Validation of two models for self‐incompatibility in autotetraploid perennial ryegrass using high resolution melting‐based markers

Perennial ryegrass (Lolium perenne L.) displays a two‐locus gametophytic self‐incompatibility (SI) system that remains intact at the tetraploid level. Two models are plausible for SI in autotetraploids. In Model I: both alleles at the S locus and both at the Z locus in diploid pollen matching the female genotype results in incompatibility. In Model II: only one allele at S and one at Z locus in diploid pollen matching the female results in incompatibility. The goals were to determine which of the models best explains SI in our autotetraploid ryegrass population and to evaluate the efficiency of high‐resolution melting (HRM) genotyping for discriminating different iso‐allelic genotypes. The progeny of a cross between two autotetraploids was characterized with three HRM‐based markers co‐segregating with Z. Segregation ratios were used to make inferences about the mode of action of the SI system. The observed segregation differed significantly (P < 0.001) from the expected under Model I, but not from the expected under Model II (P = 0.463). Thus, Model II explains SI in this population, and HRM is an efficient tool to distinguish different iso‐allelic genotypic classes.     

In vitro induction of tetraploids in colchicine-treated cocoyam plantlets

A self-compatible (SC) variant of a wild diploid potato species, Solanum chacoense, which is normally self-incompatible (SI), was investigated for the nature and genetics of self-compatibility. It was crossed with a SI cultivated diploid potato species, S. phureja. The F₁ progeny segregated SC vs. SI. Diallel crosses were made among 15 F₁'s. Self-compatibility was tested in a selfed family of a parental SC variant and in sib-mated and selfed families of F₁ progeny. All the data suggest that there is a single dominant gene (Sli) with sporophytic action inhibiting S gene expression in the pollen. Plants having a ‘Sli’ gene, produce pollen which is compatible to its own parent and plants with similar S genes. The ‘Sli’ gene has been maintained in a heterozygous condition through eight selfing generations (S₈) implying that dominant homozygotes might be associated with lethality. This revised version was published online in July 2006 with corrections to the Cover Date.     

甘蓝自交不亲和性信号传导元件与传导过程

甘蓝自交不亲和性是由多态性的S位点基因编码的蛋白质介导的信号传导途径实现的。该信号传导途径由8个蛋白质元件(SLG、SCR、SRK、MLPK、THL、ARC1、Exo70A1和MOD/MIP-MOD)组成,本文详细综述了这些元件的编码基因、蛋白质元件的结构和功能,以及元件间的相互作用所构成的信号传导过程。在此基础上,根据新进展提出了今后可能的研究重点,以期为包括甘蓝在内的芸薹属自交不亲和性的深入研究提供新的内容。     

Occurrence of self-compatibility, self-incompatibility and unilateral incompatibility after crossing diploid S. tuberosum (SI) with S. verrucosum (SC): I. Expression and inheritance of self-compatibility

Diploid Solanum tuberosum (tbr), 2n=2x=24,can be crossed with S. verrucosum (ver) only when the latter is used as a pistillate parent but not reciprocally. This conforms to the phenomenon of unilateral incompatibility (UI) where a self-compatible species, like ver (SC) cannot be used as a male parent to cross with a self-incompatible (SI) parent like tbr. Even if ver × tbr hybrids are made, the F1 hybrids possess cytoplasmic male sterility and thus hinder genetic analysis of crossing barriers. Exceptionally, however, some diploid genotypes of tbr (SI) can be used as pistillate parents to cross with ver, and such exceptional tbr clones are called `acceptors'. Repeated backcrossing of acceptors to ver have resulted in male fertile genotypes that possess tbr cytoplasm and ver nucleus. These genotypes were used for the genetic analysis of `acceptance' and UI in thse experiments. It was found that acceptance of ver-pollen by tbr-pistils is based on a dominant gene A that expresses only in the absence of an inhibitor I. In the F₁ hybrids, only the S-allele of tbr was expressedbut not that of ver. Concomitant with this observation, it was shown that ver does not produce style-specific S-glycoproteins that are responsible for self-incompatible reaction in diploid potato. Although the the F₁ populations were SC, they segregated into SC and SI genotypes giving skewed segregation ratios for this trait. Because of this as well as the disappearance and re-appearance of SC trait in the offspring generations, it was necessary to postulate a more complex interaction between A and I. Models are presented in order to explain acceptance, non-acceptance and the expression of UI. It is concluded that at least four different loci are involved in the expression of UI. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics of self-compatibility in a self-incompatible wild diploid potato species Solanum chacoense. 2. Localization of an S locus inhibitor (Sli) gene on the potato genome using DNA markers

A self-compatible (SC) hybrid plant F₁-1 was obtained from a cross between a SC variant of a wild diploid potato species, Solanum chacoense, and a self-incompatible (SI) cultivated diploid species, S. phureja. The clone F₁-1 has previously been proposed to have a dominant S locus inhibitor gene (Sli) in a heterozygous condition. It was crossed as a male parent with a selected clone from a S. stenotomum-S. phureja population, resulting in a segregating population consisting of 116 hybrid plants. Self-compatibility was assessed by selfing each of the hybrids. Sixty-six of them were SC, while 35 were SI, showing a significant distortion from an expected Mendelian ratio of 1:1. A genetic linkage map was constructed using DNA markers to localize the Sli gene. A total of 28 RAPD and 127 RFLP markers identified 109 mapping positions on 12 linkage groups. The Sli gene was mapped at a distal end of chromosome 12. Since the S locus has been localized on chromosome 1 on the potato RFLP map, it is confirmed that the Sli gene is independent of the S locus. This revised version was published online in August 2006 with corrections to the Cover Date.     

Compatibility and incompatibility in witloof-chicory (Cichorium intybus L.). 1. The influence of temperature and plant age on pollen germination and seed production

Summary For the production of inbred lines and F₁ hybrids in witloof-chicory information is wanted on characteristics such as the incompatibility system. These characteristics can only be studied properly if the influence of temperature and physiological status of the plant on pollen germination and seed production is known. Investigations were carried out with 9 self-incompatible (SI) and 6 self-compatible (SC) clones in glasshouses of the IVT phytotron at constant temperatures of 10, 14, 17, 20, 23 and 26°C. In general, in vivo pollen germination percentages were rather low after self pollination with an optimum for germination around 17–20°C. No seeds were formed at the lowest temperature (10°C) while seed production for SC clones was usually (rather) good at higher temperatures. At 26°C seed production in some clones decreased. Both pollen germination and seed production decreased at the end of the flowering period. There was a rather positive relationship at e.g. 17 and 20°C between pollen germination after selfing and seed production. When no pollen germination was observed, no seed formation occurred. When pollen grains did germinate, seed development would not necessarily occur in all cases. So this relationship only enables negative mass selection for SC.     

利用 DDRT-PCR 鉴定芸芥自交不亲和系与自交亲和系的差异表达 cDNA

芸芥与芸薹属植物具有亲缘关系,也是芸薹属植物的重要育种资源。自交亲和性是芸芥的一种重要变异性状。为了探明芸芥自交亲和基因的表达器官,并分离与自交亲和性有关的 cDNA 片段,以芸芥的一对近等基因系,自交亲和系（SC）与自交不亲和系（SI）为试材,利用差异显示 RT-PCR 技术分别对开花前和开花后的叶片、花药和柱头进行鉴定。结果表明,不论开花前还是开花后,芸芥自交亲和系与自交不亲和系的叶片或花药间的扩增带型是一样的,但在近等基因系的柱头间得到了差异表达条带。这证明芸芥自交亲和基因不是组成型表达,而是组织特异性表达,柱头是其唯一的表达器官。在开花前的自交亲和系中共得到了2条 cDNA 片段,一条小于100 bp,另一条为750～1000 bp,在开花后的自交亲和系中得到了1条300 bp 的 cDNA 片段。据分析这3条 cDNA 片段可能与芸芥的自交亲和性密切相关。在开花前的自交不亲和系中共得到了2条 cDNA 片段,一条为500 bp,另一条为750 bp,同时在开花后的自交不亲和系中得到了1条500～600 bp 的 cDNA 片段。这些 cDNA 片段可以用来区分芸芥的自交亲和系与自交不亲和系,还可用于克隆自交亲和基因。     

Nuclear genetic control of variation in simazine tolerance in oilseed brassicas

Summary Brassica napus is a natural allotetraploid derived from the diploid species B. rapa L. (syn. campestris L.) and B. oleracea L. Somatic hybrids synthesized from highly heterozygous lines of these two diploid species were evaluated for fertility. The hybrids were obtained from two fusion experiments which differed in the B. rapa full-sibling parent used as the source of protoplasts. Both B. rapa siblings were lelf-incompatible (SI) yet contained different S-alleles; the B. oleracea species parent was self-compatible (SC). Eight tetraploid hybrids examined had very high female and male fertility; eight hybrids with higher ploidy had low fertility. Hybrids derived from one B. rapa sibling were self-incompatible, whereas those derived from the other B. rapa sibling were fully self-compatible. These data suggest that the different S-alleles of each B. rapa sibling displayed varying penetrance relative to the SC of the B. oleracea parent when combined in B. napus.Abbreviations SC self-compatibility - SI self-incompatibility     

Development of self-incompatible Brassica napus: (III) B. napus genotype effects on S-allele expression

Use of self‐incompatibility (SI) as a pollination control method for Brassica napus hybrid production requires the development of a sufficient number of S‐alleles that are expressed consistently in a range of B. napus lines. Self‐incompatibility (SI) alleles have been transferred from Brassica oleracea and Brassica rapa into B. napus var. oleifera. An understanding of expression of these alleles in B. napus is essential for their commercial use. Four SI B. napus doubled haploids containing the B. oleracea S‐alleles S2, S5, S13 and S24 were crossed to three B. napus cultivars to measure the B. napus genetic background effect on S‐allele expression. A line x tester analysis indicated that the largest source of variation in the expression rate of SI was the S‐allele itself. The B. napus genotypes tested contained modifier gene(s), some that enhanced SI expression and others that inhibited SI expression. The B. napus Canadian cultivar ‘Westar’ generally had a negative effect on SI expression while the European cultivar ‘Topas’ had a positive effect on the B. oleracea S‐allele expression. The B. oleracea S‐allele S24 was very similar in expression to the B. rapa allele W1. The application of these results for the use of B. oleracea S‐alleles for hybrid production in B. napus is discussed.     

Development of self-incompatible Brassica napus: (II) Brassica oleracea S-allele expression in B. napus

Brassica napus var. oleifera varieties have traditionally been developed as open‐pollinated varieties. The successful introduction of several high‐yielding hybrids based on cytoplasmic male sterility or transgenic pollination control systems has generated interest in the development of new hybrid systems. Self‐incompatibility could be an additional useful pollination control system for B. napus if a sufficient number of S‐alleles could be developed in this species. The S‐alleles, S2, S5, S13, S24 and S39, were identified in five hybrids of B. oleracea var. italica and subsequently transferred to B. napus. Doubled haploid lines were produced for the self‐incompatible (SI) lines in B. napus and intercrossed to produce SI heterozygotes in order to study allele interaction. There was a greater incidence of interallelic dominance in the stigmas and pollen of B. napus than was reported for the S‐alleles in B. oleracea. Allele S24 exhibited the greatest degree of dominance over the other alleles tested, while allele S2 was generally recessive or codominant with other alleles. Self‐incompatible expression was very similar in the SI homozygotes and heterozygotes, thus no weakening of the SI trait in the heterozygote was observed. The implications of S‐allele interaction for the use of SI in B. napus are discussed.     

Independence of self-compatibility and potentiality for self-pollination in peach x almond hybrids

Summary The almond of commerce (Prunus dulcis (Mill.) D.A. Webb) is self-incompatible (SI) and requires honey-bees to effect the transfer of pollen among cultivars that flower simultaneously. Four year old trees from the F₂ generation of several peach x almond hybrids were studied to determine whether self-compatibility (SC) and the potentiality for natural, i.e., abiotic, self pollination (NSP) are genetically related or are inherited independently. Both SC and the high potentiality for NSP are characteristic of peach (Prunus persica (L.) Batsch) but not almond. Forty percent of SC genotypes exhibited adequate NSP (SC, +NSP) for good fertility i.e., without insect-mediated pollination. The remaining 60% of SC genotypes (SC,-NSP) exhibited an average 61% reduction in fruit set on limbs bagged to exclude honeybees during anthesis relative to fruit set on open pollinated limbs. Our data are consistent with the concept that fertility is dependent upon the load of compatible pollen deposited on the stigma. Fruit set reduction on bagged limbs, compared with bagged and self-pollinated limbs, was presumably due to a) lack of/insufficient pollination for fertilization and/or b) post-zygotic abortion of genetically inferior recombinants. Selection following manual self-pollination may result in SC genotypes with or without the capacity for NSP. In contrast, significant fruit set on limbs enclosed during pistil receptivity necessitates that the genotype selected express both SC and the potentiality for NSP.     

Inheritance of pseudo-self compatibility in self-incompatible garden and greenhouse chrysanthemums, Dendranthema grandiflora Tzvelv

Summary Self incompatibility (SI) can be used to alleviate costly hand emasculation and pollination in F₁ hybrid chrysanthemum seed production. SI, however, disrupts the progression of inbreedig (selfing or full-sib mating). Consequently, inbreds are selected for breakdown of the SI system or the presence of pseudo-self compatibility (PSC). PSC inbreds, recombinant inbreds, and noninbred cultivars were selfed and/or intercrossed to determine PSC expression across environments and generate 1–3 inbred generations (I₁–I₃). Percent PSC ranged from 0–68.8% for inbred parents, 0.2–99.7% for recombinant inbreds, and 0.6–25.7% for noninbred cultivars. There was no indication of end-of-season PSC. The majority of parents (78%) were classified as low PSC and this trend continued in the I₁ (70.1%), I₂ (65.6%), and I₃ (83.6%) generations; mid PSC was rarer (11.9–18.8%) and high PSC the least common (4.5–15.6%). PSC distributions were primarily continuous, rather than discrete, indicating quantitative inheritance. In several inbred families, 100% of the I₁ individuals were SI; this was not correlated with parental PSC level. Inbred families derived from selfing low and mid PSC parents were the most likely to reach extinction due to inbreeding depression. High PSC was not highly heritable, since I₁ progeny were predominantly SI or had low to mid PSC levels. Most 153-1 values for PSC:SI segregations (1:1, 1:3, 3:1) were not significant at the 5% level. Realized heritability (H _R ) estimates for PSC ranged from a low of 0.05% to 10.19%, although increased H _R values did not account for inbreeding depression or genetic mechanisms preventing selection for high PSC. The highest individual %PSC increased over the high parent with SI × low PSC or SI × mid PSC parents in all cases; progeny means did so only in SI × low PSC. Low × low crosses were split evenly between an increase and decrease in progeny or highest individual mean. Since all low × low crosses and low selfs produced 43–50% of the progeny with PSC levels higher than the parents, it appears that most low parents possess some unexpressed PSC genes. Mid PSC parents responded similarly to low PSC genotypes. An increase in PSC was found when crossing SI × PSC parents, illustrating a threshold effect. PSC × PSC crosses (high × low, low × low) produced SI, low, and mid PSC I₁ individuals but did not show a heterotic effect, since the PSC parents had already surpassed the PSC threshold. Selfing high PSC parents, however, suggested different genetic control. Progeny and highest individual means behaved the same; 83% decreased and 17% remained the same for PSC levels. The drop in PSC indicated non-additive gene action. Thus, the PSC threshold with additive gene action holds when selection for higher PSC levels is being done from low and mid PSC parents, but once high PSC levels are obtained, non-additive gene action prevails.Abbreviations self pollinated - H _R Realized Heritability - PSC Pseudo-Self Compatibility - SC Self Compatibility - SI Self Incompatibility     

Self-incompatibility as a pollination control mechanism for spring oilseed rape,Brassica napus L.

Summary Self-incompatibility was shown to be an effective method of pollination control in spring rapeseed (B. napus L. ssp. oleifera (Metzg.)) by comparing the yield of a Westar-Topas syn-1 produced by crossing two SI lines with the yield of the corresponding syn-1 produced by hand pollination. Although the trial showed high-parent heterosis in the syn-1s, there was insufficient replication to determine the level of heterosis.Abbreviations SI self-incompatible - SC self-compatible     

甘薯组(Batatas Section)种间、种内交配不亲和特性研究

以甘薯及其近缘野生种为材料,研究甘薯组种内和种间不亲和特性,主要结果如下:1.无论种内或种间,交配不亲和性是存在的;2.种间不亲和表现特点依组合不同,表现为3种类型:(1)花粉不萌发或产生极短花粉管,柱头的乳突细胞有胼胝质反应。(2)花粉萌发延迟,花粉管生长缓慢、停滞。(3)花粉正常萌发,花粉管生长受阻。几乎没有观察到正常     

Statistical discrimination between pollen tube growth and seed set in establishing self incompatibility in Gaura lindheimeri 1

The University of Minnesota Gaura breeding program is developing USDA Z3-4 winter-hardy genotypes via interspecific hybridization of G. lindheimeri (Z5-6) and G. coccinea (Z2-4). Prior to commencing interspecific hybridization, the reproductive barriers operating in both parental species need to be characterized. The objective of this research was to determine the type and stability of reproductive barriers operating in G. lindheimeri by statistical comparisons between pollen tube growth and seed set in a full-sib diallel. Slowed or aborted pollen tube growth in the style indicated the presence of a gametophytic self incompatibility (SI) system. A statistical method, female (FCC) and male (MCC) coefficients of crossability, was used to verify that a stable SI system was operating and that other reproductive barriers were present. Several genotypes also expressed stage-specific inbreeding depression and incongruity. The simple linear regression equation for FCC/MCC, using pollen tube growth, was Y = 0.0124 + 0.974X, which was much closer to the expected Y = 0.0 + 1.0X (indicating a stable SI system) than the equation for seed set, Y = 0.012 + 0.910X. Using pollen tube length, both general combining ability (GCA) and specific combining ability (SCA) values were highly significant for G. lindheimeri (P ≤ 0.001). Histograms were used to delineate cut-offs to identify intra-incompatible/inter-compatible classes and S allele groups. Four possible classes were identified, but further research is needed to verify S allele genotypes.Scientific Research Paper No. 031210120 of the Department of Horticultural Science. This research was supported by a grant from the Perennial Plant Association and, in part, by the Minnesota Agricultural Experiment Station     

Resynthesis of Brassica napus L. for self-incompatibility: self-incompatibility reaction, inheritance and breeding potential

Self-incompatibility (SI) in Brassica has been considered as a pollination control mechanism for commercial hybrid seed production, and so far has been extensively used in vegetable types of Brassicas. Oilseed rape Brassica napus (AACC) is naturally self-compatible in contrast to its parental species that are generally self-incompatible. Introduction of S-alleles from its parental species into oilseed rape is therefore needed to use this pollination control mechanism in commercial hybrid seed production. Self-incompatible lines of B. napus , carrying SI alleles in both A and C genomes, were resynthesized from self-incompatible B. oleracea var. italica (CC) cv.'Green Duke' and self-incompatible B. rapa ssp. oleifera (AA) cv. 'Horizon', 'Colt' and 'AC Parkland'. All resynthesized B. napus lines exhibited strong dominant SI phenotype. Reciprocal cross-compatibility was found between some of these self-incompatible lines. The inheritance of S-alleles in these resynthesized B. napus was digenic confirming that each of the parental genomes contributed one S-locus in the resynthesized B. napus lines. However, the presence of two S-loci in the two genomes was found not to be essential for imparting a strong SI phenotype. Possible use of these dominant self-incompatible resynthesized B. napus lines in hybrid breeding is discussed.     

6个木薯品种光合特性的研究

利用GFS-3000便携式光合-荧光测量系统,对6个木薯品种在生长发育过程中的净光合速率(Pn)、蒸腾速率(E)、气孔导度(Gs)、胞间CO2浓度(Ci)进行了研究。结果表明,6个木薯品种的净光合速率（Pn）在生育期变化呈先增后降的曲线,蒸腾速率(E)和胞间CO2浓度(Ci)的升降并不完全受气孔导度(Gs)的影响。经邓肯氏新复极差比较,华南6（SC6）和华南7（SC7）的Pn 显著高于其它各个木薯品种,华南205（SC205）、华南（SC5）的Pn 显著高于华南9（SC9）,而与华南8（SC8）差异不显著     

Development of a molecular CAPS marker for the self-incompatibility locus in Brassica napus and identification of different S alleles

Using primers annealing to S locus sequences the cleaved amplified polymorphic sequences (CAPS) method was applied to develop a marker and to characterize different alleles at the self‐incompatibility locus in Brassica napus. A segregating F₂ population from a cross of a self‐incompatible (SI) and a self‐compatible parent, as well as seven SI lines representing four different S alleles were used. Several primers specific to the S locus in B. oleracea and B. campestris, chosen from the literature, allow polymerase chain reaction (PCR) amplification of genomic DNA. However, only one primer pair amplified a single specific and reproducible PCR fragment of the expected length in B. napus. Digestion with restriction endonucleases revealed polymorphisms for two CAPS markers absolutely linked to the S locus. Using the codominant marker efMboI it was possible to discriminate all three F₂ genotypes. With this marker and an additional marker using another primer pair it was possible to distinguish between three of the four different S alleles and five of the seven SI lines, respectively.     

禾本科植物自交不亲和性及其分子生物学研究进展

禾本科植物自交不亲和性是禾本科植物中广泛存在的一种生殖隔离现象,有利于防止近交衰退、保持遗传变异。已报道自交不亲和禾本植物有着相同的自交不亲和系统,是一种特殊的配子体自交不亲和类型,和单一位点控制的自交不亲和性不同,其不亲和性由非连锁的两个复等位基因位点S和Z控制。自交不亲和反应中涉及了花粉蛋白质的磷酸化、Ca2 浓度的变化和蛋白激酶的参与,因此可能存在着复杂的信号传导级联反应,详细机制尚不清楚。目前S、Z基因的克隆和编码产物的鉴定均未有成功的报道,天蓝虉草可作为禾本自交不亲和性研究的一个模式作物,运用分离群体和比较基因组学方法构建S与Z位点的精细连锁图谱,以对自交不亲和基因进行图位克隆,是当前禾本科植物自交不亲和性研究的一个方向和热点。     

大豆花叶病毒(SMV)株系SC4和SC8的抗性遗传分析

选用我国黄淮和长江流域大豆产区发生频繁的SMV株系SC4和SC8,利用大豆抗病材料和感病材料配制抗感和抗抗杂交组合,研究抗病材料对SC4和SC8株系的遗传方式以及不同大豆材料对SMV抗性基因位点间的等位性关系。结果表明, 接种SC4株系后,由冀LD42、徐豆1号、跃进4号、科丰1号、PI96983、晋大74、汾豆56、大白麻和齐黄22为抗源配制的9个抗感组合的F₁均表现抗病,经卡方测验, F₂抗感分离比例3∶1,F_2:3家系分离比例为1(抗)∶2(分离)∶1(感),表明这些抗源均有1对基因控制对SC4株系的抗性,且抗病表现为显性;5个抗抗组合的F₁均表现抗病,F₂群体分离比例15(抗)∶1(感),表明大白麻与汾豆56、科丰1号和齐黄1号携带抗SC4的基因是不等位的,冀LD42与汾豆56,晋大74与中作229是不等位的。接种SC8株系后,用齐黄1号、中作229、NY58、科丰1号、PI96983、晋大74、汾豆56、大白麻和齐黄22为抗源配制的抗感组合杂交后代分离符合1对基因的分离比例且F₁均表现抗病,说明这些品种对SC8株系的抗性也均由1对显性基因控制。抗抗组合晋大74×汾豆56接种SC8株系后的F₂群体全部表现抗病,F_2:3家系没有抗感分离,表明抗病品种晋大74与汾豆56携带的抗病基因是等位的;齐黄1号×科丰1号、大白麻×汾豆56的F₂群体分离比例15(抗)∶1(感),表明抗病亲本齐黄1号与科丰1号、大白麻与汾豆56携带抗SC8的基因是不等位的,而且独立遗传。