Almond Hybrid Research Articles

Botryosphaeriaceae Infections on Prunus Germplasm: Evaluation of Pathogenicity, Resistance Loci, and Detached Assays of Southeastern United States Isolates

Research of peach fungal gummosis (PFG), which is a vascular disease caused by fungi in the Botryosphaeriaceae family, is particularly important in the southeastern United States, southern China, South Africa, and Western Australia. This disease has been a significant concern for the peach industry in the southeastern United States since the 1970s. The changing climatic conditions in the prunus production areas of the world have worsened the severity of PFG disease. A study of the morphological and genetic profiles of Botryosphaeriaceae species from diseased peach trees found four species in Georgia, Florida, Alabama, and South Carolina. Botryosphaeria dothidea, Lasiodiplodia theobromae, Diplodia seriata, and Neofusicocoum parvum were isolated and identified using conidiospore characters and rDNA sequences of internal transcribed spacer regions and elongation factor α-1 genes. B. dothidea was the most common species from diseased peach trees. A significant implication of this research is the potential resistance in Prunus germplasm, which was genotyped for the resistance locus Botd8 and evaluated for relative susceptibility to one isolate each from B. dothidea, L. theobromae, and D. seriata. Pathogenicity evaluations of peach, almond, and interspecific hybrids used detached stem and leaf assays for susceptibility to PFG based on lesion lengths and gumming scores. L. theobromae inoculation resulted in the most extensive lesions on stems and leaves. Detached stem and leaf assays indicated that Prunus with the Botd8 locus significantly differed in lesion size when infected with B. dothidea and D. seriata. However, the resistant locus had no significant effect on the relative susceptibility of Prunus to L. theobromae. Field and detached stem and leaf assays identified almond cultivars Pioneer and Golden State and Peach × Almond hybrids with Botd8 (+) as tolerant to PFG. Correlations between detached assays and field gumming scores suggested that inoculations on detached stems or leaves under controlled conditions can be used to preliminarily screen for resistance to PFG. These detached assays for specific pathogen isolates provide an opportunity for a relatively fast, nondestructive evaluation of Prunus germplasm and are tools that can be used to identify the components of disease resistance.

Diversity of microbial, biocontrol agents and nematode abundance on a susceptible Prunus rootstock under a Meloidogyne root gradient infection.

Root-knot nematodes (RKNs) of the genus Meloidogyne are one of the most damaging genera to cultivated woody plants with a worldwide distribution. The knowledge of the soil and rhizosphere microbiota of almonds infested with Meloidogyne could help to establish new sustainable and efficient management strategies. However, the soil microbiota interaction in deciduous woody plants infected with RKNs is scarcely studied. This research was carried out in six commercial almond groves located in southern Spain and infested with different levels of Meloidogyne spp. within each grove. Several parameters were measured: nematode assemblages, levels and biocontrol agents in Meloidogyne's eggs, levels of specific biocontrol agents in rhizoplane and soil, levels of bacteria and fungi in rhizoplane and soil, fungal and bacterial communities by high-throughput sequencing of internal transcribed spacer (ITS), and 16S rRNA gene in soil and rhizosphere of the susceptible almond hybrid rootstock GF-677 infested with Meloidogyne spp. The studied almond groves showed soil degradation by nematode assemblies and fungi:bacterial ratio. Fungal parasites of Meloidogyne eggs were found in 56.25% of the samples. However, the percentage of parasitized eggs by fungi ranged from 1% to 8%. Three fungal species were isolated from Meloidogyne eggs, specifically Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperellum. The diversity and composition of the microbial communities were more affected by the sample type (soil vs rhizosphere) and by the geographical location of the samples than by the Meloidogyne density, which could be explained by the vigorous hybrid rootstock GF-677 and a possible dilution effect. However, the saprotrophic function in the functional guilds of the fungal ASV was increased in the highly infected roots vs the low infected roots. These results indicate that the presence of biocontrol agents in almond fields and the development of new management strategies could increase their populations to control partially RKN infection levels.

Grafting commercial cultivars of almonds on accurate rootstocks mitigates adverse effects of drought stress

Tolerance to drought can be improved by grafting commercial varieties onto drought tolerant rootstocks. The interaction of rootstock and scion might be a mechanism for resistance to the environmental stresses such as drought in almonds. The aim of this research was to study if short-term exposure to drought in grafted plants using diferent rootstocks would show tolerance to drought now. To fulfill this objective, some parameters (proline content, soluble carbohydrates, malondialdehyde (MDA), electrolyte leakage (EL) and antioxidant enzymes activity such as ascorbate peroxidase (ASC) and peroxidase (POD), relative water content (RWC), stem water potential (ΨSWP or SWP) and water use efficiency (WUE)) of scions (5 commercial almonds) grafted on 3 rootstocks were analyzed. Factorial study based on randomized complete block design with three replications was carried out to determine the most tolerance compound. The factors included cultivars in 5 levels (‘Supernova’, ‘Texas’, ‘Marcona’ ‘Shokoufeh’ and ‘K13–40′), rootstocks in 3 levels [(peach × almond hybrids: ‘GF677’, ‘GN22’ and ‘seedling bitter almond ‘No.32′] and drought stress in 4 levels (No: -0.1 MPa (NS), Moderate: -0.7 MPa (MS), Severe: -1.1 MPa (SS) and very severe: ΨSWP ≤ -2.8 MPa (VSS). The results revealed that increasing drought stress leads to a decrease in the proline content, soluble carbohydrates, MDA, EL, and the activity of ASC and POD enzymes in various rootstock-scion grafted were increased. In the VSS, the highest content of proline in comparison with control (+ 73.43%) was related to the ‘K13–40′ on ‘GF677’. The highest MDA (46.50 and 45.29 nmol/gfw) was in ‘Supernova’ and ‘K13–40′ cultivars on the ‘No.32′ rootstock, which increased 76.47% and 75.43%, in the compared to the control, respectively. Drought stress in sensitive rootstock and scion grafted (‘K13–40′ on ‘No.32′), reduced RWC by 44%, also ΨSWP in resistant rootstock and scion grafted (‘Shokoufeh’ on ‘GF677’), WUE increased up to 9 times. In essence, all cultivars, especially ‘Shokoufeh’ grafted on ‘GF677’ rootstock, were more resistant to the VSS in comparison with the grafts of the same cultivars on the ‘No.32′ and ‘GN22’ rootstocks in this study.

Preliminary Results in the Study of Two Local Almond Populations from Dobrogea Region

The almond (Prunus dulcis L.) is a very popular nut, being one of the most complex fruits for the benefit of the human health. Nowadays in Romania, this crop started to decrease as covered land and production. At the global level the cultivated surfaces and the production is on raise. The aim of our study was to select better almond genotypes suitable for breeding. The study’s goal was to monitor two spontaneous populations of almond hybrids naturally formed in two distinct localities from the Dobrogea region, namely Greci, from Tulcea county and Crucea, from Constanta county. Naturally formed almond hybrids were studied and observations have been performed for the phenophases in the years 2018 and 2019, also observing the presence of different pathogenic diseases on the phyllosphere of the plants. There were also accomplished morphological measurements for the hybrids of high interest according to the purpose of the present research work.

Investigation of tensile, flexural and impact properties of Neem-Indian almond hybrid fiber based epoxy composites

Composite materials are used in place of conventional material as they reduce the weight of the structure and increase the strength. Hybrid composite consists of two or more reinforcing fillers of different properties. In this investigation, a Tri layer Hybrid composites of Neem and Indian almond fruit fiber were prepared using hand layup method. Neem was used in outer layer and Indian almond fruit fiber was used in inner layer and vice versa while fabricating the hybrid composites. The tensile, flexural and impact properties of prepared hybrid composites were studied. The results displayed that the tensile and flexural properties of hybrid composite made with Neem as outer layer increased by 6.8% & 5.5% respectively compared to that of hybrid composite made with Indian almond fruit fiber as outer layer. The improvement of tensile and flexural properties was due to the presence of high strength Neem fiber at outer most layers. Moreover, the impact strength of hybrid composite made with Indian almond fruit fiber as outer layer exhibited better impact strength (5.1 kJ m−2) compared to the impact strength of hybrid composite made with Neem fiber as outer layer. The impact strength enhanced due to the surface cracks of Indian almond fruit fiber as it absorbs more impact energies while loading and finally improved the impact strength of hybrid composite.

Rootstock performance in the 2009 NC-140 peach trial across 11 states

From 14 to 18 Prunus rootstocks budded with ‘Redhaven’ peach were planted at 16 locations in North America in 2009. Seven-year performance from 12 remaining locations in 11 states showed that significant differences among rootstocks and sites were found for survival, root suckers, growth, bloom date, fruit maturity date, fruit size, cumulative yield, and yield efficiency. Survival was highest for peach seedling rootstocks at all locations. In contrast, survival of non-peach species and hybrid rootstocks was poor to fair in Missouri (winter cold, wet feet conditions) and Alabama, Georgia, North Carolina, and South Carolina due to bacterial canker. Krymsk®1, Krymsk®86, Penta, Controller(TM) 5 and Mirobac (a.k.a. Replantpac or Rootpac®R) were the most susceptible to tree death from Pseudomonas syringae canker in the four southeastern states. Overall, Imperial California had the lowest survival followed by Fortuna and Krymsk®1. Rootstock suckering was excessive on Prunus americana seedlings with lesser suckering noted on, Mirobac, Krymsk®1 and Penta. Largest trees were three Prunus × almond hybrids (Viking, Atlas, Brights Hybrid #5) and Guardian®. Fruit size varied with location and crop load (i.e., some rootstocks had few fruit). Atlas produced the largest fruit and Fortuna the smallest fruit across all sites. Cumulative yields were highest in the peach rootstocks such as Guardian®, Lovell and KV010127 and on Atlas. The lowest yields were from plum hybrids and plum species. Cumulative yield efficiency was higher on the non-peach rootstocks, but these rootstocks also produced trees much smaller than the peach and almond hybrid cultivars. The clonal P. persica rootstocks HBOK 10 (Controller(TM) 8) and HBOK 32 (Controller(TM) 7) appeared to be the most promising of the size-controlling rootstocks tested. These data suggest there was no demonstrated advantage to increase yield ha-1 by using clonal interspecific Prunus hybrids for peach production under current cultural practices. However, on higher pH soils in Colorado and Utah, peach seedlings were not the superior rootstocks for production so continuing evaluation of non-peach rootstocks is warranted.

Long-term graft compatibility study of peach-almond hybrid and plum based rootstocks budded with European and Japanese plums

The introduction of some new rootstocks requires knowledge of the potential ‘translocated’ and ‘localized’ graft incompatibilities before releasing these rootstocks into the market. Trials were established at the Aula Dei Experimental Station (Zaragoza, Spain) to assess graft compatibility between five European plum (Prunus domestica L.) and six Japanese plum (Prunus salicina L.) cultivars with thirty-eight rootstocks belonging to peach × almond hybrids, as well as slow-growing, fast-growing and interspecific hybrid plum groups. Some of these rootstocks are under process of selection and others are commercial rootstocks already introduced into the European market. External visual diagnosis of the scion-rootstock graft combinations was performed by observing symptoms of the ‘translocated’ incompatibility in the nursery. Visual symptoms of ‘translocated’ incompatibility were only found on the Japanese plum cv. ‘Golden Japan’ budded on the plum-apricot hybrid AP-45. The ‘localized’ graft incompatibility was assessed after internal macroscopically examination of graft unions. In the case of the European plum cvs., ‘President’ and ‘Reine Claude Tardive of Chambourcy’ exhibited good graft compatibility with all the tested rootstocks, with the exception of ‘President’ budded on the pentaploid plum hybrid rootstock Damas GF 1869. ‘Reine Claude Verte’ cv. showed ‘localized’ incompatibility with Myrobalan B and Myrobalan GF 3-1 since the second year after budding. ‘Stanley’ cv. showed ‘localized’ incompatibility with the six evaluated peach × almond hybrid rootstocks, although it was compatible with all plum based rootstocks. In the case of Japanese plums, four cultivars (‘Angeleno’, ‘Black Amber’,’ Delbarazur’ and ‘Songold’) did not show any graft incompatibility, but ‘Friar’ showed ‘localized’ incompatibility on Myrobalan B. In the case of peach-almond and P. cerasifera based rootstocks (Adarcias, GF 677, Damas GF 1869, Myrobalan B, Myrobalan 29 C, Myrobalan GF 3-1 and Marianna GF 8-1), ‘Golden Japan’ trees showed similar symptoms to those caused by TomRV in Myrobalan and peach rootstocks and ‘localized’ incompatibility. Finally, this study confirmed the interest of P. insititia specie as well as several interspecific Prunus hybrids as a good source of rootstocks for the plum industry.

Influence of peach–almond hybrids and plum-based rootstocks on mineral nutrition and yield characteristics of ‘Big Top’ nectarine in replant and heavy-calcareous soil conditions

The agronomic performance and leaf mineral nutrition for ‘Big Top’ nectarine budded onto twelve Prunus rootstocks were evaluated. Seven Prunus amygdalus×Prunus persica hybrids (Adafuel, Adarcias, Felinem, Garnem, Monegro, GF 677, and Mayor), two Prunus davidiana×P. persica hybrids (Barrier, Cadaman), a Prunus insititia plum (Adesoto), a Prunus domestica plum (Tetra), and another selection considered to be an hybrid of Prunus cerasifera×P. amygdalus parentage (Replantpac). Rootstocks were budded during the summer of 1999, and trees were established in a replant site in March 2001. The trial was located in the Ebro Valley (Northeastern, Spain) on a heavy-textured and calcareous soil typical of the Mediterranean area which supported a previous peach orchard until 2000. At the thirteenth year after budding, growing conditions generated varying levels of tree mortality, the highest with peach-almond hybrids: Adafuel, Garnem and Monegro. In contrast, all Replantpac trees survived well and the mortality rate was low on the other rootstocks. Adesoto, Tetra, and Adarcias proved to be the most dwarfing rootstocks, while Cadaman and Replantpac were the most invigorating and generated greater cumulative yields. However, the highest yield efficiency was recorded on GF 677, although it did not differ significantly from other peach-almond (Adarcias, Felinem) and plum (Adesoto, Tetra) rootstocks. The highest fruit weight was observed on Barrier and the lowest on Felinem and Mayor, but they did not differ significantly from the rest of rootstocks. Leaf mineral analysis of trees showed all rootstocks induced N and Fe deficiency and P optimum value according to reference values. Nevertheless, the tendency of plum Adesoto to induce higher Fe leaf concentration could indicate higher tolerance to iron-chlorosis in calcareous soils. The most invigorating rootstock Replantpac seems to induce higher SPAD values and adequate K, Mg and Mn values according to reference values. Tetra induced the best balanced nutritional values (ΣDOP), especially when compared with Barrier and Cadaman, although it did not differ significantly from GF 677 and Mayor.

FIRST RESULTS OF THE EVALUATION OF SIX PRUNUS INTERSPECIFIC ROOTSTOCK SELECTIONS IN COMPARATIVE TRIALS SET UP IN TWO DIFFERENT ENVIRONMENTS

Peach culture is increasingly extended to areas which often do not offer soil conditions truly suited to this crop. Replanting, limestone chlorosis, soilborne pests and pathogens are among the most common problems in many Mediterranean basin countries. In a collaborative project supported by EU (1999-2003), interspecific crosses among different Prunus species originated several hybrid progenies, from which potential new rootstocks for the main stone fruit crops were selected for their resistance to biotic and/or abiotic stresses. Six of these were agronomically evaluated in two rootstock comparative trials set up in two important peach-growing areas located in the North (Romagna, Southern Po Valley) and South of Italy (Metaponto, Basilicata). In both trials, the rootstock selections P.2175 A— P. davidiana-1, P.2175 A— Garnem-3, P2175 A— P. davidiana-4, P2175 A— Garnem-16, P2980 A— Felinem-23 and P2980 A— Garnem-9 were compared with the peach A— almond hybrid GF677, susceptible to root-rot disease and by far the widest spread rootstock in Italy. The trial in Romagna was set up on a replanting soil infected by A. mellea, which had caused the explanting of the previous peach orchard; in addition to GF677, this trial included also GF43 (P. domestica) and Adesoto 101 (P. insititia) as control rootstocks, known as being endowed with some tolerance to this fungal disease. Although evaluation is still in progress, preliminary results showed variability for graft compatibility and induced vigour depending on the rootstock and on the scion cultivar. Total yield/tree was generally higher onto GF667, but some of the hybrid rootstock selections positively affected fruit size and sugar content, yield efficiency and/or significantly anticipated harvest time.

Asymmetrasca decedens (Cicadellidae, Typhlocybinae), a natural vector of ‘Candidatus Phytoplasma phoenicium’

Abstract‘Candidatus Phytoplasma phoenicium’ is associated with a lethal disease of almond, peach and nectarine named almond witches'‐broom disease (AlmWB). The disease spread rapidly in Lebanon from coastal areas to elevations exceeding 1200 m, killing over 150,000 trees in a span of two decades. The mode of spread suggested the involvement of efficient vector(s) and Asymmetrasca decedens (Hemiptera, Cicadellidae) was suspected as it is the most abundant leafhopper species present in Lebanese stone fruit orchards. Living A. decedens specimens were collected from fields heavily infested by AlmWB and used in transmission trials on healthy peach almond hybrid GF‐677 and peach GF‐305 seedlings with an inoculation‐access period of 30 days. PCR analysis supported by sequencing showed that A. decedens is a carrier of the phytoplasma, and that the phytoplasma was detected in insect salivary glands and in some inoculated GF‐677 and GF‐305 seedlings. One year post‐inoculation, ‘Ca. P. phoenicium’ was detected in newly emergent leaves of inoculated seedlings. However, the characteristic symptoms of witches'‐broom were not observed. PCR amplified fragments from phytoplasma‐positive seedlings and from A. decedens samples showed 99.9% nucleotide identity in their 16S RNA region and phylogenetic analysis using a neighbour jointing tree confirmed that the phytoplasmas detected in both insects and inoculated seedlings belonged to 16SrIX‐B (D). The present manuscript is the first known report for a leafhopper vector of ‘Ca. P. phoenicium’ and shows that the incubation period of the disease in plants may be longer than 1 year. The importance of phytosanitary control measures, the adoption of a national strategy and regional cooperation in order to contain the further spread of the disease are discussed.

Resistance of nectarine and peach-common almond hybrids by leaf curl

Purpose. Isolation of genotypes of distant nectarine and peach-common almond hybrids with a low susceptibility to the peach curl pathogen.Methods. The investigations were carried out in 2009-2013 on the breeding plots of the Nikitsky Botanical Garden. Susceptibility to the peach curl was studied by the method of VI Mitrofanov & AV Smykov using a nine-point scale, where 1 point means minimal damage, 9 points mean maximal damage. The source material was 48 forms of distant nectarine and peach-common almond hybrids created with the involvement of Persica vulgaris Mill., Persica vulgaris subsp. nectarina (Ait.) Shof., Persica mira Kov. et. Kostina, Persica davidiana Carr., Amygdalus communis L. characterized by a low degree of susceptibility to peach leaf curl under the field conditions on the natural infectious background. The nectarine varieties Rubinovyy 8 and Stark Sanglo, the almond variety Primorskiy, and the peach variety Podvoynyy 1 were used as controls.Results. Of the 48 studied forms of distant hybrids 29 forms with a very low susceptibility to the peach curl pathogensusceptibility to the peach curl pathogen, eight forms with a low susceptibility, seven forms with a medium susceptibility, and four forms with high susceptibility were isolated. In other words, the majority (37 of 48, or 77 %) of the hybrids were found to be very low-susceptible or low-susceptible to peach leaf curl. These genotypes can be recommended for use in nectarine and peach breeding to create varieties with a low susceptibility to Taphrina deformans (Berk.) Tul. It was revealed that nectarine-almond hybrids of the first generation were hardly affected by peach leaf curl. In further crosses with nectarine varieties many hybrids of the second and subsequent generations retain a low susceptibility to this pathogen, and this trait is inherited.Conclusions. The usage of common almond in nectarine breeding for resistance to leaf curl is beneficial, and breeding via distant hybridization within the subfamily Prunoideae Focke requires further research and development.

Relationship between endogenous hormonal content and somatic organogenesis in callus of peach (Prunus persica L. Batsch) cultivars and Prunus persica × Prunus dulcis rootstocks

The relationship between endogenous hormones content and the induction of somatic peach plant was studied. To induce multiple shoots from callus derived from the base of stem explants of the scion cultivars 'UFO-3', 'Flariba' and 'Alice Bigi', and the peach×almond rootstocks 'Garnem' and 'GF677', propagated plants were cultured on Murashige and Skoog salts augmented with 0.1mgL(-1) of indolebutyric acid, 1mgL(-1) of 6-benzylaminopurine and 3% sucrose. The highest regeneration rate was obtained with the peach×almond rootstocks. Endogenous levels of abscisic acid (ABA), indole-3-acetic acid (IAA), zeatin (Z), zeatin riboside (ZR), ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), salicylic acid (SA), and jasmonic acid (JA) were analyzed in the organogenic callus. Lower levels of several hormones, namely Z, ZR, ABA, and ACC were found in the peach×almond rootstock compared to peach cultivars, while IAA and SA presented inconclusive returns. These results suggest that the difference in somatic organogenesis capacity observed in peach and peach×almond hybrids is markedly affected by the endogenous hormonal content of the studied genotypes.

Using putrescine to increase the rooting ability of hardwood cuttings of the peach × almond hybrid GF677

Abstract GF677 is an interspecific hybrid which has important value in terms of economic and horticultural characteristics. The use of this rootstock for some stone fruit trees including almond and peach has been increased dramatically in recent years. It has some useful characteristics i.e. high tolerance to calcareous soil, a strong root system and suitability for poor soils, but its propagation is difficult. This study aimed to evaluate the effect of putrescine (PUT) on the rooting of GF677 cuttings under mist conditions. Treatments used include PUT concentrations (2 and 4 mM for 5 minutes), indole-3-butyric acid (IBA) using the quickdip method (1500 and 3000 mg l-1 for five seconds), and a commercial rooting powder and control (without any rooting substances). Treatments were applied at the end of the dormant season. Growth data were obtained 120 days after the treatments. The results showed that application of 1500 mg l-1 of IBA and commercial rooting powder improved GF677 rooting, but 3000 mg l-1 of IBA resulted in toxic effects on rooting and foliage of the cuttings. Cuttings treated with PUT solutions showed the best roots and shoots in terms of the number and quality. In conclusion, IBA may be replaced by PUT in the rooting process of GF677 cuttings.

THE EFFECT OF ROOTSTOCK ON AGRONOMICAL PERFORMANCE AND FRUIT QUALITY OF 'ELEGANT LADY®' PEACH CULTIVAR

The agronomical performance and fruit quality of 'Elegant Lady (Merdame)' peach cultivar grafted on 22 rootstocks were evaluated over 1996-2005 and 1996-2003 periods at IRTA's Experimental Stations of Lleida and Mas Badia (Spain), respectively. Rootstock origin was: peach seedlings, peach × almond hybrids, inter-specific hybrids and different plum species. Blooming period was not consistently affected by the rootstock, except for Barrier which tended to advance bloom from 2 to 3 days. Tree vigour was significantly affected by the rootstock, thus, three groups of vigour were established from more to less vigour: 1) Felinem (GxN-22), Myran (Yumir), Titan, INRA GF-677, Garnem (GxN-15), Barrier and Cadaman (Avimag); 2) peach seedlings: INRA GF-305, Montclar (Chanturgue), Rubira, PS-A5, PS-A6, PS-B2, Nemared, Nemaguard; 3) Isthara (Ferciana) and plum rootstocks. Annual and cumulative yield were affected by location and rootstock, obtaining higher yields in Lleida than in Girona. More vigorous rootstocks also provided, in general, greater yields per tree. When cumulative yield and vigour were related (yield efficiency), all rootstocks resulted in a good efficiency which was greater in less or medium vigorous rootstocks as Jaspi (Fereley), Isthara (Ferciana), Barrier, Cadaman (Avimag), plum and peach seedling rootstocks than in the most vigorous ones as Myran (Yumir), Titan or Felinem (GxN-22). From the vigorous rootstocks, INRA GF-677 provided the greater yield efficiency in both locations. Sensitivity to iron chlorosis was also affected by the rootstock: Nemaguard, Nemared and Myran (Yumir), were the most sensitive, and INRA GF-677 and Titan being the most tolerant, and providing the rest intermediate values. INRA GF 655/2 was the most sensitive to root suckering, followed by the rest of plum rootstocks and Jaspi (Fereley). Inter-specific hybrids and peach seedlings were not sensitive to root suckering. Fruit colour was enhanced by plum rootstocks and Ishara (Ferciana). Fruit firmness was greater for Barrier, Cadaman (Avimag), INRA GF-677, Garnem (GxN-15) and Felinem (GxN-22), intermediate for peach seedlings and lower for plum rootstocks and Ishara (Ferciana), depending on the location. Soluble solids content was in the opposite sense than fruit firmness, and titratable acidity was not affected by the rootstock.

EFFECT OF ORGANIC FERTILIZATION, RIPENING STAGE AND STORAGE ON QUALITY OF FRUITS OF 'STARK REDGOLD' NECTARINE

The objectives of this experiment were to evaluate the effect of 1) application of compost, 2) ripening stage and 3) storage time on composition and antioxidant activity of nectarine fruit. The investigation was conducted in 2009 in an experimental orchard of ‘Stark RedGold’ nectarine (Prunus persica var. nectarine) grafted on GF677 (peach (P. persica) × almond (P. amygdalus) hybrid rootstock that, since its plantation (2001), was subjected to the following experimental treatments: 1. control not fertilized; 2. mineral fertilization including N (70-130 kg ha-1 year-1) split in two applications at 40 days after full bloom (60%) and in September (40%); 3. compost (10 t dw ha-1 year-1) split as above. As a result of compost application, soil N and organic matter concentration were statistically increased. Samples of 20 fruit were collected one month (2 July) and one week (22 July) before commercial harvest, at commercial harvest (fruit ripening) (4 August), after 2 weeks at 6°C (cold storage, 17 August) and after 4 days at 24°C (shelf life, 21 August). At each sampling date fruit were weighed, lyophilised and milled to evaluate the concentration of organic acids, soluble sugars and antioxidant activity. At commercial harvest fruit yield, precocity index and, on 20 additional fruit, skin colour, fruit firmness, pH, acidity and soluble solid content (SSC) were determined. After cold storage and shelf life fruit firmness and SSC were determined. Nine years of soil application of different fertilizers did not modify sugar and soluble acid concentrations. Fruit firmness and acidity were increased by the application of compost as well as starch concentration that was higher, compared with control. Fruit sugar concentration increased while soluble acid and starch concentration decreased as ripening proceeded. Antioxidant activity was highest in unripe fruit and lowest after shelf life. In conclusion, the application of compost delayed fruit ripening; moreover antioxidant activity decreased with the development of fruit ripening.

Effects of Myo-Inositol and Thiamine on Micropropagation of GF677 (Peach × Almond Hybrid)

GF677 is a vigorous rootstock, used for both peach and almond worldwide. Nowadays, it is propagated is mainly through micro propagation. Widening and undesirable growth of leaves as well as poor rooting are major problems during its in vitro culture. In this study, effects of myo-inositol at 10 and 100 mg/l In MS medium were studied at explants establishment and shoot growth stages. Thiamine was also used in LS medium at 0, 1.6, 2.8 and 4 mg/l at rooting stage. This experiment was conducted in Randomized Complete Design with 10 replications. Myo-inositol at 10mg/l could prevent undesirable widening of leaves as well as rosetting of shoots. Thiamine at 1.6 mg/l was highly effective in rooting of shoots.

Physiological responses and differential gene expression in Prunus rootstocks under iron deficiency conditions

Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach–almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed.

Compost can successfully replace mineral fertilizers in the nutrient management of commercial peach orchard

AbstractThe objective of this experiment was to evaluate in the long‐term (9 years), the suitability of compost as a fertilizer in commercial peach orchard. The experiment was carried out on nectarine trees (Prunus persica var.nectarina), Stark RedGold grafted on GF677 peach × almond (P. amygdalus L.) hybrid. The treatments were: (1) unfertilized control; (2) mineral fertilization including phosphorus (P at 100 kg/ha) and potassium (K at 200 kg/ha) applied at planting and nitrogen (N at 70–130 kg/ha/yr) split in two applications at 40 days after full bloom (60%) and in September (40%); (3) cow manure supplied at planting [10 t dry weight (dw)/ha] and then, from the forth year at the rate of 5 t dw/ha/yr in spring; (4) compost supplied at planting (10 t dw/ha) and then, from the forth year at the rate of 5 t dw/ha/yr in spring; (5) compost supply at a rate of 5 t dw/ha/yr, and (6) 10 t dw/ha/yr, both treatment 5 and 6 split as described for treatment 2. Nitrate‐N soil concentration was usually not affected by treatments. Soil microbial carbon, organic matter, total N, P, K were increased by application of organic fertilizers. SOM and total N were positively correlated to soil microbial biomass. Aggregate stability, humic and fulvic acid concentration were not affected by fertilization treatment. Only the application of compost at 10 t dw/ha/yr (6) increased fruit production.

EFFECTS OF MINERAL AND ORGANIC FERTILIZATION AND RIPENING STAGE ON THE EMISSION OF VOLATILE ORGANIC COMPOUNDS AND ANTIOXIDANT ACTIVITY OF 'STARK REDGOLD' NECTARINE

Our objective was to investigate the effect of fertilization (mineral vs. organic) and ripening stage (pre-climacteric vs. climacteric) on the emission of volatile organic compounds (VOCs) and antioxidant activity of nectarine [Prunus persica, Batsch var. nectarina (Ait) Maxim.]. The trial was carried out in 2007 in an experimental orchard of cv. Stark RedGold grafted to GF677 peach x almond hybrid planted in 2001. The trees were subjected to mineral (N, 120 kg ha -1 year -1 ) or organic (compost, 10 t DW ha -1 year -1 ) fertilization from plantation, with treatments applied 40 days after full bloom at 60% of the annual rate and in September at 40%. A fruit sample was collected every day from 22 July to 3 August. The difference in the absorbance index (I AD ) of each fruit at each sampling date was measured by visible/near infrared spectroscopy (VIS/NIRs). Fruits were sorted into two groups corresponding to two ripening stages: pre-climacteric (l AD >0.9 and flesh firmness > 50N) and climacteric (I AD <0.4 and flesh firmness <15N). The day after each sampling, two nectarines per treatment (8 per day) were sealed in a jar for 50 minutes and VOC emission was measured in overhead air samples by gaschromatographic analysis. VOCs increased from pre-climacteric to climacteric ripening stage and were higher in fruit fertilized with compost than in those treated with mineral fertilizers. Linalool, dodecane, methyl-4-decenoate, 1-decene were among the molecules increased by compost dressing. While antioxidant activity was unaffected by ripening stage and fertilization, it was higher in fruit peel than in flesh.

EFFECTIVENESS OF SOIL-APPLIED FRESH-GROUND MELIA (MELIA AZEDARACH L.) FRUITS ON NITROGEN UPTAKE FOR PEACH TREES

We assessed the effect of soil-applied fresh-ground fruits of melia (Melia azedarach L.) on N uptake for peach nutrition. Forty one-year-old 'Rome Star' peach trees (Prunus persica) grafted to GF677 peach x almond hybrid rootstock were planted in 20-L pots in April 2006. On 16 May, 20 pots were fertilized with compost at a rate of 100 g/pot and 20 pots were dressed with urea at 1.4 g/pot. On September 11, the two sets of trees received the same amount of N (0.64 g/pot) as urea (urea-treated pots) and blood meal (compost-treated pots). The following compounds were applied as nitrification inhibitors to 4 pots each: untreated control; 3,4-dimethylpyrazole phosphate (DMPP) at 10 mg/pot; commercial neem cake at 20 g kg -1 of soil; and fresh-ground fruits of melia at 20 and 40 g kg -1 of soil. All inhibitors were incorporated into the soil at planting except for DMPP, which was supplied along with the fertilizer (urea and compost/blood meal) applications. In our experimental conditions, all the nitrification inhibitors did not delay soil N mineralization, indeed the application of neem cake increased soil NO 3 - -N concentration in all sampling dates. An increase in leaf N concentration and microbial respiration was observed after application of neem cake and ground melia fruits at both concentrations, although only the latter increased shoot length.