Breeding‐site vagrancy and hybridization in albatrosses

Given the rarity of hybridization in seabirds, which presumably relates to their very high philopatry, the degree of breeding‐site vagrancy should correspond with the incidence of mixed‐species pairing, although not necessarily with the production of hybrids if there are behavioural or genetic barriers to successful reproduction. Using molecular methods, we verified that two of the three chicks hatched by a vagrant male White‐capped Albatross Thalassarche steadi paired with a female Black‐browed Albatross Thalassarche melanophris at South Georgia were genuine hybrids (these chicks died before fledging, but a third chick – the result of an extra‐pair copulation – fledged successfully). In a wider review, we could find only five known or suspected mixed‐species pairs, and three different hybrids in albatrosses, mostly between closely related species. This appears to reflect behavioural barriers to hybridization in sympatric species and the low incidence of breeding‐site vagrancy (which mainly involves single individuals that invariably associate with the most phenotypically similar local taxon). Breeding‐site vagrancy is most frequent in the ‘shy‐albatross’ complex, which could explain why genetic divergence occurred more recently in this group than in other Thalassarche, and hence exploratory behaviour appears to be more important than numerical abundance or breeding distribution in driving colonization as well as hybridization processes in albatrosses.     

Effects of fragmentation and hybridization on geographical patterns of song variation in the endangered Yellow Cardinal Gubernatrix cristata

The song learning process may lead to small‐scale geographical variation in vocalizations of oscine birds. This variation can be further enhanced by the effects of habitat fragmentation or hybridization. Populations of the endangered Yellow Cardinal Gubernatrix cristata are now patchily distributed in the southern South American thorny shrubland forests and are small as a consequence of the pressure exerted by increased habitat transformation and illegal trade. We study the Yellow Cardinal's vocalizations throughout its distribution and assess how habitat characteristics and fragmentation, as well as hybridization with the Common Diuca Diuca diuca, have affected song patterns of different populations. We expected to find song differences among populations and songs to be more similar to those of the Common Diuca in areas where hybridization occurs. Multivariate analyses revealed significant differences in song between the four populations studied and confirmed that songs are more similar to those of Common Diuca where hybridization takes place. These results, in conjunction with genetic studies, can help to establish management units that preserve genetic and cultural variation in this endangered species.     

Comparison of DNA marker and pedigree-based methods of genetic analysis in plantain and banana (Musa spp.) clones. II. Predicting hybrid performance

 Pedigree and DNA marker-based methods were used to predict the performance of triploid progeny from tetraploid-diploid crosses, based on parental heterozygosity, genetic relatedness, and expected contribution to their progeny. There was no significant correlation between parental and progeny performance. Prediction of progeny bunch weight was best when based on genealogical distance and equal parental contribution. Predicted fruit size was most accurate when DNA marker data were used and the assumption of an unequal parental contribution was made. Consideration of parental heterozygosity produced larger residuals for all traits. No statistically significant differences were found between the mean residuals obtained under the assumption of an equal vs an unequal contribution of the 4x and 2x genotypes to their 3x progeny, regardless of the method used to estimate genetic relationships. Received: 29 October 1997 / Accepted: 14 July 1998     

向普通小麦导入纤毛鹅观草抗黄矮病基因的研究──Ⅰ.F_1和BC_1的产生及其细胞遗传学

为了将纤毛鹅观草Z1010对黄矮病毒株系PAV和RPV的抗性基因转入普通小麦,通过幼胚拯救,获得了纤毛鹅观草Z1010×普通小麦品种莱州953的杂种F1,以及用5个普通小麦品种（系）回交的BC1衍生系。对杂种F1及BC1植株的细胞学分析表明,纤毛鹅观草Z1010不仅对Ph基因具有很强的抑制作用,而且能使杂种F1形成未减数配子,对细胞遗传学资料的进一步分析认为,通过部分同源染色体间的交换将纤毛鹅观草Z1010的抗黄矮病基因转入小麦是可能的。     

Biosystematic studies on Hystrix longearistata from Japan and Hystrix duthiei from China (Poaceae: Triticeae)

Morphological comparison, cytogenetic study and fertility analysis of Hystrix duthiei (2n = 28) from China, Hystrix longearistata (2n= 28) from Japan and their artificial hybrids were carried out. Morphologically H. duthiei was similar to H. longearistata. H. longearistata had longer lemma awn, wider leaf and 2～3 florets per spikelet, while H. duthiei had 1～2 florets per spikelet. These two taxa can be easily crossed. F_l hybrids showed very high degree of bivalent pairing (13～14 bivalents) at the metaphase- I of meiosis. No multivalents were found. The fertility of pollen and seed set of the parents were normal, while the F_l hybrids were of only partial fertility. H. longearistata was closely related to H. duthiei. They should be included in the same species. Because of the differences of their distributions and habitats, some morphological divergency and a little sterility barrier have had appeared between them. It is reasonable to treat Hystrix longearistata as a sub-species of Hystrix duthiei .     

染色体倍数与杂种优势之关系初探

杂种优势是植物界的一个普遍现象,也是提高栽培作物产量的一个十分重要的途径。目前,除少数栽培作物外,大部分作物都已成功地利用了杂种优势。杂种优势的利用基本上集中在二倍体,在生产上大面积利用的以收获种子为目的的多倍体并不多,如小麦（异源六倍体）、大豆（异源四倍体）、花生（异源四倍体）等。其原因除制种较困难外,关键是杂种优势多不及二倍体,但到目前为止,尚未有一个完整的理论对此进行系统解释,本文将就这一问题进行讨论,以供同行参考。１　内源优势与外源优势笔者认为,多倍体作物杂种优势不强与其染色体组成有关。…     

尖音库蚊复合组杂交子一代4龄幼虫形态性状的研究

对我国尖音库蚊复合组（Culex pipiens complex）中的尖音库蚊Cx. Pipiens pipiens、淡色库蚊Cx. Pipiens pallens和致倦库蚊Cx. Pipiens quinquefasciatus之间杂交的F₁代幼虫形态进行了方差和典型变量分析,结果发现杂交组F₁代4龄幼虫在呼吸管指数、1-S第1对毛和第2对毛的分枝数3个性状上与亲本有明显的差异,而且介于两亲本之间。     

青海仲彬草和黑药仲彬草的生物系统学研究

黑药仲彬草Kengyilia melanthera(Keng)J．L. Yang,Yen et Baum和青海仲彬草K．kokonorica (Keng)J.L．Yang,Yen et Baum是分布于我国西部的两种多年生六倍体植物。将其分别与鹅观草 Roegneria kamoji Ohwi(2n=42,StStHHYY)、糙毛仲彬草K．hirsuta(Keng)J．L. Yang,Yen et Baum (2n=42,PPStStYY)进行了杂交;对亲本及杂种F_l代花粉母细胞减数分裂中期I染色体配对行为进行 了观察。杂种F1减数分裂染色体配对平均构型分别为：R．kamoji×K．melanthera,18.201+11.74 Ⅱ 十0.09Ⅲ十0.01V;K．hirsuta×K．melanthera,1.06Ⅰ十20.47Ⅱ;R．kamoji×K．kokonori- ca,19.36Ⅰ十11.26Ⅱ十0.04Ⅲ;K．hirsuta×K．kokonorica,2.46Ⅰ十19.44Ⅱ 十0.14Ⅲ十0.06 Ⅳ。根据以上结果,并结合形态特征,将黑药仲彬草和青海仲彬草从鹅观草属拟冰草组Roegneria sect．Paragropyron Keng中组合到仲彬草属Kengyilia Yen et Yang更为恰当,而不应划分到披碱草属E-lymus L．或偃麦草属Elytrigia Desv．中。     

The role of domestication and maternal effects on seed traits of crop–wild sunflower hybrids (Helianthus annuus)

Hybridisation between crops and their wild relatives may promote the evolution of weeds. Seed germination and dormancy are the earliest life‐history traits and are highly influenced by the maternal parent. However, the ecological role of the maternal effect on seed traits in the evolution of crop–wild hybrids has received little attention. In this study, we test the relative importance of maternal and hybridisation effects on seed traits of the first generation of crop–wild sunflower hybrids (Helianthus annuus). Seed germination was tested in two wild populations with contrasting dormancy, two cultivated materials and their reciprocal crosses at four different times after harvest and three different temperatures. Seed germination at each of the four times, after ripening response and secondary dormancy were recorded along with four morphological traits. Additionally, the pericarp anatomy was analysed with light and scanning electron microscopy. We observed strong maternal effects on all seed traits. Seed germination, morphology and pericarp anatomy differed largely between the crop and wild seeds and these traits in the crop–wild hybrids resembled their female parent. Slight but significant hybridisation effects were observed in germination, mainly in seeds produced on wild plants. Crop hybridisation changed seed germination, the after ripening response and secondary dormancy in the crop direction. Morphological and anatomical traits associated with domestication strongly correlated with the observed differences in seed germination and dormancy in crop–wild sunflower hybrids. The large maternal effects along with the evolutionary divergence in seed traits were responsible for the large phenotypic differences observed in crop–wild hybrids with the same genetic composition. Wild‐like seed traits of hybrids suggest that there are no barriers to crop gene introgression at the seed level whereas crop‐like seed traits could be strongly selected against, conditioning the selection of traits expressed later in the life cycle and in the next generations.     

Production and characterization of intergeneric somatic hybrids between <Emphasis Type="Italic">Brassica napus</Emphasis> and <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> and their backcrossing progenies

Alien chromosome addition lines have been widely used for identifying gene linkage groups, assigning species-specific characters to a particular chromosome and comparing gene synteny between related species. In plant breeding, their utilization lies in introgressing characters of agronomic value. The present investigation reports the production of intergeneric somatic hybrids Brassica napus (2n = 38) + Orychophragmus violaceus (2n = 24) through asymmetric fusions of mesophyll protoplasts and subsequent development of B. napus-O. violaceous chromosome addition lines. Somatic hybrids showed variations in morphology and fertility and were mixoploids (2n = 51–67) with a range of 19–28 O. violaceus chromosomes identified by genomic in situ hybridization (GISH). After pollinated with B. napus parent and following embryo rescue, 20 BC₁ plants were obtained from one hybrid. These exhibited typical serrated leaves of O. violaceus or B. napus-type leaves. All BC₁ plants were partially male fertile but female sterile because of abnormal ovules. These were mixoploids (2n = 41–54) with 9–16 chromosomes from O. violaceus. BC₂ plants showed segregations for female fertility, leaf shape and still some chromosome variation (2n = 39–43) with 2–5 O. violaceus chromosomes, but mainly containing the whole complement from B. napus. Among the selfed progenies of BC₂ plants, monosomic addition lines (2n = 39, AACC + 1O) with or without the serrated leaves of O. violaceus or female sterility were established. The complete set of additions is expected from this investigation. In addition, O. violaceus plants at diploid and tetraploid levels with some variations in morphology and chromosome numbers were regenerated from the pretreated protoplasts by iodoacetate and UV-irradiation. Z. Zhao and T. Hu make equal contributions to this work.