Citrus canker caused by Xanthomonas citri subsp. citri is a disease affecting the yield and fruit quality of lime ( Citrus aurantiifolia ). This research investigated endophytic bacteria obtained from six healthy Citrus spp. to inhibit the pathogen and to control citrus canker on lime plants. Numbers of the endophytic bacteria isolated from C. aurantifolia , C. hystrix , C. maxima , C. nobilis , C. reticulata and C. sinensis were 28, 25, 29, 42, 12 and 34 isolates, respectively. The selected endophytic bacteria that were effective against X. citri subsp. citri were Bacillus amyloliquefaciens LE109, B. subtilis LE24 and B. tequilensis PO80. The optimum culture medium for an antagonistic effect on the pathogen in B. amyloliquefaciens LE109 and B. tequilensis PO80 was yeast extract peptone dextrose broth, and in B. subtilis LE24 was modified soluble starch broth. To control citrus canker in lime, young expanded leaves of lime plants were aseptically punctured and inoculated with 30 μl of bacterial suspension of the pathogen (10 8 CFU/ml in 0.85% NaCl) per punctured location. After the pathogenic inoculation for 24 h, the leaves were then inoculated with 30 μl of the selected endophytic bacteria (10 8 CFU/ml in 0.85% NaCl), and treated with 30 μl of the culture media containing bioactive compounds produced by the selected endophytic bacteria. The leaves inoculated with cell suspensions of B. amyloliquefaciens LE109 or B. subtilis LE24 could completely control citrus canker. However, the leaves inoculated with B. tequilensis PO80 displayed 10% disease incidence. Additionally, the leaves treated with the crude bioactive compounds of B. amyloliquefaciens LE109 or B. subtilis LE24 could completely control citrus canker. Notably, the leaves treated with the crude bioactive compounds of B. tequilensis PO80 displayed 5% disease incidence. The results of this study showed that the Bacillus strains play important roles in the biocontrol of citrus canker in lime.

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Nitrogen (N) is an essential element for the growth and yield of rice. Some endophytic bacteria can fix N 2 from the air and convert to nitrogen compounds that can be utilized by plants. In this study, endophytic bacteria were isolated from one-month-old seedlings of five rice (Oryza sativa L.) varieties (Muey Nong 24, Muey Nong 25, Pathum Thani 1, Suphan Buri 1 and Chai Nat 1) growing without nitrogen fertilizer in the farmers' field. One hundred and twenty-three isolates of endophytic bacteria were obtained from the roots, stems and leaves of these rice varieties. Nitrogenase activity of the bacteria in N-free culture medium was determined by acetylene reduction assay. Seven isolates of the bacteria with highest nitrogenase activity were identified by phylogenetic analysis of the 16S rRNA genes, and found to belong to Burkholderia cepacia (CS5), Citrobacter sp.

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Thailand is part of Southeast Asia that covers the center of diversity of citrus species, where various species of the genus are widely grown. One of the most common is tangerine (Citrus reticulata), which is commonly grown by grafting on rootstocks of different tangerine varieties or other citrus species. The objective of this study is to investigate responses of some Citrus spp. seedlings to arbuscular mycorrhizal (AM) fungi, and thus their potential as rootstocks. The experiment was done with four tangerine varieties, Cleopatra, Fremont, Ocean and Sainamphung; and four other citrus species, lime (C. aurantifolia), pomelo (C. maxima), sweet orange (C. sinensis) and Troyer citrange (Citrus sinensis Poncirus trifoliata), in pots for five months. Roots of non-inoculated plants were not infected with AM fungi, while inoculated plants were heavily infected with AM fungi, and contained 14-28 AM spores per 10 g of rhizosphere soil. Most of the citrus responded positively to AM fungi, but with different magnitudes among the varieties and species. Lime and pomelo seedlings were fast growing compared to other citrus species. Total dry weight and N, P, K and Mg contents were increased most strongly by AM fungi in lime, pomelo and tangerine varieties Ocean, Fremont and Sainamphung, but little or none in Cleopatra, Troyer and sweet orange. Lime was the most outstanding in the response to AM fungi, followed by Ocean tangerine and pomelo. The potential of lime, pomelo and Ocean tangerine as rootstock for tangerine should be further investigated.