Preliminary investigation of water and nitrogen use efficiency in Mango

The aims of this preliminary investigation were to identify if natural abundance carbon (δ13C) and nitrogen (δ15N) stable isotopes reflect the dynamics of carbon and nitrogen between mango varieties, canopy function and management practices (fertilization and/or irrigation). This preliminary investigation has identified factors that increase water use efficiency, nitrogen efficiency and tree productivity. The natural abundance of stable isotopes of carbon and nitrogen show promise as new tools to study the drivers of mango productivity efficiency and will be useful in studying mango orchard systems and in selecting and evaluating breeding parents and progeny in mango breeding programs. Measurement of stable isotopes of carbon (δ13C) in three mango varieties grown under similar irrigation and environmental conditions (in Summer 2015) have shown significantly different WUE between the varieties. These findings were supported by traditional gas exchange analysis, taken during winter 2016 and foliar N concentrations in these varieties. There were significant relationships, between WUE and foliar N concentrations, in both the heredity and crop load experiments indicating an effect of both genotype and terminal function on terminal WUE and foliar N concentration. Results from the gas exchange assessments supported δ13C heredity results indicating greater WUE in the Keitt variety when compared to Calypso variety. The methods used in this project can help us better understand the integrated carbon and nitrogen dynamics of tree canopies and how nitrogen allocation is influenced by nitrogen nutrition. They also help us understand the photosynthetic components that influence light harvesting and electron transport efficiencies and hence contribute to growth and productivity. The report also discuss how gas exchange characteristics between varieties may be used to evaluate the productivity and canopy efficiency of different mango varieties growing in different planting configurations with varying light and shading characteristics. Finally, when measurements in trees with varying crop load from three sites data where pooled together, the δ15N was able to identify nitrogen dynamics in high and low nitrogen sites. This preliminary investigation of the use of stable isotopes of carbon (δ13C) and nitrogen (δ15N) to identify water use efficiency and productivity efficiency’s in mango has been successful and has potential application in studying orchard systems and in mango breeding. Application of these methods in future projects would enhance current studies of mango canopy architecture efficiency in the Small tree High productivity initiative and provide a new way of assessing mango breeding lines for production efficiency