Pear Genotypes Research Articles

QTLS FOR BROWN SPOT RESISTANCE IN EUROPEAN PEAR

Brown spot (Stemphylium vesicarium) is one of the most serious fungal disease that affects the pear tree orchards in the Po valley. In this region, which produces 90% of the pears in Italy, several antifungal treatments must be repeated along the period between flowering and harvest. In addition, many of the most widely grown varieties of pear (e.g., ‘Abbe Fetel’) are very susceptible to this fungus, while others, such as William and his mutated sports are substantially resistant. With the aim to develop molecular markers linked with brown spot resistance, plants derived from the cross ‘Abbe Fetel’ × ‘Max Red Bartlett’ were challenged for two consecutive years with a suspension of conidia both on leaves and fruits of each seedling. As a control, both the parents of the progeny and the varieties ‘Conference’ and ‘William’ were inoculated. On the genetic maps of the two parents QTL analysis revealed the presence of two QTLs, one for resistance to brown spot in ‘Max Red Bartlett’ and another for the susceptibility in ‘Abbe Fetel’. The availability of molecular markers in the regions of QTLs is an important step forward towards the selection of new pear genotypes resistant to brown spot by Marker-Assisted Selection (MAS).

Molecular and flow cytometric evaluation of pear (Pyrus L.) genetic resources of the German and Romanian national fruit collections

A total of 188 German and 28 Romanian pear accessions were evaluated using flow cytometry and molecular markers to detect homonymous and synonymous genotypes, triploids, which are not useful for breeding, and genotypes having favorable traits for breeding. Genotyping was done using a set of 11 simple sequence repeat markers proposed by the European Cooperative Program for Plant Genetic Resources, along with a standard set of six reference pear genotypes used in previous studies. The observed number of alleles ranged between 21 and 38 per locus. Twenty-three accessions could be confirmed as triploids. Because of the expected cross-incompatibility they are only of limited interest for breeding. The study confirmed that 180 of the 188 tested German accessions represent unique genotypes, while some accessions were found to be genetically identical. In parallel additional markers, which are known to be linked to resistance/susceptibility to major pathogens (e.g. black spot, aphid, fire blight, and apple scab), were applied to the German accessions. The comparative screening of the Romanian pear genetic resources demonstrated that only a few accessions with identical/very similar names to German accessions really have an identical fingerprint. Mislabeling and homonymous designation of different genotypes seems to occur frequently in different collections.

Fruchtgewicht, Gesamt-Phenolgehalt, Säure- und Zuckergehalt zum Verzehr geeigneter Früchte der Wildbirne (Pyrus elaeagnifolia Pall. = Ölweidenblättrige Birne)

Wild pear (Pyrus eleagnifolia) is a naturally grown species mainly in inner Anatolia and its edible small fruits are traditionally consumed by local peoples and are called “Ahlat” in Turkey. Its seedlings are also used as rootstock for commercial pear cultivars. In this study, we reported first time pomological characteristics and biochemical compositions in fruits of a wide number selected wild pears genotypes (Pyrus eleagnifolia Pall.) from inner Anatolia. The obtained results revealed that there were significant differences among wild pear genotypes for all analyzed parameters. Fruit weight, total phenolics, total acidity and total sugar contents of the fruits varied from 4.71 to 27.09 g, 42.79 to 119.14 mg GAE/100 g, 0.20 to 1.40 g/100 g and 8.36 to 19.31 g/100 g, respectively. Considering these values, it was concluded that naturally grown wild pears of Anatolia with their rich salubrious biochemical compounds could reliably be used as a food source for humans.

Role of electron transport chain of chloroplasts in oxidative burst of interaction between Erwinia amylovora and host cells.

Erwinia amylovora is a necrogenic bacterium, causing the fire blight disease on many rosaceous plants. Triggering oxidative burst by E. amylovora is a key response by which host plants try to restrain pathogen spread. Electron transport chain (ETC) of chloroplasts is known as an inducible source of reactive oxygen species generation in various stresses. This research was performed to assess the role of this ETC in E. amylovora-host interaction using several inhibitors of this chain in susceptible and resistant apple and pear genotypes. All ETC inhibitors delayed appearance of disease necrosis, but the effects of methyl viologen, glutaraldehyde, and DCMU were more significant. In the absence of inhibitors, resistant genotypes showed an earlier and severe H2O2 generation and early suppression of redox dependent, psbA gene. The effects of inhibitors were corresponding to the redox potential of ETC inhibitory sites. In addition, delayed necrosis appearance was associated with the decreased disease severity and delayed H2O2 generation. These results provide evidences for the involvement of this ETC in host oxidative burst and suggest that chloroplast ETC has significant role in E. amylovora-host interaction.

English

The genetic divergence among twenty-three pear genotypes under the present study was of medium quantum. The studied genotypes, on the basis of total variability were grouped into three distinct clusters. Maximum number of cultivars were accommodated in Cluster II (Ishiwase, Seckel, Anjou, Beurre Hardy, Lisnova Karavista, Jargonelle, Kala Hathi, Autumn of Yaklove, Kashmir Pear, Hengal, Flemish Beauty, Awal Number and Basuidse Favourite) followed by Cluster III (William Bon Chretien, Luhimtsa Kalapa, Manning Elizabeth, Red Bartlett, Max Red Bartlett and Starkrimson) and Cluster I (Kiskusui, Yakumo, Bodde Cappiament and Nouveau Poiteau). Cluster II had highest intra cluster value and was therefore the most divergent and Cluster III had least intra cluster value so was least divergent. Highest value for inter cluster distance was recorded between Cluster I and III while it was lowest between Cluster I and II. Cluster means were maximum in Cluster II. Kala Hathi was found to be best cultivar for fruit yield/tree and tree height while Red Bartlett was for fruit length and breadth. Cultivars Beuree Hardy and Ishiwase proved best for different vegetative characters. Key words: Pear, Pyrus commmunis L., cluster analysis, D2 statistics, genetic divergence.

Evaluation of new IRAP markers of pear and their potential application in differentiating bud sports and other Rosaceae species

Inter-retrotransposon amplified polymorphisms (IRAP) are one of the main components of the retrotransposon-based molecular marker system, but currently have no applications in pear. In this context, new IRAP markers were developed and used to study the genetic polymorphism of pear cultivars and bud mutants. In total, eight polymorphic IRAP markers were selected in ten genotypes of pear with a wide variation in genetic backgrounds and for further genotypic identification of cultivars and bud sports. A total of 76 alleles with an average of 9.5 per locus were amplified and 96.05 % showed polymorphism. Through genetic structure analysis, 62 pear cultivars were divided into two groups, i.e., Oriental and Occidental pears, with a few samples showing a distinct admixed genetic background. When polymorphic IRAP markers were tested on a total of 33 bud sports and their corresponding parent cultivars, the genetic similarity coefficient ranged from 0.54 to 0.96. Each bud mutation was separated from its original variety, and 92.3 % of bud sports clustered perfectly with their original varieties. Furthermore, the transferability of pear IRAP to apples and other Rosaceae species was very high, ranging from 87.5 to 100 %. Our results demonstrate that IRAP markers are an excellent tool for the study of genetic relationships and comparative genomics analysis in pear and Rosaceae species.

Screening genetically diverse pear species for in vitro CaCl2, MgSO4 and KH2PO4 requirements

Conservation of important plant germplasm is often difficult due to the specific growth requirements of genetically diverse species including in vitro culture collections. Recently the mesos components (CaCl2, MgSO4, KH2PO4) of Murashige and Skoog medium were identified as one of the most influential groups of nutrients for five pear genotypes. To determine if this requirement also applied to a larger germplasm collection, 18 genotypes in six species were screened. Shoot quality, shoot length, leaf spots and leaf color were the most affected responses. Seven of nine Pyrus communis cultivars had improved shoot quality, five had significantly longer shoots, better leaf color and fewer leaf spots while two had more shoots. Two of the four Pyrus pyrifolia cultivars had improved shoot quality while three had better leaf color and fewer leaf spots. Pyrus calleryana ‘Capital’, Pyrus cordata and Pyrus ussuriensis ‘Harbin’ had longer shoots while Pyrus koehnei had less callus. P. ussuriensis ‘Hang Pa Li’ was the only genotype where shoot quality declined at high mesos concentrations. Quantitative ion analysis detected substantially higher concentrations of Ca, Mg and K, but significantly less Fe, in the shoots cultured on increased mesos compared to controls. This study confirms that increased mesos improved growth of P. communis and P. pyrifolia cultivars, but produced fewer significantly improved responses for four other species.

Susceptibility of European pear germplasm to Cacopsylla pyri under Mediterranean climatic conditions

The response of 160 European pear genotypes to the attacks of Cacopsylla pyri in natural conditions of infestation was studied in the ex situ germplasm collection of the IVALSA Institute – CNR located in Follonica (Grosseto, Italy) during three years. ANOVA showed that both the year and the period of survey have a significant effect upon pear infestation assessed by seven variables. The overall average values of the studied accessions for the variables taken into account were used for grouping the genotypes into 5 putative classes of susceptibility by cluster analysis. Four variables (number of colonies, small nymphs, large nymphs and length of the colonies) selected on the basis of discriminant analysis allowed us to classify 70% of the cultivars into the correct group of susceptibility by jackknifed classification matrix. Taking into account the mean values of the variables and their upper and lower limits all the genotypes were grouped into 5 different classes of susceptibility. On the whole, the number of highly tolerant or resistant cultivars were 8.1% of the investigate genotypes; part of them were ancient cultivars of Italian origin as ‘Eletta Morettini’, ‘Fiorenza’, ‘Gentile’, ‘Moscatellina’, ‘Pera Volpina VP7’, ‘Precoce di Cassano’ and ‘Precoce di Masi’, but there were also the French ‘Notaire Lepin’ and ‘Président Loubet’, the German ‘Forelle’ and the American ‘Starking Delicious’. The remaining 91.9% of the germplasm collection showed different levels of susceptibility to psylla attack. The largest part of the genotypes (56.9%) was identified as slightly susceptible, often with minor infestation (that is some isolated larvae, few colonies and reduced honeydew) only in one or two out of three years. Several cultivars (46.3%) were scored as susceptible, suffering medium or high damage, including the widespread cultivated ‘Conference’, ‘Doyenné du Comice’, ‘Highland’ ‘Curè’, ‘Etrusca’, ‘Kaiser’, and ‘William’, these last 3 being classified as highly susceptible. The influence of the environment and growth condition of trees are discussed together with screening methods applied for the evaluation of pear susceptibility to psylla attack reported in world literature.

Respostas de genótipos de palma forrageira a diferentes densidades de cultivo

Considerando-se a importância da palma forrageira como alternativa alimentícia para os rebanhos do semiárido brasileiro e o efeito do espaçamento de cultivo entre plantas, este estudo objetivou avaliar a morfometria, produtividade e composição químico-bromatológica de genótipos de palma forrageira, em diferentes densidades de cultivo. O delineamento experimental utilizado foi em blocos completos casualizados, em esquema fatorial 3x4. Os tratamentos constituíram-se da combinação de três genótipos de palma forrageira (Gigante, Redonda e Miúda) e quatro densidades de cultivo (10.000 plantas ha-1, 20.000 plantas ha-1, 40.000 plantas ha-1 e 80.000 plantas ha-1), com três repetições. Os genótipos de palma forrageira apresentaram comportamentos diferentes, quanto à morfometria, produtividade e composição químico-bromatológica, e, independentemente da espécie, o plantio adensado elevou a produtividade (toneladas ha-1). A palma Miúda apresentou maior produtividade de matéria seca e, consequentemente, maior acúmulo de nutrientes digestíveis totais, proteína bruta e água por hectare, bem como maior digestibilidade in vitro da matéria seca.

Some morphological and fruit characteristics of naturally grown Pyrus elaeagrifolia Pall. of Kayseri Province (Central Anatolia, Turkey)

Rapid increase in human populations and consequent increase in agricultural activities and infrastructures to feed such huge populations have brought several naturally-grown wild fruit species face to face with extinction. Wild pears (Pyrus elaeagrifolia Pall.—oleaster-leafed pear) are naturally grown in Kayseri and surrounding nature of Anatolia and traditionally consumed as fruit. These wild fruits are also under the threat of extinction. They are locally called as “Ahlat”. Since, there aren’t any, the present study deals with the morphological and pomological characteristics of these wild fruits. Initial observations yielded that wild pears of Kayseri Province were mostly populated over the valleys in Talas, Talas–Koscagiz, Sariz, Sariz–Tufanbeyli (Adana Province) border and they widespread over these valleys. Pomological analyses yielded the fruit weights as between 27.09 (38-AK-003) and 4.71 g (38-TA-002); fruit lengths as between 36.14 mm (38-AK-003) and 17.26 mm (38-TA-002); fruit widths as between 36.55 mm (38-TO-004) and 20.82 mm (38-SA-013); fruit pedicle lengths as between 24.23 mm (38-SA-012) and 6.89 mm (38-TA-014); water soluble dry matter contents as between 20.00 % (38-TA-016) and 10.00 % (38-TA-001). Significant variations were observed in morphological characteristics of oleaster-leafed pear genotypes through pomological analyses and field observations. Our results may provide useful information for management of wild pear genetic resources.

Genetic variation, heritability and correlation analysis of forty seven pear genotypes under subtropics

Genetic variation, heritability and correlation analysis of forty seven pear genotypes under subtropics

English

Twenty four (24) ‘Kashmiri Nakh’ pear (Pyrus pyrifolia) genotypes were studied to assess the overall degree of polymorphism, detect similarities among important tree, pomological, fruit quality and yield parameters. Eleven (11) variables were scored and subjected to multivariate analysis. Results show a considerable phenotypic diversity among ‘Kashmiri Nakh’ pear genotypes and differed significantly for the above traits. The cluster analysis classified the genotypes into two major groups according to their potential characteristics. The first group was found superior in terms of fruits total soluble solids (TSS), TSS/acidity and yield related characteristics and second group in fruits morphological (length, diameter, weight) and tree characteristics attributes. Principal component analysis (PCA) revealed that traits positively related to tree height, tree spread (N-S), tree spread (E-W), yield per tree, fruit weight, fruit length, fruit diameter and acidity, however negatively related to TSS and TSS/acidity. The first principal components expressed 33.58% of the total variation and second PC2 accounted for 23.76% of the total variation. A large proportion of variability observed in genotypes ‘TB-3, CHB-4, TBP-3, THP-7, TB-1, THP-1, TBP-1 and TB-2 were found unique for tree, fruit and yield attributing traits during PCA.   Key words:  Genetic variability, genotypes, cluster analysis, principal component analysis (PCA).

INTERSPECIES HYBRIDIZATION OF PYRUS SPECIES ALONG THE SILK ROAD, DETECTED BY USING SPECIES-SPECIFIC S-ALLELES

The interspecies hybridization within the Pyrus genus is compatible and natural hybrids in the interference regions of pear species could be detectable. Iran plateau has been one of these regions for thousands of years where natural hybridizations, germplasm entry along the Silk Road, and selection by human and natural factors caused significant diversity in this genus. Pear species have gametophytic self-incompatibility that is controlled by multi allelic S locus that seems to be species specific. The target of this research was determination of the S alleles of several pears including some considerable genotypes demonstrating special forms and characteristics. Detection of S alleles was achieved by DNA extraction, followed by PCR amplification of S locus using Sall-F/FB-R1 primers pairs and subsequent sequencing of these fragments. The S alleles in all cultivars were amplified and generally 5 different alleles were identified. Most interesting results were observed in ‘Khoj-57, ‘Konjuni’, Kaftar Bache’ and ‘Shirin Torkan’ genotypes that S allele of ‘Khoj-57 showed 99% similarity to S19 in Pyrus×bretschneideri, while the S allele in other cultivars had 95% similarity to S35 in P. ussuriensis. In the ‘Shekari' cultivar, two alleles were identified of which the smaller allele was similar to S7(Sh) in European pear and the larger allele was in 99% similarity to S19 in P.×bretschneideri. ‘Shahak’, ‘Shah Mive’ and ‘Khoj-1’ had a S7(Sh) allele, while S alleles of pears originated from upper latitudes of central Asia, including ‘Krus Siehan’ (S4) and ‘Krusalun’ (S8) contained normal P. communis S alleles. Neither of tested pears possessing S alleles of P.×bretschneideri and P. ussuriensis did not demonstrate morphological characteristics of these species, but exclusively have minor similarities such as round fruits and sandy texture of pulp. The results present the possible translocation and interspecies hybridization from East Asian species to the Iranian pear genotypes and in this process, The Silk Road may play a main role during past centuries.

A Novel Set of EST-Derived SSR Markers for Pear and Cross-Species Transferability in Rosaceae

Pear is a fruit species with worldwide distribution belonging to the Rosaceae family. In this study, transcriptomes of 12 different tissues of pear were newly assembled, with a total of 17,353 SSR loci identified. Within these, repetitive sequences with dinucleotide and trinucleotide motifs were more abundant than other types. We developed 194 EST-SSR makers from the assembled sequences to test on seven pear varieties from different genetic backgrounds, on which 132 EST-SSR primers had amplicons. There were 108 primers with dinucleotide and trinucleotide motifs detecting a total of 311 alleles, with an average per primer of 2.88 and 2.86, respectively. These had better quality than primers with tetranucleotides, pentanucleotides, and hexanucleotides. Fifty polymorphic markers divided 36 pear genotypes into two groups with a similarity coefficient of 0.62. Results showed that Japanese pears had a comparatively close relationship with Chinese pears, indicating the great potential of the novel EST-SSR makers in future evaluations of pear germplasm. Furthermore, 54 EST-SSR markers were selected to test transferability to 96 other Rosaceae cultivars from eight species, including Japanese apricot, plum, apricot, peach, cherry, apple, strawberry, and loquat. Seventeen EST-SSR primers had PCR amplification products in at least one of the 96 accessions, with the highest transferability was from pear to apple at 29.63 %. Transferability from pear to Japanese apricot, plum, apricot, peach, cherry, strawberry, and loquat was 9.26, 14.81, 11.11, 12.96, 5.56, 3.7, and 12.96 %, respectively. Therefore, the newly developed EST-SSR markers can contribute to exploring the genetic relationship, evolution and comparative genomics, and gene introgressions in the Rosaceae family.

Expression and genomic structure of the dormancy-associated MADS box genes MADS13 in Japanese pears (Pyrus pyrifolia Nakai) that differ in their chilling requirement for endodormancy release

We isolated three dormancy-associated MADS-box (DAM) genes (MADS13-1, MADS13-2 and MADS13-3) and showed regulated expression concomitant with endodormancy establishment and release in the leaf buds of Japanese pear 'Kosui'. Comparative analysis between 'Kosui' and Taiwanese pear TP-85-119 ('Hengshanli'), a less dormant pear cultivar, showed reduction of MADS13-1 expression level in 'Hengshanli' earlier than in 'Kosui' towards endodormancy release, suggesting the possible relationship between chilling requirement and MADS13-1 expression. Application of hydrogen cyanamide accelerated endodormancy release with a reduction in MADS13 expression, whereas heat treatment in autumn inhibited endodormancy establishment without induction of MADS13 expression, indicating a close relationship between the MADS13 expression pattern and endodormancy phase transitions. Moreover, both the cis-acting regulatory elements and the methylation status in the 5' upstream region of the MADS13-1 gene were not largely different between 'Kosui' and 'Hengshanli'. Genomic structures of MADS13-1 from 'Kosui' and 'Hengshanli' revealed a 3218 bp insertion in the first intron of 'Hengshanli' that might be ascribed to the lower expression of MADS13-1tw; however, this insertion was also found in pear genotypes with a high chilling requirement. These results indicated that the low expression of MADS13-1 in 'Hengshanli' towards endodormancy release could not be explained by the identified cis-acting regulatory elements, the methylation status of the putative promoter or by intron insertion.

Assessment of European pear (Pyrus communis L.) genetic resources in Bosnia and Herzegovina using microsatellite markers

The pear germplasm of Bosnia and Herzegovina (B&H) consists of cultivars introduced both from Asia Minor and Western Europe and until now has not been adequately investigated. In this study, 64 pear accessions, 27 traditional B&H cultivars and 9 international reference cultivars, maintained at the ex situ apple and pear collection Srebrenik (Northeast Bosnia), together with 28 presumed traditional pear accessions collected from a number of backyards and small farms in Sarajevo, were assessed using 13 microsatellite markers. Of the thirteen primer pairs which were used, two primer pairs (CH02C06 and CH05e03) either did not amplify or produced poor amplification in our samples. Eleven remaining primer pairs successfully amplified 159 distinct alleles, or on average 14.5 alleles per locus. Presence of a third allele was detected for 31% of the analyzed accessions. After elimination of duplicates, 53 pear genotypes remained for further investigation. Analysis of molecular variance (AMOVA) revealed a significant genetic differentiation between both groups of traditional pear accessions and the international reference cultivars, but found no significant differentiation among traditional B&H cultivars from Srebrenik and accessions from Sarajevo. Factorial correspondence analysis (FCA) confirmed results obtained by AMOVA. Bayesian method and admixture analysis of the allele frequency allowed for classification of all accessions analyzed into five RPPs. Most (78%) of the international reference cultivars grouped in RPP2, whereas traditional B&H cultivars from the ex situ collection at Srebrenik and accessions from Sarajevo grouped in all five RPPs. None of the international reference cultivars grouped in either RPP1 or RPP5. Analyses of molecular variance detected significant differentiation among RPPs (fCT=0.082; P<0.001). Results of various analyses used, indicate that many traditional B&H cultivars from Srebrenik and Sarajevo represent an interesting genetic resource.

Transferability of Newly Developed Pear SSR Markers to Other Rosaceae Species

A set of 120 simple sequence repeats (SSRs) was developed from the newly assembled pear sequence and evaluated for polymorphisms in seven genotypes of pear from different genetic backgrounds. Of these, 67 (55.8 %) primer pairs produced polymorphic amplifications. Together, the 67 SSRs detected 277 alleles with an average of 4.13 per locus. Sequencing of the amplification products from randomly picked loci NAUPy31a and NAUpy53a verified the presence of the SSR loci. When the 67 primer pairs were tested on 96 individual members of eight species in the Rosaceae family, 61.2 % (41/67) of the tested SSRs successfully amplified a PCR product in at least one of the Rosaceae genera. The transferability from pear to different species varied from 58.2 % (apple) to 11.9 % (cherry). The ratio of transferability also reflected the closer relationships within Maloideae over Prunoideae. Two pear SSR markers, NAUpy43c and NAUpy55k, could distinguish the 20 different apple genotypes thoroughly, and UPGMA cluster analysis grouped them into three groups at the similarity level of 0.56. The high level of polymorphism and good transferability of pear SSRs to Rosaceae species indicate their promise for application to future molecular screening, map construction, and comparative genomic studies among pears and other Rosaceae species.Electronic supplementary materialThe online version of this article (doi:10.1007/s11105-013-0586-z) contains supplementary material, which is available to authorized users.

Mesos components (CaCl2, MgSO4, KH2PO4) are critical for improving pear micropropagation

Pear accessions and species show a broad response to tissue culture media due to the wide genetic diversity that exists in the available pear germplasm. An initial study of mineral nutrition using a systematic response surface approach with five Murashige and Skoog medium mineral stock solutions indicated that the mesos factor (CaCl2, MgSO4, and KH2PO4) affected most plant responses and genotypes, suggesting that additional studies were needed to further optimize these three mesos components for a wide range of genotypes. Short stature, leaf spots, edge necrosis, and red or yellow coloration were the main symptoms of poor nutrition in shoot cultures of 10 diverse pear genotypes from six species. A surface response experimental design was used to model the optimal factor and factor levels for responses that included overall quality, leaf character, shoot multiplication, and shoot height. The growth morphology, shoot length, and multiplication of these pear shoots could be manipulated by adjusting the mesos components. The highest quality for the majority of genotypes, including five P. communis cultivars, P. koehnei, P. dimorphophylla, and P. pyrifolia ‘Sion Szu Mi’, required higher concentrations (>1.2× to 2.5×) of all the components than are present in Murashige and Skoog medium. ‘Capital’ (P. calleryana) required high CaCl2 and MgSO4 with low KH2PO4; for ‘Hang Pa Li’ (P. ussuriensis), low CaCl2 and moderate to low MgSO4 and KH2PO4 produced high-quality shoots. Suitable combinations of the meso nutrients produced both optimum shoot number and shoot length in addition to general good plant quality.

Improving in vitro mineral nutrition for diverse pear germplasm

Mineral nutrition in the media used for growth of in vitro plants is often difficult to optimize due to complex chemical interactions of required nutrients. The response of plant tissue to standard growth media varies widely due to the genetic diversity of the plant species studied. This study was designed as the initial step in determining the optimal mineral nutrient requirements for micropropagation of shoot tips from a collection of genetically diverse pear germplasm. Five mineral nutrient factors were defined from Murashige and Skoog salts: NH4NO3, KNO3 ,m esos (CaCl 2·2H20- KH2PO4-MgSO4), micronutrients (B, Cu, Co, I, Mn, Mo, and Zn), and Fe-EDTA. Each factor was varied over a range of concentrations. Treatment combinations were selected using response surface methods. Five pears in three species (Pyrus communis 'Horner 51, '' Old Home×Farmingdale 87, '' Winter Nelis,' Pyrus dimorphophylla ,a ndPyrus ussuriensis 'Hang Pa Li') were grown on each treatment combination, responses were measured, and each response was analyzed by analysis of variance. The analyses resulted in the identification of the following factors with the single largest effects on plant response: shoot quality (mesos), leaf spotting/necrosis (mesos), leaf size (mesos), leaf color (mesos, NH4NO3, and KNO3), shoot number (NH4NO3 and Fe), nodes (NH4NO3 and KNO3), and shoot length (mesos and Fe). Factors with the largest effects (mesos and Fe) were similar among the genotypes. This approach was very successful for defining the appropriate types and con- centrations of mineral nutrients for micropropagation of diverse pear genotypes.

In vitro induction of multiple buds from cotyledonary nodes of Balsam pear (Momordica charantia L.)

In this study, cotyledonary nodes of Changbai, Dabai and Youlv Balsam pear (Momordica charantia L.) were used for tissue culture to establish regeneration system, and the effects of different genotypes of Balsam pear, hormone combinations, seedling ages, dark period and AgNO3 concentrations on the bud regeneration were compared. The results show that eight-day old seedling was the best for multiple buds regeneration. The combination of 6-benzylaminopurine (6-BA) and indole-3-butyric acid (IBA) had the best effect on the induction of multiple buds. The optimum medium for the induction of multiple buds in Balsam pear was Murashige and Skoog (MS) medium supplemented with 2.5 mgL -1 of 6-BA and 0.1 mgL -1 of IBA. Inducing frequency varied with the genotypes, of which Changbai showed highest percentage of induction. One week dark treatment could increase the rate of shoot regeneration from 76.91 to 80.91%. The addition of AgNO3 which varied from 1 to 6 mg L -1 in the medium could not help to