QTL analysis of morphological traits in an intergeneric BC1 progeny of Citrus and Poncirus under saline and non-saline environments

Abstract

The effects of salinization with 40 mM sodium chloride on Poncirus trifoliata (L.) Raf., Citrus grandis (L.) Osb., their F1, and a BC1 progeny population [C. grandis × (F1)] were investigated by measuring growth and dry mass production of different tissues and by QTL (quantitative trait locus) mapping. A total of 36 traits related to growth (six traits) and tissue or whole plant dry mass production (30 traits) in salinized and non-salinized BC1 progeny clones were evaluated. The comparison of the three parental types to the BC1 progeny under control and saline conditions showed that the BC1 progeny plants segregated transgressively for many of these traits. Mapping analyses of these quantitative traits resulted in a total of 70 potential quantitative trait loci (PQTL) with LOD scores greater than or equal to 3.0 located on a previously generated linkage map. Sixty-nine percent of the mapped PQTLs were for traits associated with salinity. The small progeny population size used made further analyses of these PQTLs necessary. By considering LOD scores, map locations, and correlation analyses of the traits, it was possible to identify 16 regions of the citrus genome of interest, six of which were involved in both growth and dry mass production. Correlation analyses and locations of PQTLs indicated that many of these regions may contain one or a few genuine QTLs of large effect. This is a first step in identifying QTLs that have a major impact on growth and dry mass production in Citrus under both optimum and stressful environments.Key words: Citrus grandis, Poncirus trifoliata, salinity stress, QTL mapping, morphological traits, transgressive segregation, NaCl, sodium, chloride, salt tolerance, citrus genetics, breeding.