Enhancement of Tomato (Lycopersicon esculentum) Tolerance to Drought Stress by Plant-Growth-Promoting Rhizobacterium (PGPR) Bacilluscereus AR156 | 根围促生细菌(PGPR)蜡质芽胞杆菌AR156对番茄的诱导耐旱性研究

صينى. 根围促生细菌(PGPR)蜡质芽胞杆菌(Bacillus cereus)AR156是具有很高应用前景的生防菌剂，为了研究其对番茄(Lycopersicon esculentum)的诱导耐旱机理，本研究通过检测干旱胁迫条件下叶片相对含水量、丙二醛(MDA)含量、相对电导率、叶绿素含量和根系还原能力，抗氧化酶活性以及胞质抗坏血酸还原酶基因(cAPX)、单脱氢抗坏血酸还原酶基因(MDHAR)和核酮糖-1, 5-二磷酸羧化酶(Rubisco)小亚基基因(rbcS)的表达情况，从表型、生理水平和分子水平上进行阐释。研究发现，干旱胁迫条件下 AR156 培养上清诱导后，番茄叶片相对含水量为 82%，与对照组相比提高了 44%； MDA 含量为 2.2×10-3 μmol/g FW，降低了 21.4%，相对电导率为 56.0%，降低了 28.2%；叶绿素 a、叶绿素 b和总叶绿素含量分别增加了 16%、20% 和 20.2%；根系还原强度为 0.336 mg/g/h，是对照组的两倍；另外，超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性也显著提高；同时，分子水平的检测发现 rbcS 在干旱处理过程中一直保持较高水平，cAPX 和 MDHAR的表达在干旱处理后期也显著高于对照组；并且干旱胁迫处理 20 d 后重新浇水24 h，番茄存活率达到 90.91%，比对照组高 1.6 倍。结果表明，AR156 培养上清可以通过保护细胞膜的完整性、维持较高水平的光合效率和提高抗氧化酶活性来提高番茄的系统耐旱性，初步阐释了PGPR AR156的诱导耐旱机理，为AR156作为优良生物类耐旱诱导因子提供了理论依据。

إنجليزي. Plant-growth promoting rhizobacterium (PGPR) Bacillus cereus AR156 is a potential bio-pesticide. In order to study the mechanism of drought tolerance in tomato (Lycopersicon esculentum) induced by B. cereus AR156, we tested relative water content, malondialdehyde(MDA) content, relative electrical conductivity and chlorophyll content of leaves and recovery intension of roots, the antioxidant enzymes activities and the expression of cytosolic ascorbate peroxidase gene (cAPX), monodehydroascorbate reductase gene (MDHAR) and ribulose-1, 5-bisphosphate carboxy/oxygenase(Rubisco) small subunit gene(rbcS) under drought stress condition. Results showed that after treated with culture supernate of AR156, relative water content of leaves was 82% comparing to control group, increased by 44%, recovery intension of roots was 0.336 mg/g/h, increased by 100%, chlorophyll a, chlorophyll b and total chlorophyll were increased by 16%, 20% and 20.2%, respectively, and the expression of rbcS maintained a stable high level, besides MDA content was 2.2×10-3 μmol/g FW, decreased by 21.4%, relative electrical conductivity was 56.0%, decreased by 28.2%, compared with control treatment. What's more, the activities of superoxide dismutase(SOD), peroxidase(POD) and hydrogen peroxidase(CAT) were increased markedly after applying with the culture supernate of AR156, and the expression of cAPX and MDHAR were up-regulated at anaphase of drought stress. Moreover the survival rate of tomato 24 h after re-watering were increased markedly, compared with control group. These results suggested that the culture supernate of AR156 increased drought tolerance of tomatoes by protecting plant cell, maintaining photosynthetic efficiency and increasing some of peroxidases activities. This made a contribution to the studies on the mechanism of systemic tolerance induced by PGPR. These results demonstrate the primary mechanism of drought torelance in tomato induced by AR156, and also provide theoretical basis for the application of AR156 as a good drought tolerance biological inducer.