Pollination, Fertilization and Seed Development in Inbred Lines and F1 Hybrids of Spring Faba Beans (Vicia faba L.)

When the flowers are not disturbed, the yield of F₁ hybrids of faba beans normally exceeds that in their inbred parents. The basis of this “heterotic autofertility” was investigated by examining flowers for pollination and fertilization throughout the flowering season and assessing the distribution of seeds and pods on mature plants. Six inbred lines and seven of their F₁ hybrids were grown without protection from bee visitation, and their autofertility was estimated’ by comparing their fertilization with that of cytoplasmic male-sterile line. The first direct evidence was obtained that heterotic autofertility acts by increasing; the proportion of flowers which were pollinated and fertilized. The autofertility was not perfect, especially in a closed-flower hybrid, as many ovules remained unfertilized. Several factors contributed to the number of seeds per pod in F₁ hybrids, being superior to parental means: (1) more ovules per flower, (2) greater fertilization of the basal ovules, (3) reduced abortion of the apical ovules and (4) greater overall maturation ovules.     

Controls over pollination and ovule fertilization in Vicia faba

Summary Variation in the frequencies of pollination and ovule fertilization was generated among faba bean (Vicia faba L.) genotypes in experiments which compared self-and open-pollination, natural and extended photoperiods, presence and absence of honey bees and a range of plant populations.There was a near-1:1 relationship between the frequencies of pollination of stigmas and the fertilization of at least one ovule within the pistil. Pollination was the major barrier to fertilization of the pistil, and ovules, since no mechanism was evident in the style to prevent pistil fertilization. The frequency with which single ovules were fertilized in pollinated pistils fell as their distance from the stigma increased, and averaged 83.5% overall.The frequency of pollination was most influenced by the level of autofertility possessed by the genotype, and the activity of pollinators. Provision of honey bees to plants in caged plots showed that high levels of pollination could be achieved under open-pollinated conditions, but this was also influenced by autofertility. Increasing plant population in the field had only a small effect on pollination, but extending photoperiod caused the levels and timing of self-pollination in three genotypes to vary.Large differences were found among genotypes in their early stigma receptivity, that is, the frequency of stigmas found to be pollinated at the erect standard stage, prior to the flower opening and being visited by bees. The implications of early stigma receptivity for producing new cultivars were discussed.     

Pollination,fertilization and seed development in winter stocks of faba beans (Vicia faba L.)

Summary Incidences of pollination and fertilization were determined in five stocks of winter bean (two populations, two inbred lines, one cultivar) in two years. In the second year, irrigation was included as an experimental treatment and the development of seeds was monitored. Large differences between years were found in the measures of pollination and fertilization, and irrigation was associated with a small but significant increase in the proportion of ovules which were fertilized within fertilized flowers, particularly in the ovules furthest from the stigma. This increase was clearly reflected in the corresponding indices of seed maturation in the irrigated plants. Irrigation was not associated with any change in the proportion of ovules which aborted. Small but statistically significant differences in all of the measures of pollination and fertilization were found among the stocks. It is suggested that the variation in the incidences of pollination and fertilization was largely associated with variation in the synchrony of anthesis within racemes. The proportion of ovules within pods which matured as seeds and the proportion which aborted both varied significantly among the five stocks. Abortion appeared to act independently of fertilization in affecting the index of seed maturation, so both mechanisms should be considered when breeding for improved filling of pods.     

Crossability of American tree peony ‘High Noon’ as seed parent with Japanese cultivars to breed superior cultivars

The tree peony (Paeonia suffruticosa Andr.) is a valuable ornamental plant. American and French cultivars have desirable flower colors, while, Japanese cultivars have larger flowers with better presentation. We hybridized an American tree peony cultivar ‘High Noon (HN)’ (the seed parent) with 57 different Japanese cultivars (pollen parents) to investigate cross compatibility, with the ultimate goal of obtaining improved hybrids. Of the 1,927 crosses performed, 135 (38 cross combinations) yielded a total of 181 seeds (86 mature) and 22 seedlings. Five of the hybrids have already flowered and exhibited their parent character with large yellow flowers. To investigate the causes of cross incompatibility, we examined pollen tube growth in a cross between ‘HN’ and a Japanese cultivar. The result indicated that there are three most important causes of incompatibility, namely, abnormal pollen tube growth, the failure of fertilized ovules, and poor seed germination. Although cross compatibility in each combination was low, crosses between ‘HN’ and Japanese cultivars might be successful with the right paternal plants. In this study, 13 Japanese cultivars had higher cross compatibility with ‘HN’ than the others. Our results will enhance tree peony breeding and guide the selection of parents for hybridization.     

Cultivar placement affects pollination efficiency and fruit production in European pear (Pyrus communis) orchards

European pear (Pyrus communis) requires insect pollination among compatible cultivars for fruit production. However, most commercial orchards have a limited number of cultivars arranged in monotypic blocks or rows. This can result in insufficient inter-cultivar pollination. We hypothesise that limitations in pollen transfer among cultivars could be explained by both insect behaviour and orchard design. We compared insect activity and pollination efficiency in two European pear cultivars, in orchards with different designs: (i) cultivars alternated in the same row or (ii) cultivars in separate rows. To assess limitations in pollen transfer, we also compared hand pollination with compatible pollen versus open pollination by insects. Insect visitors mainly foraged on neighbouring trees within a row, with few movements across rows (1%). Honey bees (Apis mellifera) and bumble bees (Bombus terrestris) visited significantly more flowers per tree (8.5 vs. 3) and more trees (2.1 vs. 1.3) than solitary bees (Andrena spp.) and hoverflies. Insect visitors deposited large amounts of pollen (∼500 pollen grains) on flower stigmas regardless of the insect type. Cultivar placement affected inter-cultivar pollination; less incompatibility signs were observed when cultivars alternated in the same row (5%) than when cultivars were in separate rows (38%). We observed limitations in pollen transfer as open pollination resulted in significant reduced fruit set, compared with hand pollination, in ‘Conférence’ (21% vs. 30.7%) and ‘Doyenné du Comice’ (7.2% vs. 16.8%). The foraging behaviour of the insects limited thus inter-cultivar pollen transfer in the orchards with cultivars in separate rows. Cultivars used for pollination (pollinizers) should be planted in the same rows as the main cultivar to increase inter-cultivar pollination.     

Microsatellite amplification in <Emphasis Type="Italic">Brassica napus</Emphasis> cultivars: Cultivar variability and relationship to a long-term feral population

Data from 83 Brassica microsatellites showed that null alleles, monomorphic loci and the amplification of multiple bands were relatively common. The data we have gathered here are essential for avoiding time consuming and costly optimization procedures. We used the data from 43 primers to assess the relationship between 13 cultivars and one long-term feral population. The established feral population was found to be most similar to, but genetically differentiated from, the winter cultivars. Some feral plants clustered tightly with the winter cultivars, suggesting that only a small proportion of the population was generated from recently spilt seed. Since there was no similarity between the spring cultivars and the feral population, we suggest that a GM trait introduced into a spring cultivar is less likely to persist in the environment.     

Do floral resources influence pollination rates and subsequent fruit set in pear (Pyrus communis L.) and apple (Malus x domestica Borkh) cultivars?

Pear and apple are among the main fruit crops worldwide. These species can be planted in mixed orchards, and they both depend on insect pollination for fruit set. As pollinating insects are attracted by the floral resources, we investigated nectar and pollen production and chemical composition in four pear (‘Concorde’, ‘Conférence’, ‘Doyenné du Comice’, ‘Triomphe de Vienne’) and five apple (‘Braeburn’, ‘Golden Reinders’, ‘Jonagored’, ‘Pinova’, ‘Wellant’) cultivars commonly grown in Belgium. We also investigated whether insect flower visitation rate and pollination efficiency are linked to floral resource quantity and quality. The pear cultivars flowered one week before the apple cultivars in early spring, and their flowers were about six times less visited by insects. The visitors foraged more on the pollen of the pear trees and the nectar of the apple trees. Pear flowers produced higher volumes of nectar than apple flowers (1.3–3.2 μl vs. 0.4-0.6 μl), but with lower sugar concentration (9.6%-10.8% vs. 28.3%-36.4%). Pear flowers also produced fewer pollen grains per anther than apple flowers (2425–4937 vs. 3284–7919), but these had higher polypeptide (346–362 μg/mg vs. 216–303 μg/mg), amino-acid (40–77 μg/mg vs. 12–18 μg/mg) and phytosterol (21–47 μg/mg vs. 15–43 μg/mg) concentrations. The foraging behavior of the insects is thus better explained by nectar and pollen quality rather than quantity. Despite the differences in flower visitation rates, pollination of both species resulted in valuable fruit production.     

天水地区蜂群室内与室外越冬效果对比

三年室内外越冬试验结果表明,室内越冬蜂平均死亡率为8.30%,室外越蜂冬平均死亡率为14.63%。室内越冬平均饲料消耗量为3.59 kg,室外越冬平均饲料消耗量为4.77 kg,室内越冬蜂的死亡率和饲料消耗量都显著低于室外越冬蜂群。室内、室外越冬的蜂群春繁都能正常进行,且室内越冬蜂群发展较好;室内外越冬温湿度记录情况看,室内温度变化不大,蜂群能够安静结团越冬,而室外温度变化较大,蜂群在越冬期间结团、散团,蜂团不稳定,越冬蜂寿命缩短。通过试验充分说明在天水地区蜂群采用室内越冬效果优于室外越冬,室内越冬是西北越冬期漫长地区较好的越冬方法。     

Is bigger better? Apidae (Xylocopinae), megachilidae and cowpea (Vigna unguiculata) pollination

Cowpea is an important grain legume crop in Africa. Cowpea flowers are capable of self-fertilization, which might be the most frequent type of reproduction. Nevertheless, the rate of cross-pollination could vary between 1% and 10%, depending on the populations of bumblebees or domestic bees that are present, the climate and the cultivar. The aim of this study was to identify and assess the efficiency rate of the pollinators of the wild cowpea, Vigna unguiculata subsp. unguiculata var. spontanea, the progenitor of the domesticated cowpea Vigna unguiculata subsp. unguiculata. Pollination study was conducted by observing patches of flowers (average 10–20/m²) from dawn to midday, approximately 05:00–12:30 hr for three years. All insects visiting the flowers were noted and identified to species level, where possible, and their foraging behaviour was monitored. Pollen grain deposit and pod set were estimated using single bee visits on plants with strictly outcrossing flowers. Major flower visitors were large bees of the family Megachilidae and the genus Xylocopa (Apidae, Xylocopinae). Xylocopa caffra (Linnaeus) was the most abundant bee species, accounting for 59% of total bees observed and 58% of total flower visited. Pod set was higher in visits by megachilid bees compared to Xylocopa bees. Within Xylocopa, there is a good correlation between size and efficiency (r = .95, p = .0477), the larger insects being more efficient. Honeybees, small bees (Ceratina and Nomia species) and Lepidopterans also visited flowers but without any effect on pollination. Cowpea pollination system is specialized, and pollinators are restricted to Megachilidae and Xylocopa species. Variation in pollen load deposit and pod set reveals that pollination success depends on the insect species involved and their size. Megachilids are the most efficient pollinators, especially since they are able to promote outcrossing more efficiently than Xylocopa species.     

Productivity and adaptive capacity of winter wheat landraces and modern cultivars grown under low-fertility conditions

In recent decades, most winter wheat (Triticum aestivum L.) breeding in the United States has been done in field nurseries in which the soil receives ample fertilization. To determine the effects of these breeding efforts on productivity under low-fertility conditions, we evaluated twenty-nine winter wheat genotypes (seven Asian landraces; thirteen standard-height U.S. cultivars released between 1874 and 1971; and nine semidwarf cultivars released between 1977 and 1988) under severe fertility stress at three Kansas, USA locations. Experiments included fertilized and unfertilized treatments. The modern, semidwarf cultivars yielded 18% and 20% more, on average, than landraces and standard-height cultivars under low and high fertility, respectively; however, only the latter difference reached the 5% significance level. At only one location (Hays) was there a significant genotype X fertility interaction: there, 89% of the semidwarf cultivars, only 8% of the standard cultivars, and 57% of the landraces responded to fertilization. The regression coefficient of mean grain yield (unfertilized) on year of introduction or release for standard and semidwarf cultivars was zero, indicating that a century of breeding has produced no genetic improvement in performance under these low-fertility conditions. Although we found that the usual yield advantage of modern cultivars is not expressed under very low fertility, we saw no evidence that older cultivars are superior under those conditions.     

RFLP diversity within and between major groups of barley in Europe

Restriction fragment length polymorphism (RFLP) diversity has been determined and analyzed as expressed by 33 single‐ or low‐copy clone/ enzyme combinations at 32 loci distributed over all chromosomes of the barley genome within a sample of 223 European barley accessions comprised of pure line (single‐head progenies) genotypes. The accessions have been selected to include landraces and widely grown cultivars derived from crossbreeding during the 20th century in North‐, West‐ and Central European countries. Genetic diversity obtained from 83 alleles across all accessions is characterized by the diversity index H = 0.385. The diversity indices determined for landraces and cultivars were almost equal, with the difference between spring (H = 0.260) and winter (H = 0.415) barley approaching statistical significance, while comparisons of other groupings only revealed statistically insignificant trends. A more detailed analysis based on differences in allele frequency distributions at each locus (clone/enzyme combinations resp.) revealed very clear differences related to the existence, continuity and dynamics of changes in group‐specific RFLP profiles. With the majority (69%) of RFLP alleles at 23 out of 32 loci on all barley chromosomes involved, contributions from chromosomes 1H, 3H, 4H and 5H seem to be of special importance. Differences in the overall average of abundance indicate higher levels of genetic diversity within both groups of winter barley compared with both groups of spring barley, from which the most frequent alleles at 15 (2‐rowed spring barley) and 17 (6‐rowed spring barley) RFLP loci approach fixation. The results of this study are discussed in relation to the history of barley cultivation and barley breeding in Europe, and possible explanations for group‐specific differences in the RFLP profiles of landraces and cultivars as well as for the high levels of (nearly) fixed alleles of both subsets of spring barley, and with respect to progress in barley breeding that it has been possible to obtain within the rather narrow RFLP profiles.     

Inheritance of resistance to wheat midge, Sitodiplosis mosellana, in spring wheat

Inheritance of resistance to a wheat midge, Sitodiplosis mosellana (Géhin), was investigated in spring wheats derived from nine resistant winter wheat cultivars. F₁ hybrids were obtained from crosses between resistant winter wheats and susceptible spring wheats, and used to generate doubled haploid populations. These populations segregated in a ratio of 1:1 resistant to susceptible, indicating that a single gene confers the resistance. The F₂ progeny from an intercross among spring wheats derived from the nine resistance sources did not segregate for resistance. Therefore, the same gene confers resistance in all nine sources of resistance, although other genes probably affect expression because the level of resistance varied among lines. Heterozygous plants from five crosses between diverse susceptible and resistant spring wheat parents all showed intermediate levels of response, indicating that resistance is partly dominant. Susceptible plants were reliably discriminated from heterozygous or homozygous resistant ones in laboratory tests, based on the survival and development of wheat midge larvae on one or two spikes. This powerful resistance gene, designated Sm1, is simply inherited and can be incorporated readily into breeding programmes for spring or winter wheat. However, the use of this gene by itself may lead to the evolution of a virulent population, once a resistant cultivar is widely grown.     

农户保护蜜蜂资源和租用蜜蜂授粉的行为研究——基于山东和福建的实证分析

笔者着眼于中国实际,提出要提高蜜蜂授粉在中国农业生产中的作用需要同时注重蜜蜂资源的保护和推动蜜蜂授粉服务的市场化。通过实证分析发现,农户对保护蜜蜂的意愿较高,租用蜜蜂授粉的意愿较低,66.83%的农户愿为保护蜜蜂资源支付一定的费用,44.56%的打算在农业生产中租用蜜蜂授粉。“当地是否有开展蜜蜂授粉推广或蜜蜂资源保护项目”显著影响农户保护蜜蜂资源和租用蜜蜂授粉的意愿,相比而言,有蜜蜂保护工程地区农户蜜蜂资源保护支付意愿要比没有的农户增加19.05%,租用蜜蜂授粉的意愿要增加32.04%;蜜蜂资源的可获得性对促进农户租用蜜蜂授粉也具有正向作用,所在村有养蜂户的农户租用蜜蜂授粉的意愿要比没有的增加21.94%。此外,农户对蜜蜂及蜜蜂授粉的认知也对农户保护蜜蜂资源和租用蜜蜂授粉的意愿有正向作用。因此,应大力宣传蜜蜂授粉在农业生产中的作用,积极推动地方政府开展蜜蜂授粉推广或蜜蜂资源保护项目,同时大力扶持养蜂业发展,提高养蜂在农村的普及率。     

Genotypic differences in callus formation and regeneration of somatic embryos in Cyclamen persicum Mill

This study was performed in order to check the applicability of a protocol for somatic embryogenesis in Cyclamen persicum and to compare the in vitro response of cultivars belonging to different cyclamen growth types and flower colours obtained from two breeders. One hundred ovules per plant were prepared from 32 tested F₁ hybrid cultivars represented by five plants each. Callus induction monitored after 8 weeks varied between 42 and 85%. Variation occurred between replications and single plants of a cultivar. Consistency and colour of the developing calluses were diverse. Only in 1 cultivar out of the 32 tested no regeneration of somatic embryos was obtained. The regeneration rates varied from 0 to 65% among cultivars. In the group of midi-type cultivars the regeneration response was lower than that in mini and giganteum types. High regeneration rates were observed in cultivars with flamed flowers.     

Impact of heat stress on pod-based yield components in field pea (Pisum sativum L.)

Elevated temperatures associated with climate change result in crops being exposed to frequent spells of heat stress. Heat stress results in reduced yield in field pea (Pisum sativum L.); it is therefore important to identify cultivars with improved pod and seed retention under heat to mitigate this loss. Objectives were to investigate the effect of heat stress on phenology, yield and pod-based yield components. Sixteen pea cultivars were evaluated at normal and late (hot) seeding dates in the field in Arizona 2012 and in growth chambers with two temperature regimes (24/18°C and 35/18°C day/night temperature for 7 days) during reproductive development. We measured variation in the pattern of pod retention at four-node positions on plants, seed retention by ovule position (stylar, medial and basal) within pods and screened cultivars for pod retention, seed retention and yield. Heat stress reduced seed yield by accelerating the crop lifecycle and reducing pod number and seed size. Heat stress had the most damaging effect on younger reproductive growth (flowers and pods developed later), resulting in ovary abortion from developing flowers. Heat also accelerated seed abortion in all ovule positions within pods. Two high-yielding cultivars under control temperature, “Naparnyk” and “CDC Meadow”, maintained high yield in heat, and “MFR043” had the lowest yield. Cultivars “40-10” and “Naparnyk” retained the most ovules and seeds per pod, and “MFR043” aborted seeds when exposed to heat. In half of the cultivars, ovules at the basal peduncle end of pods were likely to abort while ovules at the medial and stylar end positions developed into seeds. For seven of the field cultivars, ovules at the medial pod position also produced mature seeds. Cultivars “40-10”, “Naparnyk” and “CDC Meadow” had greater pod and ovule retention or maintained high yield under heat stress, and were identified as heat-tolerant cultivars. Our results allow for a better understanding of pod-based yield components in field pea under heat stress and developing heat-tolerant cultivars.     

Extent, variation and breeding impact of natural cross-fertilization in German winter faba beans using hilum colour as marker

Faba bean is a partially allogamous grain legume, mostly sown as spring crop in Central Europe, and in few mild coastal areas of UK and France as a winter crop. A population with a genetically wide base, conceived and selected for superior winter hardiness showing promise as winter crop in Germany was evaluated. The reproductive behaviour of this population was evaluated for its degree of cross-fertilization at five German environments (1999–2001), and inbred lines bred from it, plus one F1 bulk and further checks, were assessed for variation in cross-fertilization at three German environments (2001). Seed hilum colour, a dominant-recessive, biallelic locus, was used as a morphological marker. Cross-fertilization (population mean value of 60%) was shown to be higher than in spring faba beans and was environmentally influenced. Genetic variation was demonstrated, heritability was high (h²= 0.75), and heterosis was negative. Inbred lines with a cross-fertilization of 70% can be easily bred. Breeding synthetic cultivars is recommended, their optimum number of components is expected to be higher than the optimum recommended for spring faba beans. This revised version was published online in July 2006 with corrections to the Cover Date.     

拉萨河谷地区粮食作物施氮效应灰色关联度评价

为了给西藏拉萨河谷地区粮食作物氮肥利用效率及生产力水平的提高提供理论支持,利用灰色关联度分析法,对不同施氮水平条件下春青稞和冬小麦农艺性状与产量性状的关联度以及施氮水平与理想施氮量的关联度进行了研究。不同施氮水平条件下,春青稞农艺性状与产量的关联度按大小排序为株高>穗粒数>穗数>穗长>千粒重>生育期>小穗数>退化小穗数;冬小麦农艺性状与产量的关联度按大小排序则为穗数>穗粒数>小穗数>株高>千粒重>穗长>生育期>退化小穗数。西藏高原地区春青稞与冬小麦的最佳施氮水平分布范围一致,都应控制在150~225 kg/hm2;培育大穗与较高秆(抗倒)品种、提高单穗小穗数与穗粒数可能应成为春青稞育种与栽培管理工作的主攻方向;而培育大穗品种、提高单位面积成穗数、单穗穗粒数与小穗数则应成为冬小麦生产的主攻目标。     

Genes for resistance to powdery mildew in European barley cultivars registered in the Czech Republic from 2011 to 2015

Barley (Hordeum vulgare) is cultivated on 49.1 million hectares worldwide with 50.2% of the area located in Europe. Powdery mildew, caused by Blumeria graminis f. sp. hordei (Bgh), occurs wherever barley is grown. Cultivar resistance plays an important role in global barley production, especially in parts of Europe where high concentrations of both spring and winter types are grown. The aim of this report was to postulate specific resistance genes in barleys from nine European countries registered in the Czech Republic from 2011 to 2015. Thirty‐five spring cultivars and 27 winter barleys were tested with 56 diverse Bgh isolates. Twenty‐five known resistance genes were postulated, and unknown genes were detected in Sandra, Saturn and Zeppelin. Unidentified specific resistance genes were also present in winter hybrids Hobbit and Wootan. Spring cultivars Arthur and Francin consisted of three and two genotypes, respectively. Resistance gene mlo was present in 26 spring cultivars, and the proportion of cultivars with this gene increased from 62.9% in 2006–2010 to 75.7% in 2011–2015. The gene Mlp1 was identified for the first time in German winter cultivar Saturn. Five spring cultivars registered in Slovakia were included in the tests. All the cultivars that were tested contained one or more specific resistance genes to powdery mildew. Adaptability of the pathogen and possibilities for breeding winter barleys are discussed.     

Race-Specific Resistance Genes Against Erysiphe graminis f. sp. hordei in Old and Recent French Barley Accessions

Leaf segments from seedlings of 68 old barley varieties and 38 more recent cultivars of past or current importance in France were infected with 6—9 powdery mildew isolates in order to identify race-specific resistance genes. No resistance gene was apparent in the 21 old winter varieties, 43 of 47 old spring varieties, 10 recent winter and 3 recent spring cultivars. Two old spring varieties (‘Colmar S 142’ and ‘Johanna’) were postulated to have Mlg and Ml(CP), and two others (‘Pontrieux’ and ‘Finistère 62-5’) had an unidentified, weakly effective gene. Mlg, Ml(CP), Mlb, Mla6 and Mlal3 were the only genes detected in recent winter cultivars. Recent spring cultivars presented the greatest diversity; the presence of one or several genes among Mlal, Mla6, Mla9, Mla12, Mlg, Ml(CP), Ml(La), Mlk and mlo was postulated in several lines.     

Genetics of Six Components of Autofertility in Vicia faba

The inheritance of six components of autofertility was studied in faba beans in two consecutive years (1989 and 1990) by analysing parents, Fl and segregating generations of 14 crosses between preselected pure lines. Genetic analysis was performed by a joint scaling test proposed by Cavalli (1952). Additive gene effects were more important than dominance effects in flowers/node, pods/flower and ovules/ovary. In contrast, characters directly related with the seed such as pods/node, seeds/pod and, to a lesser extent, seeds/ovule showed high positive values of dominance. The three latter traits in general exhibited strong heterosis, probably due to genetic interactions. In order to produce selection gain, any breeding programme has to consider that dominance and heterosis vary according to the character involved. The present study reveals different degrees of dominance expression depending on cross specificity as well as on environmental conditions. The advantages of studying segregating generations instead of diallel crosses and the need for a simultaneous study of many crosses are emphasized in this paper.