剂学杂志

ObjectiveTo study the effects of different plant growth-promoting rhizobacteria （PGPR） on the growth of Paris polyphylla var. yunnanensis seedlings and the quality of its medicinal parts， in order to provide reference for the cultivation of high-quality P. polyphylla var. yunnanensis. MethodThe pot culture experiment at room temperature and the single-factor completely random design were employed for exploring the effects of five PGPR on physiological characteristics and inorganic elements of P. polyphylla var. yunnanensis. ResultThe results showed that the exogenous inoculation of different PGPR promoted the growth and development of P. polyphylla var. yunnanensis to varying degrees， delayed the senescence of leaves， and improved the medicinal value of new and old rhizomes. Compared with the non-inoculated control， the exogenous inoculation of compound microbial fertilizer （FH） and microbial agent Sanju Guanjin liquid （SJ） enhanced the root vigor， increased the content of photosynthetic pigments and the activities of anti-oxidant enzymes ［superoxide dismutase （SOD）， catalase （CAT）， and peroxidase （POD）］， and reduced the content of malondialdehyde （MDA） in leaves. Their inhibition rates against MDA were 10.46%-39.62% and 20.99%-53.12%， respectively. With the growth of P. polyphylla var. yunnanensis， the inhibition rate against MDA gradually increased， which effectively delayed the senescence of P. polyphylla var. yunnanensis leaves. In addition， the exogenous inoculation of different PGPR promoted the accumulation of nutrient elements in new and old rhizomes， lowered the heavy metal content to varying degrees， and improved the medicinal value of P. polyphylla var. yunnanensis rhizomes. ConclusionFH and SJ have exhibited the best promoting effect on the growth of P. polyphylla var. yunnanensis seedlings and also the best regulatory effect on the medicinal value of P. polyphylla var. yunnanensis rhizomes， which has provided reference for the application and promotion of PGPR in the growth of P. polyphylla var. yunnanensis.

In vitro screening and identification of plant growth-promoting rhizobacteria against pathogen causing Astragalus root rot / 中国中药杂志

The antagonistic effect of Bacillus spp. against Fusarium solani was evaluated by living body dual culture and Oxford cup method. The plant growth promoting properties of those strains that had obvious and stable antifungal activity were then tested. The results showed that the living body and bacteria-free fermentation filtrate of strain G10 both had obvious and stable antifungal effect to F. solani. Besides, the strain possessed such growth promoting properties as phosphate solubilization, nitrogen fixation, and production of IAA, amylase and HCN. Strain G10 was classified and identified as B. subtilis by a combination of morphological, physiological and biochemical tests, 16 SrDNA gene sequence analysis and the BBL CrystalTM bacteria identification. In conclusion, B. subtilis G10 has the basic characteristics of multifunctional strains and could be one of the microbiological resources for developing special bio-control agent against Astragalus root rot.

Developing novel bacterial based bioformulation having PGPR properties for enhanced production of agricultural crops.

Plant growth promoting rhizobacteria (PGPR) are beneficial rhizobacteria which enhance plant growth as well as the productivity by a variety of mechanisms. PGPR were isolated from the rhizosphere region of som plants (Machilus bombycina King) maintained at the Central Muga Eri Research and Training Institute, Lahdoigarh, Jorhat. A bacterial based bioformulation was prepared and sprayed over the experimental crops including tomato (Solanum lycopersicum), cauliflower (Brassica oleracea var botrytis), chili (Capsicum annuum) and brinjal (Solanum melongena). Biochemical analysis was done on these PGPR treated crops as well as the untreated crops. The bioformulations prepared from Bacillus cereus (MTCC 8297), Pseudomonas rhodesiae (MTCC 8299) and Pseudomonas rhodesiae (MTCC 8300) was found to be the most effective in increasing the shoot height, number of leaves, early fruiting and total biomass content of the plants after treatment.

Ultrastructures of Colletotrichum orbiculare in the Leaves of Cucumber Plants Expressing Induced Systemic Resistance Mediated by Glomus intraradices BEG110

The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

Resistance Induction and Enhanced Tuber Production by Pre-inoculation with Bacterial Strains in Potato Plants against Phytophthora infestans

Efficacy of resistance induction by the bacterial isolates Pseudomonas putida (TRL2-3), Micrococcus luteus (TRK2-2) and Flexibacteraceae bacterium (MRL412), which were isolated from the rhizosphere of plants growing in Jeju Mountain, were tested in a greenhouse. The disease severity caused by Phytophthora infestans was effectively reduced in the potato plants pre-inoculated with bacterial isolates compared with those of the untreated control plants growing in a greenhouse. In order to estimate the level of protection by the bacterial isolates, Mancozeb WP (Diesen M(R), Kyong nong) and DL-3-amino butyric acid (BABA) were pre-treated, whereas Dimethomorph WP (Forum(R), Kyong nong) and phosphonic acid (H3PO3) were post-treated the challenge inoculation with the pathogen. Disease severities of chemical pre-treated as well as post-treated plants were reduced compare to those of the untreated. The disease reduction in the plants pre-treated with Mancozeb WP was the highest, whereas that of post-treated with Dimethomorph WP was the lowest. The yields of plants pre-inoculated with three bacterial isolates were greatly increased than those of control plants. These results suggest that biological control by bacterial isolates might be an alternative strategy against late blight disease in potato plants growing in greenhouse.

Different Mechanisms of Induced Systemic Resistance and Systemic Acquired Resistance Against Colletotrichum orbiculare on the Leaves of Cucumber Plants

Defense mechanisms against anthracnose disease caused by Colletotrichum orbiculare on the leaf surface of cucumber plants after pre-treatment with plant growth promoting rhizobacteria(PGPR), amino salicylic acid(ASA) or C. orbiculare were compared using a fluorescence microscope. Induced systemic resistance was mediated by the pre-inoculation in the root system with PGPR strain Bacillus amylolquefaciens EXTN-1 that showed direct antifungal activity to C. gloeosporioides and C. orbiculare. Also, systemic acquired resistance was triggered by the pre-treatments on the bottom leaves with amino salicylic acid or conidial suspension of C. orbiculare. The protection values on the leaves expressing SAR were higher compared to those expressing ISR. After pre-inoculation with PGPR strains no change of the plants was found in phenotype, while necrosis or hypersensitive reaction(HR) was observed on the leaves of plants pre-treated with ASA or the pathogen. After challenge inoculation, inhibition of fungal growth was observed on the leaves expressing both ISR and SAR. HR was frequently observed at the penetration sites of both resistance-expressing leaves. Appressorium formation was dramatically reduced on the leaves of plants pre-treated with ASA, whereas EXTN-1 did not suppress the appressorium formation. ASA also more strongly inhibited the conidial germination than EXTN-1. Conversely, EXTN-1 significantly increased the frequency of callose formation at the penetration sites, but ASA did not. The defense mechanisms induced by C. orbiculare were similar to those by ASA. Based on these results it is suggested that resistance mechanisms on the leaf surface was different between on the cucumber leaves expressing ISR and SAR, resulting in the different protection values.