Plant growth promoting bacteria on in vitro rooting of Pyrus sp.

Abstract

Plants of the Rosaceae family, such as those of the Pyrus genus, have reduced in vitro rooting ability, requiring the use of growth regulators. In many cases, bacteria are also observed in the culture medium, leading to plants being discarded. However, it is known that numerous bacteria have the ability to promote plant growth. This study sought to investigate the presence of these microorganisms in plant tissue culture of Pyrus communis rootstocks by isolating, identifying, and selecting auxin-producing bacteria. The selected microorganisms were also inoculated in vitro to assess their effect on the rooting process of plants and their behavior during the acclimation phase. The results showed the presence of endophytic microorganisms in plant tissue cultures of the ‘OHxF87’ and ‘PDW’ selections. A predominance of the genus Acinetobacter and low diversity of the microorganism population originating from in vitro plants were observed, and the bacterial species Acinetobacter ursingii, Bacillus subtilis, and Micrococcus luteus were isolated. Microorganism selection was performed using the auxin production test, given the difficulty of rooting these plants. Of all the identified microorganisms, 30.36% had auxin production ability. In the in vitro inoculation, two A. ursingii strains showed efficiency similar to that of synthetic auxin for genotype ‘OHxF87’. A genotype-dependent variation in response was observed. The clones derived from the ‘PDW’ selection showed reduced rooting when inoculated with microorganisms; however, rooting occurred using the A. ursingii strains. During the acclimation phase, all plants showed a high level of rooting, favoring the development of rootstocks.