The breeding of crop ideotypes

Abstract

Most plant breeding is based on "defect elimination" or "selection for yield". A valuable additional approach is available through the breeding of crop ideotypes, plants with model characteristics known to influence photosynthesis, growth and (in cereals) grain production. Some instances of the successful use of model characters of this kind are quoted.It is postulated that a successful crop ideotype will be a weak competitor, relative to its mass. Thus the like plants in the crop community will compete with each other to a minimum degree. This relationship of plant form to the exploitation of the enviroment may lead to two negative relationships among genotypes, namely : (a) Between the performance of cultivars at low density and at high density respectively, and (b) Between the competitive ability of cultivars against other genotypes on the one hand, and their capacity for yield in pure culture on the other.A crop ideotype will make a minimum demand on resources per unit of dry matter produced. Further, in cereals, each unit of dry matter will include such a number of florets as to ensure that the ear has sufficient capacity to accept all photosynthates either from its own green surfaces or from other parts of the plant. These criteria are to be satisfied especially at high fertility, and when the total pressure by the community on environmental resources is intensified by high density of population.A wheat ideotype is described. It has a short, strong stem; few, small, erect leaves; a large ear (this specifically means many florets per unit of dry matter of the tops); an erect ear; awns; and a single culm.The design of crop ideotypes is likely to involve concurrent modifications of the environment. The wheat ideotype here described will call for consideration of the density of planting, the fertilizer rate, the plant arrangement and weed control.Eventually most plant breeding may be based on ideotypes.

Utility of basic research in plant/crop physiology in relation to crop improvement: a review and a personal account

“…This species was the third discovered C 4 member in the family Amaranthaceae and known to be domesticated and largely cultivated by the Aztecs and the Incas before Cortez and still cultivated today in minor acreages in the Andean highland of Argentina, Peru and Bolivia (Connor et al, 1980;Saunders and Becker, 1983;BOSTID, 1984;ElSharkawy and Hesketh, 1986). Our conclusion was that these species were capable of reassimilating their internal respiratory CO 2 via a very efficient photosynthetic machinery (El-Sharkawy et al, 1967, 1968. That was done shortly before the C 4 biochemical photosynthetic pathway was elucidated Slack, 1966, 1970).…”

“…Loomis and W.A. Williams, University of California, Davis (ElSharkawy et al, 1967, 1968. Perhaps, this story might help young students, particularly those from developing countries with limited resources and support for science, not to be inhibited by whatever they may consider to be unfavorable conditions.…”

“…Moreover, desired morphological, structural and functional plant traits can be identified using this type of analysis. This has led to the proposition and formulation of the so-called plant ideotype concept (i.e., ideal phenotype) for plant breeding by Donald (1968) based on characterization and identification of plant traits crucial to yield formation and enhancement, and that may confer better adaptation to prevailing environments, in contrast to the traditional breeding philosophy based on the empirical approach for selecting only for yield. According to Donald s ideotype concept, pre-designed biological plant models, when developed into new cultivars, may perform better and in a predictable manner when grown in a particular environment.…”

Toward a Bayesian procedure for using process-based models in plant breeding, with application to ideotype design

“…The objective is to explain or predict how plants respond to their environment, or to determine how plants can be improved by breeding. Nearly five decades ago, Donald (1968) introduced the concept of the 'ideotype', defined as a set of plant traits that, if brought together in one new genotype, would lead to high performance. He used the example of breeding for high-yielding wheat cultivars that would pose low demands on external inputs.…”

Yield comparisons and unique characteristics of the dwarf wheat cultivar ‘USU-Apogee’

“…These traits are desirable in high yield conditions (Donald, 1968;1979 Assuming that the root mass was 6% of the total biomass at harvest, the harvest index including roots in these trials would be 50 and 54%. The harvest index of Veery-10 (without roots) was 48 and 49% in these same trials.…”