Endophytic Bacillus subtilis P10 from Prunus cerasifera as a biocontrol agent against tomato Verticillium wilt

Isolation and identification of the causal agent of gummy stem blight disease in Cucumis sativus caused by a bacterial pathogen in China

Recently, a new bacterial disease was detected on cucumber stalks. In order to study the pathogenesis of this disease, the pathogenic bacteria were isolated and identified on the basis of morphological and molecular characteristics, and further analyzed for pathogenicity and antagonistic evaluation. Pathogenicity analysis showed that HlJ-3 caused melting decay and cracking in cucumber stems, and the strain reisolated from re-infected cucumber stalks was morphologically identical to HlJ-3 colonies, which is consistent with the Koch's postulates. The pathogenic strain HlJ-3 was identified as having similar morphological characteristics to Bacillus subtilis. Meanwhile, its internal transcribed spacer sequence (ITS) and DNA gyrase A subunit (gyrA) were both more than 99% homologous and clustered on the same branch with B. subtilis. Therefore, combined with morphological and molecular biological features, strain HlJ-3 was identified as B. subtilis. In addition, B. subtilis, which has a wide range of hosts, was able to infest other common crop species, including potato, tomato, pepper, melon, and radish. Furthermore, antagonistic evaluation confirmed that strain HlJ-3 strongly inhibited the mycelial growth of Colletotrichum coccodes and Alternaria tenuissima in vitro, with antagonistic effects of 69.92% and 68.08%, respectively. In conclusion, our results showed that strain HlJ-3 is B. subtilis, which is pathogenic to cucumber in vivo and can infect plants of Solanaceae, Cucurbitaceae and Brassicaceae with a wide range of hosts. In addition, this strain has good biocontrol effects against C. coccodes and A. tenuissima in vitro. The findings of this research will help to prevent and control the occurrence of this pathogen and regulate its use as a biocontrol agent.

Invisible Inhabitants of Plants and a Sustainable Planet: Diversity of Bacterial Endophytes and their Potential in Sustainable Agriculture

Uncontrolled usage of chemical fertilizers, climate change due to global warming, and the ever-increasing demand for food have necessitated sustainable agricultural practices. Removal of ever-increasing environmental pollutants, treatment of life-threatening diseases, and control of drug-resistant pathogens are also the need of the present time to maintain the health and hygiene of nature, as well as human beings. Research on plant-microbe interactions is paving the way to ameliorate all these sustainably. Diverse bacterial endophytes inhabiting the internal tissues of different parts of the plants promote the growth and development of their hosts by different mechanisms, such as through nutrient acquisition, phytohormone production and modulation, protection from biotic or abiotic challenges, assisting in flowering and root development, etc. Notwithstanding, efficient exploitation of endophytes in human welfare is hindered due to scarce knowledge of the molecular aspects of their interactions, community dynamics, in-planta activities, and their actual functional potential. Modern "-omics-based" technologies and genetic manipulation tools have empowered scientists to explore the diversity, dynamics, roles, and functional potential of endophytes, ultimately empowering humans to better use them in sustainable agricultural practices, especially in future harsh environmental conditions. In this review, we have discussed the diversity of bacterial endophytes, factors (biotic as well as abiotic) affecting their diversity, and their various plant growth-promoting activities. Recent developments and technological advancements for future research, such as "-omics-based" technologies, genetic engineering, genome editing, and genome engineering tools, targeting optimal utilization of the endophytes in sustainable agricultural practices, or other purposes, have also been discussed.