Veronica Zamora-Gutierrez
The world population reached the milestone of 8 billion people in November 2022. This number poses a huge challenge to humanity in securing enough resources (e.g. clean water, food) for the present and future population. Currently, 90% of our main food supply comes from 15 staple crops and agricultural practices are being constantly intensified and extensified to produce enough food to feed our growing population. However, this is highly unsustainable since agricultural intensification also produces alarming rates of pollution of other important resources. There are many lesser-known cultivated or semi-cultivated plant species with a high potential to contribute towards the diet of humans, maintain their nutrition and at the same time, enhance the diversity and resilience of our food systems. These crops are often cultivated by resource-constrained farmers in challenging environments and that do not required expensive technology. These crops therefore present opportunities for enhancing yields through the integration of contemporary agricultural and genetic approaches.
Stenocereus queretaroensis (pitaya) is a columnar cactus under cultivation in Mexico, with more than 500 years of artificial selection and management in several arid and semi-arid regions. This fruit has great economic and cultural importance in the areas where it is cultivated, and the income of some groups depend up to 60% on this crop. Wild pitaya plants and pitaya plantations from different varieties can be found in the same area. However, pitaya plantations are mainly dominated by one variety named “mamey” and the propagation of this cultivar is mostly clonal, restricting genotypic and phenotypic diversity. In recent years, pitaya producers have been facing several challenges as the presence of pest and diseases have increased. This may be due to the impoverishment of soils, changes in water regimes resulting in drought, and plausible genetic erosion of the crop due to its clonal propagation. We need to increase our understanding of the relationship between the species’ genetic diversity and the farmers management and cultivation strategies.
In this project, we aim to generate novel genetic information for the pitaya cultivar by characterizing the genetic diversity of wild plants and the dominant cultivars. To do so, we will collect tissue sample from the six most important varieties and from wild plants in the state of Jalisco, Mexico, hosting the regions with one of the highest production of pitayas in the country. We will collect tissue from three plants from three different plantations across three municipalities that host the highest variety of cultivars. We will extract DNA from the samples using a modified CTAB and send it for sequencing to genotype up to 100,000 single nucleotide polymorphism (SNP) markers across our diversity panel. This data will then be used to quantify population structure and relationships among samples and locations, and to determine the degree of monoculture/clonality and the proportion of novel variation in the wild absent from the cultivated types.
This proposed project will provide the first analysis of the genetic diversity in pitaya, where no other CAM crop has been characterized genetically at this level of detail. Our results will also contribute in the understanding the extent to which cultivars are indeed clones and to assess the proportion of genetic diversity present in the cultivated types. Beyond the project proposed here, our data can be used in the future to understand the genetic basis of adaptive traits, for example fruit quality and yield. We plan to use the genetic information from this study to establish a project to secure the germplasm of this species and to encourage the protection and propagation of wild pitaya plants among farmers.
