Using wild relatives and related species to build climate resilience in Brassica crops

Abstract

Climate change will have major impacts on crop production: not just increasing drought and heat stress, but also increasing insect and disease loads and the chance of extreme weather events and further adverse conditions. Often, wild relatives show increased tolerances to biotic and abiotic stresses, due to reduced stringency of selection for yield and yield-related traits under optimum conditions. One possible strategy to improve resilience in our modern-day crop cultivars is to utilize wild relative germplasm in breeding, and attempt to introgress genetic factors contributing to greater environmental tolerances from these wild relatives into elite crop types. However, this approach can be difficult, as it relies on factors such as ease of hybridization and genetic distance between the source and target, crossover frequencies and distributions in the hybrid, and ability to select for desirable introgressions while minimizing linkage drag. In this review, we outline the possible effects that climate change may have on crop production, introduce the Brassica crop species and their wild relatives, and provide an index of useful traits that are known to be present in each of these species that may be exploitable through interspecific hybridization-based approaches. Subsequently, we outline how introgression breeding works, what factors affect the success of this approach, and how this approach can be optimized so as to increase the chance of recovering the desired introgression lines. Our review provides a working guide to the use of wild relatives and related crop germplasm to improve biotic and abiotic resistances in Brassica crop species.

Global Phylogeny of the Brassicaceae Provides Important Insights into Gene Discordance

“…In many of these genetic studies, comparative studies to extend what is known from model species to close or more distant allies require a robust evolutionary framework encompassing the ∼4,000 currently accepted species that are divided among 349 genera and 50-60 tribes (Koch et al 2018). This is also true for studies on the wild relatives of crops that aim to deliberately introgress desirable traits (e.g., increased drought tolerance, disease resistance) from closely related species in the wild into crop species using plant breeding (Castañeda-Álvarez et al 2016; Castillo-Lorenzo et al 2019; Quezada-Martinez et al 2021). It is unsurprising then that the taxonomy and evolution of Brassicaceae have been the subject of study for a long time, with the ultimate goal of producing a complete and robust family phylogeny (Al-Shehbaz et al 2006; Bailey et al 2006; Franzke et al 2009; Beilstein et al 2010; Couvreur et al 2010; Warwick et al 2010; Huang et al 2016; Nikolov et al 2019; Huang et al 2020; Walden et al 2020).…”

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

“…Cultivars with tolerance to drought, heat, salinity, soils with extreme pH (alkaline or acidic) and low fertility, as well as various biotic factors are known to be required in marginal environments ( Redden, 2013 ; Quezada-Martinez et al, 2021 ). Irrespective of the pre-breeding technique it is important to understand the phenotypic traits that confer adaptation for identification in any given marginal environment and for agronomic management ( Wilke and Snapp, 2008 ).…”

Exploring the gene pool ofBrassica napusby genomics‐based approaches

“…Compared with B. napus , other Brassica species show rich genetic diversity (Warwick, 2011) and obvious genetic differences and subgenomic variation relative to B. napus (Chalhoub et al ., 2014; Parkin et al ., 2014; Zou et al ., 2016a). These species also have many desirable traits and high genetic diversity, as shown in Table S1 and Figure 2 (Quezada‐Martinez et al ., 2021; Warwick, 2011). These traits have been or could be further introduced into the B. napus gene pool to provide genetic diversity, and germplasm types suited to changing environments and industry requirements.…”