Syrian pear (Pyrus syriaca) as a pollinator for European pear (Pyrus communis) cultivars

In Israel four European pear cultivars are grown: ‘Spadona’ is the main cultivar and ‘Coscia’, ‘Gentile’ and ‘Spadochina’ are its pollinators. However, molecular S-genotyping revealed that ‘Spadona’ is semi-compatible with its three pollinators. This explains, at least in part, the relatively low pear yield in Israel. The Syrian pear (Pyrus syriaca) grows wild in Israel and blooms intensively, overlapping the blooming of the cultivated European pears. Cross-fertilization between Syrian pear and ‘Spadona’ was shown to be efficient suggesting that Syrian pear might be a potent pollinator for ‘Spadona’. Twenty-six Syrian pear seedlings, from different sites in north-east Israel were S-genotyped identifying 11 that are fully compatible with the four European pear varieties cultivated in Israel. By this screening, 24 different S-RNases were cloned; ten of them are new, whereas the other fourteen had been identified previously. In addition, seedlings of two wild pear species were also S-genotyped. Two seedlings from Pyrus betulifolia and one from Pyrus korshinskii were found to be genetically compatible with the four European pear cultivars. From these seedlings four S-RNases were cloned, two are new, one had been cloned previously and one was identical to an S-RNase allele cloned from Syrian pear in this work.     

Identification of S-alleles in pear (Pyrus communis L.) cv. ‘Rocha’ and other European cultivars

In this work we report the cloning and identification of S-RNase alleles responsible for gametophytic self-incompatibility (GSI) of ‘Rocha’ pear and of 13 other European pear cultivars that might be used as its pollinators. Partial sequences of S-RNase alleles were amplified by PCR with specific primers hybridising in conserved regions of previously identified S-RNase alleles of Pyrus communis, cloned and sequenced and the S-genotype of eight pear cultivars was fully determined. Three cultivars (‘General Léclerc’ (SqSl), ‘Tosca’ (SbSl) and ‘Alexandrine Douillard’ (SbSk)) shared no S-alleles with ‘Rocha’ (SaSe) and shall be totally compatible with this cultivar. None of the cultivars analysed showed an identical amplification pattern to the one observed in ‘Rocha’, so the other cultivars shall be at least semi-compatible. One new allele was identified in P. communis cv. ‘Beurré d’Avril’ (designated as St). The determination of both S-RNase alleles of cvs ‘Rocha’, ‘Beurré Precoce Morettini’ (SeSk) and ‘Tosca’ and the identification of one S-RNase allele in cvs ‘Carapinheira’ (Sb), ‘Amêndoa’ (Se), ‘Pérola’ (Sk) and ‘Beurré d’Avril’ (St) are important contributions for the effort recently developed worldwide to establish groups of sexual compatibility among European pears.     

Identification of seven haplotype-specific SFBs in European pear (Pyrus communis) and their use as molecular markers

The European pear (Pyrus communis) carries the S-RNase-mediated gametophytic self-incompatibility (GSI) system. The S-haplotype is conferred by an S-locus, which contains the style-specific expressed S-RNase, and the pollen-specific expressed F-box genes (SFB). Both the S-RNase and the SFB genes are multi-allelic and each is characteristic of one of the S-haplotypes. Therefore, they are ideal markers for molecular S-genotyping. In this work, for the first time, seven haplotype-specific SFBs were isolated from European pears. Particular primers for each of these SFBs were generated, thus providing an additional tool for S-genotyping of European pear cultivars.     

Content levels of various fruit metabolites in the ‘Conference’ pear response to branch bending

The response of ‘Conference’ pear subjected to branch bending in the content levels of various metabolites in its fruit was investigated. The fruits in commercial maturity were sampled in 2004 and 2005 from branches bent in the late summer of 2003 (the summer treatment), from branches bent in the late spring of 2004 (the spring treatment) and from control branches. The content levels of carbohydrates, organic acids and phenolic compounds were compared among treatments in two successive years. The fruit revealed various responses in content levels of metabolites. In the first year after bending, no significant differences were found in the content of each carbohydrate, but in 2005 by far the highest content level of glucose and fructose and the lowest content level of sucrose were found in fruits from the control. The control fruit showed significantly higher content levels of malic acid and lower content levels of some phenolics (chlorogenic and vanillic acid) in the first year after bending, but in the next year the opposite reaction occurred—the control fruit had the lowest content level of malic acid and the highest content level of epicatechin, quercetin-3-d-galactoside and quercetin-3-β-d-glucoside. The comparison of the two bending treatments alone in 2004 showed that the summer treatment often produced a slightly higher value of each phenolic in comparison to the spring treatment. However, in 2005 the significantly highest content of chlorogenic acid was in fruit from the spring treatment. Sorbitol, as well as citric acid, catechin and sinapic acid showed no clear tendency among treatments, neither in 2004 nor in 2005. It is suggested that these variations of ‘Conference’ fruit subjected to different bending treatments could not be the result of bending alone, but that they could be indirectly affected by other physiological responses of the fruit tree. However, it seemed that variations are affected by the time of bending and by the year-to-year, and such responses can be attributed to the ‘Conference’ genotype only.     

Genetic diversity in local Tunisian pears (Pyrus communis L.) studied with SSR markers

Few records are available about local Tunisian pear cultivars characterized by low chilling requirements and adaptation to dry conditions. In this work, seven SSRs derived from apple were successfully transferred to 25 local Tunisian pear genotypes and 6 common varieties of Pyrus communis cultivated in Europe. The 7 SSRs used amplified a total of 36 fragments. All the microsatellites except one seem to amplify more than one locus in some of the genotypes studied. Only 12 different fingerprinting patterns could be distinguished among the 25 Tunisian cultivars studied indicating a high number of synonymies. The mean expected and observed heterozygosities in the 25 Tunisian cultivars analyzed averaged 0.71 indicating a high level of genetic diversity among the local Tunisian pear germplasm. These markers will be useful to optimize the conservation of this highly threatened germplasm.     

Effect of synthetic auxins on fruit development of ‘Bing’ cherry (Prunus avium L.)

The main cherry cultivar grown in the warm climate of Israel, ‘Bing’, produces relatively small fruit. Over three consecutive years (2003–2005), application of 50 mg l⁻¹ 2,4-dichlorophenoxypropionic acid [2,4-DP; as its butoxyethyl ester (Power™)], 10 mg l⁻¹ 3,5,6-trichloro-2-pyridyloxyacetic acid [3,5,6-TPA; as the free acid (Maxim^®)], or 25 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) plus 30 mg l⁻¹ naphthaleneacetic acid (NAA; 0.3% Amigo™), at the beginning of pit-hardening when fruitlet diameter was ca. 13 mm caused appreciable and significant increases in fruit size and total yield, except when the crop load was heavy. Anatomical studies revealed that the main effect of these synthetic auxins was via direct stimulation of fruit cell enlargement. The above auxins had no negative effect on fruit quality, either at harvest or after 1 month of storage at 0 °C, or on return yield in the following year.     

Influence of nine dwarfing apple rootstocks on vigour and productivity of apple cultivar ‘Granny Smith’

The influence of nine dwarf apple rootstocks (M.9 T 984, M.9 T 337, Jork 9, Mark 9, Budagowski 9, M.9 EMLA, Pajam 1, Pajam 2, and Supporter 4) on the vegetative characteristics, yield and yield efficiency, was evaluated on ‘Granny Smith’ apple variety (Malus domestica Borkh.).     

Identification of RAPD marker linked to fruit skin color in Japanese pear (Pyrus pyrifolia Nakai)

In Japanese pear, fruit skin color is a very important trait for growers because the russet skin protects the fruit against external stress caused by disease, insects, bad weather, and shipping. This report describes the development of a randomly amplified polymorphic DNA (RAPD) marker linked to major genes controlling the fruit skin color in Japanese pear. Two F₁ progenies from the cross of ‘Kousui’ × ‘Kinchaku’ and ‘Niitaka’ × ‘Chikusui’ segregated by fruit skin color were used for bulked segregant analysis. Four kinds of bulked DNA were constructed and used for the polymerase chain reaction in RAPD analysis. After 200 random primers were screened against four bulks, a band named OPH-19₄₂₅ was selected in cooperation with green bulks. The recombination rate between OPH-19₄₂₅ and the green skin phenotype was 7.3%. The RAPD marker (OPH-19₄₂₅) could select green fruit with probability as high as approximately 92%. The marker was apparently useful for the selection of green-skinned individuals in a breeding program. This is the first report on developing a DNA marker closely linked to the fruit phenotype in Japanese pear.     

Relationship between inbreeding coefficients and plant height of 1-year-old seedlings in crosses among Japanese pear (Pyrus pyrifolia Nakai) cultivars/selections

Plant height, a vigor trait, in 1-year-old seedlings made from Japanese pear (Pyrus pyrifolia) cultivars/selections was measured using 994 individuals from 29 families. The family mean of plant height was negatively correlated (r = −0.72**) to the inbreeding coefficients (F). The regression of the family mean (Fm) on the F value (Fm = 130 − 104F) showed that inbreeding depressions were 8%, 20%, and 40% for F = 0.1, 0.25, and 0.5, respectively. According to the regression, the family mean at F = 0 was estimated at 130 cm. These results showed that the vigor was greatly influenced by inbreeding in Japanese pear. Within-family variances, the genetic segregation of offspring in a family, differed according to family. The proportions of offspring with plant height above 130 cm (estimated Fm for F = 0) were extremely low, i.e., 0–17% for 0.5 ≤ F < 0.60 and 0–8% for F = 0.75.     

Feathering of ‘Doyenné du Comice’ pear in the nursery using repeat sprays of benzyladenine and gibberellins

This work sets out to examine the effectiveness of a number of cytokinins or products with cytokinin-like activity, with and without additional sprays of gibberellins or leaf plucking, on the production of feathers (sylleptic shoots) on trees of the European pear cultivar ‘Comice’ in a fruit tree nursery. It covers the results from three successive years experimentation.     

Performance of Prunus rootstocks for apricot in Mediterranean conditions

The influence of five rootstocks (Evrica, Krymsk^® 86, Torinel, PAC 00-08 and PADAC 01-47) on flowering, fruit set, trunk cross-sectional area, yield efficiency and fruit quality parameters of apricot cultivars (Prunus armeniaca L.) grown in a Mediterranean agro-climatic environment was evaluated. The five rootstocks were grafted with ‘E-101’ and ‘E-404’ apricot cvs., and established in an experimental orchard in the Region of Murcia (South-eastern of Spain) in 2004. Rootstock had no significant influence on the number of flowers but affected fruit set. Evrica, PAC 00-08 and PADAC 01-47, induced a higher percentage of fruit set on the apricot cultivar ‘E-101’. The greatest TCSA was exhibited with Torinel, Evrica and PADAC 01-47. The yield efficiency was significantly greater on PADAC 01-47, because of its higher yield and cumulative production compared with the other rootstocks. Thus, differences in precocity among rootstocks became evident, PADAC 01-47 being the most efficient rootstock for the first bearing years. The fruit quality traits were also significantly affected by rootstocks. In the case of ‘E-101’, the highest fruit weight was induced by Evrica, Krymsk^® 86 and Torinel. In relation to fruit size, the smallest equatorial, suture and polar diameters were produced by fruit on PADAC 01-47 for both cultivars. The highest firmness was induced by PAC 00-08 for ‘E-101’, while in ‘E-404’ the highest firmness was induced by PADAC 01-47. The colour of fruit was also affected by the rootstock. The brightest coloured skin (high L* values) was found on Evrica, PADAC 01-47, Torinel and Krymsk^® 86. The fruit weight was positively correlated with pulp yield and negatively correlated with TCSA. According to these results, higher fruit quality was found on PADAC 01-47 and Evrica.     

Tree performance and fruit yield and quality of ‘Okitsu’ Satsuma mandarin grafted on 12 rootstocks

The citriculture in Brazil, as well as in other important regions in the world, is based on very few mandarin cultivars. This fact leads to a short harvest period and higher prices for off-season fruit. The ‘Okitsu’ Satsuma (Citrus unshiu Marc.) is among the earliest ripening mandarin cultivars, and it is considered to be tolerant to citrus canker (Xanthomonas citri subsp. citri Schaad et al.) and to citrus variegated chlorosis (Xylella fastidiosa Wells et al.). Despite having regular fruit quality under hot climate conditions, the early fruit maturation and absence of seeds of ‘Okitsu’ fruits are well suited for the local market in the summer (December through March), when the availability of citrus fruits for fresh consumption is limited. Yet, only a few studies have been conducted in Brazil on rootstocks for ‘Okitsu’. Consequently, a field trial was carried out in Bebedouro, São Paulo State, to evaluate the horticultural performance of ‘Okitsu’ Satsuma mandarin budded onto 12 rootstocks: the citrandarin ‘Changsha’ mandarin (Citrus reticulata Blanco) × Poncirus trifoliata ‘English Small’; the hybrid Rangpur lime (Citrus limonia Osbeck) × ‘Swingle’ citrumelo (P. trifoliata (L.) Raf. × Citrus paradisi Macfad.); the trifoliates (P. trifoliata (L.) Raf.) ‘Rubidoux’, ‘FCAV’ and ‘Flying Dragon’ (P. trifoliata var. monstrosa); the mandarins ‘Sun Chu Sha Kat’ (C. reticulata Blanco) and ‘Sunki’ (Citrus sunki (Hayata) Hort. ex. Tanaka); the Rangpur limes (C. limonia Osbeck) ‘Cravo Limeira’ and ‘Cravo FCAV’; ‘Carrizo’ citrange (Citrus sinensis × P. trifoliata), ‘Swingle’ citrumelo (P. trifoliata × C. paradisi), and ‘Orlando’ tangelo (C. paradisi × Citrus tangerina cv. ‘Dancy’). The experimental grove was planted in 2001, using a 6 m × 3 m spacing, in a randomized block design. No supplementary irrigation was applied. Fruit yield, canopy volume, and fruit quality were assessed for each rootstock. A cluster multivariate analysis identified three different rootstock pairs with similar effects on plant growth, yield and fruit quality of ‘Okitsu’ mandarin. The ‘Flying Dragon’ trifoliate had a unique effect over the ‘Okitsu’ trees performance, inducing lower canopy volume and higher yield efficiency and fruit quality, and might be suitable for high-density plantings. The ‘Cravo Limeira’ and ‘Cravo FCAV’ Rangpur limes induced early-ripening of fruits, with low fruit quality. ‘Sun Chu Sha Kat’ and ‘Sunki’ mandarins and the ‘Orlando’ tangelo conferred lower yield efficiency and less content of soluble solids for the latter rootstock.     

Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storage

Fruit thinning in pear is feasible for mitigation of water stress effects. However, it is not well known how fruit quality at harvest and after cold storage is affected by pre-harvest water stress. Even less is known about the effects of fruit thinning on quality under these circumstances. To elucidate these, we applied deficit irrigation (DI) and fruit thinning treatments to ‘Conference’ pear over the growing seasons of 2008 and 2009. At the onset of Stage II (80 and 67 days before harvest in 2008 and 2009, respectively), two irrigation treatments were applied: full irrigation (FI) and DI. FI trees received 100% of crop evapotranspiration (ETc). DI trees received no irrigation during the first three weeks of Stage II to induce water stress, but then received 20% of ETc to ensure tree survival. From bud-break until the onset of Stage II and during post-harvest, FI and DI trees received 100% of ETc. Each irrigation treatment received two thinning levels: no thinning leaving commercial crop load (∼180 fruits tree⁻¹), and hand-thinning at the onset of Stage II leaving a light crop load (∼85 fruits tree⁻¹). Under commercial crop loads, DI trees were moderately water-stressed and this had some positive effects on fruit quality. DI increased fruit firmness (FF), soluble solids concentrations (SSC) and acidity at harvest while no changes were observed in fruit maturity (based on ethylene production). Differences in FF and acidity at harvest between FI and DI fruit were maintained during cold storage. DI also reduced fruit weight loss during storage. But fruit size was reduced under DI. Fruit thinning under DI resulted in better fruit composition with no detrimental effect on fresh-market yield compared to un-thinned fruit. Fruit size at harvest and SSC values after five months of cold storage were higher in fruit from thinned trees than fruit from un-thinned trees. Fruit thinning increased fruit ethylene production, indicating advanced maturity. This may lead to earlier harvest which is desirable in years with impending drought. Fruit thinning is therefore a useful technique to enhance pear marketability under water shortage.     

Nitrogen distribution,remobilization and re-cycling in young orchard of non-bearing ‘Rocha’ pear trees

In newly planted orchards, special attention must be paid to fertilization to build up the permanent structure of the trees so that high yield and fruit quality can be reached later on. Nitrogen (N) plays a major role in the fertilization plan, although few studies have assessed its use efficiency in young non-bearing trees, especially in field conditions. In this work, 1–3 years old ‘Rocha’ pear trees, grafted on quince BA29, were planted in a Mediterranean region, and fertigated with 6 g N tree⁻¹ year⁻¹ as ammonium nitrate with 5 at.% ¹⁵N enrichment to study the fertilizer N uptake during the vegetative cycle, the overall fertilizer N use efficiency at the end of each year, and the plant–soil N balance for this period. Nitrogen remobilization and the re-cycling of N from senescent leaves were also studied by fertilizing some pear trees with 10 at.% ¹⁵N enrichment.     

Water spray as a potential thinning agent for date palm flowers (Phoenix dactylifera L.) c.v. ‘Lulu’

Flower or fruit thinning is a critical cultural practice in the date palm production chain that affects fruit development, quality and yield and regulates tree yearly bearing. Development of a save and economic thinning agent for date palm is critically required especially under harsh conditions. During 2004 and 2005 seasons, water spray for 3 min was applied at different times following mechanical pollination on ‘Lulu’ date palm cultivar growing under Al-Ain oasis conditions. The results showed that water spray following pollination generally decreased fruit set percentage to different extent depending of the time of application. In this respect, the most effective treatment was water spray after 4 h following pollination. This treatment significantly decreased fruit set percentage (48%) compared to the control (79%), as the mean of both seasons. However, the other treatments including water spray 1 h before pollination also decreased fruit set percentage but to a lesser extent. Fruit quality characteristics especially fruit and flesh weight, length and diameter were significantly increased by water spray treatments during the 2004 season, in contrast to the 2005 season. Thinning with water significantly decreased both bunch weight and total yield per tree at the Tamr stage especially when applied after 4 h following pollination. To the best of our knowledge, this is a pioneer study investigating the role of water as a potential thinning agent for date palm flowers. The use of water spray as a save and economic thinner needs, however, more research work to justify the time following pollination and duration of application which may vary upon cultivar, method of pollination and district.     

Performance of ‘Tahiti’ lime on twelve rootstocks under irrigated and non-irrigated conditions

Faced with new challenges, such as emerging diseases, shortening of orchard longevity, and larger social and environmental demands from consumers, practices such as rootstock diversification, irrigation and high density plantings have become relevant for the Brazilian citrus industry. This research had the objective to evaluate the performance of irrigated and non-irrigated ‘Tahiti’ lime trees grafted on 12 rootstocks and one interstock. Plots were distributed following a randomized block design, with four replicates and one plant per plot. Rootstocks influenced plant vigor, especially ‘Flying Dragon’ trifoliate, which reduced tree height by approximately 47% compared to the ‘Rangpur’ lime. Trees that were budded on more vigorous rootstocks showed higher yield when grown without irrigation than with irrigation. The ‘1646’ citradia and ‘Morton’ citrange rootstocks performed particularly well. On the other hand, the plants on less vigorous rootstocks showed better performance in terms of yield under irrigation than the same combinations without irrigation, especially those grafted on the tetraploid ‘Carrizo’ and ‘Troyer’ citranges, ‘Swingle’ citrumelo, ‘Davis A’ trifoliate and ‘Flying Dragon’ trifoliate. Plants budded on the ‘1708’ citradia had high yields under irrigated and non-irrigated conditions. The effect of interstock on plant vigor was dependent of rootstock. Interstocked plants on ‘Davis A’ trifoliate were higher than those without interstock. On the other hand, interstocked plants on Catania 2 ‘Volkamer’ lemon were less vigorous than those without interstock.     

Vegetative and productive responses of ‘Conference’ and ‘Williams’ pear trees planted at different in-row spacings

The effect of in-row spacing on the vegetative and productive performance of 4-year-old ‘Conference’ (CON) and ‘Williams’ (WIL) pear trees was studied. Analysis of digital images was used to estimate canopy growth and conformation. Fruit quality was determined by measuring fruit weight, flesh firmness, peel color, soluble solid content, and titratable acidity. WIL produced more and more efficiently than CON, especially at closer spacings. WIL canopies were generally bigger than CON canopies, and reduced spacing penalized stem growth and influenced canopy conformation. Root growth and conformation was similar for both cultivars, whereas decreasing in-row spacing reduced root dry weight, length, volume, and spread area only in WIL. Also, WIL trees partitioned more to fruit and leaves compared to CON, and increasing spacing resulted in a relative shift toward vegetative growth. CON fruit was smaller but sweeter and less acidic than WIL fruit. Increasing spacing influenced negatively WIL fruit quality parameters, with the only exception of fruit weight, which was increased. For the range of in-row spacing considered, our results indicate that WIL may represent a more efficient and competitive option than CON for high-density plantings, at least in the early stages of orchard life.     

A pilose fruit mutant in banana (Musa spp. ‘Williams’)

A mutant of Musa spp. ‘Williams’ was isolated by screening the plants from tissue culture and rapid propagation. We studied the morphological characteristics of the fruit epidermis by scanning electron microscopy (SEM). The results showed that the pericarp of mutant was covered with trichomes. These trichomes were pointless and the length of the trichomes ranges from 0.02 to 0.37 mm. However, this kind of trichome was not observed on the pericarp of the wild type.     

Contributions of short- and long-shoots to yield of ‘Kerman’ pistachio (Pistacia vera L.)

The canopy of a mature ‘Kerman’ pistachio (Pistacia vera L.) tree is composed of two types of shoots: short-shoots composed entirely of preformed nodes, and long-shoots composed of both preformed and neoformed nodes. Since the production of these two types of shoots is known to be related to rootstock and rootstock influences yield of pistachio the relationship of these two types of shoots to yield was investigated during two cropping years. Individual short-shoots produced significantly less yield and had fewer fruit clusters per shoot compared with long-shoots, but collectively produced 55–60% of the total yield. Long-shoots positively affected yield components in one year, but had no effect in the other year. Whether the differences in the one year were due to canopy position and light interception or differences in the carbohydrate allocation within the two types of shoots could not be determined from the current data. Long-shoots initiated more inflorescence buds, although inflorescence bud formation was restricted to the preformed growth and only the 3–4 earliest neoformed nodes. However, when expressed as a percentage, long-shoots retained a lower percentage of initiated inflorescence buds, compared with short-shoots. Regardless of shoot type, less than half of the retained inflorescence buds produced mature fruit clusters. Thus, inflorescence bud retention, a previously hypothesized mechanism of pistachio alternate bearing, may not be the primary limiting factor to yield in pistachio.