The objectives of this proposal are: 1) conduct a field trial using the selected grapefruit seedlings to ensure the productivity of the trees in Florida where HLB is endemic; and 2) evaluate the quality of the fruit produced. Achievement of these goals will produce a more resistant/tolerant variety that could be available in the near future since its use would not require the regulatory approval. Based on two year’s graft-inoculation assays in greenhouse with two HLB isolates and the performance of individual seedlings in the field, four lines of the seedlings (with greater HLB resistance/tolerance) were selected for further propagation on three different rootstock (commercial sour orange, newly selected USDA-sour orange and 942). The fruit quality (Brix, sucrose, glucose and fructose, soluble solids, pH, % TA and total ascorbic acid) of the four selected seedlings showed no significant difference from their maternal trees. First group of the propagates on three different rootstock from the selections of Scott Grove’s seedling variants were grown in our research farm, Picos farm, where the plants are under extreme high HLB disease pressure with very aggressive HLB pathogens. These new plantings (July, 2017; Nov, 2017; and May, 2018) showed different disease index, the longer the planting was, the higher the disease index, which was also highly correlated with the titers of Ca. Liberibacter asiaticus (Las) in infectd plants. It is worth noting that the new HLB isolate from Picos farm caused severe HLB disease on most of grapefruit selections of seedlings and bud sports in our latest greenhouse evaluation. Those selections were either resistant or tolerant to the previous HLB isolates we maintained in greenhouse. By the end of this year, we will expect to draw a better conclusion if the selected seedling variants display better resistance/tolerance to HLB pathogens at the Picos Research Farm. Second group of the propagates on three different root stocks mentioned above (Ca. 750 plants) have been budded and grown in our greenhouse, and are expected to be planted in Scott grove this month. All the propagates have been tested for the presence of Las. The propagates that carry a low titer of Las will be palnted separately and serve as the experiment for “Cross-protection”.