Application of physiological understanding in soybean improvement. I. Understanding phenological constraints to adaptation and yield potential

摘要

Abstract. The purpose of this paper and its companion1nis to describe how, in eastern Australia, soybean improvement, innterms of both breeding and agronomy, has been informed and influenced over the past four decades by physiologicalnunderstanding of the environmental control of phenology. This first paper describes how initial attempts to grow soybean inneastern Australia, using varieties and production practices from the southern USA, met with limited success due to largenvarietyu0001environment interaction effects on seed yield. In particular, there were large varietyu0001location, varietyu0001sowingndate, and varietyu0001sowing dateu0001density effects. These various interaction effects were ultimately explained in terms of theneffects of photo-thermal environment on the phenology of different varieties, and the consequences for radiation interception,ndry matter production, harvest index, and seed yield. This knowledge enabled the formulation of agronomic practices tonoptimise sowing date and planting arrangement to suit particular varieties, and underpinned the establishment of commercialnproduction in south-eastern Queensland in the early 1970s. It also influenced the establishment and operation over the nextnthree decades of several separate breeding programs, each targeting phenological adaptation to specific latitudinal regions ofneastern Australia. This paper also describes how physiological developments internationally, particularly the discovery ofnthe long juvenile trait and to a lesser extent the semi-dwarf ideotype, subsequently enabled an approach to be conceivednfor broadening the phenological adaptation of soybeans across latitudes and sowing dates. The application of this approach,nand its outcomes in terms of varietal improvement, agronomic management, and the structure of the breeding program, arendescribed in the companion paper.