Recently we focused primarily on the effects of burrowing nematode on selected UFR rootstocks. Previously we planted six UFR rootstocks in sandy soil, and inoculated the soil with burrowing nematode (BN). After four months, the plants were removed from the soil, cleaned thoroughly, vacuum packed and placed in the freezer. For three of the UFR rootstocks (UFR-4, -6, and -17), we compared healthy roots to those exposed to BN. We processed the roots and extracted them with hexane for volatile metabolites, and with methanol/chloroform/water for non-volatile metabolites such as sugars, organic acids and amino acid. In all, 48 samples were processed and run on the GC-MS, 24 for VOCs (3 RS x 2 treatments x 4 replicates) and 24 for non-VOCs, the chromatograms were integrated and compounds were identified. For the citrus root volatile extracts, we found that roots with BN from UFR 4 and UFR 6 contained low levels of monoterpenes in control roots (without BN damage), but monoterpenes were increased up to 6-fold in roots with BN. However, in UFR-17, all monoterpenes except d-limonene were reduced in BN+ root extracts, suggesting a different response to nematodes than in the other two rootstocks. Thirteen sesquiterpenes and 16 sesquiterpene alcohols were tentatively identified in the root extracts, with a large number of them increased consistently in all three rootstocks with BN. These may perhaps be defense compounds. One group identified were isomers of geyrene and pregeijerene, which are known to attract entomopathic nematodes in response to feeding by root weevils. We also found that the roots contained large amounts of coumarins (at least 9 different coumarins) which were reduced by half or more in roots with BN. In the root extracts for non-volatile compound determination, we detected 14 amino acids, 7 organic acids, 8 sugars, 6 coumarins and 3 sterols. We found that the amino acids were greatly reduced in roots with BN, especially L-proline and L-asparagine. Sugars, especially the monosaccharides such as fructose and glucose increased at least two-fold in UFR-4 and UFR-17, and about 1.6-fold in UFR-6. Disaccharides, mainly sucrose, also increased dramatically in BN-infested roots. The coumarins in the hexane fractions were much higher in roots with BN unlike the methanolic fractions. In UFR-4 and UFR-17, total organic acids such as malic acid increased, but were reduced in URF-6, which was the most abundant organic acid found in the roots. Citric acid decreased in all three rootstocks exposed to BN. Three sterols were tentatively identified as sitosterol, stigmasterol and campestrol, and the levels of these compounds was low.These chemical response data need to be correlated with the degree of root damage to determine which rootstock is more tolerant to burrowing nematode, and further investigation of the the phytochemicals responsible for the response to the pathogen attack is warranted. New rootstock evaluations – We received the seeds from the USDA in Ft. Pierce for evaluating their susceptibility to nematodes. These included US-802, 812, 897, 942, 1283, 1284, 1516. After germination, the rootstock seedling were moved outside to encourage growth, repotted into larger pots, and are now about 6 inches tall and 7 months old. We hope they will be ready for evaluations soon. We plan to challenge these rootstocks with burrowing nematodes to determine their susceptibility/tolerance.