Genetic Erosion from Modern Varieties into Traditional Upland Rice Cultivars (Oryza sativa L.) in Northern Thailand

The purpose of this study was to assess the extent of genetic erosion of traditional upland germplasm in northern Thailand as a result of gene-flow from distinct strains carrying different genotypes. Even modern variety specific markers have not been developed, there is a comparative population in Laos. Thus, both populations were compared with various characters to evaluate gene-flow from modern variety to landraces. Glutinous and glabrous strains are predominated in Laos. However, such strains were drastically decreased in north–east Thailand. Gene diversity is higher in Thailand, compared to Laos at seven isozyme loci. This was a result of the higher frequencies of Indica strains and heterozygotes in Thailand. Plastid type was also determined by using an INDEL marker. Nearly half of Indica strains carried the Japonica plastid. Heterozygotes also tended to carry Japonica cytoplasm. Such nuclear–cytoplasm substituted strains and heterozygotes were probably generated by natural hybridization. Japonica strains tended to be a maternal donor rather than Indica ones. Or Indica strains would easily release pollens, which grow outside of upland fields.     

Genetic variation in desiccation tolerance of Dendrobaena octaedra cocoons originating from different climatic regions

The aim of this study was to examine genetic variation in desiccation tolerance in cocoons of the parthenogenetically reproducing earthworm Dendrobaena octaedra by comparing populations originating from different geographic regions (Denmark, Norway and Finland), representing large differences in precipitation and temperature. In one experiment, the tolerance of the three populations to increasing desiccation stress in the range from 100 to 91.6% relative humidity (RH) was examined, aiming to represent ecologically relevant RH values. In a second experiment, the effect of cocoon size on desiccation tolerance was investigated at 92.3% RH in the same three populations. There were highly significant differences in desiccation tolerance between populations, indicating a high genetic differentiation of this trait in D. octaedra. Cocoons from Denmark were much more sensitive (71±14% mortality at 91.6% RH) than cocoons from Norway (21±4% mortality) and Finland (4±5% mortality). Cocoons of worms from Finland and Norway were significantly larger than cocoons produced by worms from Denmark suggesting that cocoons from Denmark lost water at a higher rate when subjected to low humidity. Assuming that slow dehydration is necessary for physiologically based protection mechanisms it may be expected that desiccation tolerance is positively correlated with cocoon size. However, within each of the populations cocoon fresh weight did not have any significant impact on desiccation tolerance. When all populations were pooled there was a significant positive effect of cocoon fresh weight on desiccation tolerance, explaining about 20% of the total variation (linear regression). It seems therefore that genetic variation of desiccation tolerance in D. octaedra cocoons is related to variation in both cocoon size and other, physiologically based tolerance mechanisms.     

Producing native seed of Stipa lagascae R. and Sch. inPresaharian Tunisia: high yields, high genetic variation orboth?

Genetic shifts are predicted to be greatest when highly diversematerial originating from an arid environment is bulk multiplied inirrigated and fertilised conditions. This is a key problem if largequantities of quality native seed are needed for restorationpurposes. In Presaharian Tunisia, we investigated two intermingledyield aspects of irrigated seed multiplication of Stipalagascae R. and Sch.: (1) nitrogen fertilisationand (2) selection for vegetative vigour. We set up twocontiguous nitrogen fertilisation trials, one withnon-selected seeds (from a nearby locality), and onewith selected seeds (48 clonal lines seeded in replicatedrows), and compared straw yields. Both selected and unselectedmaterial did not respond to more than 50 kg of nitrogenper ha. Unfertilised yields of both trials were similar,but the straw yield of fertilised selected material was more than100% higher than the straw yield of fertilised unselectedmaterial. In the trial with selected material, we collected straw andleaf yields per row, and scored each row for vigour and for phenologyduring three successive growing seasons. Genotypic differences inseed output and in mortality were large and mainly driven byvariation in potential straw for leaf ratios.The compromise between high yields and high genetic variation couldconsist of the following principles. (1) Create driergrowing conditions so that the actual straw forleaf ratio stays below the genotypic potential. (2) Useinstead fertilisation and selection to enhance seed yields.(3) Avoid bulk multiplication.     

Combined use of gliadins and SSRs to analyse the genetic variability of the Spanish collection of cultivated diploid wheat (Triticum monococcum L. ssp. monococcum)

This work studied the combined use of gliadins and SSRs to analyse inter- and intra-accession variability of the Spanish collection of cultivated einkorn (Triticum monococcum L. ssp. monococcum) maintained at the CRF-INIA. In general, gliadin loci presented higher discrimination power than SSRs, reflecting the high variability of the gliadins. The loci on chromosome 6A were the most polymorphic with similar PIC values for both marker systems, showing that these markers are very useful for genetic variability studies in wheat. The gliadin results indicated that the Spanish einkorn collection possessed high genetic diversity, being the differentiation large between varieties and small within them. Some associations between gliadin alleles and geographical and agro-morphological data were found. Agro-morphological relations were also observed in the clusters of the SSRs dendrogram. A high concordance was found between gliadins and SSRs for genotype identification. In addition, both systems provide complementary information to resolve the different cases of intra-accession variability not detected at the agro-morphological level, and to identify separately all the genotypes analysed. The combined use of both genetic markers is an excellent tool for genetic resource evaluation in addition to agro-morphological evaluation.     

基于酶切的简化基因组测序在水禽品种进化关系研究中的应用

以基于酶切的简化基因组测序技术对5个鹅品种[狮头鹅(ST)、溆浦鹅(XP)、皖西白鹅(WX)、豁眼鹅(HY)、朗德鹅(LD)]进行测定,通过序列比较发现品种间存在SNP,在分析品种群体遗传参数的基础上,建立系统发生树。研究结果表明,所有样本酶切位点在20万左右,测序覆盖度在10%以上。狮头鹅群体平均突变位点26 172个,溆浦鹅群体34 153个,皖西白鹅群体35 179个,豁眼鹅群体为29 182个,朗德鹅群体18 675个。朗德鹅与其他鹅品种的Fst均在0.08以上,说明朗德鹅和其他鹅品种序列差异较大,狮头鹅与其他3个白鹅品种之间的Fst在0.04左右,3个白鹅品种的Fst较小。系统发生树分析表明,5个鹅品种大致分为三大类,溆浦鹅和狮头鹅聚为一类,皖西白鹅和豁眼鹅聚为一类,朗德鹅单独为一类。品种之间存在大量的SNP,该研究为鹅品种识别和进化提供依据。     

新疆早熟陆地棉SSR标记遗传多样性分析及指纹图谱构建

采用SSR分子标记对41份北疆地区早熟陆地棉品种进行遗传多样性分析,并构建其DNA指纹图谱。最终100对引物筛选出8对多态性较好引物,共检测50条带,其中多态性33条,多态性比率66%,每对引物平均扩增到6.25条条带。多态信息含量(PIC)为0.568 0~0.784 6,平均值为0.646 2。聚类分析表明,供试材料在遗传距离为0.42时可划分为3类,第3大类又可以划分为2大亚类,多数品种属于第3大类。利用其中7个特异性标记引物获得的数据构建供试材料的分子指纹图谱。新陆早系列在选育过程中亲本的来源较为广泛,遗传背景较复杂,获得的SSR分子指纹图谱能够用于新疆早熟陆地棉品种及相关材料的鉴定。     

棉花苗期耐盐性主基因和多基因混合遗传分析

为探讨棉花苗期耐盐性遗传规律,以2个耐盐性差异明显的棉花品种(系)NY1和中棉所12,以及NY1×中棉所12衍生的F1、F2和F2∶3群体为材料,采用主基因和多基因混合遗传模型分析法,以盐害级别为鉴定指标,对棉花苗期耐盐性进行遗传分析。结果表明,棉花盐害级别的遗传受1对加性-显性效应和加性-显性-上位性多基因遗传模型控制,主基因以负向加性效应为主,呈不完全负显性,在F2和F2∶3代的遗传率分别为64.006%和40.847%,明显高于多基因遗传率。说明棉花苗期耐盐性受1对主效基因控制,在育种中可以通过杂交方法转移主效基因并在F2世代进行单株选择。     

2个国家区试棉花品种的遗传特异性分析

为对棉花品种进行特异性鉴别,利用SSR(simple sequence repeats)方法对参加国家区试的2个棉花品种(A1、A2)的遗传特异性进行了研究。同时,根据棉花植物新品种DUS(distinctness,uniformity and stability)测试指南,对上述2份材料进行了20个农艺性状的特异性分析。结果表明,2个棉花品种的指纹图谱相同且田间性状相似,是同一个品种。该方法弥补了以往只考虑利用SSR鉴定品种的特异性而没有考虑田间农艺性状鉴定与SSR鉴定差异的不足,可以更客观地反映品种的特异性。     

烤烟品种主要农艺性状的遗传分析

选用12个烤烟品种(系),对烤烟主要农艺性状进行了广义遗传力的估算和相关分析.结果表明:产量遗传力最高为97.54%,有效叶数遗传力相对较低为74.44%,各性状遗传力的大小依次为产是、叶宽、茎围、株高、节间距、叶长、有效叶数.表型变异系数均大于遗传变异系数.产量的遗传变异系数最大,为17.59%;而叶片的长度、宽度、有效叶数及茎围,都与产量呈正相关,只有节间距与产量呈负相关.     

夏大豆F_2-F_4世代间产量及产量性状的遗传关系

10个夏大豆杂交组合的F_2、F_3和F_4代同期播种。结果表明,各组合世代间产量差异不显著。F_2与F_4世代间单株粒重等的相关系数都达到显著标准。各产量性状的遗传力和遗传进度在F_2代较低,不宜选择,至F_4代有较大提高,可进行选择。采用C.A.Brim的改良系谱法时,应结合早期世代组合鉴定,逐代淘汰不良组合,提高选择效果。