Morphometry of the organs of cherimoya (Annona cherimola Mill.) and analysis of fruit parameters for the characterization of cultivars, and Mexican germplasm selections

Three commercially available cherimoya cultivars (Campas, Burtons and White), one cultivar recently obtained and registered in Mexico (Cortés-II-31) and seven Mexican germplasm selections (S-196, S-256, S-260, S-266, S-9651, S-Selene and S-Carapan) were characterized by using the morphometric traits of various organs of the adult plant, together with several agronomical and chemical characteristics. The objectives were: (i) to seek an alternative approach to the definition of cherimoya cultivars through multivariate analysis, using commercial varieties and Mexican germplasm selections and (ii) to elucidate the grouping of cultivars and selections obtained by multivariate analysis on the basis of their origin and geographical distribution. Plant material was collected in 2002 from adult plants 3 years after grafting. Twenty-one morphometric characteristics (seven of leaves, nine of flowers, two of fruits and three of seeds), plus five fruit characteristics of agronomical importance and three chemical parameters of the fruit were selected for characterizing accessions. The intra-accession variability recorded for the traits selected made them suitable for identifying cultivars. All of the traits but one were capable of showing up differences between accessions at a significance level of 0.001. Principal Component Analysis (PCA) showed that the traits which yielded the maximum separation between accessions were: leaf blade form factor, angle of the fifth vein of leaves, upper angle of leaves, area of the cross-section of petals, sepal maximum projected area, weight of fruits, total soluble solids in fruits, resistance of the skin of fruits to a penetrometer and width-to-length ratio of the maximum projected area of seeds. Consequently, all of these characteristics may be of interest as descriptors for cherimoya varieties. Furthermore, four consistent groups of accessions were defined by the three-dimensional plot obtained through projecting the accessions onto the first three principal components and the tree-diagram, or dendrogram, obtained through Cluster Analysis (CA). Two of these groups were made up of accessions with a well-defined common origin. The first consisted of selections S-196, S-256, S-260 and S-266 obtained from Coatepec Harinas in Mexico State, while the second comprised selections S-Selene and S-Carapan from Purépecha native Indian communities in Michoacán State. For the other two groups the origin of the accessions forming them is not fully known. Hence, further studies, based on molecular markers, might be carried out in order to ascertain if these accessions are genetically related.