Rhizobacteria strains as promoters of rooting in hybrids of Eucalyptus nitens × Eucalyptus globulus

Abstract

In Chile, the Eucalyptus nitens (H. Deane & Maiden) Maiden × E. globulus Labill. hybrid presents the highest production potential due to its desirable characteristics for the production of cellulose. Nevertheless, its low ability to rooting complicates the clonal propagation in nurseries, with the need for new alternatives to increase rooting. The objective of this research was to evaluate the effect of rhizobacteria in the adventitious rooting of mini-cuttings of two hybrid E. nitens × E. globulus clones, wherein 106 rhizospheric bacterial isolates from five species and hybrids of Eucalyptus spp. were used. The mini-cuttings were treated at the base with a 20 mL liquid suspension of rhizobacterial strains. In addition, cultured bacteria were applied by manual sprinklers in the rooting substrate. In the first trial, 38% of rhizobacteria increased significantly rooting of X-64 clone mini-cuttings. Of these, in a second trial, 50% of rhizobacteria maintained their effect in promoting the rooting in two clones, and in the third trial among the 20 strains evaluated, 10 strains increased rooting in both clones. The rhizobacteria that had the most consistent effect in the rooting increase of the mini-cuttings were species of Bacillus and Pseudomonas sp., as well as the genera Chryseobacterium, Mucilaginibacter and Rhodococcus sp., with these results, it is concluded that 10 rhizobacterial isolates have increased the adventitious rooting of minicuttings of two hybrid clones of E. nitens × E. globulus, and these inoculants could be used in periods of underperformance of minicuttings, in order to optimize their performance.

Plant Growth and Microbiota Structural Effects of Rhizobacteria Inoculation on Mahogany (Swietenia macrophylla King [Meliaceae]) under Nursery Conditions

“…Results derived from in vitro validation using A. thaliana, also demonstrated clear effects of rhizobacteria inoculation on root architecture. Similar morphological changes in response to rhizobacteria inoculation have been reported in a wide number of tropical tree species as Cedrela fissilis [16], Acacia auriculiformis [19], Cecropia pachystachya, Heliocarpus popayanensis Trema micrantha, Cabralea canjerana, Cariniana estrellensis, Trichilia elegans [32], Eucalyptus nitens [33], Jatropha curcas [34] and others. Reported changes in root architecture are associated with the modulation of cell division and the differentiation of the apical meristem and lateral root primordia sites [35].…”

Effects of Plant Growth Promoting Rhizospheric Bacteria (PGPR) on Survival, Growth and Rooting Architecture of Eucalyptus Hybrid Clones

“…Thereafter samples were diluted and plated on potato dextrose agar (PDA) and R2A agar using an easySpiral ® Pro automatic plater (interscience, Saint Nom, France). Plates were incubated at 25 • C for 48 h. After incubation, representatives of bacterial colonies presenting different morphological variations (colour, shape, and size) were isolated and purified by sequentially streaking single colonies onto fresh agar plates [31,32]. Purified isolates were cryo-preserved at −80 • C in a Microbank™ (Pro-Lab Diagnostics, Bromborough, UK).…”

Adverse Effects of Salt Stress on Rootability of Rosmarinus officinalis Cuttings and their Alleviation by Indole-3-Butyric Acid (IBA) and Bacillus subtilis

“…On the other hand, many studies have showed that inoculation of plants with PGPR such as B. subtilis improves plant growth, yield and nutrient uptake under salt stress conditions (Abdel-Rahman et al, 2011, Mohamed & Gomaa, 2012and Abd Allah et al, 2017. In addition, PGPR in the genera of Bacillus, Agrobacterium, Azospirillum and Pseudomonas have recently been used to induce adventitious root formation in stem cuttings (Abdel-Rahman &El-Naggar, 2014 andGonzález et al, 2018). These bacteria are able to exert a beneficial effect upon plant growth such as increases root growth and root weight (Karakurt et al, 2009 andAbdel-Rahman et al, 2019).…”