Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2007
Publication Date: 3/14/2008
Citation: Lopez, P.A., Widrlechner, M.P., Simon, P.W., Rai, S., Boylston, T.D., Isbell, T., Bailey, T.B., Gardner, C.A., Wilson, L.A. 2008. Assessing phenotypic, biochemical, and molecular diversity in coriander (Coriandrum sativum L.) germplasm. Genetic Resources and Crop Evolution. 55:247-275. Interpretive Summary: We evaluated 60 coriander populations from diverse origins, conserved by the USDA-ARS North Central Regional Plant Introduction Station in Ames, IA. We measured a wide range of phenological (timing of plant development) and morphological traits. We also extracted essential oils (aroma compounds) and fatty acids (lipids) from the seeds of these populations and used gas chromatography and mass spectrometry to separate and quantify the components and identify them. The main essential oils and nearly all fatty acids were identified and their abundances estimated. Finally, we extracted DNA from seedlings of these populations and analyzed the DNA for genetic variation in amplified fragment length polymorphisms (AFLPs). We used various statistical methods to describe AFLP variation, determine genetic similarity among populations, and relate this variation to patterns of morphological and biochemical variation. Groups of populations defined by morphological and phenological variation resemble those defined by past classifications. However, patterns of variation based on seed chemistry differ from those based on morphology, and patterns of genetic variation resemble neither morphological nor biochemical variation. There was extensive genetic variation within populations and among populations within groups, but little variation attributable to the groups themselves. Thus, we conclude that coriander populations are weakly differentiated genetically, supporting the hypothesis that genetically diverse coriander germplasm has been widely shared, with farmers repeatedly selecting for specialized traits from a dynamic and environmentally plastic gene pool. These findings are the first reports of patterns of genetic variation in coriander and should be valuable for this crop's genetic improvement.
Technical Abstract: This research was conducted to elucidate phenotypic and biochemical diversity in 60 coriander (Coriandrum sativum L.) accessions maintained at the North Central Regional Plant Introduction Station and examine relationships between amplified fragment length polymorphisms (AFLP) and patterns of phenotypic and biochemical diversity. We evaluated phenotypic and biochemical traits, and performed analyses of variance and mean comparisons on the resulting data. Euclidean distances from phenotypic (PD) and biochemical (BD) data were estimated, and modified Rogers’ distances were estimated for 80 polymorphic AFLP markers. These data were subjected to cluster analyses and principal components analyses (PCA) and to analyses of molecular variance (AMOVA) for grouping patterns from PD and BD based on the 80 polymorphic AFLP markers. Our results describe significant differences among populations for all phenotypic traits, and dendrograms obtained from PD and BD revealed complex phenetic patterns, as did groups from PCA. The primary seed essential oils and nearly all fatty-acid components were identified and abundances measured; the primary chemical constituents of corresponding PCA groups are described herein. AFLP evidence supported phenotypic and biochemical subgroups. But the variation attributed among subgroups and groups was very low, while variation among populations within groups was intermediate and that within populations was large, reflecting weak differentiation among subgroups and groups, which was confirmed by values for fixation indices. Phenotypic subgroups described in our study differed somewhat from previous classifications.