Delaying the decline of germination ability of pecan pollen by yeast Pichia fermentans 15B1

Abstract

Microorganisms may be critical to the final outcome of pollination, but there are few studies on the effects of microorganisms on pollination process, especially the direct effects of microorganisms on pollen germination after pollination. Studies have shown that yeast can inhibit pollen germination regardless of in vitro germination and stigma germination, while bacteria like Acinetobacter pollinis can promote pollen germination. Pecan (Carya illinoinensis (Wangenh.) K. Koch) is a kind of wind-pollinated hybrid plant and the in vitro germination system of pecan pollen is well-established. In this paper, pecan pollen was used to reveal the special influence of yeast microorganisms on the pollen germination. It is well known that storage at room temperature will usually lead to a decrease in pollen viability and the study here showed that the germination ability of pecan pollen decreased by about 19.0% after two-day storage at room temperature. Although the culture of Pichia fermentans Lodder (strain 15B1) had no significant effect on the in vitro germination of pecan pollen without storage at room temperature, it could significantly improve the germination ability of pecan pollen after two-day storage at room temperature, with an average increase of 33.6%. It proved that the group with supernatant part of whole strain culture had the strongest promotion effect on pollen germination including pollen germination rate and pollen tube length among the whole strain culture, supernatant part and precipitation part, indicating that the pollen germination was mainly promoted by extracellular substances of strain rather than strain 15B1 itself. This promoting effect was more like a recovery of the lost germination ability of pecan pollen due to room temperature. Further experiments showed that the extracellular substances of strain 15B1 had good thermal stability. This study is of great significance to explore the biological role of microorganisms in pollination, and also provides an important idea for improving fruit pollination by microbial ways.