Seed and endocarp traits as markers of the biodiversity of regional sources of germplasm of tejocote (Crataegus spp.) from Central and Southern Mexico

The genus Crateagus (Rosaceae: Maloideae), is distributed all around the world, but only in the Northern Hemisphere. In Mexico there is a considerable biodiversity with around 15 species, most of them authoctonous and it is called tejocote, a multi-purpose tree with economic importance. However the taxonomy of the Crategus species from Central and Southern Mexico still remains unclear. The gemplasm bank of tejocote of the Universidad Autónoma Chapingo (UACh) (State of Mexico) contains almost 100 accessions of Crataegus from Central and Southern Mexico. Based on previous studies that demonstrated that seeds and inner parts of the fruits are useful for germplasm characterization, the general objective was to investigate the usefulness of seeds and endocarps for the characterization of tejocote genetic pools, using 86 accessions from the tejocote germplasm bank of the UACh, with the specific objectives being: (i) to select from 37 morphological and morphometrical variables, the most informative for the assessment of the biodiversity; (ii) to contribute to the elucidation of the variability of the tejocote genetic pools from Central and Southern Mexico. The traits related with the size and shape of the endocarp, seed and seed cavity, plus the presence or absence of normal vs. abortive seeds, and the number of endocarps per fruit, were the characters that accounted for more variability and in conclusion the most adequate for the characterization of tejocote and some of them have been adopted for the official Crataegus descriptors. The present work confirms prior results with the same germplasm and other characters which postulated that the source from Chiapas is different from the rest of the sources and also that the sources from the State of Mexico and Puebla were not significantly different genetic pools. The accessions from the Chiapas source showed smaller endocarps and seed cavity, lower percentage of endocarps with normal seeds, higher percentage of endocarps without seed, and higher number of endocarps per fruit.