Endophytic strains of the yeast Metschnikowia pulcherrima positive for phytohormones production

Strains of the ascomycetous yeast Metschnikowia pulcherrima isolated from the internal tissues of fruits were evaluated for phytohormonal activity. IAA production in the culture liquid was determined by the chromatographic method (HPLC-UV). The production of the phytohormones zeatin and gibberellin (GA3) in the culture liquid was determined by a chromatographic method using a quadrupole time-of-flight mass spectrometry detector (Q- TOF LC / MS). IAA and zeatin were detected in the culture liquid of all strains studied. Synthesis of gibberellin (GA3) was detected in only 5 of 18 strains examined. On average, the strains showed the highest activity in the synthesis of IAA (6.668 mu g/mL and 2.135 mg/g). Zeatin content was 3 orders of magnitude lower (0.365 ng/mL and 0.129 mu g/g) and GA3 content was 4 orders of magnitude lower (0.076 ng/mL and 0.027 mu g/g). According to our results, the yeast M. pulcherrima is not an active producer of zeatin and GA3 in amounts relevant to the plant. On the other hand, the average level of IAA synthesis detected in M. pulcherrima strains in this study is within the range of concentrations that can stimulate plant development and growth. Thus, endophytic strains of M. pulcherrima that produce plant-relevant levels of IAA could be improved to increase their synthesis ability and used as plant growth promoters in agricultural crops.

Automated summary

This study evaluated the phytohormonal activity of Metschnikowia pulcherrima yeast strains isolated from the internal tissues of fruits. The production of IAA, zeatin, and GA3 was determined using chromatographic methods. The results showed that the strains had the highest activity in IAA synthesis, while the levels of zeatin and GA3 were much lower. These findings suggest that M. pulcherrima yeast strains may have a role in promoting plant development and growth.