The transition of muscadine grapes ( Vitis rotundifolia Michx.) from a wild fruiting plant to a domesticated crop has taken place in the last 150 years. Muscadine grapes are one of only two species in the Muscadinia subgenera of the Vitis genus. The Muscadinia differ substantially genetically and morphologically from the other Vitis species (subgenus Vitis ). Chromosomal differences between Muscadinia (2 x = 2 n = 40) and Vitis (2 x = 2 n = 38) have generally, although not completely, prevented the movement of genes between the subgenera. Partly due to this genetic isolation, muscadine grapes have been domesticated into a unique fruit crop with many differences from other grape cultivars. Muscadine grapes are grown throughout the southeastern United States and are one of the few fruit crops well suited to this hot and humid growing environment. Muscadines are prized in this region for their unique flavor and aroma and are grown as juice and wine grapes as well as for fresh consumption. Muscadine grapes are also gaining recognition for their high levels of beneficial phytochemicals. Despite these advantages, muscadines are not well known outside of the southeast United States. This is due in part to difficulties in long-term storage of the crop and also to the inherent difficulties in marketing an unfamiliar product. Several long-term breeding programs have transformed this crop from a functionally dioecious species bearing small berries with a tough skin and soft pulp to a hermaphroditic vine with large berries having a firm flesh and crisp skin. Recent success in intersubgeneric hybridization has resulted in the successful incorporation of stenospermocarpic seedlessness into muscadine. These breeding advances have opened exciting possibilities and positioned muscadine to transform from a niche to a mainstream crop.
After decades of prohibition of the cultivation and breeding of hemp ( Cannabis sativa < 0.3% ∆9-tetrahydrocannabinol [THC]), there is untapped potential for genetic improvement of this crop to provide food, feed, fiber, and medicinal compounds. Successful breeding efforts will require the development and characterization of germplasm resources, optimization of crossing methods, better understanding of sex determination, high-throughput phenotyping platforms, and deployment of genomic tools for rapid selection. This review provides a brief overview of these topics and some key opportunities for genetic improvement of hemp to support an emerging industry utilizing this newly legalized crop.
Genetic vulnerability refers to (sometimes catastrophic) actual or potential losses in the production of a crop (in quantity and/or quality), attributable to spatial or temporal reduction in the crop's biodiversity. Conversely, genetic resilience refers to the natural and anthropic capabilities of this biodiversity to mitigate these reductions in crop production. Here, an assessment is provided of genetic vulnerability and resilience of Phaseolus beans, which provide an abundant and sustainable source of protein and micronutrients for populations around the world. We provide an overview of the economic, nutritional, and cultural role of Phaseolus beans and phylogenetic and diversity analyses of the genus, its five domesticated species, and seven domestications, which provide key foundational information for this appraisal. We then assess the uniformity of the crop in the United States and the main drivers of genetic erosion in the centers of origin of the genus in the Americas. Next, the current and emerging breeding constraints are discussed for biotic and abiotic stresses, morphological and phenological traits, and dietary and cooking needs. To address these vulnerabilities, several resources have been developed and, which have been applied to increase the genetic resilience of Phaseolus beans. The resilience resources include genetic resources collections such as the global collection at the Centro Internacional de Agricultura Tropical (CIAT, Colombia), national collections in the United States, Brazil, the European Union, and elsewhere, which include wild and domesticated types across the genus but focus primarily on domesticated species. Resilience resources also include genome-wide reference DNA sequences for three of the five domesticated species, multiple diversity panels and recombinant inbred populations, and large sets of whole-genome diversity data based on single-nucleotide polymorphism (SNP) arrays, genotyping by sequencing, and whole-genome sequencing of germplasm sets. Numerous marker–trait associations and genes affecting agronomic traits have also been characterized in the genus. In turn, these resources have been successfully utilized to make Phaseolus beans more resistant against biotic and abiotic stresses (including those incurred by climate change) and to improve dietary and culinary quality through significant breeding efforts in the United States, at CIAT (mainly Latin America and Africa) and in national programs in Latin America and Eastern Africa. Future challenges remain, however, which include (1) a continued need for ex situ and in situ conservation of diversity, with agroecologically informed germplasm explorations and integration of farmers into conservation and breeding activities; (2) increased pre-breeding efforts involving gene bank curators and bean improvement scientists; (3) expansion of breeding of domesticated species other than common bean, where appropriate based on their potential adaptation to global climate change and consumer preferences; (4) an increased focus on culinary and dietary improvement; and (5) inclusion of microorganisms (both pathogenic and beneficial) in genetic conservation. We conclude that in the short term (~5 years), Phaseolus beans have limited genetic vulnerability. However, over the longer term, vulnerability due to several factors will increase, which can be addressed by a wide range of the resilience resources presented here.
