A method of screening for spike fertility in wheat

Abstract

SUMMARYWheat grain yield is often associated with grain number/m2. Spike fertility (SF), i.e. the quotient between grain number and spike chaff dry weight, is a major component of grain number/m2 determination. Several methodologies have been proposed in the literature for field determination of SF, but they are tedious and expensive. Also, no comparison between methodologies has been done. The feasibility of using wheat SF as a selection criterion in a breeding programme or as a variable of interest in crop physiology studies depends largely upon the availability of a simpler and faster method for collecting and processing samples. Thus, the objective of the present study was to determine: (1) the association between SF calculated with the non-grain spike dry weight at anthesis (reference method) or at crop maturity, (2) the association between SF evaluated at the plot level (i.e. both non-grain spike dry weight and grain number determined as per area unit) and at the individual spike level and (3) the minimum number of individual spikes that should be sampled for the development of a screening method that can be applied in wheat breeding programmes or in crop physiology studies. Associations between variables were determined by correlation analysis of treatment means, and by a test of agreement for categorical rating (low, medium and high SF) between individual data of each variable. Four experiments (BY95, BC96, BC97 and ML07) were performed with five, ten, eight and eight wheat cultivars, respectively, under no environmental limitations, except for experiment ML07 which was not irrigated. In the first three experiments, SF was determined both at the beginning of grain filling and at maturity, in plot-size samples (0·8 m2/plot). In experiments BC96 and BC97, SF was determined both in plot-size samples and in individual spikes (five spikes per plot), at the beginning of grain filling. In experiment ML07, increasing numbers of individual spikes were sampled at maturity to assess SF. As a result: (1) a significant association (R2=0·78; P<0·001; d.f.=20) was detected between SF determined at the beginning of grain filling and at maturity, and the test of agreement for categorical rating showed that the classification of data into categories of SF was equivalent between methods (P>0·05); (2) when comparing SF determined in large plot-size samples v. in small samples of individual spikes, a good adjustment (R2=0·77; P<0·001; d.f.=6) was also observed, with no significant cultivar×experiment interaction and a good agreement between methods in the classification of data into categories of SF (P>0·05); and (3) increasing sample size from 5 to 40 spikes gradually decreased the average relative standard error of the mean (from 0·034 to 0·012, respectively). In conclusion, wheat SF can be determined in a fairly accurate way by sampling a small group of individual spikes at crop maturity, thereby allowing the evaluation of a large number of treatments in a timely fashion and the screening of breeding material from early generations.

Grain yield of durum wheat as affected by waterlogging at tillering

“…For dry weight determination, samples were oven dried at 65 °C to constant weight. The spike fertility index was calculated as the relation between the grain number and the dry weight of chaff representing the non-grain biomass of the spike (Abbate et al 2013). The harvest index was calculated as the ratio between grain yield and total aboveground biomass.…”

Wheat grain number: Identification of favourable physiological traits in an elite doubled-haploid population

“…Works that evaluated the genetic progress or the performance of modern cultivars have reported a positive association between fruiting efficiency and GN, in both bread (Abbate et al, 1998;Acreche et al, 2008;González et al, 2011) and durum wheat (Ferrante et al, 2012). These results, together with evidence of cultivar's variability (Shearman et al, 2005;Serrago et al, 2008;González et al, 2011) and likely responsiveness to selection (Abbate et al, 2013), position fruiting efficiency as a relevant trait to improve GN, although keeping in mind that a trade-off between fruiting efficiency and spike dry weight may occur Ferrante et al, 2012;Lázaro and Abbate, 2012). Therefore, when testing the opportunities to raise GN through improved fruiting efficiency, it is necessary to evaluate whether the improved in this trait does bring about a trade-off in spike dry weight.…”

The effect of duration of the vegetative phase in irrigated semi-dwarf spring wheat on phenology, growth and potential yield across sowing dates at low latitude

“…This assumed an extinction coefficient of 0.40 for GAI and half of total solar radiation energy as being photosynthetically active; because of generally high GAI values RUE values were insensitive to the assumed value for the extinction coefficient. Following Abbate et al (2012) the ratio of GN to SDM a (grains/g) was calculated, this ratio now being defined as fruiting efficiency (Slafer et al, 2015). Finally in these experiments it was possible to calculate GDM as a% of the change in DM from anthesis to physiological maturity (DM pm − DMa).…”

“…Spike dry matter at anthesis (SDM a ) points to a small (6%) but significant superiority of Cajeme relative to Yecora (Table 7); the values were highest with optimum sowings, and in favourable years (not shown), changes which were paralleled by those in GN. A more accurate measure of spike structure, owing to the larger sample size, could be chaff dry weight at maturity (Table 7), although the relationship of chaff dry weight to SDWa is subject to some poorly understood dry weight changes between SDW a and CDW (Abbate et al, 2012;Slafer et al, 2015). Thus going from the spikes just after anthesis to the chaff at maturity there was average 23% increase in weight.…”