PLOIDY EFFECTS ON REPRODUCTIVE BIOLOGY OF ACACIA MANGIUM
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Transcript of PLOIDY EFFECTS ON REPRODUCTIVE BIOLOGY OF ACACIA MANGIUM
CP 3x seedlings
We thank FSIV and the Australian Centre for International Agricultural Research (ACIAR) collaboration projects (FST 2003/002 and FST 2008/007) for plant material, and Hong, Xuan and Dzung for field assistance. Funding and in-kind support for N.Q.Chi was provided by a John Allwright Fellowship from ACIAR.
PLOIDY EFFECTS ON REPRODUCTIVE BIOLOGY OF ACACIA MANGIUM
1. Introduction
2. Methods
3. Key results
An Acacia hybridizing seed orchard was established in southern Vietnam. Ramets of clones of colchicine-induced autotetraploid A. mangium (AM-4x) [1], diploid A. mangium (AM-2x) and diploid A. auriculiformis (AA-2x) were planted in alternate rows to promote inter-ploidy pollination.
Despite heavy and largely synchronous flowering and seed production of all three species/ploidy types, the orchard produced very few open-pollinated triploid (3x) seeds. We examined possible barriers to fertilisation and/or successful development of triploids.
References
1School of Plant Science, University of Tasmania, Hobart, TAS. 7001, Australia2CSIRO Ecosystem Sciences, Hobart, TAS. 7001, Australia
3Research Centre for Forest Tree Improvement, Forest Science Institute of Vietnam, Hanoi, Vietnam
Acknowledgements
4. Conclusions
N. Q. Chi1,3, C. Harwood2, R. Griffin1, J. Harbard1, H. H. Thinh3, and A. Koutoulis1
• Hand pollination was conducted following [2]• Floral morphology and pollen tube growth was studied using light and fluorescence
microscopy • Pollen tube growth was studied using a clear squash technique [3]• One ramet of each of 3 different clones of AM-2x, AM-4x, and AA-2x was selected
for CP treatment• Treatment mean comparisons were performed by Tukey-Kramer’s multiple range
test at α = 0.05
• Stigma cup width was greater than polyad diameter for all species/ploidy combinations
[1] Blakesley D, Allen A, Pellny TK, Roberts AV (2002) Natural and induced polyploidy in Acacia dealbata Link. and Acacia mangium Willd. Annals of Botany 90, 391-398.
[2] Sedgley M, Harbard J, Smith RM, Wickneswari R (1992) Development of hybridisation techniques for Acacia mangium and Acacia auriculiformis. ACIAR Proceedings Series, 63-69
[3] Martin FW (1959) Staining and observing pollen tubes in the style by means of fluorescence. Stain Technology 34, 125-128.
[4] Nghiem CQ, Harwood CE, Harbard JL, Griffin AR, Ha TH, Koutoulis A. (2011). Floral phenology and morphology of colchicine-induced tetraploid Acacia mangium compared with diploid A. mangium and A. auriculiformis: implications for interploidy pollination. Australian Journal of Botany 59, 582-592.
3.1 Floral morphology [4]• AM-4x flowers were intermediate between those of AM-2x and AA-2x
Species/ploidy
Spike Flower
Spike length (cm)
Flowers per spike
Flower length (mm)
Style length (mm)
No. of ovules per
ovary
A. mangium 2x 10.8 a 230.4 a 5.1 a 4.2 a 14.2 ab
A. mangium 4x 8.0 b 161.4 b 4.8 a 3.9 b 13.0 b
A. auriculiformis 2x 5.8 c 99.4 c 4.3 b 3.4 c 15.5 a
Mean diameter of stigma cups and polyads. Error bars show critical difference (P<0.05) between treatments.
3.2. Pollen tube growth and ovule penetration (72 h after pollination)
pt
Treatments Normal seeds
Abnormal seedsType I Type II Type III
Intra-ploidy crosses AM-2x X AM-2x 152 0 5 7 AA-2x X AA-2x 62 1 19 21 AA-2x X AM-2x 162 5 17 42
Inter-ploidy crossesAM-2x X AM-4x 8 67 19 18AA-2x X AM-4x 24 180 286 5
Species/ploidy (taxa)
Types of cross-combination (types)
Ovaries with at least one ovule penetrated (%)
Mean no. of ovules
penetrated per ovary
Mean no. of pollen tubes
per style
AM-2x AM-2x X AM-2x 29.7 abc 1.36 bc 6.7 abcAM-2x X AA-2x 17.6 bc 1.64 bc 6.0 abcAM-2x X AM-4x 14.3 bc 1.33 bc 4.2 c
AM-4x AM-4x X AM-4x 20.6 bc 1.00 c 4.6 bcAM-4x X AM-2x 35.9 abc 1.29 bc 5.3 bcAM-4x X AA-2x 35.6 abc 1.33 bc 6.0 abc
AA-2x AA-2x X AA-2x 46.0 ab 1.85 bc 7.8 abAA-2x X AM-2x 59.9 a 2.77 a 8.9 aAA-2x X AM-4x 34.7 abc 1.92 b 7.0 abc
Significance of differences among taxa-by-types ** *** **
Note: ** = 0.001≤ P ≤ 0.01 and *** = P ≤ 0.001. Different letters denote significant (P < 0.05) differences among nine cross-types
Pollen tubes grew well in the style Ovules penetrated in the ovary Ovule development 5 weeks post-pollination
• Differences in floral morphology were not sufficient to prevent interploidy pollination
• No pre-zygotic reproductive barriers were detected for intra- and inter ploidy mating of A. mangium and A. auriculiformis
• However, yields of pods and normal seeds from inter-ploidy crosses were extremely poor, compared to those from intra-ploidy crosses.
• Post-fertilization genic imbalance may limit the production of viable triploid progeny.
pt
pollen tube
AA-2x AM-4x AM-2x
3.3. Normal and abnormal seeds harvested from different cross-combinations
Note: Different letters denote significant (P < 0.05) differences within species/ploidy combinations
AA-2x
pollen tube
AM-2x x AM-4x
0
10
20
30
40
50
60
70
AM-2x AM-4x AA-2x
Dia
met
er (
µm)
Stigma Polyad
AA-2xAM-2x AM-4x
60 m
Mature seed category
ovule penetrated
30 µm
Normal seed5
mmAbnormal seedType I
Type II
Type III
Normal seed
5 mm
Abnormal seed
Type I Type II Type III
AM-2x AM-4x
Style
polyad
stigma
AM-2x x AM-4x
50 m
pollen tubes
polyad
45 m