Box 1
Definitions: holobiont, holobiome, microbiome Recent reports proposed that multicellular organisms (e.g., animals and plants) and their associated unicellular organisms (e.g., microbes) could be considered as super-organisms, or holobionts (in ancient Greek, holos means whole and biont means unit of life) (Gilbert, 2019, Suarez & Stencel, 2020). However, the definition and concept of a holobiont is still debated. We consider a holobiont as an ecological unit (assembly) of a group of organisms that gather together based on their evolutionary capability to achieve a common purpose, which is survival of the holobiont. The holobiome includes all living organisms, their genetic materials, and their primary and secondary metabolites and molecules produced within a particular habitat (Berg, Rybakova, Fischer, Cernava, Vergès, Charles, Chen, Cocolin, Eversole & Corral, 2020, Sharifi & Ryu, 2017). The microbiome includes the microbial community living in a particular habitat and their metabolites, mobile genetic elements, and relic DNA (Berg et al., 2020). The microbiome helps the holobiont survive during biotic and abiotic stresses. The presence and abundance of specific microbial species in the microbiome change during successive phases of plant ontogeny and during biotic/abiotic stresses (Carrión, Perez-Jaramillo, Cordovez, Tracanna, de Hollander, Ruiz-Buck, Mendes, van Ijcken, Medema & Raaijmakers, 2019, Cotton, Petriacq, Cameron, Meselmani, Schwarzenbacher, Rolfe & Ton, 2019, Edwards, Santos-Medellın, Liechty, Nguyen, Lurie & Eason, 2018, Gu, Wei, Wang, Friman, Huang, Wang, Mei, Xu, Shen & Jousset, 2016).