Fungal endophyte inoculation, suppression, and growth of black grama. Abbott, Laurie^*,1, Smith, Steven¹, Ulery, April³, ¹ Animal and Range Sciences, Las Cruces, NM, USA³ Agronomy and Horticulture, Las Cruces, NM, USA

ABSTRACT- Black grama (Bouteloua eriopoda), a keystone species of the Chihuahuan Desert Grassland, has recently declined in abundance and distribution. This species occurs on sites where extreme drought and nutrient stress are common and the ability to tolerate these stresses may be critical in determining its establishment and persistence. Black grama roots are extensively colonized by endophytic fungi whose biology is poorly understood. We hypothesize that fungal endophytes associated with black grama may influence plant nutrient and water uptake in a mutualistic relationship. Specifically, we propose that: 1) growth of black grama plants would be positively related to conditions that foster fungal activity in the soil, and 2) the positive effects of fungal presence on grass growth would increase under water-stress conditions. To elucidate the role of soil-specific fungi in growth and development of black grama plants, factorial experiments are being conducted in which black grama plants are grown in sterile soil with and without fungal inoculum derived from black grama roots. A second treatment involves monthly treatment with or without a broad-spectrum fungicide (Benomyl). Preliminary results indicate that seedling growth is positively associated with fungicide treatment, and negatively associated with the addition of fungal inoculum. These results do not support our hypothesis for black grama response under non-stress conditions. Application of a water-stress treatment was initiated in summer 2004.

KEY WORDS: Desert grassland, Bouteloua eriopoda, Mutualism, Fungicide