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The J. Derek Bewley Career Lectures presented at the triennial meetings of the International Society of Seed Science support early-career seed scientists by providing retrospective views, from those late in their careers, of lessons learned and future implications. Ambition, ability, inspiration, foresight, hard work, and opportunity are obvious career requirements. The importance of mentoring and teamwork combined with the clear communication of results, understanding, and ideas are emphasized. The role of illustration in research, and its dissemination, is outlined: illustration can support hypothesis development, testing, and communication. Climate change may perturb the production of high-quality seed affecting conservation as well as agriculture, horticulture, and forestry. An illustrative synthesis of the current understanding of temporal aspects of the effects of seed production environment on seed quality (assessed by subsequent seed storage longevity) is provided for wheat (Triticum aestivum L.) and rice (Oryza sativa L.). Seed science research can contribute to complex global challenges such as future food supplies from seed-propagated crops in our changing climate whilst conserving biological diversity (through seed ecology and technologies such as ex situ plant genetic resources conservation by long-term seed storage in genebanks), but only if that research can be - and then is - applied.

All supplementary materials referenced in the manuscript.

Grain yield of continuous wheat (Section 1) with 192 kg N ha-1 applied (●, solid line), or first ( , dot-dash line) and second (+, dotted line) rotational wheat with 288 kg N ha-1 applied from 1997 to 2016 in the Long Term Experiment at Broadbalk

Description of the Sirius parameters of three winter wheat varieties used in the study

Dioscorea hirtiflora Benth. is an indigenous wild edible tuberous climbing plant native to Zambia. Known as lusala, the tubers are sold in markets across southern Zambia. Lusala collection, consumption and trade was investigated through interviews with rural households (four districts) and market traders (three towns), and supplementary focus group discussions. Of 278 households interviewed, high proportions collected (83%), consumed (96%), and sold (59%) lusala, not varying amongst district or wealth category. Lusala populations were perceived to be declining in the wild by 79% of households. Tuber collection, largely by females and mainly from March to September, peaked in April when households engaged in each activity collected 27.9kg, consumed 12.0kg, and sold 35.7kg (from 129, 108, and 69 reporting households, respectively) that month, regardless of district, wealth category, or gender. Those sales provided an average household income of USD 16 in April 2017. In August 2017, each market trader purchased an average of 899kg for USD 383. Local knowledge of D. hirtiflora was considerable. Lusala collected from forests is an important edible wild tuber in the local economy of the Southern Province of Zambia: it provides a seasonally-important food supply and income to rural households and supplies demand from urban populations.

Introgressing the Submergence1 (Sub1) allele into chromosome 9 of high-yielding rice (Oryza sativa L.) cultivars introduced the flood-tolerant trait, but this chromosome also includes quantitative trait loci for seed storage survival. Loss in seed dormancy and viability during post-harvest storage were investigated in cvs IR64 and IR64-Sub1 to test if the introgression of Sub1 affected seed longevity. They were grown in the same controlled environment, mature seeds harvested, and ability to germinate monitored during subsequent hermetic storage at 40°C with 13.5-13.9% moisture content. The overlapping patterns of loss in dormancy and loss in viability during storage were quantified well by a multiplicative model, with similar responses in the two near-isogenic cultivars: both showed almost full dormancy initially with complete, similar, loss in dormancy during the first seven days of storage, loss in viability after 43 days, and 50% viability periods (p50) of 26.4-28.1 days. Hence, introgression of the submergence-tolerant allele Sub1A-1 in rice cv. IR64 did not affect seed dormancy or survival after harvest substantially, but duration to flowering was nine days longer and seed yield also greater in cv. IR64-Sub1.

Flooding damages rice crops and its incidence is increasing. Foliar spray applications of molybdenum (100, 600 or 3000 mg Mo L-1), abscisic acid (ABA, 50 μM), or deionised water (control) were made to pot-grown plants of the Japonica rice cv. Gleva at flag leaf appearance to determine their effects on seed yield and pre-harvest sprouting after flooding. Plants were submerged , to simulate flooding, for four days from 20 or 30 days after anthesis (DAA). Seed yield per plant, seed weight, and pre-harvest sprouting were determined after harvest at 37 DAA. Seed yield and weight were substantially reduced and pre-harvest sprouting promoted by submergence, with greater sprouting after the later treatment. Prior treatment with molybdenum or ABA reduced pre-harvest sprouting (P < 0.05), and possibly reduced damage to seed yield (0.10 > P > 0.05), compared with deionised water. The molybdenum concentration in both sprouted and non-sprouted seeds harvested at 37 DAA responded positively to molybdenum application rate. Molybdenum application rate had no consistent effect on seed ABA concentration. Foliar application of 100 mg Mo L-1 at 200 L ha-1 provided the most promising mitigation of flood damage, but benefits were minor in the context of seed damage from submergence.

The resilience of seed quality in rice (Oryza sativa L.) to flooding was investigated. Pot-grown plants of the japonica cv. Gleva, the indica cv. IR64, and the introgressed line IR64-Sub1 were submerged in water, to simulate flooding, for 3-5 days at different stages of seed development and maturation. Mean seed weight, pre-harvest sprouting, ability to germinate, and subsequent longevity in air-dry storage were assessed. Whereas seed quality in both IR64 and IR64-Sub1 was resilient to submergence, in Gleva the longer the duration of submergence and the later in development when plants were submerged the greater the pre-harvest sprouting. Thousand seed dry weight was reduced more by submergence in Gleva than IR64 or IR64-Sub1. At harvest maturity, few pre-harvest sprouted seeds were able to germinate upon rehydration after desiccation to 11-12% moisture content. Seed longevity of the non-sprouted seed fraction in air-dry hermetic storage (40 °C, 15% moisture content) was not affected greatly by submergence, but longevity of the japonica rice was less than that of the indica rices due to the former’s steeper seed survival curves. Longevity of the two indica rices was predicted well by the seed viability equation and previously-published estimates of viability constants for rice. The greater dormancy of IR64 and IR64-Sub1, compared to Gleva, enhanced resilience to pre-harvest sprouting and reduced thousand seed dry weight from plant submergence. There was little or no effect of plant submergence on subsequent air-dry storage longevity of non-sprouted seeds in any genotype.

Background and Aims Short periods of extreme temperature may affect wheat (Triticum aestivum L.) seed weight, but also quality. Temporal sensitivity to extreme temperature during seed development and maturation was investigated. \ud Methods Plants of cv. Tybalt grown at ambient temperature were moved to growth cabinets at 29/20°C or 34/20°C (2010), or 15/10°C or 34/20°C (2011), for successive 7-d periods from 7 DAA (days after anthesis) onwards, and also 7-65 DAA in 2011. Seed samples were harvested serially and moisture content, weight, ability to germinate, subsequent longevity in air-dry storage, and bread-making quality determined. \ud Key Results High temperature (34/20°C) reduced final seed weight, with greatest temporal sensitivity at 7-14 or 14-21 DAA. Several aspects of bread-making quality were also most sensitive to high temperature then, but whereas protein quality decreased protein and sulphur concentrations improved. Early exposure to high temperature provided earlier development of ability to germinate and tolerate desiccation, but had little effect on maximum germination capacity. All treatments at 15/10°C resulted in ability to germinate declining between 58 and 65 DAA. Early exposure to high temperature hastened improvement in seed storage longevity, but the subsequent decline in late maturation preceded that in the control. Long (7-65 DAA) exposure to 15/10°C disrupted the development of seed longevity, with no improvement after seed filling ended. Longevity improved during maturation drying in other treatments. Early (7-14 DAA) exposure to high reduced and low temperature increased subsequent longevity at harvest maturity, whereas late (35- or 42-49 DAA) exposure to high increased and low temperature reduced it.\ud Conclusions Temporal sensitivity to extreme temperature was detected. It varied considerably amongst the contrasting seed variables investigated. Subsequent seed longevity at harvest maturity responded negatively to temperature early in development, but positively later in development and throughout maturation.

The effects of simulated additional rain (ear wetting, 25 mm) or of rain shelter imposed at different periods after anthesis on grain quality at maturity and the dynamics of grain filling and desiccation were investigated in UK field-grown crops of wheat (Triticum aestivum L., cvar Tybalt) in 2011 and in 2012 when June–August rainfall was 255.0 and 214.6 mm, respectively, and above the decadal mean (157.4 mm). \ud Grain filling and desiccation were quantified well by broken-stick regressions and Gompertz curves, respectively. Rain shelter for 56 (2011) or 70 d (2012) after anthesis, and to a lesser extent during late maturation only, resulted in more rapid desiccation and hence progress to harvest maturity whereas ear wetting had negligible effects, even when applied four times. Grain-filling duration was also affected as above in 2011, but with no significant effect in 2012. In both years, there were strong positive associations between final grain dry weight and duration of filling. \ud The treatments affected all grain quality traits in 2011: nitrogen (N) and sulphur (S) concentrations, N:S ratio, sodium dodecyl sulphate (SDS) sedimentation volume, Hagberg Falling Number (HFN), and the incidence of blackpoint. Only N concentration and blackpoint were affected significantly by treatments in 2012. Rain shelter throughout grain filling reduced N concentration, whereas rain shelter reduced the incidence of blackpoint and ear wetting increased it. In 2011, rain shelter throughout reduced S concentration, increased N:S ratio and reduced SDS. Treatment effects on HFN were not consistent within or between years. Nevertheless, a comparison between the extreme treatment means in 2012 indicated damage from late rain combined with ear wetting resulted in a reduction of c. 0.7 s in HFN/mm August rainfall, whilst that between samples taken immediately after ear wetting at harvest maturity or 7 d later suggested recovery from damage to HFN upon re-drying in planta. \ud Hence, the incidence of blackpoint was the only grain quality trait affected consistently by the diverse treatments. The remaining aspects of grain quality were comparatively resilient to rain incident upon developing and maturing ears of cvar Tybalt. No consistent temporal patterns of sensitivity to shelter or ear wetting were detected for any aspect of grain quality.

Climate change will alter rainfall patterns. The effect of rainfall during seed development and maturation on wheat (Triticum aestivum L.) seed quality (ability to germinate normally; air-dry longevity in hermetic storage at 40oC with c. 15% moisture content) was investigated in field experiments (2011, 2012) by providing rain shelter or simulating additional rainfall. High ability to germinate was detected from mid seed filling until after harvest maturity. Subsequent longevity was more sensitive to stage of development. It increased progressively reaching maximum values during maturation drying at 53-56 DAA, 5-11 (2011) or 8-14 (2012) days beyond mass maturity; maximal values were maintained thereafter in 2011; longevity declined with further delay to harvest in 2012. Post-anthesis protection from rain had no major effect: in later harvests longevity was slightly greater than the control in each year, but in 2011 wetting treatments were also superior to the control. Wetting ears at all stages of development reduced longevity immediately, but considerable recovery in subsequent longevity occurred when seeds re-dried in planta for several days. The greatest damage to longevity from ear wetting occurred with treatments at about 56 DAA, with poorest recovery at 70 DAA (i.e. around harvest maturity) in absolute terms but at 56-70 DAA relative to gross damage. Hence, seed quality in highly-dormant wheat varieties was resilient to rain. Net damage was greatest from rain late in maturation. The phase of seed quality improvement in planta was dynamic with deterioration also occurring then, but with net improvement overall.

Poor wheat seed quality in temperate regions is often ascribed to wet production environments. We investigated the possible effect of simulated rain during seed development and maturation on seed longevity in wheat (Triticum aestivum L.) cv. Tybalt grown in the field (2008, 2009) or a polythene tunnel house (2010). To mimic rain, the seed crops were wetted from above with the equivalent of 30mm (2008, 2009) or 25mm rainfall (2010) at different stages of seed development and maturation (17 to 58 DAA, days after 50% anthesis), samples harvested serially, and subsequent air-dry seed longevity estimated. No pre-harvest sprouting occurred. Seed longevity (p50, 50% survival period in experimental hermetic storage at 40°C with c. 15% moisture content) in field-grown controls increased during seed development and maturation attaining maxima at 37 (2008) or 44 DAA (2009); it declined thereafter. Immediate effects of simulated rain at 17-58 DAA in field studies (2008, 2009) on subsequent seed longevity were negative but small, e.g. a 1-4 d delay in seed quality improvement for treatments early in development but with no damage detected at final harvests. In rainfall-protected conditions (2010), simulated rain close to harvest maturity (55-56 DAA) reduced longevity immediately and substantially, with greater damage from two sequential days of wetting than one; again, later harvests provided evidence of recovery in subsequent longevity. In the absence of pre-harvest sprouting, the potentially deleterious effects of rainfall to wheat seed crops on subsequent seed longevity may be reversible in full or in part.