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Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum.

Yang Z, van Oosterom EJ, Jordan DR, Hammer GL - J. Exp. Bot. (2009)

Bottom Line: The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum.Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related.The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, School of Land, Crop and Food Sciences, Brisbane, Qld 4072, Australia.

ABSTRACT
Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

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Whole-mount cleared floret meristems at a stage immediately before the initiation of stamen primordia in developing florets. (A) KS115; (B) ATx642/RQL36. Scale bars: 100 μm.
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fig3: Whole-mount cleared floret meristems at a stage immediately before the initiation of stamen primordia in developing florets. (A) KS115; (B) ATx642/RQL36. Scale bars: 100 μm.

Mentions: Genotypic differences in size of reproductive organs were apparent early in floret development. Immediately before initiation of stamen primordia, sessile spikelets of KS115, ATx642/KS115, and ATx642/RQL36 differed significantly in the diameter of floret apical meristems (Table 2; Fig. 3), with the meristem diameter of ATx642/KS115 (146.7 μm) close to the mean of the other two genotypes (146.9 μm). Assuming the meristem is a hemisphere, these diameters translated into a volume of 10.8, 8.3, and 6.3×105 μm3 for KS115, ATx642/KS115, and ATx642/RQL36, respectively. Ovary volume at anthesis differed similarly among genotypes. KS115 produced the largest ovaries in both experiments (Table 2; Fig. 4), whereas the ovary volume of ATx642/KS115 (1.20 mm3 and 1.12 mm3 in Experiments I and II, respectively) was close to the mean of KS115 and the normal seeded genotypes (1.30 mm3 and 1.13 mm3 in Experiments I and II, respectively). The lower final kernel weight in Experiment II compared with Experiment I was associated with a reduction in ovary volume at anthesis. Across experiments and genotypes, ovary volume at anthesis was positively associated with the maximum kernel water content attained during early kernel filling (r2=0.99, P <0.001), the maximum kernel volume attained during mid-kernel-filling (r2=0.97, P <0.001), the filling rate during the linear filling period (r2=0.94, P <0.001) (Fig. 5) and, ultimately, the kernel dry weight at maturity (r2=0.93, P <0.001).


Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum.

Yang Z, van Oosterom EJ, Jordan DR, Hammer GL - J. Exp. Bot. (2009)

Whole-mount cleared floret meristems at a stage immediately before the initiation of stamen primordia in developing florets. (A) KS115; (B) ATx642/RQL36. Scale bars: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2657540&req=5

fig3: Whole-mount cleared floret meristems at a stage immediately before the initiation of stamen primordia in developing florets. (A) KS115; (B) ATx642/RQL36. Scale bars: 100 μm.
Mentions: Genotypic differences in size of reproductive organs were apparent early in floret development. Immediately before initiation of stamen primordia, sessile spikelets of KS115, ATx642/KS115, and ATx642/RQL36 differed significantly in the diameter of floret apical meristems (Table 2; Fig. 3), with the meristem diameter of ATx642/KS115 (146.7 μm) close to the mean of the other two genotypes (146.9 μm). Assuming the meristem is a hemisphere, these diameters translated into a volume of 10.8, 8.3, and 6.3×105 μm3 for KS115, ATx642/KS115, and ATx642/RQL36, respectively. Ovary volume at anthesis differed similarly among genotypes. KS115 produced the largest ovaries in both experiments (Table 2; Fig. 4), whereas the ovary volume of ATx642/KS115 (1.20 mm3 and 1.12 mm3 in Experiments I and II, respectively) was close to the mean of KS115 and the normal seeded genotypes (1.30 mm3 and 1.13 mm3 in Experiments I and II, respectively). The lower final kernel weight in Experiment II compared with Experiment I was associated with a reduction in ovary volume at anthesis. Across experiments and genotypes, ovary volume at anthesis was positively associated with the maximum kernel water content attained during early kernel filling (r2=0.99, P <0.001), the maximum kernel volume attained during mid-kernel-filling (r2=0.97, P <0.001), the filling rate during the linear filling period (r2=0.94, P <0.001) (Fig. 5) and, ultimately, the kernel dry weight at maturity (r2=0.93, P <0.001).

Bottom Line: The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum.Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related.The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, School of Land, Crop and Food Sciences, Brisbane, Qld 4072, Australia.

ABSTRACT
Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

Show MeSH