Development and Commercialization of Improved New Disease Resistant Scions and Rootstocks – the Key For a Sustainable and Profitable Florida Citrus Industry

Development and Commercialization of Improved New Disease Resistant Scions and Rootstocks - the Key For a Sustainable and Profitable Florida Citrus Industry

Report Date: 11/15/2017
Project: 15-010   Year: 2017
Category: Plant Improvement
Author: Fred Gmitter
Sponsor: Citrus Research and Development Foundation

Activities are reported by project objectives below. 1. Development of rootstocks that can impart HLB tolerance/resistance to grafted scions. Planted ~2000 seeds from 20 2017 rootstock crosses in calcareous/Phytophthora infested soil (“Gauntlet”), and completed stick grafting of approximately 100 new �gauntlet� rootstock candidates selected from 2015 crosses. Propagated 5 “super-root” mutants from tissue cultured UFR1, UFR-3, and UFR-6, and begun testes for HLB tolerance. 2. Breeding of HLB tolerant/resistant processing sweet oranges and orange-like hybrids. Recovered ~ 400 plants from interploid crosses targeting HLB tolerant sweet orange/mandarin type hybrids. Planted 203 transgenic plants (73 independent lines, mostly oranges but some Duncan and W. Murcott) containing Valencia-derived BG or LTP at out APHIS approved transgenic site at the SWFREC. 3. Screening of the UF-CREC germplasm collection to identify and validate HLB tolerant or resistant selections. We continue to monitor our germplasm collection and breeding families for performance against HLB. We have initiated a genomic selection effort based on phenotypic assessments and using a high density SNP chip for genotyping. Interesting genomic regions have been highlighted that contain putative disease resistance and defense mechanism genes. Worked with Dr. Johnny Ferrarezi to plant the entire population of cybrid grapefruit clones (kumquat cytoplasm) at the IRREC. These include cybrids of Flame, Ruby somaclone N11-11 and White Marsh showing significantly improved canker tolerance in greenhouse assays. The original N11-11 somaclone, derived from Ruby red, has shown a strong recovery response from HLB; thus the cybrids made from this clone are potentially improved for both canker and HLB tolerance. In addition to the original population, propagations of selected clones were also planted, and many were on the rootstocks propagated via the previous CRDF grant with Barrett Gruber. Approximately 340 trees were planted. 4. Advanced field trials, release and commercialization of promising HLB tolerant/resistant scion and rootstock cultivars. Field planted promising new OLL sweet oranges/new rootstock candidates in 2 locations. Planted 150 E.V. (Early Valencia) trees on promising new rootstocks in a high Diaprpres pressure area, in an effort to identify a rootstock that doesn�t drop fruit after HLB infection. Harvested seed from all available UFR seed trees; seed kindly extracted by John Gose @ Lykes, now being distributed to participating licensed nurseries. Other related activities: Scored trees in a high-peel oil lemon selection trial in the IR region, after 7 days of Irma flooding. This will serve as a baseline for future evaluations of flood damage over time. Speaking of Irma, we spent much of September going through all CREC plots and field trials, standing up and staking trees blown over by the storm.

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