How Could the Use of Crop Wild Relatives in Breeding Increase the Adaptation of Crops to Marginal Environments?

Abstract

Alongside the use of fertilizer and chemical control of weeds, pests, and diseases modern breeding has been very successful in generating cultivars that have increased agricultural production several fold in favorable environments. These typically homogeneous cultivars (either homozygous inbreds or hybrids derived from inbred parents) are bred under optimal field conditions and perform well when there is sufficient water and nutrients. However, such optimal conditions are rare globally; indeed, a large proportion of arable land could be considered marginal for agricultural production. Marginal agricultural land typically has poor fertility and/or shallow soil depth, is subject to soil erosion, and often occurs in semi-arid or saline environments. Moreover, these marginal environments are expected to expand with ongoing climate change and progressive degradation of soil and water resources globally. Crop wild relatives (CWRs), most often used in breeding as sources of biotic resistance, often also possess traits adapting them to marginal environments. Wild progenitors have been selected over the course of their evolutionary history to maintain their fitness under a diverse range of stresses. Conversely, modern breeding for broad adaptation has reduced genetic diversity and increased genetic vulnerability to biotic and abiotic challenges. There is potential to exploit genetic heterogeneity, as opposed to genetic uniformity, in breeding for the utilization of marginal lands. This review discusses the adaptive traits that could improve the performance of cultivars in marginal environments and breeding strategies to deploy them.

Persistence of cultivar alleles in wild carrot (Daucus carotaL.) populations in the United States

“…Gene flow between crop species and their wild relatives has played an important role in the evolution of both wild and cultivated plants (Ellstrand & Rieseberg, 2016). Introgression of wild alleles into cultivated germplasm constitutes an important source of new genetic variation for crop breeding (Hajjar & Hodgkin, 2007;Prohens et al, 2017;Renzi et al, 2022). However, introgression from crops to nearby wild populations can have a negative impact on wild populations by decreasing genetic diversity and even causing local extinction of the recipient populations (Hegde, Nason, Clegg, & Ellstrand, 2006;Todesco et al, 2016); it may also facilitate the evolution of agricultural weeds (Ellstrand et al, 2010;Le Corre, Siol, Vigouroux, Tenaillon, & Délye, 2020;Schierenbeck & Ellstrand, 2009).…”

Crop Wild Relatives: A Valuable Source of Tolerance to Various Abiotic Stresses

“…Notably, much effort has been undertaken across countries to generate prioritized inventories for crop wild relatives (annual and perennial plants). These aim at proper assessment and efficient conservation, both in situ (land protection) and ex situ (seed banks), of unexplored or underexploited wild genetic resources [ 9 , 178 , 179 , 180 , 181 ]. Breeding programs focusing on introgression of wild genetic material into cultivated crops will result in climate-resilient varieties with low-input requirements.…”

“…Grain legumes are often cultivated in marginal lands and confront unfavorable environmental conditions [ 15 ] that prevail in these areas. Typically, marginal areas are characterized by poor soil fertility and are usually prone to abiotic stresses, such as drought and salinity [ 9 ]. Breeding for tolerant grain legume genotypes to various abiotic stresses is therefore of primary importance, especially given the impending climate change.…”

“…Furthermore, these varieties tend to emphasize reproduction rather than defense and competition mechanisms. These are major problems nowadays as agriculture is threatened by extreme conditions [ 9 ].…”

“…Wild relatives, unlike domesticated species, were not subjected to strict anthropogenic selection pressure with an emphasis on traits related to plant yield under optimal controlled conditions [ 14 ]. Instead, throughout evolutionary history they were exposed and adapted in an abundance of adverse environments and kept evolving to adjust and survive under such harsh conditions [ 9 ]. Crop wild relatives possess a plethora of genes that confer increased resistance to abiotic stresses [ 14 ] and represent a source of alleles that are absent from modern cultivars that have significant agronomic value.…”