Eco-Geography of Feral Cotton: A Missing Piece in the Puzzle of Gene Flow Dynamics Among Members of Gossypium hirsutum Primary Gene Pool

Mexico is the center of origin and genetic diversity of upland cotton (Gossypium hirsutum L.), the most important source of natural fiber in the world. Currently, wild and domesticated populations (including genetically modified [GM] varieties) occur in this country and gene flow among them has shaped the species’ genetic diversity and structure, setting a complex and challenging scenario for its conservation. Moreover, recent gene flow from GM cultivars to wild Mexican cotton populations has been reported since 2011. In situ conservation of G. hirsutum requires knowledge about the extent of its geographic distribution, both wild and domesticated, as well as the possible routes and mechanisms that contribute to gene flow between the members of the species wild-to-domesticated continuum (i.e., the primary gene pool). However, little is known about the distribution of feral populations that could facilitate gene flow by acting as bridges. In this study, we analyzed the potential distribution of feral cotton based on an ecological niche modeling approach and discussed its implications in the light of the distribution of wild and domesticated cotton. Then, we examined the processes that could be leading to the escape of seeds from the cultivated fields. Our results indicate that the climatic suitability of feral plants in the environmental and geographic space is broad and overlaps with areas of wild cotton habitat and crop fields, suggesting a region that could bridge cultivated cotton and its wild relatives by allowing gene flow between them. This study provides information for management efforts focused on the conservation of wild populations, native landraces, and non-GM domesticated cotton at its center of origin and genetic diversity.

Development and characterization of tetraploid castor plants

Castor is a prime industrial crop belonging to a monotypic genus and its genetic improvement depends on creating desired variability in the primary gene pool. This study reports the development of tetraploid castor plants through colchicine treatment. Seeds of three castor genotypes were soaked in aqueous solutions of colchicine with variable concentrations, and the LD50 value was determined. Of 1010 treated field-raised plants, three were identified as potential polyploids based on increases in a guard cell size and reductions in the number of stomata. The putative polyploid plants were selfed and the progeny were subjected to meiotic analysis. All the progeny were found to be tetraploid. The pairing of chromosomes was abnormal with univalent to octavalent configurations during meiosis-I, but the later parts of meiosis were normal. Seasonal variations in pollen fertility indicated the possible role of temperature-sensitive male sterility in causing the sterility in tetraploid plants. The tetraploid plants were phenotypically comparable with their diploid counterparts, but produced substantially bigger seeds. Thus, these tetraploid plants are valuable resources for basic and applied research in castor.

The wild gene pool of globe artichoke

Globe artichoke is an important vegetable of the Mediterranean basin. Its primary gene pool (GP1) consists of wild types ofCynara cardunculus. Crosses between the wild types and the cultivars (artichoke and cardoon) are fully fertile. In accordance, analyses of molecular markers revealed high genetic identity between the wild types and the cultivars. Hence, all these taxa are grouped together as conspecific varieties withinC.cardunculus. Several other wildCynaraspecies thrive in the Mediterranean basin. Of these,C. syriaca,C. algarbiensis,C. baeticaandC. humiliswere tested and found to be part of the secondary gene pool (GP2) of artichoke, as they were rather difficult to cross with either wild or cultivatedC. cardunculusand the few hybrids obtained were semi-sterile. In accordance, molecular genetic markers suggest that these wildCynaraspecies indeed diverged fromC. cardunculus. Four additionalCynaraspecies thrive in the Mediterranean basin, namelyC. cornigera,C. cyrenaica,C. tournefortiiandC. makrisii. There is no information on the crossability of these four species with artichoke, but molecular markers suggest that they may also belong to the secondary gene pool of the crop. Considering some attractive, variable characteristics of each of the GP2 species, such as earliness, albinism, dwarfism and diverse flavors, these wild species might be of great interest for artichoke breeders.