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  • Author or Editor: Jorge Pinochet x
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The influence of temperature and age of the plant was determined on nematode reproduction on a susceptible almond (Prunus amygdalus Batsch.) and on a resistant peach-almond hybrid (P. persica Stok. × P. amygdalus Batsch.) rootstock inoculated with Meloidogyne javanica (Treub) Chitwood. Experiments were conducted under greenhouse conditions in heated and unheated sand beds. `Garrigues' almond inoculated with 3000 nematodes per plant showed extensive galling, high final nematode population levels, and high counts of nematodes per gram of root at 27 and 32C. The hybrid G × N No. 1 showed minimal galling and reproduction at 27C but higher levels of galling and final population and nematode counts per gram of root at 32C, suggesting a partial loss of resistance with temperature increase. One-month-old and 1-year-old plants of `Garrigues' were susceptible following inoculation with 2000 nematodes per plant, although plantlets (l-month) were significantly more affected. Plantlets of hybrid G × N No. 1 were also susceptible, but 1-year-old plants were resistant. Resistant genotypes (G × N selections) seem to require root tissue maturation before expressing full resistance.

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This paper reports the effects of inoculation with arbuscular mycorrhizal fungi on early plant development, field establishment, and crop yield of the olive (Olea europaea L.) cultivar Arbequina. The response of olive plants to the fungi Glomus intraradices (Schenck and Smith) and G. mosseae (Nicol.& Gerd.) Gerdemann & Trappe in different potting mixes was studied in two different nursery experiments. Pre-inoculation with selected arbuscular mycorrhizal fungi prior to transplanting in the field improved plant growth and crop yield up to three years after inoculation. G. intraradices was more efficient at promoting plant growth than both G. mosseae and the native endophytes present in the orchard soil. Inoculation at the time of transplanting enhanced early plant growth in all the field situations studied. Diminishing mycorrhizal effects over time resulted from natural colonization of noninoculated seedlings and related to the native arbuscular mycorrhizal (AM) fungal population of the field soil. Early inoculation of olive seedlings enhances early plant development and crop productivity of olive trees.

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Twenty-nine commercial and experimental Prunus rootstocks, most with incorporated root-knot nematode [Meloidogyne javanica (Traub.) Chitwood] resistance, were evaluated against mixtures comprising nine populations of the root-lesion nematode Pratylenchus vulnus Allen and Jensen. Nearly all tested materials were susceptible. Five cultivars with high resistant levels were further challenged with seven P. vulnus populations individually. `Redglow' (Prunus salicina Lindl. × P. munsoniana Wight and Hedrick) was the only rootstock that showed broad resistance to all populations. The rootstocks `Torinel' (P. domestica L.), AC-595 (P. domestica × P. insititia L.), `Marianna 4001' (P. cerasifera Ehr. × P. munsoniana), and `Felinem' [P. dulcis (Mill.) D. A. Webb × P. persica (L.) Batsch] showed resistance to one or a few P. vulnus populations. Several supposedly resistant sources proved to be susceptible. Tests of crosses made between parents of diverse genetic background with partial resistance to P. vulnus indicate that a descendant with potential P. vulnus resistance is difficult to obtain. Pathogenic diversity among P. vulnus populations appears to be high.

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The effects of the interaction between the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenk and Smith and the root-knot nematode Meloidogyne javanica (Treub) Chitwood on growth and nutrition of micropropagated `Grand Naine' banana (Musa AAA) were studied under greenhouse conditions. Inoculation with G. intraradices significantly increased growth of plants in relation to nonmycorrhizal plants and was more effective than P fertilization in promoting plant development. Mycorrhizal colonization did not affect nematode buildup in the roots, although plants with the nematode and mycorrhiza were more galled. Meloidogyne javanica had no effect on the percentage of root colonization in mycorrhiza-inoculated plants. No element deficiency was detected by foliar analysis. All elements were within sufficiency levels for banana with exception of N, which was low. Potassium levels were lower in mycorrhizal plants, while Ca and Mg levels were higher with mycorrhiza than without, with or without the nematode. Early inoculation with G. intraradices appears to favor growth of banana plants by enhancing plant nutrition.

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Fourteen Prunus rootstocks were evaluated against mixtures of several isolates of the root-lesion nematode Pratylenchus vulnus Allen and Jensen in three greenhouse experiments. Most of the tested rootstocks are new releases or materials in advanced stages of selection that also have incorporated root-knot nematode resistance. The plums Torinel (Prunusdomestica L.) and Redglow (P. salicina Lindl. P. munsoniana Wight and Hedrick cv. Jewel) showed a moderately resistant response; their final nematode population levels were lower or slightly higher than inoculation levels. Low nematode reproduction also was found in the peach–almond hybrid G N No 22 [P. persica (L.) Batsch P. dulcis (Mill.) D.A. Webb] and the plum Bruce (P. salicina P. angustifolia Marsh.), and although these rootstocks did not perform as well as Torinel and Redglow, they also appear to be poor hosts for P. vulnus.

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Trials were established at Aula Dei Experimental Station (EEAD-CSIC, Zaragoza, Spain) to assess graft compatibility between peach cultivars [Prunus persica (L.) Batsch] and new Prunus spp. rootstocks or selections. Peach cvs. `Catherina' and `Tebana' and nectarine cvs. `Big Top' and `Summergrand' were grafted on peach seedlings, plum rootstocks, almond × peach hybrids, and other interspecific rootstocks. Part of the evaluated material belongs to the EEAD-CSIC selection program, which has showed good adaptation to Mediterranean growing conditions. Other rootstocks such as Bruce, Evrica, Hiawatha, Ishtara, Tetra, and Krymsk-1 have been recently introduced in Spain. A peach and a plum source, GF 677 and Adesoto 101, respectively, were used as compatible reference rootstocks. Both are widely used for peach and nectarine production in the Mediterranean area.

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New Prunus rootstocks and selections were evaluated for their reaction to Meloidogyne arenaria (Neal) Chitwood, M. incognita (Kofoid & White Chitwood), or M. javanica (Treub) Chitwood. Most of the clones were peach-almond hybrids (P-AHs) [P. persica (L.) Batsch × P. dulcis (Mill.) D.A. Webb] or plums of Spanish and French origin. In a first experiment, the P-AH Hansen 2-168 and plums GF-31 (P. cerasifera Ehr.) and GF 8-1 (P. cerasifera × P. munsoniana Weigth et Hedr.) were highly resistant to the mixture of five isolates of M. javanica. The P-AHs Barrier and Titan × Nemared were resistant and moderately resistant, respectively; GF-677, MB 3-13, MB 2-2, and MB 2-6 were susceptible. In the second and third experiment, the plums P 1079, P 2175, the hybrids Afgano (P. dasycarpa Ehrh.), G × N No 22, and G × N No 15, both P-AHs, and Nemared peach were highly resistant to mixtures of five isolates of M. incognita or M. arenaria. The plums P 2980 (P. cerasifera) and GF 8-1 tested against either root-knot species were also highly resistant. Cachirulo × (G × N No 9), a P-AH, showed less resistance to M. arenaria than to M. incognita. Montclar (P. persica) and the P-AHs Torrents AC and GF-677 were susceptible to both species.

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The use of rootstocks tolerant to iron deficiency represents the best alternative to prevent Fe chlorosis for peach production in calcareous soils. Early detection laboratory screening procedures allow the selection of new Fe-efficient rootstock genotypes. Seventeen Prunus rootstocks were tested for root ferric chelate reductase (FC-R) enzymatic activity, leaf SPAD values, and field performance. Some rootstocks were used as a reference to compare with new Prunus selections. Micropropagated plants were grown in hydroponic culture with half-strength Hoagland's nutrient solution containing 90 μm Fe(III)-EDTA as a control treatment. Plants were transferred to iron-free fresh solutions for 4 days and were thereafter resupplied with 180 μm Fe(III)-EDTA for 1 or 2 days. In vivo FC-R activity was measured in all treatments, i.e., control, Fe-deficient, and 180 μm Fe(III)-EDTA resupplied plants. The FC-R activity after Fe resupply was higher in Fe-efficient genotypes such as AdesotoPVP, FelinemPVP, GF 677, Krymsk 86™, and PAC 9921-07 than in the controls. No induction of FC-R activity was found in other genotypes such as Barrier, Cadaman™-AvimagPVP, PAC 9907-23, and PAC 9908-02. An intermediate response was observed in GarnemPVP, Gisela 5PVP, Krymsk 1PVP, Torinel™-AvifelPVP, VSL-2™, and PAC 9904-01. According to the induction of FC-R activity after Fe resupply, genotypes were classified as tolerant, moderately tolerant, or nontolerant to iron-induced chlorosis. These results were compared with SPAD values of plants grown under controlled conditions and in the nursery. Rootstocks that show high induction of FC-R activity also showed high or very high SPAD values in the field.

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