School of Crop Protection, College of Post-Graduate Studies in Agricultural Sciences, Central Agricultural University (Imphal), Umiam, Meghalaya, 793 103, India.
School of Natural Resource Management, College of Post-Graduate Studies in Agricultural Sciences, Central Agricultural University (Imphal), Umiam, Meghalaya, 793 103, India.
Arch Microbiol. 2022 Sep 1;204(9):587. doi: 10.1007/s00203-022-03211-2.
Beauveria bassiana, a potential entomopathogenic biocontrol agent, has recently drawn attention worldwide for its other additional beneficial roles such as plant disease antagonist, beneficial rhizosphere colonizer, plant growth promoter and an endophyte. In the present study, endophytic colonizing behaviour of five (5) B. bassiana isolates viz., Bb4, Bb16, Bb25, Bb44 and Bb53 were studied in rice following three (3) artificial inoculation techniques viz., seed treatment, root inoculation and foliar spray and the endophytic colonizing ability were determined by culture-based assay. After B. bassiana inoculation, rice plants were challenged with Rhizoctonia solani and disease incidence and plant growth promotion were assessed. Per cent colonization of rice stems, leaves and roots were influenced by inoculation technique, post-inoculation time (7th, 14th, 21st and 28th dpi) and plant growth medium (sterile soil, non-sterile soil), recorded maximum on 14th-day post-inoculation (dpi) i.e., 96% in stems, 92% in leaves and 28% in roots, whereas, lower colonization was recorded on 7th, 21st and 28th dpi. Whereas, the foliar spray was found best as compared to seed and root inoculation techniques, and maximum fungal recovery was observed in stems and leaves and least in roots. Upon colonization, the physical presence of B. bassiana in rice was localized by light microscopy-based studies. Potential B. bassiana strains with endophytic ability were re-isolated and their identity was determined based on morphometric and PCR-based techniques. Further, the present study also identified several virulent genes viz., BbChit1, Cdep1, Bbhog1 and Bbjen1 and extracellular hydrolytic enzymes viz., α-amylase, cellulase, lipase, pectinase and xylanase secreted by endophytic B. bassiana strains as determinants responsible for establishing the endophytic association in rice. On the other hand, a significant reduction in disease incidence was observed in the endophytic B. bassiana Bb4-, Bb16- and Bb44-inoculated plants as compared to the non-endophytic B. bassiana Bb25- and Bb53-inoculated plants along with enhanced plant growth promotion. This is one of the few studies investigating the colonization of B. bassiana in rice and its promising role as a plant disease antagonist and plant growth promoter in rice.
球孢白僵菌是一种有潜力的昆虫病原生物防治剂，最近因其其他有益作用，如植物病原菌拮抗剂、有益根际定殖体、植物生长促进剂和内生菌，而引起了全世界的关注。在本研究中，研究了五种（5）球孢白僵菌分离株（Bb4、Bb16、Bb25、Bb44 和 Bb53）在水稻中的内生定殖行为，采用了三种（3）人工接种技术，即种子处理、根系接种和叶面喷雾，并通过基于培养的方法来确定内生定殖能力。在接种球孢白僵菌后，用立枯丝核菌对水稻植株进行了挑战，并评估了发病率和植物生长促进作用。接种技术、接种后时间（7 天、14 天、21 天和 28 天）和植物生长介质（无菌土、非无菌土）对水稻茎、叶和根的定殖率有影响，在接种后 14 天（dpi）记录到最大定殖率，即茎部 96%、叶片 92%和根部 28%，而在 7 天、21 天和 28 天 dpi 时记录到较低的定殖率。与种子和根系接种技术相比，叶面喷雾被发现是最好的，并且在茎和叶中观察到最大的真菌回收，而在根中回收最少。通过基于光镜的研究，定位了球孢白僵菌在水稻中的物理存在。具有内生能力的潜在球孢白僵菌菌株被重新分离，并根据形态计量学和基于 PCR 的技术确定了它们的身份。此外，本研究还鉴定了一些毒力基因，如 BbChit1、Cdep1、Bbhog1 和 Bbjen1，以及由内生球孢白僵菌菌株分泌的胞外水解酶，如α-淀粉酶、纤维素酶、脂肪酶、果胶酶和木聚糖酶，这些酶是决定内生菌与水稻建立内生关系的因素。另一方面，与非内生球孢白僵菌 Bb25 和 Bb53 接种植物相比，内生球孢白僵菌 Bb4、Bb16 和 Bb44 接种植物的发病率显著降低，同时促进了植物生长。这是为数不多的研究球孢白僵菌在水稻中的定殖及其作为植物病原菌拮抗剂和植物生长促进剂在水稻中的应用潜力的研究之一。
