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Abstract: Genetic progress in yield will increase if more traits conferring better agronomic and physiological performance are brought together in the same variety through full exploitation of genotyping and phenotyping techniques in breeding. A set of 288 spring wheat advanced lines was tested in different countries in North Africa, Western and South Asia, as well as in Mexico (total of 12 environments) to: identify high yielding germplasm adapted to the former regions; identify sources of variation for physiological traits; and test the ability of physiological traits to predict yield. A group of high yielding advanced lines has been selected in these environments, but significant genotype by environment interactions were observed and were significantly explained (21% of yield variation) by soil pH and air temperature. Associations between traits were dependent on the environment, specifically TKW was positively associated with yield in almost all environments however in Sudan, negative associations were observed. In contrast cooler CT was consistently associated with yield and the trait showed moderate heritability. Agronomic and physiological variables were able to predict 27% of yield variation across advanced lines (R 2% by ridge regression) using means of all environments and this model became more significant under stress environments (explaining around 34% of yield variation). Results suggested that if drought and heat adaptive traits are brought together in one genotype, yields can be further increased particularly in low yielding environments. [Copyright &y& Elsevier]

Abstract: This paper focuses on the interaction between genotype and environment, a critical aspect of plant breeding, from a physiological perspective. We present a theoretical framework largely based on Bradshaw''s principles of phenotypic plasticity (Adv. Gen. 13: 115) updated to account for recent developments in physiology and genetics. Against this framework we discuss associations between plasticity of yield and plasticity of phenological development. Plasticity was quantified using linear models of phenotype vs environment for 169 wheat lines grown in 6 environments in Mexico, 32 sunflower hybrids grown in at least 15 environments in Argentina and 7 grapevine varieties grown in at least 14 environments in Australia. In wheat, yield ranged from 0.6 to 7.8tha−1 and the range of plasticity was 0.74–1.27 for yield and 0.85–1.17 for time to anthesis. The duration of the post-anthesis period as a fraction of the season was the trait with the largest range of plasticity, i.e. 0.47–1.80. High yield plasticity was an undesirable trait as it was associated with low yield in low-yielding environments. Low yield plasticity and high yield in low-yielding environments were associated with three phenological traits: early anthesis, long duration and low plasticity of post-anthesis development. In sunflower, yield ranged from 0.5 to 4.9tha−1 and the range of plasticity was 0.72–1.29 for yield and 0.72–1.22 for time to anthesis. High yield plasticity was a desirable trait as it was primarily associated with high yield in high-yielding environments. High yield plasticity and high yield in high-yielding environments were associated with two phenological traits: late anthesis and high plasticity of time to anthesis. In grapevine, yield ranged from 1.2 to 18.7tha−1 and the range of plasticity was 0.79–1.29 for yield, 0.86–1.30 for time of budburst, 0.84–1.18 for flowering, and 0.78–1.16 for veraison. High plasticity of yield was a desirable trait as it was primarily associated with high yield in high-yielding environments. High yield plasticity was associated with two phenological traits: plasticity of budburst and plasticity of anthesis. We report for the first time positive associations between plasticities of yield and phenology in crop species. It is concluded that in addition to phenology per se (i.e. mean time to a phenostage), plasticity of phenological development merits consideration as a distinct trait influencing crop adaptation and yield. [Copyright &y& Elsevier]

Discusses the potential application of selection technologies in breeding of wheat to improve the probability of identifying higher-yielding genotypes. Trends in yield potential from 1966 to the present, and future demand; Physiological basis of genetic improvement in yield; Genetic basis of yield improvement.

This study examines genotype×organ–temperature depression (TD) interactions and whether differences in plant morphology influence organ-TD and its correlation with canopy temperature depression (CTD) and grain yield. Field experiments were conducted with 13 spring wheat genotypes planted on three dates in the 2000–2001 winter cropping cycle in NW Mexico. Surface temperatures of flag leaves, peduncles, spikes and canopy were measured with a hand-held infrared thermometer. Morphological and yield components were also measured. Results indicated that there is genetic variability for organ-TD. CTD showed strong positive correlations with organ-TD and grain yield. Organ-TD and CTD were positively correlated with leaf area index, and CTD was probably little affected by leaf rolling. Spike temperature was generally higher than leaf temperature, but lower than ambient air temperature. The interactions between grain yield and spike-TD and CTD were not significant. Results of this study indicate that CTD does not mask confounding interactions between organ temperatures and thus can be used reliably to measure TD during grain filling under heat stress conditions. [Copyright &y& Elsevier]

A model of the lodging process has been successfully adapted for use on spring wheat grown in North-West Mexico (NWM). The lodging model was used to estimate the lodging-associated traits required to enable spring wheat grown in NWM with a typical yield of 6 t ha −1 and plant height of 0.7 m to achieve a lodging return period of 25 years. Target traits included a root plate spread of 51 mm and stem strength of the bottom internode of 268 N mm. These target traits increased to 54.5 mm and 325 N mm, respectively, for a crop yielding 10 t ha −1 . Analysis of multiple genotypes across three growing seasons enabled relationships between both stem strength and root plate spread with structural dry matter to be quantified. A NWM lodging resistant ideotype yielding 6 t ha −1 would require 3.93 t ha −1 of structural stem biomass and 1.10 t ha −1 of root biomass in the top 10 cm of soil, which would result in a harvest index (HI) of 0.46 after accounting for chaff and leaf biomass. A crop yielding 10 t ha −1 would achieve a HI of 0.54 for 0.7 m tall plants or 0.41 for more typical 1.0 m tall plants. This study indicates that for plant breeders to achieve both high yields and lodging-proofness they must either breed for greater total biomass or develop high yielding germplasm from shorter crops. [ABSTRACT FROM AUTHOR]