Gajera H P, Hirpara Darshna G, Katakpara Zinkal A, Patel S V, Golakiya B A
Department of Biotechnology, College of Agriculture, Junagadh Agricultural University, Junagadh-362 001, India.
Department of Biotechnology, College of Agriculture, Junagadh Agricultural University, Junagadh-362 001, India.
Infect Genet Evol. 2016 Nov;45:383-392. doi: 10.1016/j.meegid.2016.09.026. Epub 2016 Oct 5.
The biocontrol agent Trichoderma (T. harzianum, T. viride, T. virens, T. hamantum, T. koningii, T. pseudokoningii and Trichoderma species) inhibited variably (15.32 - 88.12%) the in vitro growth of Rhizoctonia solani causing root rot in cotton. The T. koningii MTCC 796 evidenced highest (88.12%) growth inhibition of test pathogen followed by T. viride NBAII Tv23 (85.34%). Scanning electron microscopic study confirmed mycoparasitism for MTCC 796 and Tv23 which were capable of completely overgrowing on R. solani by degrading mycelia, coiling around the hyphae with hook-like structures. The antagonists T. harzianum NBAII Th1 and, T. virens NBAII Tvs12 exhibited strong antibiosis and formed 2-4 mm zone of inhibition for 70.28% and 46.62%, respectively growth inhibition of test pathogen. Mycoparasitism is a strong mode of action for biocontrol activity compared with antibiosis. The antagonists Trichoderma strains were performed for start codon targeted (SCoT) polymorphism to acquire biocontrol genes from potent antagonist. The six unique SCoT fragments amplified by genomic DNA of best mycoparasitic antagonist MTCC 796 strain are subjected to DNA sequencing resulted to confirm two functional sequences for activity related to biocontrol genes. The phylogenetic and molecular evolution of functional 824 bp of SCoT-3 and 776 bp of SCoT-6 fragments signify sequence homology with biocontrol genes endochitinase (partial cds of 203 amino acids) and novel hmgR genes (partial cds of 239 amino acids), respectively and the same were annotated and deposited in NCBI GenBank database. The hmgR gene is liable to be express hmg - CoA reductase which is a key enzyme for regulation of terpene biosynthesis and mycoparasitic strains produced triterpenes during antagonism to inhibit growth of fungal pathogen as evidenced with GC-MS profile. The biocontrol genes are found in best antagonist T. koningii MTCC 796 for mycoparasitic activity to restrain the growth of test pathogen R. solani.
生物防治剂木霉（哈茨木霉、绿色木霉、绿粘帚霉、哈曼木霉、康宁木霉、拟康宁木霉及木霉属其他种）对引起棉花根腐病的立枯丝核菌的体外生长有不同程度（15.32% - 88.12%）的抑制作用。康宁木霉MTCC 796对受试病原菌的生长抑制率最高（88.12%），其次是绿色木霉NBAII Tv23（85.34%）。扫描电子显微镜研究证实MTCC 796和Tv23存在重寄生现象，它们能够通过降解菌丝体在立枯丝核菌上完全生长，并以钩状结构缠绕菌丝。拮抗木霉哈茨木霉NBAII Th1和绿粘帚霉NBAII Tvs12表现出强烈的抗生作用，对受试病原菌的生长抑制率分别为70.28%和46.62%，抑菌圈直径为2 - 4毫米。与抗生作用相比，重寄生是生物防治活性的一种强大作用方式。对木霉菌株进行起始密码子靶向（SCoT）多态性分析，以从高效拮抗菌中获取生物防治基因。最佳重寄生拮抗菌MTCC 796菌株的基因组DNA扩增出的6个独特SCoT片段经DNA测序，证实了两个与生物防治基因相关的活性功能序列。功能片段SCoT - 3的824 bp和SCoT - 6的776 bp的系统发育和分子进化分别表明与生物防治基因几丁质内切酶（203个氨基酸的部分编码序列）和新型hmgR基因（239个氨基酸的部分编码序列）具有序列同源性，这些序列已进行注释并保存在NCBI基因银行数据库中。hmgR基因可能表达hmg - CoA还原酶，这是调节萜类生物合成的关键酶，气相色谱 - 质谱分析表明，重寄生菌株在拮抗过程中产生三萜类物质以抑制真菌病原菌生长。在最佳拮抗菌康宁木霉MTCC 796中发现了用于重寄生活性以抑制受试病原菌立枯丝核菌生长的生物防治基因。
