Chromosome number in germplasm accessions of Paspalum (Plicatula group) from different regions in Brazil

We determined the chromosome number of 52 accessions of Paspalum from the germplasm collection of the Centro de Pesquisa de Pecuária do Sudeste (CPPSE/EMBRAPA) originating from different regions in Brazil. All accessions belonged to the Plicatula group, 13 of them being P. plicatulum, three P. guenoarum, two P. yaguaronense, two P. compressifolium, one P. atratum, and 31 still unidentified Paspalum sp. Except for a P. yaguaronense accession that presented 2n=60, all the remaining ones presented 2n=40 chromosomes. This is the first report of the chromosome number of P. atratum. Considering that the basic number for most species in the genus Paspalum is ×=10, the accessions analyzed are tetraploids (2n=4×=40) and hexaploids (2n=6×=60). This revised version was published online in July 2006 with corrections to the Cover Date.     

Delay of the egg activation process in the Black Tiger Shrimp Penaeus monodon by manipulation of magnesium levels in spawning water

The aim of this study was to determine whether magnesium (Mg²⁺) in seawater is required for egg activation of the black tiger shrimp Penaeus monodon and whether manipulation of Mg²⁺ levels can be used to delay the process and thereby synchronize egg activation. Female P. monodon broodstock were allowed to spawn in artificial seawater containing Mg²⁺ at varying levels with respect to the normal (100%) level: 100%, 50%, 20% and 0%. Egg activation occurred normally at 100% Mg²⁺, incompletely at 50% and 20% Mg²⁺ levels and did not occur at all with 0% Mg²⁺. The fertilization rate with 100% Mg²⁺ was observed to be 83%, but fertilization failed to take place in all the other groups. The fertilization rate was restored from 0% to 76% following the 20% Mg²⁺ level treatment when Mg²⁺ levels returned to normal (100%) as soon as spawning was completed. This study suggests that the level of Mg²⁺ in seawater plays a vital role in P. monodon egg activation, and that commencement of this process could be delayed by manipulation of the Mg²⁺ level during and immediately after spawning.     

秋水仙素对‘琼露’猕猴桃多倍体诱导的影响

为了获得大果、质优的多倍体品种,以猕猴桃‘琼露’无菌苗叶柄为材料,分别利用抽滤灭菌的0.05%、0.10%的秋水仙素溶液浸泡3、4、5 h,培养再生植株,利用流式细胞仪进行倍性鉴定。结果表明:0.05%的秋水仙素处理3 h,存活率和再生频率分别达到85.19%和82.61%,低于对照;当0.10%的秋水仙素处理5 h时,其存活率和再生频率分别降低至36.00%和44.44%。其中,以0.05%的秋水仙素处理4 h诱导效果最佳,变异率为28%。倍性鉴定结果表明,共获得四倍体植株7株,嵌合体5株。多倍体与二倍体相比,叶片变大,叶面变厚,节间变短,与二倍体差异显著。     

Chimerical structure and carotenoid inheritance in Chrysanthemum morifolium (Ramat.)

Summary Progeny analysis showed that yellow-flowered chrysanthemum sports with carotenoid only in L1 are indistinguishable from their white progenitors in breeding behaviour; those with carotenoid in L2 breed quite differently. Chimerical structure has, therefore, to be considered when analysing flower colour inheritance data. Segregations were consistent with the action of the single dominant gene I. Such simply inherited characters may be useful in studies to distinguish between the several alternative patterns of inheritance which can be suggested in the species.     

A generalized framework for AMOVA with multiple hierarchies and ploidies

The analysis of molecular variance (AMOVA) is a widely used statistical method in population genetics and molecular ecology. The classic framework of AMOVA only supports haploid and diploid data, in which the number of hierarchies ranges from two to four. In practice, natural populations can be classified into more hierarchies, and polyploidy is frequently observed in extant species. The ploidy level may even vary within the same species, and/or within the same individual. We generalized the framework of AMOVA such that it can be used for any number of hierarchies and any level of ploidy. Based on this framework, we present four methods to account for data that are multilocus genotypic and allelic phenotypic (with unknown allele dosage). We use simulated datasets and an empirical dataset to evaluate the performance of our framework. We make freely available our methods in a new software package, polygene , which is freely available at https://github.com/huangkang1987/polygene .     

秋水仙素诱导甘菊多倍体研究

以甘菊种子为试验材料,研究了不同秋水仙素浓度和处理时间对甘菊多倍体诱导的影响。结果表明:500mg/L的秋水仙素水溶液浸渍种子12h,变异率为23%,达到了极显著差异。根尖染色体压片检查表明,四倍体染色体数为2n=4x=36,并且获得了同源四倍体甘菊1株(2n=4x=36)。四倍体植株表现出叶片下表皮气孔保卫细胞变大,叶绿体数变多,叶片变小,花径变大,舌状花数目减少,管状花数目增多。     

一系法杂交水稻研究的技术策略探讨

通过一系法利用和固定水稻的远缘杂种优势是一项具有极大诱惑力但难度颇大的科研难题。我国水稻无融合生殖研究尚处在探索性阶段,还没有筛选到具有实用价值的无融合生殖种质。由于多倍体水稻的有性生殖能力明显变弱,在多倍性水平筛选和创造水稻无融合生殖种质有可能成为一系法杂交稻研究的突破口。     

水产动物染色体操作育种研究进展

随着科学技术的高速发展,我国水产动物育种技术有了很大的提高。染色体操作育种技术作为现代遗传育种的重要组成部分,在水产动物育种中得到了广泛应用。本文就近年来水产动物染色体操作育种技术,包括人工诱导多倍体与检测多倍体的方法、雌核发育和雄核发育的研究现状和发展前景进行综述。     

Transmission of a Bacillus thuringiensis cry3Aa transgene from diploid to tetraploid potato using 4x-2x hybridization: effect of ploidy increase on transgene expression and implications for TPS hybrid production

The study examined the effect of ploidy elevation through unreduced gametes on transgene expression in potato. Tetraploid transgenic progenies were obtained from one tetraploid potato cultivar crossed with 2n pollen producing diploid clones harbouring an exogenous transgene (cry3Aa). Both single‐ and multiple‐insert diploid transgenic lines that were regenerated by Agrobacterium tumefaciens leaf disc inoculation were used in crosses. A DAS‐ELISA system and no‐choice feeding bioassay enabled characterization of the parental lines as either ‘high’ or low’ expressers of the Cry3Aa protein. High Cry3Aa expression was observed for both single‐insert transgenic diploids and their 4x‐2x progeny. On the contrary, 68% of 4x‐2x progeny derived from a multiple‐insert, diploid transgenic had significantly reduced Cry3Aa expression compared with the parent, with 32% demonstrating nearly complete silencing of the transgene. Multiple copies of a transgene, like homologous native genes, may be susceptible to transgene silencing following polyploidization. Therefore, incorporation of exogenous transgenes into a true potato seed (TPS) production system is feasible if a single‐insert diploid parent is used. Gene‐centromere mapping of the cry3Aa transgene demonstrated that a non‐transgenic refuge might be naturally created in a TPS hybrid system through genetic recombination.