THE ROLE OF PHYSIOLOGICAL UNDERSTANDING IN PLANT-BREEDING - FROM A BREEDING PERSPECTIVE

The role of physiological understanding in improving the efficiency of breeding programs is examined largely from the perspective of convent ional breeding programs. Impact of physiological research to date on b reeding programs, and the nature of that research, was assessed from ( i) responses to a questionnaire distributed to plant breeders and phys iologists, and (ii) a survey of literature abstracts. Ways to better u tilise physiological understanding for improving breeding programs are suggested, together with possible constraints to delivering beneficia l outcomes. Responses from the questionnaire indicated a general view that the contribution by crop physiology to date has been modest. Howe ver, most of those surveyed expected the contribution to be larger in the next 20 years. Some constraints to progress perceived by breeders and physiologists were highlighted. The survey of literature abstracts indicated that from a plant breeding perspective, much physiological research is not progressing further than making suggestions about poss ible approaches to selection. There was limited evidence in the litera ture of objective comparison of such suggestions with existing methodo logy, or of development and application of these within active breedin g programs. It is argued in this paper that the development of outputs from physiological research for breeding requires a good understandin g of the breeding program(s) being serviced and factors affecting its performance. Simple quantitative genetic models, or at least the ideas they represent, should be considered in conducting physiological rese arch and in envisaging and evaluating outputs. The key steps of a gene ralised breeding program are outlined, and the potential pathways for physiological understanding to impact on these steps are discussed. Im pact on breeding programs may arise through (i) better choice of envir onments in which to conduct selection trials, (ii) identification of s election criteria and traits for focused introgression programs, and ( iii) identifying traits for indirect selection criteria as an adjunct to criteria already used. While many breeders and physiologists appare ntly recognise that physiological understanding may have a major role in the first area, there appears to be relatively Little research acti vity targeting this issue, and a corresponding bias, arguably unjustif ied, toward examining traits for indirect selection. Furthermore, rese arch on traits aimed at crop improvement is often deficient because ke y genetic parameters, such as genetic variation in relevant breeding p opulations and genetic (as opposed to phenotypic) correlations with yi eld or other characters of economic importance, are not properly consi dered in the research. Some areas requiring special attention for succ essfully interfacing physiology research with breeding are discussed. These include (i) the need to work with relevant genetic populations, (ii) close integration of the physiological research with an active br eeding program, and (iii) the dangers of a pre-defined or narrow focus in the physiological research.