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.     

Identification of self-incompatibility alleles in pear cultivars (Pyrus communis L.)

Self and cross-incompatibility determination by means of fruit and seed set experiments or pollen tube growth observations in the style has been frequently reported to be unclear in pear (Pyrus communis L.). Thus,in order to develop a reliable in vivo method to test pollen-pistil incompatibility in pear, pollen tube performance has been studied along the pistil following self and cross-pollinations. Results show that, while pollen tube growth in the style may be an unclear test, ovule observation at the microscope for the presence of pollen tube in the nucellus is a proper method to test incompatibility in this crop. With this analysis we could identify S-alleles of ‘Williams’ (S₁S₂) and ‘Coscia’(S₃S₄), and three of the four possible S-genotypes resulting from the ‘Williams’ × ‘Coscia’ cross, as represented by ‘Butirra Precoz Morettini’ (S₁S₃), ‘Santa Maria Morettini’ (S₂S₃)and ‘Tosca’ (S₁S₄). This result demonstrates that ‘Williams’ and ‘Coscia’ cultivars do not share any allele in common. We also established two new inter-incompatibility groups in pear. Furthermore, the presence of a common allele between ‘Williams’ and ‘Agua de Aranjuez’,and ‘Coscia’ and ‘Agua de Aranjuez’, three apparently unrelated old cultivars, may indicate a narrower genetic base than expected for European pear. This finding together with the fact that 40% of new released cultivars have direct or indirect parental relationship with the cultivars ‘Coscia’ and/or ‘Williams’, anticipates the possibility of new cases of cross-incompatibility for this crop in the future. Both the method described and the determination of the S-genotypes will facilitate the characterisation of self and cross-incompatibility relationships in this species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of QTLs controlling harvest time and fruit skin color in Japanese pear (Pyrus pyrifolia Nakai)

Using an F₁ population from a cross between Japanese pear (Pyrus pyrifolia Nakai) cultivars ‘Akiakari’ and ‘Taihaku’, we performed quantitative trait locus (QTL) analysis of seven fruit traits (harvest time, fruit skin color, flesh firmness, fruit weight, acid content, total soluble solids content, and preharvest fruit drop). The constructed simple sequence repeat-based genetic linkage map of ‘Akiakari’ consisted of 208 loci and spanned 799 cM; that of ‘Taihaku’ consisted of 275 loci and spanned 1039 cM. Out of significant QTLs, two QTLs for harvest time, one for fruit skin color, and one for flesh firmness were stably detected in two successive years. The QTLs for harvest time were located at the bottom of linkage group (LG) Tai3 (nearest marker: BGA35) and at the top of LG Tai15 (nearest markers: PPACS2 and MEST050), in good accordance with results of genome-wide association study. The PPACS2 gene, a member of the ACC synthase gene family, may control harvest time, preharvest fruit drop, and fruit storage potential. One major QTL associated with fruit skin color was identified at the top of LG 8. QTLs identified in this study would be useful for marker-assisted selection in Japanese pear breeding programs.     

α-Farnesene and antioxidative enzyme systems in Asian pear (Pyrus serotina Rehd.) fruit

The effects of 1-methylcyclopropene (1-MCP) on ripening, superficial scald and concentrations of α-farnesene, conjugated trienols (CTols) and antioxidant enzyme activity of ‘KS₆’ Asian pear (Pyrus serotina Rehd.) were studied. 1-MCP treated (2 μL L^?1) or untreated control fruit were stored at 1 °C and 90–95% RH for up to 120 days. 1-MCP treated fruit were firmer than untreated fruit. Application of 1-MCP delayed skin color change. Scald appeared after shorter storage duration and was reduced, but not entirely controlled, with 1-MCP. Accumulation of α-farnesene and oxidation were slower in skin of 1-MCP treated fruit compared with controls. Catalase and peroxidase activities in untreated fruit either increased while activities decreased in 1-MCP treated fruit. Superoxide dismutase activity remained stable. The treatment of Asian pears with 1-MCP followed by cold storage maintained textural characteristics with less scald incidence.     

The inheritance of the red colour character in European pear (Pyrus communis) and its map position in the mutated cultivar ‘Max Red Bartlett’

The inheritance of the red colour character in European pear (Pyrus communis L.) was studied over 3 years in seven progeny obtained by using the cultivars ‘Max Red Bartlett’, ‘Cascade’ and ‘California’ as red‐skinned fruit parental lines. One of these progeny (derived from the cross ‘Abbé Fétel’ × ‘Max Red Bartlett’, a red mutation of ‘Bartlett’) was already used to construct two linkage maps and, being ‘red colour’ a monogenic dominant trait, it was possible to locate it as morphological marker in the linkage group 4 of ‘Max Red Bartlett’. For the first time, this trait has been mapped out of linkage group 9 in a species belonging to the Maloideae subfamily moreover in a mutated sport. An improved knowledge of the genetic basis of production and accumulation of red pigments in the fruit skin will better support the pear breeding programmes aimed to select new cultivars carrying this appealing trait.     

Identification of QTLs associated with spring vegetative budbreak time after dormancy release in pear (Pyrus communis L.)

Dormancy release is greatly affected by chilling unit (CU) accumulation. Lack of CU has a major impact on spring vegetative budbreak (VB). To understand the genetic mechanism governing the chilling requirement (CR), we conducted a QTL analysis of VB date in F₁ population, derived from a cross between ‘Spadona’ (low CR) and ‘Harrow Sweet’ (high CR). Using a unique methodology of tree mobility, replicates of the same genotypes were exposed during the winter, over two consecutive years, to climates that differ greatly in their CU and to the same heat conditions to induce VB, in order to evaluate CR genetic impact and to distinguish it from the heat factor. Broad‐sense heritability within locations ranged from 0.62 to 0.66. Due to a strong impact of GxE interaction, it was reduced to 0.46 for the overall mean. We examined the previously discovered apple QTLs detected in linkage groups (LG) 9 and 8, based on the synteny between the species. Our analysis confirms significant QTLs in LG8 (R² = 12%–24%) and LG9 (R² = 20%–38%) for all locations and years     

Pithy brown core in ‘d’Anjou’ pear (Pyrus communis L.) fruit developing during controlled atmosphere storage at pO2 determined by monitoring chlorophyll fluorescence

Physiological responses and fruit quality of ‘d’Anjou’ pear fruit from five orchard lots were evaluated after cold storage in air or controlled atmospheres (CA) with the O₂ concentration based on assessment of fruit chlorophyll fluorescence (CF) or standard conditions (1.5 kPa O₂). The pCO₂ for all CA fruit was 0.5 kPa. Softening, acid loss, and peel degreening of all lots were delayed at one or more evaluation dates (2, 4, 6, 8 months) by previous storage at the CF pO₂ compared with fruit stored in 1.5 kPa O₂ or in air. Superficial scald developed on fruit previously stored in air but not on fruit stored in a CA. Pithy brown core developed on fruit from all lots stored at the CF pO₂ and on fruit stored at 1.5 kPa in 3 of the 5 lots. Pithy brown core incidence decreased with advanced harvest maturity. Post-storage ethylene and CO₂ production were in most instances lowest for fruit stored at the CF pO₂. A significant relationship between fruit ethanol content and pithy brown core incidence was observed. Results indicate low pO₂ storage based on CF monitoring slows fruit ripening relative to fruit stored at 1.5 kPa O₂, prevents superficial scald development compared with fruit stored in air, however, development of pithy brown core in fruit stored at the CF pO₂ was not accompanied by a change in CF.     

Fine mapping of the gene for susceptibility to black spot disease in Japanese pear (Pyrus pyrifolia Nakai)

Black spot disease, which is caused by the Japanese pear pathotype of the filamentous fungus Alternaria alternata (Fries) Keissler, is one of the most harmful diseases in Japanese pear cultivation. We mapped a gene for susceptibility to black spot disease in the Japanese pear (Pyrus pyrifolia Nakai) cultivar ‘Kinchaku’ (Aki gene) at the top of linkage group 11, similar to the positions of the susceptibility genes Ani in ‘Osa Nijisseiki’ and Ana in ‘Nansui’. Using synteny-based marker enrichment, we developed novel apple SSR markers in the target region. We constructed a fine map of linkage group 11 of ‘Kinchaku’ and localized the Aki locus within a 1.5-cM genome region between SSR markers Mdo.chr11.28 and Mdo.chr11.34. Marker Mdo.chr11.30 co-segregated with Aki in all 621 F₁ plantlets of a ‘Housui’ × ‘Kinchaku’ cross. The physical size of the Aki region, which includes three markers (Mdo.chr11.28, Mdo.chr11.30, and Mdo.chr11.34), was estimated to be 250 Kb in the ‘Golden Delicious’ apple genome and 107 Kb in the ‘Dangshansuli’ Chinese pear genome. Our results will help to identify the candidate gene for susceptibility to black spot disease in Japanese pear.     

Floral morphology affects seed productivity through pollination efficiency in radish (<Emphasis Type="Italic">Raphanus sativus</Emphasis> L.)

To examine the effect of stigma position and size on seed productivity through pollination efficiency in radish, the numbers of self and cross pollen grains on the stigmas and the seed productivity under insect-pollination were compared among four bred lines. Lines with a small stigma or a high stigma relative to the anthers on long stamens tended to receive fewer self and total (self + cross) pollen grains but showed a higher cross-pollination percentage (ratio of cross pollen grains to total pollen grains on stigmas) than those with a large stigma or a lower stigma. Additionally, a higher cross-pollination percentage was associated with a higher outcrossing percentage. This result suggests that variations in the two stigma traits affect the outcrossing percentage via the cross-pollination percentage. Therefore, it should be possible to prevent loss of F₁ purity by selecting new parental lines with floral morphology that favors cross-pollination percentage.     

新型COS标记技术及其在梨属植物分子系统关系研究中的应用前景

摘要：植物系统关系的研究以DNA序列比较分析应用最为广泛;目前,DNA序列分析的发展趋势由常用DNA片段（cpDNA, nrDNA）向低拷贝核基因（Low-copy nuclear gene, LCNG）分析发展,COS（Conserved Ortholog Set）标记就属于这一类低拷贝核基因,本文对新型COS标记的特点、COS标记的开发和应用进行综述,同时探讨其在梨属植物系统关系研究中的应用前景,从而为解决梨属植物的系统演化问题提供一种新的手段.     

Water availability affects nectar sugar production and insect visitation of the cup plant Silphium perfoliatum L. (Asteraceae)

The perennial cup plant (Silphium perfoliatum L.) is considered as an alternative feedstock to maize for biogas plants. Due to its ecological advantages of an extensive management and function as food resource for pollinators, it can be grown in Ecological Focus Areas (EFAs) since 2018. However, studies at the Julius Kühn-Institute in Braunschweig (Germany) showed that the assumed advantage of the cup plant of a high drought tolerance could not be confirmed regarding aspects of crop production and yield. We complemented this experiment by assessing how different soil moisture conditions affect the production of floral resources and insect visitation. In 2014, we sampled three irrigated and three rainfed plots of the cup plant. We quantified the nectar volume and sugar mass per inflorescence, the number of inflorescences per plant and calculated the total nectar sugar production. We further counted insect visitation on the inflorescences. Due to reduced numbers of inflorescences per plant and an earlier harvest, the estimated nectar sugar production was 58 kg/ha regarding irrigated and 20 kg/ha regarding rainfed plots. Honeybee visitation per inflorescence was about twice as high in the irrigated plots. Furthermore, the early harvest is a disadvantage for wild pollinators with a late activity period.     

红将军苹果的脱毒与检测技术研究

以中熟红富士品种红将军的继代培养4～5代试管苗为试材,进行脱毒处理,并利用ELISA和RT-PCR技术检测脱毒效果.结果表明:红将军苹果试管苗在38℃高温条件下恒定热处理20 d,再二次茎尖培养后,试管苗脱毒率达86.4%～100%,可以有效脱除ASSVd、ASGV、ASPV、ApMV和ACLSV等主要的苹果病毒.     

Postharvest pigmentation in red Chinese sand pears (Pyrus pyrifolia Nakai) in response to optimum light and temperature

The development of red color in the peel of red Chinese sand pears (Pyrus pyrifolia Nakai) is influenced by temperature and light; however, the response patterns vary among different cultivars. In this study, we systematically investigated the influence of postharvest treatment with various temperatures (low, high, variant and constant) on detached mature fruit of red Chinese sand pear ‘Mantianhong’ and ‘Meirensu’. Fruit of red apple (Malus domestica Borkh.) ‘Royal Gala’ and red European pear (P. communis L.) ‘Cascade’ received the same treatments for comparison. Furthermore, the effects of light quality and irradiance level on ‘Mantianhong’ pears were evaluated at the optimum temperature for anthocyanin accumulation. Fruit firmness and concentrations of total soluble sugars and organic acids were measured to determine fruit quality. The effect of temperature on red Chinese sand pear fruit color was similar to that of apples, but not European pear. Moreover, low temperature more effectively induced red coloration in ‘Mantianhong’ and ‘Meirensu’ pears than high temperature; anthocyanin levels increased with increasing irradiance level from 0 to 532 μmol m⁻² s⁻¹, and UV-B and visible light synergistically improved the red color of the fruit. Therefore, a combination of low temperature and high intensity of UV-B/visible light could improve the postharvest coloration of red sand pear fruit. The results will contribute to an improved understanding of the mechanism responsible for the coloration of red Chinese sand pears and will aid development of new techniques to improve color in postharvest fruit.     

西洋梨品种间糖酸及风味物质含量差异性比较

以4个西洋梨品种为材料,通过测定果实糖酸含量和芳香成分,并计算其风味指数,研究、比较了西洋梨品种间糖酸含量、风味指数及香味成分差异。结果表明：各个西洋梨品种间糖、酸组分及含量差异较大;在其他因素一致的条件下,风味指数考虑了各个糖组分对果实风味的贡献,更能体现各个品种间果实风味的差异。4个品种中均检测到乙酸乙酯、乙酸丁酯、乙酸己酯、乙酸辛酯、丙酸乙酯、丁酸乙酯及(2E,4Z)-癸二烯酸乙酯等7种特征香味成分,但各个品种间芳香成分含量存在较大差异,而酯类芳香成分相对含量较其他特性芳香成分的相对含量较高。本研究中,从风味指数（味感物质）角度考虑,‘早红考密斯’风味最佳,‘巴梨’和‘康佛伦斯’次之,‘三季梨’风味较淡。从香味成分（嗅感物质）角度考虑,‘康佛伦斯’香味最浓,而‘早红考密斯’香味较淡。     

野生稻和非洲栽培稻抗稗草种质资源筛选和评价

以盆栽试验对20份野生稻和５份非洲栽培稻材料的稗草出苗率、距离稻株不同范围播种的稗草株高和干重的抑制效果进行评价,并通过聚类分析和方差分析,将其划分为6类。再以稻叶水提液培养稗草,依其发芽抑制率、芽长抑制率、根长抑制率和发芽指数,再次聚类并划分为5类。盆栽和浸提液试验中效果均好的3份野生稻S37、S68、S72和