Preface to Special Issue: Complex traits and plant breeding—can we understand the complexities of gene-to-phenotype relationships and use such knowledge to enhance plant breeding outcomes?

摘要

Some would argue that the answer to the question we pose innthe title of this introductory paper is already known, and is yes.nFor some traits, e.g. resistance to particular pests and diseases,nthere is no doubt that we have used detailed knowledge of thengenetics that underlies trait phenotypic variation to enhancenthe performance of the product outcomes from plant breedingn(e.g. Cahill and Schmidt 2004). However, we also recognisenthat plant breeding is fundamentally an undertaking in multitraitnimprovement and that there are many important traitsnwhere we do not yet have a sufficient knowledge of the causalngenetic variation to enable similar approaches. Therefore, wenuse these initial successes as encouragement and to argue forna continuation of research on other traits.nThe papers included in this Special Issue of the AustraliannJournal of Agricultural Research are focussed aroundntwo related questions that impinge on our ambitions andnabilities to enable knowledge-based approaches to molecularnenhanced breeding: (1) the feasibility of, and (2) appropriatenstrategies for, constructing predictive gene-to-phenotypenmodels of complex traits. Although it can be argued that thentraits manipulated in plant breeding programs range fromngenetically simple to complex, most of the important traitsnthat have preoccupied the field of quantitative genetics andnplant breeders are towards the complex end of this continuum.nPlant breeders have consistently demonstrated significantncapacity to make desirable changes to many of the complexnyield, quality, and agronomic traits of crop plants that arenconsidered important for sustainable production in theirnrespective target agricultural systems. Most often studiesnconducted to quantify genetic progress from breeding havenfocussed on the key endpoint traits, such as the improvementnof grain yield and associated changes in other traits (e.g.nFehr 1984; Duvick et al. 2004). Although several of thesenretrospective studies have found a tendency for increasednyield to arise from change in biomass partitioning rathernthan increased total biomass production, many of the geneticnand physiological details underpinning the improvementsnin yield varied among breeding programs and with thenperiod of investigation (Duvick et al. 2004). Further, theirneffect in the intended target environments depended on thencrop and on features of the environments within the targetnproduction system (Allard 1999). It is widely recognised thatnrealising much of the genetic improvements from breeding isnconditional on the use of appropriate agronomic managementnpractices. The interplay between genotype, management, andnenvironment is critical in realising improvements in cropnperformance (Cooper and Hammer 1996; Cooper et al. 2002;nYin et al. 2004). The ubiquitous nature of these interactions,nand the degree to which they are considered in breedingnprograms, have contributed to an ongoing debate about thenextent of the outcomes from breeding that are realised byndifferent groups of farmers in the diversity of the global targetnproduction systems.