Selecting for floral character associations in wild radish,Raphanus sativus L.

ESS models of reproductive allocation have been used extensively to explain patterns of floral diversity in angiosperms. These theoretical explorations assume that proportional allocation to pollen, ovules, and seeds, as well as to secondary features such as showy petals and nectar rewards, can evolve independently within the limits set by total resource availability. In populations of California wild radish, we have shown previously that petal size, a strong determinant of visitation by honey bee pollinators, is positively correlated with both pollen and nectar production, but not with ovule or seed number per flower. These phenotypic associations may reflect selection, environmental correlation, and/or genetic constraint. By exerting selection on the petal size : pollen number ratio over two generations, we eliminated the positive correlation between petal size and pollen production, with both characters showing significant change after a single selection episode. Once these two floral traits became uncoupled, nectar sugar production was significantly correlated only with petal size. Our results suggest that natural selection could readily alter reproductive allocation in these flowers, and that the phenotypic correlations observed in nature may be maintained by selection for effective reproductive phenotypes.     

Mechanisms of differential pollen donor performance in wild radish, Raphanus sativus (Brassicaceae)

In order to understand the characters on which sexual selection might operate in plants, it is critical to assess the mechanisms by which pollen competition and mate choice occur. To address this issue we measured a number of postpollination characters, ranging from pollen germination and pollen tube growth to final seed paternity, in wild radish. Crosses were performed using four pollen donors on a total of 16 maternal plants (four each from four families). Maternal plants were grown under two watering treatments to evaluate the effects of maternal tissue on the process of mating. The four pollen donors differed significantly in number of seeds sired and differed overall in the mating characters measured. However, it was difficult to associate particular mechanistic characters with ability to sire seeds, perhaps because of interactions among pollen donors within styles or among pollen donors and maternal plants. The process of pollen tube growth and fertilization differed substantially among maternal watering treatments, with many early events occurring more quickly in stressed plants. Seed paternity, however, was somewhat more even among pollen donors used on stressed maternal plants, suggesting that when maternal tissue is more competent, mating is slowed and is more selective.     

Interactions between elicitins and radish Raphanus sativus

Two responses to elicitins are described in cultivars of radish (Raphanus sativus L.). Type I, exhibited by the cultivar Daikon, is characterised by wilting and desiccation within 24 h of elicitin application and was previously reported as the sensitive response (S. Kamoun et al. 1993, Mol Plant-Microbe Interact 6: 15–25). At 1 μg elicitin · g⁻¹ FW radish tissue, symptoms appeared after 8 h, a sensitivity comparable to that shown by tobacco to β elicitins (J.-C. Pernollet et al., 1993, Physiol Mol Plant Pathol 42: 53–67; S. Kamoun et al., 1993, Mol Plant-Microbe Interact 6: 15–25). Elicitin failed to induce these symptoms in the cultivar White Icicle, even at 100 μg · g⁻¹ FW of tissue. However, a different response (Type II) with symptoms resembling senescence appeared in White Icicle after 48 h and were fully developed by 72 h. The Type II response was induced at levels of elicitin above 0.3 μg · g⁻¹ FW. Elicitin-treated Daikon leaves held at 100% relative humidity, rather than ambient (50–60%) did not wilt and by 72 h displayed Type II symptoms. When treated Daikon leaves were removed to ambient humidity at any time during the latent period, they developed Type I symptoms within 2 h. Although Type I symptoms were suppressed in Daikon at high humidity, there was no indication that leaf diffusion resistance or plant water conductance were affected. Protoplasts from the cultivar Daikon responded to elicitin by H⁺ uptake and K⁺ release, with maximal response at 300 pM. The response was eliminated by K252a or staurosporine. Daikon protoplasts also showed transient uptake/secretion of Ca²⁺ on elicitin addition. Protoplasts from White Icicle gave neither of these responses. Both Daikon and White Icicle phenotypes could be transferred to progeny of Daikon-White Icicle crosses and in the F2 generation three phenotypes, including a null, segregated. Only those F2 plants which exhibited the Daikon phenotype produced protoplasts which responded to elicitin. Received: 13 May 1997 / Accepted: 27 August 1997     

Evolution of enhanced reproduction in the hybrid-derived invasive, California wild radish (Raphanus sativus)

Evolution is receiving increased attention as a potentially important factor in invasions. For example, hybridization may have stimulated the evolution of invasiveness in several well-known plant pests. However, the mechanism for success of such hybrid-derived lineages remains unknown in the majority of the cases studied. Here we ask whether increased reproductive success (in terms of maternal fitness) has evolved in an invasive lineage with confirmed hybrid ancestry. We compare the relative fitness of the non-native, hybrid-derived California wild radish (Raphanus sativus) to that of its two progenitor species in field experiments at different sites and in different years. We found that California wild radish has high survivorship and produces more fruits per plant and more seeds per plant than either of its progenitors in several environments. Furthermore, populations of California wild radish display a strong genotype-by-environment interaction, indicating that maintenance of genetic and phenotypic diversity between populations may be responsible for the weed’s ability to invade a wide breadth of California habitats. Our results suggest that hybridization may contribute the evolution of enhanced invasiveness and, also, that by limiting the introduction and subsequent hybridization of congeners, we may be able to prevent the evolution of new invasive lineages.     

Bidirectional history of hybridization in California wild radish, Raphanus sativus (Brassicaceae), as revealed by chloroplast DNA

The evolutionary processes that take place in invasive plant populations are not well documented or understood. Interspecific hybridization between cultivated radish (Raphanus sativus) and R. raphanistrum is known to be responsible for the origin of the invasive California wild radish, but little is known about the nature of the hybridization events that produced the hybrid-derived lineage. We analyzed the trnL-rpl32 intergenic region of chloroplast DNA (cpDNA) obtained from 37 cultivated radish individuals from four different cultivars, 53 R. raphanistrum individuals from six European populations and 104 California wild radish individuals from 11 populations covering its entire range throughout the state. We found that cultivated radish and R. raphanistrum shared no cpDNA haplotypes but that they both shared haplotypes with California wild radish, evidence for bidirectional hybridization between the progenitor species in the creation of the California lineage. We also found evidence that multiple cultivars and multiple European source populations contributed to the diversity of cpDNA haplotypes within California. Studies like this will continue to be important for our understanding of the origin of invasive populations and the mechanisms by which they succeed.     

Effects of pollen load size and composition on pollen donor performance in wild radish, Raphanus sativus (Brassicaceae)

A critical concern in the debate over the importance of sexual selection in plants is whether the nonrandom mating demonstrable in greenhouse crosses can occur in the field. Field populations likely experience smaller and more variable pollen load sizes than those that have been used in many greenhouse experiments. Therefore, we performed a greenhouse experiment in which we varied both pollen load size and composition in wild radish, Raphanus sativus, and examined the paternity of seeds. We used five maternal plants and four pairs of pollen donors. We were able to produce pollen loads of 40, 118, and 258 grains per stigma. The smallest of the pollen loads was scant enough to result in a slight, but significant reduction in seed number per fruit. While variation in pollen load composition significantly affected the proportions of seeds fathered by different donors, variation in pollen load size did not. The relative performance of different donors was constant across pollen load sizes, suggesting that, for this species, differential performance of pollen donors can occur at pollen load sizes that are likely to occur in field populations.     

Growth of radish (Raphanus sativus) seedlings in magnetic fields

Radish seedlings were grown in asymmetric magnetic fields. The number of seeds germinated and the dry weight of the plants were the two criteria by which possible effects were examined. Two experiments were done; in the first the plants were grown for an average of 7.7 days and in the second for 14.1 days. A statistical analysis of the results failed to reveal any significant difference between control plants grown in dummy magnets and those subjected to the magnetic influence.     

Dynamics of maternal and paternal effects on embryo and seed development in wild radish (Raphanus sativus)

Background and Aims

Variability in embryo development can influence the rate of seed maturation and seed size, which may have an impact on offspring fitness. While it is expected that embryo development will be under maternal control, more controversial hypotheses suggest that the pollen donor and the embryo itself may influence development. These latter possibilities are, however, poorly studied. Characteristics of 10-d-old embryos and seeds of wild radish (Raphanus sativus) were examined to address: (a) the effects of maternal plant and pollen donor on development; (b) the effects of earlier reproductive events (pollen tube growth and fertilization) on embryos and seeds, and the influence of embryo size on mature seed mass; (c) the effect of water stress on embryos and seeds; (d) the effect of stress on correlations of embryo and seed characteristics with earlier and later reproductive events and stages; and (e) changes in maternal and paternal effects on embryo and seed characteristics during development.

Methods

Eight maternal plants (two each from four families) and four pollen donors were crossed and developing gynoecia were collected at 10 d post-pollination. Half of the maternal plants experienced water stress. Characteristics of embryos and seeds were summarized and also compared with earlier and later developmental stages.

Key Results

In addition to the expected effects of the maternal plants, all embryo characters differed among pollen donors. Paternal effects varied over time, suggesting that there are windows of opportunity for pollen donors to influence embryo development. Water-stress treatment altered embryo characteristics; embryos were smaller and less developed. In addition, correlations of embryo characteristics with earlier and later stages changed dramatically with water stress.

Conclusions

The expected maternal effects on embryo development were observed, but there was also evidence for an early paternal role. The relative effects of these controls may change over time. Thus, there may be times in development when selection on the maternal, paternal or embryo contributions to development are more and less likely.     

Effects of ethylene on tuberization in radish (Raphanus sativus)

The effects of ethylene on the elongation of radish hypocotyls and on dry matter partitioning between tubers and shoots were analysed in order to gain insight into the possible role of ethylene in the regulation of tuberization. Treatment of very young seedlings with ethylene results in heavier tubers (Vreugdenhil et al. 1984). Here we report that addition of ethylene or ethephon two days after germination inhibited the elongation of the hypocotyl; trapping of endogenously produced ethylene had a stimulative effect on elongation. Ethephon, sprayed at a later stage, changed the partitioning of assimilates between tubers and shoots, resulting in lower tuber weights. It is concluded that ethylene had a dual effect on tuberization in radish: at a very early stage of development it inhibited elongation of the hypocotyl, resulting in earlier tuber formation and heavier tubers. At a later stage, it had a negative effect on tuber weight by changing dry matter partitioning.     

QTL mapping of clubroot resistance in radish (Raphanus sativus L.)

A QTL analysis for clubroot resistance (CR) of radish was performed using an F₂ population derived from a crossing of a CR Japanese radish and a clubroot-susceptible (CS) Chinese radish. F₃ plants obtained by selfing of F₂ plants were used for the CR tests. The potted seedlings were inoculated and the symptom was evaluated 6 weeks thereafter. The mean disease indexes of the F₃ plants were used for the phenotype of the F₂. The results of two CR tests were analyzed for the presence of QTL. A linkage map was constructed using AFLP and SSR markers; it spanned 554 cM and contained 18 linkage groups. A CR locus was observed in the top region of linkage group 1 in two tests. Therefore, the present results suggest that a large part of radish CR is controlled by a single gene or closely linked genes in this radish population, although minor effects of other genomic areas cannot be ruled out. The CR locus was named Crs1. Markers linked to Crs1 showed sequence homology to the genomic region of the top of chromosome 3 of Arabidopsis, as in the case of Crr3, a CR locus in Brassica rapa. These markers should be useful for breeding CR cultivars of radish. As Japanese radishes are known to be highly resistant or immune to clubroot, these markers may also be useful in the introgression of this CR gene to Brassica crops.     

Interrelationship between chromocentres and chiasmata in radish (Raphanus sativus L.)

A comparative study of the number and distribution of chromocentres in interphase nuclei and mean chiasma frequency at diakinesis has been made in three varietal populations of radish (Raphanus sativus L.), Scarlet Globe, Japanese White and Chinese White. The study showed a significant difference between the varietal populations in mean chiasma frequency and number of chromocentres (P<0.001), indicating that these nuclear characters are genotypically controlled. The correlation analysis revealed a significant negative correlation between chromocentres and chiasma frequency (r= -0.87). It was concluded that an increase in the amount of constitutive heterochromatin, as inferred by chromocentre counts, adversely affects the chiasma frequency and, consequently, genetic recombination in radish.     

Genetic control of the wavy shoots character in radish Raphanus sativus L

The results of genetic analysis of the wavy shoots character supported the hypothesis on the existence of two genes, Wsh1 and Wsh2, whose mutations caused wavy shoots in radish lines 16 and 26, respectively. As shown by analysis of joint inheritance with marker characters, wavy shoots were inherited independently of the biochemical markers (genes Lap1, Ep, Dia1, and Aat). Gene Wsh1 was shown to be linked to genes A, ac, and ar; the mode of inheritance depended on the cross combination. In hybrids with mutant line 16, plants with novel morphological defects, which were absent in the parental forms, were detected. Possible mechanisms of new morphological abnormalities and change of linkage in the combinations analyzed are discussed.     

Adsorption of peroxidase on Celite 545 directly from ammonium sulfate fractionated white radish (Raphanus sativus) proteins

This paper demonstrates the direct immobilization of peroxidase from ammonium sulfate fractionated white radish proteins on an inorganic support, Celite 545. The adsorbed peroxidase was crosslinked by using glutaraldehyde. The activity yield for white radish peroxidase was adsorbed on Celite 545 was 70% and this activity was decreased and remained 60% of the initial activity after crosslinking by glutaraldehyde. The pH and temperature-optima for both soluble and immobilized peroxidase was at pH 5.5 and 40°C. Immobilized peroxidase retained higher stability against heat and water-miscible organic solvents. In the presence of 5.0 mM mercuric chloride, immobilized white radish peroxidase retained 41% of its initial activity while the free enzyme lost 93% activity. Soluble enzyme lost 61% of its initial activity while immobilized peroxidase retained 86% of the original activity when exposed to 0.02 mM sodium azide for 1 h. The K_m values were 0.056 and 0.07 mM for free and immobilized enzyme, respectively. Immobilized white radish peroxidase exhibited lower V_max as compared to the soluble enzyme. Immobilized peroxidase preparation showed better storage stability as compared to its soluble counterpart.     

Tests for major genes affecting quantitative traits in wild radish,Raphanus raphanistrum

The number of gene loci coding for quantitative traits is an important issue in genetics. However, there are still very few empirical data on this point, especially in natural populations. I tested for major gene effects on ten quantitative traits in wild radish, using an indirect method based on the patterns of family means and within and between family variances for traits. This method should reveal whether a single locus is responsible for most of the variation in a trait. Eight of the traits measured were morphological dimensions of leaves and flowers; no strong evidence for major gene effects on these traits was found. In contrast, evidence for major gene effects was found in the other two traits, emergence time and flowering time.     

Thiocyanate content in relation to the quality features of radish Raphanus sativus L

Relationships between radish thiocyanate content and its dry weight, the content of sugar, protein, fibre, ascorbic acid, some minerals, the incidence of plant shooting, the firmness and pithiness of storage-roots, and the ratio of leaves to storageroot (wt/wt) were investigated. The analysis of linear correlation was based on numerous data from the 4-year field experiment with six radish cultivars and different sowing and harvest dates. The content of thiocyanate in radish roots was found to be positively correlated with their dry weight, and the content of total protein, crude fibre, and soluble sugar. A strong relationship was found between the content of thiocyanate and dry weight of radish leaves. The negative correlation between the thiocyanate content in the leaves and the firmness of storageroots and the positive correlation with their pithiness might indicate the translocation of this compounds into green plant parts during the ageing of root tissue. The root thiocyanate content and the percentage of shooting correlated significantly only in the case of Tokinashi. The closeness of relations between the ratio of leaves/storage-root and thiocyanate content, though in general small, was affected also by a cultivar. A similar effect was observed for the correlations between the thiocyanate contents in leaves and storage-roots.     

青海地区萝卜黑心病病原

2018-2021年自青海西宁及其周边地区采集萝卜黑心病样品66份,采用组织分离法对样品进行分离并纯化,获得80株轮枝菌属菌株,编号为VL1-VL80。供试菌株在PDA上生长十分缓慢,培养后产生微菌核和轮枝状分生孢子梗。微菌核不规则形,53.91-164.42×8.91-29.81 μm,平均长宽比大于2。分生孢子透明且较长,5.35-9.31×2.12-4.78 μm,不产生厚垣孢子和休眠菌丝。ITS和ACT序列测定分析表明,供试菌株均属于长孢轮枝菌A1/D1株系。测定4株代表性菌株的ITS、ACT、EF、GPD、OX和TS的片段序列,分别构建ITS片段和多基因系统发育树,ITS发育树表明供试菌株与长孢轮枝菌位于同一个分支,多基因系统发育分析表明供试菌株与长孢轮枝菌A1和D1株系位于同一个分支。致病性测定结果表明,可侵染萝卜引起黑心病症状。以上研究结果表明,青海地区萝卜黑心病菌病原为长孢轮枝菌A1/D1株系,这是我国首次报道长孢轮枝菌A1/D1株系。     

Leaf damage by herbivores affects attractiveness to pollinators in wild radish, Raphanus raphanistrum

 We carried out two experiments to determine the effect of leaf damage on plant attractiveness to pollinators using wild radish, Raphanus raphanistrum (Brassicaceae), a self-incompatible annual herb. Pairs of plants from 36 full-sib families were grown in pots in the greenhouse. One member of each pair was damaged by Pieris rapae larvae that were allowed to remove half of the leaf area of each of the first four rosette leaves. The plants were subsequently taken out for pollinator observations once a week from the beginning of flowering in late June until the end of August. We conducted two experiments to examine how foliar damage affected visitation by pollinators. In the first experiment, numbers of pollinators visiting plants were compared between damaged and control sibling plants. In the second experiment, the number of open flowers during observations was controlled to be the same for both damaged and undamaged sibs. Damage significantly decreased the number and size of flowers during the first observations in late June. Damaged plants received fewer visits by native bees during the first week of observations. Since damage did not affect native bee visits when the number of open flowers was equalized between treatments, flower number was probably the main cue attracting native bees to plants. In the experiment without flower number control, syrphid flies, the other abundant pollinator taxon, spent more time per flower on the undamaged than on the damaged plants. When flower number was controlled, flies probed significantly more flowers during each visit on the undamaged than on the damaged plants and had higher visitation rates to undamaged plants early in the season. Since syrphid flies preferred undamaged plants both with and without flower number control, they apparently used cues apart from flower number for visitation. The difference between undamaged and damaged plants in floral characteristics and pollinator visitation vanished within a few weeks after the start of flowering. This result suggests that early damage may not have a strong fitness effect through reduction in mating success. However, poor weather conditions can cause early mortality of plants in the field, and nutrient depletion and competition decrease fruit set of later flowers. Therefore, conditions exist under which visitation to early flowers may affect plant fitness. Received: 30 July 1996 / Accepted: 10 February 1997