Plant & Animal Genome V Conference
Town & Country Hotel, San Diego, CA, January 12-16, 1997.
PAG-V: W42 - QTL MAPPING IN <i>Citrus</i>
W42
QTL MAPPING IN Citrus
MOORE, GLORIA A.(1), Ilhami Tozlu(2), Courtney A. Weber(2)
1. Horticultural Sciences Department, Plant Molecular and Cellular Biology Program, IFAS, University of Florida, Gainesville, FL 32611
2. Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL 32611
Studies are underway to map quantitative trait loci (QTLs) for salt tolerance and for cold tolerance in Citrus. For salt tolerance mapping studies, the intergeneric Citrus grandis (L.) Osb. x [C. grandis x Poncirus trifoliata (L.) Raf.] BC1 population that was previously used to construct our genetic linkage map was utilized. P. trifoliata is rapidly growing, deciduous, very cold-hardy, and considered to be extremely salt sensitive compared to Citrus species. The salt tolerance of C. grandis has not been previously tested, but it is a slow-growing, large, evergreen type and among the most cold-sensitive of the Citrus species. Each of 54 BC1 individuals was cloned multiple (up to 8) times. Four clones were used as a control while the other four were watered with 40 mM NaCl for 16 weeks. The BC1 progeny segregated widely and in a continuous fashion for tissue-specific growth parameters and mineral contents. Thus it was possible to map a number of QTLs influencing growth and ion accumulation in response to salinization. Cold tolerance is being assayed in a much larger C. grandis x P. trifoliata F1 population, i.e. a pseudo-testcross. Freezing tests following cold acclimation are being done to determine the cold tolerance of individual progeny. Bulked segregant analysis of cold hardy and cold sensitive types will be used to map QTLs affecting cold tolerance. There will be discussion of the problems involved in mapping QTLs in large, slow-growing plants and of the importance of the assay chosen for analysis.