Bacillus Spp.Promote Plant Growth And The Volatiles Of The Strains

We have always been depending on chemical pesticides to control pests and diseases to reduce the loss of pests and diseases on crop yield. Meanwhile it also brings a series of problems, such as environment pollution, generation of pest and disease resistant to chemicals, damage to non-target organisms, which have a serious impact on the sustainable development of agricultural systems. However, microbial pesticides have the advantages of environmentally friendly, strong adapt ability, safe to non-target organisms, no chemical residues and coupled with the improvement of genetic engineering technology, which shows a good application prospect and attention of more and more people. Bacillus spp. is a kind of common rhizosphere promoting in bacteria (PGPR). In the past two decades, PGPR is widely used in the development of sustainable agriculture in the worldwide. A large number of reports confirm that the PGPR are able to promote the growth of field crops by increasing the rate of seed germination, increased plant weight and crop yields. In addition, some studies also found that PGPR can promote a variety of fruits growth and improve fruit yield such as apples, citrus, blueberry, mulberry and apricot. Currently, Bacillus promoting mechanism includes:1, Improve the plant rhizosphere nutrient availability such as promoting the release of insoluble phosphorus, iron and trace elements;2, Generating plant hormone indole-3-acetic acid (IAA), cytokinins (cytokinin) and gibberellin (Gibberellins gas), as well as produce ACC deaminase (1-amino-cyclopropane-1-carboxylic acid ester deaminase) reduces the level of ethylene in plants;3, Produce volatile compounds. In addition to those, they also employ indirectly promoting effects to promote the growth of plants. In the presence of the pathogen, they reduce the incidence of plant disease by increasing the resistance of the plants. But so far, research on the Bacillus promoting mechanism is not fully.In this experiment, we used the marked strainB42-gfp. We used suspension with different concentration to soaking the seeds of wheat, and found that this strain can promote the growth of wheat seedlings by improving the germination rate, root length, shoot length and the fresh weight. According to the results, we observed that the most suitable concentration is3.65×106CFU/ml, and the higher one would inhibit the growth of the wheat. To understand the survival ability of FZB42, we survey the population dynamic of strain FZB42-gfp in sterile and unsterile soil respectively, and observed that the population dynamic of this strain in the unsterile soil is stronger than that in the sterile one which indicate that the competitive ability of this is strong in the natural environment. In the field experiment, using Bacillus the seedlings of wheat can significantly promote the field of the wheat by9.04%。 While using one kind of water soluble fertilizer could develop the field by only1.7%。At the same time, we screened several strains which can promote the growth of tobacco by producing volatiles, including OKB105and FZB42.We collected and analyzed the compounds of the volatiles. In the result, we found that the interaction effect between the volatiles and the plant depends on the type of the medium and the inoculation amount. And among the compounds we analyzed in the volatiles of these two strains, we observed several components which has the ability to kill the nematodes or inhibit the growth of fungi, like Phenol, Nonanal and Hexadecanol, which means that there may be some unknown function of these two strains in resistance to some disease. In this experiment, by studying the promoting ability and the volatiles of Bacillus spp., we lay the foundation for the development of new bio-fertilizer and plant induced systemic inducer or elicitor.