Decimal growth stages for precision wheat production in changing environments?

Abstract

The utility of the Decimal Growth Stage (DGS) scoring system for cereals is reviewed. The DGS is the most widely-used scale in academic and commercial applications due to its comprehensive coverage of cereal developmental stages, the ease of use and definition provided, and adoption by official agencies. The DGS has demonstrable and established value in helping to optimise the timing of agronomic inputs, particularly with regards to plant growth regulators, herbicides, fungicides and soluble nitrogen fertilizers. Additionally the DGS is used to help parametise crop models, and also in understanding the response and adaptation of crops to the environment. The value of the DGS for increasing precision relies on it indicating, to some degree, the various stages in the development of the stem apex and spike. Coincidence of specific growth stage scores with the transition of the apical meristem from a vegetative to a reproductive state, and also with the period of meiosis, is unreliable. Nonetheless, in pot experiments it is shown that the broad period of booting (DGS 41-49) appears adequate for covering the duration when the vulnerability of meiosis to drought and heat stress is exposed. Similarly, the duration of anthesis (61-69) is particularly susceptible to abiotic stresses: initially from a fertility perspective, but increasingly from a mean grain weight perspective as flowering progresses to DGS 69 and then milk development. These associations with DGS can have value at the crop level of organisation: for interpreting environmental effects, and in crop modelling. However, genetic, biochemical, and physiological analysis to develop greater understanding of stress acclimation during the vegetative state, and tolerance at meiosis, does require more precision than DGS can provide. Similarly, individual floret analysis is needed to further understand the genetic basis of stress tolerance during anthesis.publishersversionpreprintPeer reviewe

Temporally and Genetically Discrete Periods of Wheat Sensitivity to High Temperature

“…Secondly we investigate whether the effect of genotype on heat stress vulnerability interacts with timing of stress. We pay particular attention to the effects of three alleles reported to influence heat stress tolerance and have adaptive significance in wheat grown in European regions with different frequencies and severities of heat stress, namely Rht8, Ppd-D1a , and Rht-D1b (Worland, 1996; Worland et al, 1998; Rebetzke et al, 2007; Gasperini et al, 2012; Alghabari et al, 2014; Barber et al, 2015; Kowalski et al, 2016; Jones et al, 2017). We also assess associations with the 1BL/1RS translocation (Schlegel and Korzun, 1997) which introduced a number of race-specific disease resistance genes (Snape et al, 2007).…”

Statistical Modeling of Phenotypic Plasticity under Abiotic Stress in Triticum durum L. and Triticum aestivum L. Genotypes

“…Above ground biomass was sampled at GS69 (i.e., about 15 days after completion of anthesis) and at full maturity from permanent geo-referenced sampling sites (0.15 m 2 from 50 cm length of three central adjacent rows) in each replicate, abiotic stress treatment, and year [47,48]. Number of plant samples per genotype per year ranged from 80 to 100.…”

“…Wheat yield is at risk of abiotic stresses throughout plant development and until physiological maturity [48]. The season-long abiotic stress treatments that were used in the current study can be considered as abiotic stress priming, and they might have contributed to wheat resilience at the maturity stage.…”

“…Phenotypic plasticity was assessed at the reproductive and full maturity stages (Table 2; Figure 2); the former is an indicator of biological processes leading to the formation of grain yield [48]; while the latter is an indicator of the reproductive biology process determining spike fertility and spike harvest index [73,74]. Wheat developmental patterns play an important role in determining spike fertility index and kernels m −2 ; both yield components can be determined accurately by sampling a small number of individual spikes at crop maturity, thereby allowing for timely evaluation of many genotypes or treatments [34].…”

“…Larger level of discrimination at FM than RP could be attributed to differences in the sequentially developed yield components, such as tiller [20,69]. The implications of differential plastic responses to the same abiotic stress as a function of growth stage (Figure 2) are of practical significance [31,48]. Reproductive plasticity (e.g., in spike fertility index, spike harvest index and kernels m −2 ) was demonstrated ( Table 2) in response to resource limitations (e.g., caused by SN and SH); however, plasticities of the final reproductive output (i.e., grain yield) and of biomass covaried in T. durum (r = 0.92) and T. aestivum (r = 0.75), but were totally non-overlapping (Figure 3).…”