QTLs for volatile compounds have been mapped in two populations. Saliba-Colombani et al. (2001) detected QTLs for 12 volatile compounds among 18 that were quantified in the progeny of a cross between cherry tomato inbred line Cervil and larger-fruited inbred line Levovil. Tieman et al. (2006) identified QTLs for 23 volatiles in the population of ILs derived from S. pennellii. Twenty-five loci altered in content of one or more volatiles were identified. Although ten volatiles were analyzed in both studies, only three QTLs were detected in the same regions, for pheny-lacetaldehyde on chromosome 8 (confirming the effect of the QTL Malodorous, named by Tadmor et al. 2002), on chromosome 9 for 2-methylbutanol, and
9 10 11 12
|J S. pennellii S. habrochaites S. pimpinellifollium S. chmielewskii
S. peruvianum S. neorickii S. lyc. cerasiforme S. cheesmaniae
Fig. 7. SummaryofQTLfor sugarcontentor relatedtraits(Brix°orhexosecontent)inone ofthefollowing progeny: S. lycopersicum x S. cheesmaniae F2 population (Patersonet al. 1991); S. lycopersicum x S. cheesmaniae recombinant inbred population (Goldman et al. 1995); S. lycopersicum x S. chmielewskii F2 and advanced backcross lines (Paterson et al. 1988, 1990; Azanza et al. 1994); S. lycopersicum x S. habrochaites advanced backcross population (Bernacchi et al. 1998b); S. lycopersicum x S. neorickii advanced backcross population (Fulton et al. 2000); S. lycopersicum x S. pimpinellifolium advanced backcross population (Tanksley et al. 1996; Doganlar et al. 2002c); S. lycopersicum x S. pimpinellifolium backcross populations (Grandillo and Tanksley 1996b; Chen et al. 1999); S. lycopersicum x S. pennellii introgression lines (Eshed and Zamir 1995; Causse et al. 2004); S. lycopersicum x S. pennellii advanced backcross population (Frary et al. 2004); S. lycopersicum x S. peruvianum advanced backcross population (Fulton et al. 1997); S. lycopersicum cv cerasiforme x S. lycopersicum recombinant inbred line population (Saliba-Colombani et al. 2001). The data concerning the advanced backcross involving S. pimpinellifolium, S. peruvianum, S. neorickii and S. habrochaites were summarized by Fulton et al. (2002a). The QTLs were positioned on the tomato reference map (Tanksley et al. 1992), based on the nearest marker on chromosome 12 for pentanol. The content of some volatile compounds appeared strongly variable across years or environments (Tieman et al. 2006). This could partly explain the small number of QTLs common to the two studies. In both studies, QTLs for several volatiles were frequently in clusters. In a few cases these clusters corresponded to volatiles derived from the same metabolic pathway (related to fatty acid, carotenoid or amino acid degradation), suggesting the action of a gene within a single pathway. More frequently, co-localizations of QTLs for volatiles derived from various metabolic pathways were shown, suggesting a regulatory gene acting on several pathways.
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