Whither crop physiology?

HALL, A.J.; ,SADRAS, V.O.

Crop Physiology- Applications for genetic improvement and agronomy

Academic Press/Elsevier

Lugar: Amsterdam; Año: 2009; p. 545 - 570

1. INTRODUCTIONIn his introduction to ‘Crop physiology: some case histories ’, Evans (1975) outlined a brief history of thediscipline. Citing Balls, he wondered whether its role might not be restricted to retrospective explanationof results obtained by breeders. Some might be tempted to add the results obtained by agronomists to thatcategory. Since then, Simmonds (1991) included crop physiology in his list of ‘bandwagons ’. Currently, a lotof emphasis is placed on the expectations aroused by molecular approaches to, say, yield improvement andstress tolerance (Chapter 14; Hammer et al., 2006 ; Struik et al., 2007 ). A further issue is privately funded,and largely unpublished, research on functional genomics and other ‘omics’, the results of which remainoutside the public domain ( Struik et al., 2007 ). In addition, growing concerns about humankind’s impacton the environment have led to a much greater emphasis on global and regional ecosystem functioning.These changes in research foci have created a whole new scenario for crop physiology.So, is crop physiology committed to irreversible decline, overtaken by alternative research perspectives,shunted to one side by emerging new fi elds, after having promised more than it could deliver and having,even in its prime, only provided retrospective explanations? We believe the answer to these questions is ‘no’.Our reasons include:■ the number of important, crop-level issues that still await systematic study from a crop physiologicalperspective before they can be reduced to a usable corpus of knowledge linked to frameworks that canhelp breeders and agronomists, among others;■ the importance of crop physiological information and knowledge for the formulation of modellingtools to quantitatively explore matters such as agro-ecosystem functioning and projected impacts ofclimate change (Chapters 4 and 20), the complexity of genotypic, environmental and G  E controlof crop yield (Chapter 10) and grain quality (Chapter 16), the design of crop rotations for riskmanagement, greater yield and profi t, more effective resource utilisation and reduced environmentalimpact (Chapters 2 –4 and 19);■ the value of crop physiological principles in the design and execution of agronomic and breedingexperiments, targeting phenological adaptation (Chapter 12), improved water- and nitrogen-use effi -ciencies (Chapters 8, 13 and 15), yield and grain quality (Chapters 15 and 16);546 CHAPTER 21: Whither Crop Physiology?■ the need for understanding and integrating potential impacts of the crop-centred products of functionalgenomics (Chapters 10 –16; Hammer et al., 2006 ; Struik et al., 2007 ; Yin et al., 2004 ).■ the need to estimate fl uxes of carbon, water and reactive nitrogen linked to the functioning of theagro-ecosystems which cover large areas of the planet. Adequate understanding of global biogeochemistrycannot emerge without good knowledge of crop functioning.According to Boote and Sinclair (2006) , early efforts in physiological studies had a narrow cell or individualplant focus (e.g. nitrate reductase) that shifted to a crop-oriented perspective in the 1960s, and then back tothe current narrow focus on specifi c genes infl uencing behaviour at molecular level. This latest shift is, theyargue, unwise in that ‘the gains in understanding the whole-plant response is not given full consideration ’ andthey contend that the cycle of focus will return to the challenge of integrating understanding at the crop level.In what follows, we present a selection of topics, drawn from a much broader range of potentially interestingissues, to illustrate some of the very many gaps in current knowledge about the physiology of crops. Ourillustrations of gaps emphasise the importance of crop-level studies carefully linked to crop development asessential to deal with the issues. We also discuss the present status of the interfaces between the disciplineand modelling, breeding and agronomy. We close with a very personal view of the present status of thediscipline and its future prospects. Readers will note that although we refer to some of the chapters of thisbook, we have made no attempt at systematic coverage of their contents.