Phenological stages of the quince tree (Cydonia oblonga)

As in other temperate species, the quince tree (Cydonia oblonga) shows different phenological stages throughout its vegetative growth period in response to changing temperatures. Two cultivars were studied, and 15 phenological stages were identified during their annual cycle, starting at bud dormancy and ending at leaf fall a year later. The different phenological stages were classified according to the BBCH General Scale and Fleckinger's code. The length of all the stages was measured in days and as cumulative day degrees. This study of the quince tree might aid to prevent and deal with any potential physiological and pathological disorders.     

Plantlet regeneration from cultured leaves of Cydonia oblonga L. (quince)

Summary Adventitious shoots of Cydonia oblonga Quince A were obtained from leaves cultured on MS-N6 medium containing thidiazuron (TDZ) and -naphthaleneacetic acid (NAA). The frequency of regeneration was high (78% of the cultured leaves with 3.2 shoots per regenerating leaf) at 32 M TDZ plus 0.3 M NAA on young leaves obtained from micropropagated shoots. Shoots were rooted by culturing them first on medium containing 5 M NAA for one week and then on auxinfree medium for four weeks. The regeneration protocol may be useful for selection of somaclonal variants with increased tolerance to low Fe and for transformation mediated by Agrobacterium.     

Factors effecting adventitious shoot regeneration from leaf explants of quince (Cydonia oblonga)

A procedure for adventitious shoot regeneration from leaf explants of quince (Cydonia oblonga Mill.) using thidiazuron (TDZ) was developed. Excised leaves of cultures grown on Murashige and Skoog (MS) medium containing 5 M benzyladenine (BA) and 0.9% Gibco Phytagar were used. Several experiments were conducted to determine optimum concentrations of thidiazuron, -naphthaleneacetic acid (NAA) and sucrose. When the medium contained 1.5 M TDZ and 2.5 M NAA, 85% of the discs regenerated shoots with an average of eight shoots per leaf disc. An incubation period of three weeks in the dark was necessary for optimum shoot regeneration. Leaves excised from four to six-week-old cultures gave a higher percent shoot regeneration than leaves from cultures older than six weeks. Regeneration percentages were significantly reduced when sucrose concentration in the medium was less than 3%. A significantly higher percentage of shoots regenerated when leaf discs were placed on the regeneration medium abaxial side down as compared to the adaxial side.Regenerated shoots were cultured on MS medium containing 5 M BA and rooted on half-strength MS medium containing 10 M NAA. Rooted plantlets were acclimatized to greenhouse conditions for evaluation of any somaclonal variation. The importance of these findings are discussed in relation to in vitro improvement of plants.Abbreviations BA benzyladenine - MS Murashige & Skoog (1962) salt mixture - NAA -naphthaleneacetic acid - TDZ thidiazuron (N-phenyl-N'-1,2,3,-thiadiazol-5-ylurea) Approved for publication by the Director, West Virginia Agric. and For. Expt. Sta. as Scientific Article No.2346     

Synthesis of the glycosidic precursor of isomeric marmelo lactones,volatile components of the quince fruit,Cydonia oblonga

The glucosidic precursor of marmelo lactones was synthesized by employing a common intermediate which had been used for the synthesis of the glucosidic precursor of marmelo oxides. The synthesis was performed by modifying the former procedure. Monochloroacetyl was adopted to protect both the glucose and aglycon hydroxyl groups for selective transesterification in the presence of the glycosyl ester. Glycosylation of the aglycon carboxyl group with 1-alpha-bromopermonochloroacetylglucose and final selective alcoholysis yielded the target glucoside.     

Changes in the volatile profile of four cultivars of quince (Cydonia oblonga) produced by codling moth (Cydia pomonella) infestation

The production of quince (Cydonia oblonga Miller) is affected worldwide by codling moth (Cydia pomonella L.), an oligophagous pest. In this study, volatile compounds in healthy and infested fruits were collected from four cultivars of quince: Champion, Portugal, Smyrna and INTA 147. Volatiles were extracted by SPME and analyzed by GC-MS. Up to 30 compounds were identified in the volatile profiles of uninfested quinces, ranging from 90.9% to 98.4% of the total relative abundance. The volatile profile of all four cultivars of quince was similar, with (E,E)-α-farnesene and octanoic acid- ethyl ester as the main components. Infested fruits presented increased levels of (E,E)-α-farnesene, while minor compounds decreased significantly. Champion and Smyrna varieties might be more susceptible cultivars to infestation as their healthy fruits presented the highest contents of (E,E)-α-farnesene and Pear Ester, both codling moth kairomones. The role of these highly recognized kairomones in the chemical ecology of codling moth in quince is discussed.     

Influence of frost damage on the sugars and sugar alcohol composition in quince (Cydonia oblonga Mill.) floral nectar

Cold stress adversely affects growth and productivity, and triggers a series of morphological, physiological, biochemical and molecular changes in plants. Since sugars are present in all floral nectars in greater amounts than any other constituent, the aim of this study was to examine how frost exposure changes sugar metabolism and how it affects on the content of sugar components in the nectar of quince. Three quince cultivars (‘Vranjska’, ‘Triumph’ and ‘Leskova?ka’) were investigated in this study. The contents of sugars (glucose, fructose, sucrose, trehalose, maltose, isomaltose, rhamnose, arabinose, ribose, melezitose, raffinose, and panose) and sugar alcohols (sorbitol, erythritol, mannitol and galactitol) were analyzed by high performance anion exchange chromatography (HPAEC) with amperometric detection. The results showed that after late spring frosts and irreversible damage of flower parts, the nectar of the three quince cultivars contained elevated levels of fructose, trehalose, arabinose, ribose, rhamnose, raffinose, galactitol and mannitol, indicating an impairment of central carbohydrate metabolism. The ratios between individual sugars, such as the glucose/fructose ratio, were changed in the nectar of damaged flowers in all three quince cultivars. The examined cultivars showed similar sugar response to cold stress. The only exception was ‘Leskova?ka’ for the glucose and melezitose pathway, which means that composition of those two sugars changed significantly according to the genotype. The larger are the carbohydrates reserves in different parts of a fruit tree, the higher is the tolerance to any form of frost damage, the results of this study could help in the understanding of how different quince cultivars react to this kind of stress and how they modulate their sugar metabolism.     

Relationship between calcium and agar on vitrification and shoot-tip necrosis of quince (Cydonia oblonga Mill.) shoots in vitro

Shoot-tip cultures of Quince C (Cydonia oblonga Mill.) initiated on Murashige & Skoog (MS) medium containing 5 M BA and 0.6% Phytagar showed both shoot-tip necrosis and severe vitrification. Culturing explants on medium containing 1.2% Phytagar and Ca levels of 3 mM (MS medium), 18 mM and 30 mM showed a decrease in growth with increasing medium Ca levels, being especially severe at 30 mM. The Ca content of the explants increased linearly with increasing medium Ca. Culturing explants on medium containing 3 mM, 9 mM, and 18 mM Ca at 0.6, 0.9, and 1.2% agar resulted in reduction in growth, shoot-tip necrosis, and vitrification when either factor was increased. The reduction in shoot-tip necrosis could be accounted for primarily by an increase in medium Ca levels but may also be affected by a change in explant growth. Increasing Ca concentration in the medium resulted in a linear increase in explant K, Ca, Mg, and B levels and a decrease in Mn and Na. Although increasing medium Ca or agar levels reduced vitrification, it is unclear whether they were the direct cause of the reduction in vitrification or whether this response was an effect of the reduction in culture fresh weight.Approved by publication by the Director, West Virginia Agriculture anf Forestry Experimental Station as Scientific Article No. 2199     

Regression association analysis of fruit traits with molecular markers in cherries

The use of molecular markers supports the study of genetic marker–trait association of biological and agronomic interest in diverse genetic material. In this research, association between simple sequence repeat (SSR) and random amplified polymorphic DNA (RAPD) markers with fruit traits were investigated in two collections of cherries by applying multiple regression analysis (MRA). Thirty-eight SSR alleles and 135 RAPD fragments were found associated with 14 of affecting fruit traits. Some of SSR and RAPD markers were associated with more than one fruit trait in MRA. Such an association may arise due to pleiotropic effect of the linked quantitative trait locus on different traits. For example, some SSR and RAPD markers were associated with all four traits including fruit cracking, fruit firmness, total soluble solid (TSS) and fruit shape. Also, some markers had correlations with all four characters of TSS, anthocyanin, fruit skin color and fruit flesh color, indicating a significant correlation among these traits. Therefore, it is possible to use these markers along with morphological traits in cherry breeding programs for identification of suitable parents to produce mapping populations and hybrid cultivars. Also, these results could be useful in marker-assisted breeding programs when no other genetic information is available.     

Genetic diversity revealed by morphological traits and ISSR markers in 48 Okras (Abelmoschus escullentus L.)

Physiology and Molecular Biology of Plants - Okra is a widely distributed crop in the tropics, subtropics, and warmer areas of the temperate zones. Its major potential uses as a vegetable, oil and...     

Approach to the study of C-glycosyl flavones by ion trap HPLC-PAD-ESI/MS/MS: application to seeds of quince (Cydonia oblonga)

Ion trap HPLC-PAD-ESI/MS/MS has been used to study C-glycosyl flavones in quince seeds. Comparative analysis of the ions [(M-H)-60]-, [(M-H)-90]- and [(M-H)-120]- from 6-C- and 8-C-glycosyl flavone isomers, together with their respective retention times, allowed deductions to be made about the nature of the sugar units and the positions of C-glycosylation. Vicenin-2 (6,8-di-C-glucosyl apigenin), lucenin-2 (6,8-di-C-glucosyl luteolin), stellarin-2 (6,8-di-C-glucosyl chrysoeriol), isoschaftoside (6-C-arabinosyl-8-C-glucosyl apigenin), schaftoside (6-C-glucosyl-8-C-arabinosyl apigenin), 6-C-pentosyl-8-C-glucosyl chrysoeriol and 6-C-glucosyl-8-C-pentosyl chrysoeriol were identified in quince seed.     

Genetic diversity in wild species of passion fruit (Passiflora trintae) based on molecular markers

In spite of the importance of and the considerable variability observed in Passiflora (Passifloraceae), little is known about the genetic diversity of most of the species of this genus. We evaluated the genetic diversity by RAPD markers in 18 genotypes of Passiflora trintae. The 15 primers generated 112 markers, 84% of which were polymorphic. The genetic distance estimated by the complement of the Dice index (average dissimilarity = 0.30) and genotype grouping based on the UPGMA algorithm showed low variability among genotypes. More attention should be given to the study and conservation of the biodiversity of this economically important genus.     

Identification of ISSR markers associated with productivity traits in silkworm, Bombyx moni L.

Bombyx mori L., commonly recognised around the world as the mulberry silkworm, is characterized by a wide variability in yield and developmental traits, which have been proven through conventional genetic analysis to be of polygenic nature. A large number of morpho-biochemical traits and RFLP and RAPD markers are mapped on different linkage groups, but to this point very little attention has been given to unravelling the genetics of yield traits. To address this issue, polymorphic profiles of 147 markers generated with 12 ISSR primers on the genomic DNA of 20 silkworm stocks of diverse yield status were subjected to multiple regression and discriminant function analyses (DFA). This led to the identification of eight markers generated by six primers, which demonstrated high beta-coefficient indices of -0.451 to -0.940. Furthermore, a significant difference between the yield traits for stocks with and without the specific marker could also be established. The inheritance pattern of one marker, L13800bp, identified at the first step of selection of markers through stepwise regression analyses for five yield parameters is discussed in the context of applying multiple regression analysis for establishing association, if not linkage, between a group of DNA markers and a particular yield trait of polygenic nature and using such markers in molecular marker-assisted breeding programs.     

Evaluation of genetic diversity within asparagus germplasm based on morphological traits and ISSR markers

Asparagus officinalis L. is a dioecious perennial plant globally known for its fine flavor and high nutritional value. An evaluation of genetic diversity in 46 asparagus accessions was carried out based on morphological and inter-simple sequence repeat (ISSR) markers. The result show that the coefficient of variation for 20 morphological characteristics is between 12.45 and 62.22%. Factor analysis revealed that nine factors explained 83.37% of the total variance. At Euclidean distance of 135.7, 46 accessions were divided into two clusters. Genetic similarity coefficient (GSC) based on ISSR data ranged from 0.60 to 0.97, suggesting a relatively abundant genetic base. Furthermore, the 46 asparagus accessions could also be grouped into three major clusters at a GSC of 0.74. And there is no significant relation between the two marker systems using the Mantel test. Clustering based on morphological traits compared with that based on ISSR data was not consistent, however, some common groupings were observed between two dendrograms. Therefore the results elucidated asparagus germplasm genetic background and determined hybrid parents, which will facilitate optimal application of asparagus germplasm resources and provide additional data for genetic improvement.

     

Characterization and identification of ISSR markers associated with resistance to dried-shrink disease in sea buckthorn

Sea buckthorn (Hippophae L.) is an economically important, globally distributed shrub with unique biochemical properties. This long-juvenile and long-lived woody plant can be more difficult to cultivate than other crop plants. Dried-shrink disease is a dangerous pathogen that destroys sea buckthorn and halts commercial production. We estimated variability of ISSR molecular markers in 52 accessions of 16 sea buckthorn varieties and lines to seek markers associated with dried-shrink resistance and help identify potential breeding varieties and lines. Fifteen ISSR primers generated 346 bands, with an average of 23 bands per primer. Genetic similarities (Jaccard coefficient) between pairs of accessions ranged from 0.216 to 0.781. At a Jaccard coefficient of 0.39, the dendrogram generated with 342 polymorphic bands clustered 51 accessions of H. rhamnoides into five groups and one H. salicifolia isolate. Four ISSR markers (887₁₉₀, 835₇₀₀, 809₂₉₀, and 811₂₈₀) were significantly correlated with resistance to dried-shrink disease (P < 0.001). These markers provide a potential method for breeding programs that select lineages resistant to dried-shrink disease, especially when no other genetic information such as linkage maps and Quantitative Trait Loci are available.     

Assessing genetic diversity of Elymus sibiricus (Poaceae: Triticeae) populations from Qinghai-Tibet Plateau by ISSR markers

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in eight populations of Elymus sibiricus L. from the southeast of Qinghai-Tibet Plateau of China. Of the 100 primers screened, 13 produced highly reproducible ISSR bands. Using these primers, 193 discernible DNA fragments were generated with 149 (77.2%) being polymorphic, indicating considerable genetic variation at the species level. In contrast, there were relatively low levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 44.04 to 54.92%. The mean gene diversity (H_E) was estimated to be 0.181 within populations (range 0.164–0.200), and 0.274 at the species level. A high level of genetic differentiation among populations was detected based on Nei's genetic diversity analysis (33.1%), Shannon's index analysis (34.5%), Bayesian method (33.2%) and AMOVA analysis (42.5%). No significant statistical differences (analysis of molecular variance [AMOVA], P = 0.08) in ISSR variation were found between the sample collection regions. However, among populations (42.5% of the variance) and within populations (57.5% of the variance), there were significant differences (P < 0.001). Populations shared high levels of genetic identity. This pattern of genetic variation was different from that for most of inbreeding Triticeae species reported. In addition, a geographical pattern of population differentiation, where the populations from south and north of sampling sites were clearly separated from each other, was revealed by both the cluster and principal coordinates analyses. Generally, the result of this study indicates that E. sibiricus contains high molecular variation in its populations. The implications of these results for the conservation of the species are discussed.     

Genetic diversity of Capsicum chinensis (Solanaceae) accessions based on molecular markers and morphological and agronomic traits

We estimated the genetic diversity of 49 accessions of the hot pepper species Capsicum chinensis through analyses of 12 physicochemical traits of the fruit, eight multi-categorical variables, and with 32 RAPD primers. Data from the physicochemical traits were submitted to analysis of variance to estimate the genetic parameters, and their means were clustered by the Scott-Knott test. The matrices from the individual and combined distance were estimated by multivariate analyses before applying Tocher's optimization method. All physicochemical traits were examined for genetic variability by analysis of variance. The responses of these traits showed more contribution from genetic than from environmental factors, except the percentage of dry biomass, content of soluble solids and vitamin C level. Total capsaicin had the greatest genetic divergence. Nine clusters were formed from the quantitative data based on the generalized distance of Mahalanobis, using Tocher's method; four were formed from the multi-categorical data using the Cole-Rodgers coefficient, and eight were formed from the molecular data using the Nei and Li coefficient. The accessions were distributed into 14 groups using Tocher's method, and no significant correlation between pungency and origin was detected. Uni- and multivariate analyses permitted the identification of marked genetic diversity and fruit attributes capable of being improved through breeding programs.     

盐胁迫对榅桲组培苗生长及其生理特征的影响

以榅桲组培苗为实验材料,采用不同质量分数的NaCl和Na2SO4处理后,观察盐胁迫对其生理生化指标的影响.结果表明:榅桲组培苗萌芽率、增殖倍数和平均株高均随2种盐质量分数的增大而降低,并在2种盐质量分数皆为1.0%时不再萌芽,平均株高降至试验最低值,而在NaCl和Na2SO4质量分数分别为0.8%和1.0%时不再增殖;榅桲组培苗叶片膜透性随着2种盐质量分数的增大而升高且与对照差异显著,并于盐质量分数为1.0%时均达到试验最大值,而当NaCl和Na2SO4质量分数分别为0.8%和1.0%时,组培苗致死率超过50%;组培苗叶片的超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性均随着2种盐质量分数的增大呈先上升后下降趋势,而过氧化物酶(POD)活性则随着2种盐质量分数的增加而持续增强.研究发现,盐胁迫榅桲组培苗的相关指标均与相应对照有显著差异,其中的叶片膜透性及其SOD、CAT以及POD均可作为鉴定榅桲耐盐性评价指标.     

Map-based molecular diversity, linkage disequilibrium and association mapping of fruit traits in melon

Melon has tremendous fruit diversity, the product of complex interactions of consumer preferences in different countries and a wide range of agro-climatic zones. Understanding footprints of divergence underlying formation of various morphotypes is important for developing sustainable and high-quality melons. Basic understanding of population structure and linkage disequilibrium (LD) is limited in melon and has lagged behind other crops. Characterization of population structure and LD are essential for carrying out association mapping of quantitative trait loci (QTL) underlying various complex traits. Mapped single-locus microsatellite markers are known to be very valuable for resolving the population structure and 268 such markers were used in the current study to resolve population structure and LD pattern using 87 accessions of melons belonging to Eastern European, Euro-North American and Asian types. A mixed linear model was implemented to detect QTL for various fruit traits. Various levels of QTL with high to moderate stringency were detected for fruit shape, fruit weight, soluble solids, and rind pressure and a majority of them was found to be in agreement with the previously published data, indicating that association mapping can be very useful for melon molecular breeding. Minor discrepancies in the position, strength and the variation explained by the QTL present between the methods of association and recombinant mapping approaches can be bridged if more melon groups and larger sets of accessions are involved in future studies, combined with high-throughput marker panels.     

用ISSR标记技术分析山药品种遗传多样性

利用ISSR标记技术对28个山药品种的遗传多样性进行分析。结果表明,从44条ISSR引物中可筛选出7条能够扩增出清晰、稳定条带的引物;这7条ISSR引物对28个山药品种扩增条带间存在较大差异,多态性条带比率为83．01％,Shannon多样性指数为0．3191;构建的分子树状图将28个山药品种划分为4组：第一组含有日本白、花山药和日本园3个品种;第二组为小叶山药;第三组为嵩野1号;其余23个品种归入第四组。而且主成分分析结果支持上述的聚类分析结果。这为利用ISSR标记技术鉴定山药品种,为有效地利用山药种质资源提供了依据。