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P. Maxima (p + maximum)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

The consequences of differential family survival rates and equalizing maternal contributions on the effective population size (Ne) of cultured silver-lipped pearl oysters, Pinctada maxima

AQUACULTURE RESEARCH, Issue 8 2010
Curtis E Lind
Abstract The effective population size (Ne) is a critical gauge of how efficiently an aquaculture operation is capturing or maintaining genetic diversity and can govern the long-term success of genetic selection programmes. In communally reared pearl oysters (Pinctada maxima), high variance in family sizes is a significant contributor towards low Ne and its severity may be compounded by differential survival rates of individual families. To determine the effect of variable survival on Ne in cultured P. maxima, families from two commercial populations were analysed using DNA parentage analyses to monitor survival and changes in relative contributions. Significant shifts in relative contributions were observed between 72 days and 18 months of age in both commercial cohorts (P<0.001). Survival rates were found to be highly variable among families (ranging from 2.5% to 49.5%) when reared in a common environment. Additionally, we investigated whether equalizing maternal family sizes before communal rearing will reduce family size variance, and increase Ne, compared with stocking at naturally produced proportions. Family equalization (E) significantly improved Ne (P=0.013) compared with rearing at natural (N) proportions (E: Ne=7.18±0.34; N: Ne=5.60±0.15); however, this practice may unintentionally magnify negative influences of poor performing families if survival is correlated with other commercially important traits. It is concluded that highly variable family survival will affect Ne in communally reared P. maxima, and the practice of equalizing family sizes in order to maximize Ne may only become consistently beneficial once further progress is made towards understanding, and then reducing variation in family survival rates. [source]

High levels of intra-specific variation in the NG repeat region of the Pinctada maxima N66 organic matrix protein

AQUACULTURE RESEARCH, Issue 9 2009
Carolyn Smith-Keune
Abstract There has been wide speculation about the functional importance, and potential contribution to the varying nacre characteristics of pearl oysters, of variation in the length of an asparagine,glycine-rich repeat domain (the NG region) within the key organic matrix proteins nacrein and N66. This speculation has centred on large inter-species differences in the length of the NG protein domain. We report for the first time the presence of significant intra-specific (allelic) polymorphism in both the length and the amino acid sequence of the NG repeat domain of N66 within both wild and hatchery populations of Pinctada maxima. We also detected the presence of a second putative N66-like locus within the P. maxima genome. Confirmation of gene expression of the various alleles at the two loci identified in P. maxima is now required, together with experimental testing of functional differences in the carbonic anhydrase activity of the alleles identified. [source]

Evaluation of tissue culture response from mature seeds of Panicum spp.

GRASSLAND SCIENCE, Issue 3 2008
Mi-Suk Seo
Abstract The genus Panicum contains important warm-season forage grasses and species with potential as biomass crops. We selected Panicum genotypes with high response to tissue culture for genetic improvement. The highest frequency of callus induction from mature seed of Panicum maximum cultivar Natsukaze was obtained on MS medium containing 4.0 mg L,1 2,4-dichlorophenoxyacetic acid and solidified with 0.3% Gelrite. We compared germination frequencies and callus induction capacities among 24 genotypes of 11 Panicum species on this medium. Callus induction frequencies varied among genotypes. Those with high germination frequencies generally had high callus induction frequencies. On the other hand, especially in P. maximum, the callus induction ratio (callus induction frequency/germination frequency) depended on the reproductive mode and ploidy. The callus induction ratio of three sexual accessions of P. maximum were very low compared to apomictic accessions, and besides, a tetraploid sexual accession Noh PL1 had very low germination and callus induction frequencies. Callus induction and regeneration capacities were independent of each other. For shoot regeneration, we transferred callus derived from the 24 genotypes onto MS medium supplemented with 1.0 mg L,1 kinetin and 0.4% Gelrite. Six of the genotypes regenerated plantlets. Among them, Panicum meyerianum produced the highest shoot regeneration frequency of 61.6% and the maximum number of shoots callus,1 in the shortest time. The callus of P. meyerianum also showed vigorous proliferation. We thus selected high-response genotypes of P. meyerianum. [source]

Isolation and characterization of microsatellite markers from guineagrass (Panicum maximum) for genetic diversity estimate and cross-species amplification

PLANT BREEDING, Issue 1 2010
A. Chandra
With 1 figure and 1 table Abstract Guineagrass (Panicum maximum Jacq.) is one of the major forage grasses in tropical and semitropical regions, largely apomictic and predominantly exist as tetraploid. Non-availability of polymorphic molecular markers has been a major limitation in its characterization and improvement. We report isolation and characterization of microsatellites in P. maximum and cross-species results with other five Panicum species. Based on microsatellite-motifs, 15 functional and polymorphic simple sequence repeat (SSR) primer-pairs were designed, validated and employed in estimating genetic relationship among 34 guineagrass accessions. Thirteen primer-pairs amplified single locus and remaining two generated more than two loci with an average of 3.57 bands per locus amounts to 63 bands with 34 guineagrass accessions. Average expected heterozygosity (HE) of 0.35 (maximum 0.97) and observed heterozygosity (HO) of 0.37 (maximum 0.91) established the efficiency of developed markers for discriminating guineagrass accessions. Dice's similarity coefficients-based unweighted pair group with arithmetic average method-clustering supported with high bootstrap values (,40) indicated its significance and distinguished all accessions except IG97-93 and IG97-6. Utility of these new SSR loci in genetic diversity study of P. maximum and other cross,amplified species is discussed. [source]