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An analysis of dormancy, ABA responsiveness, after-ripening and pre-harvest sprouting in hexaploid wheat (Triticum aestivum L.) caryopses.

Gerjets T, Scholefield D, Foulkes MJ, Lenton JR, Holdsworth MJ - J. Exp. Bot. (2009)

Bottom Line: Isolated embryos showed relatively little dormancy during grain-filling and most varieties exhibited a window of decreased ABA-responsiveness around the period of maximum dry matter accumulation (physiological maturity).However, the velocity of AR of a variety was closely associated with the degree of susceptibility to PHS during AR suggesting that these characters are developmentally linked.Investigation of genetic components of AR may therefore aid breeding approaches to reduce susceptibility to PHS.

View Article: PubMed Central - PubMed

Affiliation: Division of Plant and Crop Sciences, School of BioSciences, University of Nottingham, Nottingham, UK.

ABSTRACT
Embryo and caryopsis dormancy, abscisic acid (ABA) responsiveness, after-ripening (AR), and the disorder pre-harvest sprouting (PHS) were investigated in six genetically related wheat varieties previously characterized as resistant, intermediate, or susceptible to PHS. Timing of caryopsis AR differed between varieties; AR occurred before harvest ripeness in the most PHS-susceptible, whereas AR was slowest in the most PHS-resistant. Whole caryopses of all varieties showed little ABA-responsiveness during AR; PHS-susceptible varieties were responsive at the beginning of the AR period whereas PHS-resistant showed some responsiveness throughout. Isolated embryos showed relatively little dormancy during grain-filling and most varieties exhibited a window of decreased ABA-responsiveness around the period of maximum dry matter accumulation (physiological maturity). Susceptibility to PHS was assessed by overhead misting of either isolated ears or whole plants during AR; varieties were clearly distinguished using both methods. These analyses allowed an investigation of the interactions between the different components of seed development, compartments, and environment for the six varieties. There was no direct relationship between speed of caryopsis AR and embryo dormancy or ABA-responsiveness during seed maturation. However, the velocity of AR of a variety was closely associated with the degree of susceptibility to PHS during AR suggesting that these characters are developmentally linked. Investigation of genetic components of AR may therefore aid breeding approaches to reduce susceptibility to PHS.

Show MeSH
Influence of misting whole plants of different wheat varieties on seed germination in-ear. Whole plants were subjected to misting treatment (see Supplementary Fig. 2B at JXB online) as described in Materials and methods. Germination of seeds in-ear (% sprouting) was assessed at increasing dpa for each variety as vertical lines. Time of physiological maturity (PM) in relation to days post-anthesis are indicated for each variety. Data represent means ±SE of the mean.
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fig4: Influence of misting whole plants of different wheat varieties on seed germination in-ear. Whole plants were subjected to misting treatment (see Supplementary Fig. 2B at JXB online) as described in Materials and methods. Germination of seeds in-ear (% sprouting) was assessed at increasing dpa for each variety as vertical lines. Time of physiological maturity (PM) in relation to days post-anthesis are indicated for each variety. Data represent means ±SE of the mean.

Mentions: Previous work has indicated a negative relationship between susceptibility to the developmental disorder PHS and level of seed dormancy at harvest, such that wheat varieties exhibiting high dormancy are genetically less susceptible to PHS under inductive conditions (Mares, 1993; Biddulph et al., 2008; Chen et al., 2008). As dormancy level at harvest only represents one point of after-ripening, the relationship between GI and susceptibility to sprouting was analysed throughout the after-ripening time-course. Two methods of inducing PHS in controlled environment rooms were used, either with whole plants or isolated ears, using a misting system that delivered defined quantity and droplet size of water at specified times throughout the assay period (see Supplementary Fig. 2B, C at JXB online). The white wheat variety JBW was used to define wet conditions leading to sprouting within ears of intact plants (see Supplementary Fig. 4 at JXB online), although it was found that sprouting in wet conditions was as high in susceptible varieties carrying the R gene as it was for JBW. Initially, the effect of misting whole plants from 55 to 115dpa on the characteristics of grain development (Table 2) was analysed. The main effect of misting plants was to delay the rate of grain drying such that moisture content was maintained at 37–41% at 100 dpa (Table 2) at a time when grains were harvest ripe under standard dry conditions (Table 1). Misting plants also delayed physiological maturity by about 10 d although there was no effect on final grain size, compared with the dry conditions (compare Tables 1 and 2). In all varieties sprouting increased from a low level at around 60 dpa (Fig. 4). In some varieties sprouting was observable soon after the initiation of misting (Haven and Claire), whereas for others sprouting was not induced until after 20 d misting. Seeds of two varieties, Solstice and Option, maintained a low level of sprouting throughout the misting period. In breeding programmes, tests for susceptibility to PHS are sometimes carried out by misting isolated ears and assaying sprouting, and QTL analyses have also been carried out using this methodology (Chen et al., 2008). An analysis was carried out using this approach to determine more precisely the influence of misting on susceptibility to PHS. Whole ears were removed from plants at increasing days post-anthesis, and incubated vertically with misting for 7 d under the same regime as that used for whole plants (see Supplementary Fig. 2C at JXB online). In this way it was possible to assess sprouting susceptibility at specific stages of grain development using a methodology (assay of germination performance after 7 d) similar to that used to assess isolated caryopses (Fig. 1). Germination of caryopses was analysed in different parts of the ear (top, middle, and bottom) in response to misting in order to determine if the within-ear position influenced the sprouting of caryopses, as ear architecture has previously been shown to contribute to sprouting susceptibility (King and Richards, 1984; Paterson et al., 1989). This analysis was carried out using representative varieties showing either slow (Option) intermediate (Malacca) or rapid (Claire and Charger) after-ripening. At early stages of analysis (from 50–80 dpa) ears of all varieties showed little or no propensity to sprout (Fig. 5). Subsequently, as observed with whole plant misting, both Claire and Charger demonstrated an increase in responsiveness to misting, with Claire showing the greatest induction of sprouting by HR. Throughout the time period analysed Option did not show any appreciable sprouting. Analysis of grain responsiveness as a function of position in-ear for both Charger and Claire revealed that caryopses located in the middle of the ear were more susceptible to misting than those located either at the top or bottom. A direct comparison between GI at different stages of after-ripening and susceptibility to sprouting either on plants or in isolated ears was carried out (Fig. 6). This analysis clearly distinguished the six varieties into two groups (Malacca, Solstice, and Option in one, and Haven Charger, and Claire in the other), with Option and Claire showing the most extreme separation. The correlation coefficients between GI and sprouting on whole plants amongst the six varieties at the respective after-ripening sampling times indicated differing associations between the two characters (60 dpa r=0.38, 70 dpa r=0.94, 80 dpa r=0.51, 90 dpa r=0.76, 100 dpa r=0.93, df=4).


An analysis of dormancy, ABA responsiveness, after-ripening and pre-harvest sprouting in hexaploid wheat (Triticum aestivum L.) caryopses.

Gerjets T, Scholefield D, Foulkes MJ, Lenton JR, Holdsworth MJ - J. Exp. Bot. (2009)

Influence of misting whole plants of different wheat varieties on seed germination in-ear. Whole plants were subjected to misting treatment (see Supplementary Fig. 2B at JXB online) as described in Materials and methods. Germination of seeds in-ear (% sprouting) was assessed at increasing dpa for each variety as vertical lines. Time of physiological maturity (PM) in relation to days post-anthesis are indicated for each variety. Data represent means ±SE of the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803222&req=5

fig4: Influence of misting whole plants of different wheat varieties on seed germination in-ear. Whole plants were subjected to misting treatment (see Supplementary Fig. 2B at JXB online) as described in Materials and methods. Germination of seeds in-ear (% sprouting) was assessed at increasing dpa for each variety as vertical lines. Time of physiological maturity (PM) in relation to days post-anthesis are indicated for each variety. Data represent means ±SE of the mean.
Mentions: Previous work has indicated a negative relationship between susceptibility to the developmental disorder PHS and level of seed dormancy at harvest, such that wheat varieties exhibiting high dormancy are genetically less susceptible to PHS under inductive conditions (Mares, 1993; Biddulph et al., 2008; Chen et al., 2008). As dormancy level at harvest only represents one point of after-ripening, the relationship between GI and susceptibility to sprouting was analysed throughout the after-ripening time-course. Two methods of inducing PHS in controlled environment rooms were used, either with whole plants or isolated ears, using a misting system that delivered defined quantity and droplet size of water at specified times throughout the assay period (see Supplementary Fig. 2B, C at JXB online). The white wheat variety JBW was used to define wet conditions leading to sprouting within ears of intact plants (see Supplementary Fig. 4 at JXB online), although it was found that sprouting in wet conditions was as high in susceptible varieties carrying the R gene as it was for JBW. Initially, the effect of misting whole plants from 55 to 115dpa on the characteristics of grain development (Table 2) was analysed. The main effect of misting plants was to delay the rate of grain drying such that moisture content was maintained at 37–41% at 100 dpa (Table 2) at a time when grains were harvest ripe under standard dry conditions (Table 1). Misting plants also delayed physiological maturity by about 10 d although there was no effect on final grain size, compared with the dry conditions (compare Tables 1 and 2). In all varieties sprouting increased from a low level at around 60 dpa (Fig. 4). In some varieties sprouting was observable soon after the initiation of misting (Haven and Claire), whereas for others sprouting was not induced until after 20 d misting. Seeds of two varieties, Solstice and Option, maintained a low level of sprouting throughout the misting period. In breeding programmes, tests for susceptibility to PHS are sometimes carried out by misting isolated ears and assaying sprouting, and QTL analyses have also been carried out using this methodology (Chen et al., 2008). An analysis was carried out using this approach to determine more precisely the influence of misting on susceptibility to PHS. Whole ears were removed from plants at increasing days post-anthesis, and incubated vertically with misting for 7 d under the same regime as that used for whole plants (see Supplementary Fig. 2C at JXB online). In this way it was possible to assess sprouting susceptibility at specific stages of grain development using a methodology (assay of germination performance after 7 d) similar to that used to assess isolated caryopses (Fig. 1). Germination of caryopses was analysed in different parts of the ear (top, middle, and bottom) in response to misting in order to determine if the within-ear position influenced the sprouting of caryopses, as ear architecture has previously been shown to contribute to sprouting susceptibility (King and Richards, 1984; Paterson et al., 1989). This analysis was carried out using representative varieties showing either slow (Option) intermediate (Malacca) or rapid (Claire and Charger) after-ripening. At early stages of analysis (from 50–80 dpa) ears of all varieties showed little or no propensity to sprout (Fig. 5). Subsequently, as observed with whole plant misting, both Claire and Charger demonstrated an increase in responsiveness to misting, with Claire showing the greatest induction of sprouting by HR. Throughout the time period analysed Option did not show any appreciable sprouting. Analysis of grain responsiveness as a function of position in-ear for both Charger and Claire revealed that caryopses located in the middle of the ear were more susceptible to misting than those located either at the top or bottom. A direct comparison between GI at different stages of after-ripening and susceptibility to sprouting either on plants or in isolated ears was carried out (Fig. 6). This analysis clearly distinguished the six varieties into two groups (Malacca, Solstice, and Option in one, and Haven Charger, and Claire in the other), with Option and Claire showing the most extreme separation. The correlation coefficients between GI and sprouting on whole plants amongst the six varieties at the respective after-ripening sampling times indicated differing associations between the two characters (60 dpa r=0.38, 70 dpa r=0.94, 80 dpa r=0.51, 90 dpa r=0.76, 100 dpa r=0.93, df=4).

Bottom Line: Isolated embryos showed relatively little dormancy during grain-filling and most varieties exhibited a window of decreased ABA-responsiveness around the period of maximum dry matter accumulation (physiological maturity).However, the velocity of AR of a variety was closely associated with the degree of susceptibility to PHS during AR suggesting that these characters are developmentally linked.Investigation of genetic components of AR may therefore aid breeding approaches to reduce susceptibility to PHS.

View Article: PubMed Central - PubMed

Affiliation: Division of Plant and Crop Sciences, School of BioSciences, University of Nottingham, Nottingham, UK.

ABSTRACT
Embryo and caryopsis dormancy, abscisic acid (ABA) responsiveness, after-ripening (AR), and the disorder pre-harvest sprouting (PHS) were investigated in six genetically related wheat varieties previously characterized as resistant, intermediate, or susceptible to PHS. Timing of caryopsis AR differed between varieties; AR occurred before harvest ripeness in the most PHS-susceptible, whereas AR was slowest in the most PHS-resistant. Whole caryopses of all varieties showed little ABA-responsiveness during AR; PHS-susceptible varieties were responsive at the beginning of the AR period whereas PHS-resistant showed some responsiveness throughout. Isolated embryos showed relatively little dormancy during grain-filling and most varieties exhibited a window of decreased ABA-responsiveness around the period of maximum dry matter accumulation (physiological maturity). Susceptibility to PHS was assessed by overhead misting of either isolated ears or whole plants during AR; varieties were clearly distinguished using both methods. These analyses allowed an investigation of the interactions between the different components of seed development, compartments, and environment for the six varieties. There was no direct relationship between speed of caryopsis AR and embryo dormancy or ABA-responsiveness during seed maturation. However, the velocity of AR of a variety was closely associated with the degree of susceptibility to PHS during AR suggesting that these characters are developmentally linked. Investigation of genetic components of AR may therefore aid breeding approaches to reduce susceptibility to PHS.

Show MeSH