2017 ASHS Annual Conference

Nickel (Ni) is an essential element for plant growth, and is particularly important for the development of pecans (Carya illinoinensis). Pecan trees have a particularly high Ni requirement and frequently exhibit Ni deficiency symptoms characterized by distinctive round shaped leaflets. It is unknown how different genotypes vary in their responses to Ni. Two distinct genotypes of clonally micro-propagated pecans were potted and acclimatized to greenhouse soil conditions and used to study responses to Ni. Testing clonal pecan trees in a greenhouse setting enabled us to observe trends in physiological response that arise from genetic uniformity and controlled conditions. We selected 30 trees from each genotype for our experiment, both of which displayed Ni deficiency symptoms, and treated them with varying concentrations of Nickel plus (Ni lignosulfonate) fertilizer. Ni treatments ranged from 100 to 1000 ppm Ni and were administered as a foliar spray once per week over the course of 8 weeks. The trees ranged from 6 to 16 centimeters tall, with a mean height of 9.9 centimeters. Nutrient analyses of acid-washed leaves were performed before and during the experiment to quantify nutrient uptake. Our studies revealed differences in Ni uptake and plant growth responses were based on both genotype and Ni concentrations. The two genotypes responded differently to nickel fertilization. The high Ni fertilizer concentrations correlated with significantly higher levels of magnesium, sulfur, manganese, boron, and nickel within the leaf tissue in both genotype groups, though all other nutrients were applied at the same rate. One genotype (Wi1) had a more positive response to Ni treatments and accumulated higher levels of zinc and molybdenum in both the low and high nickel treatment groups in foliar tissue. The second genotype (We1) had a response towards Ni and accumulated higher levels of iron and nitrate in the foliar tissue. We1 also had a tendency to develop compound leaves compared to Wi1. We have made progress in characterizing physical symptoms of Ni deficiencies and toxicities that will aid growers as they improve Ni fertilization practices. This study enabled us to gain a deeper understanding of the nutritional requirements and development of two unique genotypes of pecan, showing that genetically unique trees within a species may have significantly varied nutritional requirements and responses. As we further investigate this phenomenon, we hope to develop ways for growers to give their trees more individualized care to create even more productive orchards.