2017 ASHS Annual Conference

Endophytes are symbionts that live in the intercellular spaces or vascular tissues of host plants. They can be fungi, bacteria, and/or yeast. Initial investigations indicate that endophytes provide a number of benefits that promote plant growth including, but not limited to, di-nitrogen fixation, plant hormone production, nutrient acquisition, stress tolerance, and increased immunological response. In exchange, they receive domicile and photosynthates. Endophytic biological and ecological services hold great potential for bioengineering and evolutionary inquiries, particularly so for sustainable agriculture. Nitrogen has historically been the nutrient limiting factor in all crop production. Moreover, sweet fruit crops require intensive nitrogen application to yield nutritionally and economically viable fruits. Considering these factors and known characteristics of nitrogen fixation and plant hormone production, we hypothesized that apple trees grown under nitrogen limited field conditions would show improved biometrics with symbiont inoculation. Our research objectives were not only to further investigate endophytic effects on plant physiology, but to also assess impact on fruiting. We examined these effects through ecophysiology metrics involving rates of photosynthesis, stomatal conductance, biomass accretion, chlorophyll content, fluorescence rate, and fruit sucrose content. Our initial results align with ongoing publications showing overall improved physiological support from endophytes. However, to our knowledge, this is the first research finding a significant increase in fruit sucrose content and biomass. This preliminary research illustrates the critical importance of better understanding how endophytes can alter fruit quality. Future research into the mechanistic underpinnings of this phenomena stand to offer novel insights into how microbiomes alter carbohydrate metabolism under nitrogen deficient conditions.