Abstract
Developmental patterns strongly influence spike fertility and grain number, which are primarily determined during the stem elongation period (i.e. time between terminal spikelet phase and anthesis). It has been proposed that the length of the stem elongation phase may, to an extent, affect grain number; thus it would be beneficial to identify genetic variation for the duration of this phase in elite germplasm. Variation in these developmental patterns was studied using 27 elite wheat lines in four experiments across three growing seasons. The results showed that the length of the stem elongation phase was (i) only slightly related to the period from seedling emergence to terminal spikelet, and (ii) more relevant than it for determining time to anthesis. Thus, phenological phases were largely independent and any particular time to anthesis may be reached with different combinations of component phases. Yield components were largely explained by fruiting efficiency of the elite lines used: the relationships were strongly positive and strongly negative with grain number and with grain weight, respectively. Although fruiting efficiency showed a positive trend with the duration of stem elongation that was not significant, a boundary function (which was highly significant) suggests that the length of this phase may impose an upper threshold for fruiting efficiency and grain number, and that maximum values of fruiting efficiency may require a relatively long stem elongation phase.
Highlights
A substantial increase in wheat yield potential is required in the coming decades, but rates of genetic gain are currently well below the level required to match the projected cereal demand (Reynolds et al, 2012; Hall and Richards, 2013; Fischer et al, 2014)
The results showed that the length of the stem elongation phase was (i) only slightly related to the period from seedling emergence to terminal spikelet, and (ii) more relevant than it for determining time to anthesis
The objective of the present study was to determine the degree of variation in patterns of phenological development within the elite germplasm of the CIMMYT Mexico Core Germplasm (CIMCOG) population, ascertaining whether the differences were related to traits determining spike fertility within the population
Summary
A substantial increase in wheat yield potential is required in the coming decades, but rates of genetic gain are currently well below the level required to match the projected cereal demand (Reynolds et al, 2012; Hall and Richards, 2013; Fischer et al, 2014). Quantifying the degree of genetic variation within elite germplasm in traits which may contribute to increased yield potential is critical to the design of strategic crosses (Slafer, 2003; Foulkes et al, 2011; Reynolds et al, 2012). As grain number is strongly source-limited and highly responsive to changes in availability of assimilates (see below), grain number is more plastic than grain weight (Peltonen-Sainio et al, 2007; Sadras, 2007; Sadras and Slafer, 2012) and yield is far more commonly related to grain number than to the average weight of grains (Fischer, 2011; Slafer et al, 2014). To achieve relevant genetic gains in yield potential it is important to identify traits responsible for the determination of grain number (Slafer et al, 2014)
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