The interaction of wheat genotypes with a specific factor of the environment

Abstract

SummarySeveral alternative statistical approaches to the analysis of genotype-environment interactions are summarized, and their inter-relationships are presented mathematically and graphically. An experiment was designed to test the ability of these analyses to satisfactorily describe genotype-environment interactions and to locate genotypes causing or contributing significantly to such interactions in a situation where environments differed in only one factor, i.e. soil nitrogen status.Twenty-five lines of wheat were grown at each of 5 levels of applied nitrogen (0–270 kg N/ha) in a sandy, nitrogen-deficient soil, and their grain yields and yield components (ears per unit area, grains per ear, weight per grain) were determined. Designating the nitrogen levels as ‘environments’, linear yield responses, and deviations from linear responses, of individual wheat entries to environment mean yield were calculated according to the various statistical procedures previously outlined. The results suggested that the linear response to environment mean yield was similar for all wheat entries. However, further inspection of the data revealed that the responses of eight entries to environment mean yield departed significantly from linearity. Although several analyses satisfactorily identified these aberrant entries, classifying them as ‘unstable’, it was concluded that the degree of departure from linearity of response was not an adequate measure of instability. Furthermore, as previously suggested by Knight (1970), it was confirmed that the relative ranking of an entry for yield stability according to such a concept varied according to the average response of the group of entries with which it was being compared.The general effects of applied nitrogen on yield components were to increase the number of ears and the number of grains per ear, and to decrease grain weight. However, only the first of these effects occurred consistently for all entries. The number and weight of individual grains per ear varied with the nitrogen treatment, often unpredictably, in a complex pattern which differed significantly between entries.

Adaptabilidade e estabilidade de cultivares de soja em cinco épocas de plantio no cerrado de Rondônia

“…Segundo Eberhart & Russell (1966), a cultivar ideal é aquela que tem produção média alta, coeficiente de regressão igual à unidade e desvio de regressão pequeno, isto é, aquele desvio que tem resposta positiva à melhoria das condições ambientais (b 1 = 1,0), e comportamento altamente previsível (s 2 d i = 0,0). Easton & Clements (1973) e Lin et al (1986 salientaram que a caracterização da adaptabilidade e estabilidade fenotípica é relativa ao conjunto dos genótipos incluídos no experimento. Como a produtividade do ambiente é expressa pelo próprio desempenho médio dos genótipos no experimento, não há qualquer segurança de que um genótipo manterá o mesmo comportamento quando avaliado com diferentes genótipos.…”

A genotype-environment experiment on strawberries in scotland

“…For inheritance studies they should therefore be considered in combination and the techniques of Thomas et al (1971) may be suitable. Easton and Clements (1973) emphasise the importance of examining individual genotypes and this applies especially to vegetatively propagated crops. Marmion and Montrose illustrate their point.…”

Statistical methods for the analysis of genotype-environment interactions

“…In such cases some plant breeders and agronomists have then found the concept of two stability parameters useful. However, Easton and Clements (1973) compared various methods for assessing stability and found them to be only moderately good at identifying genotypes with atypical behaviour; by choosing a subset of genotypes it was possible to make a previously stable genotype appear unstable. Similarly, found that the selection of a subset of environments changed the relation between mean performance and both linear and non-linear components of stability.…”