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E. Ortega, J. Egea, and F. Dicenta

In almond [Prunus dulcis (Mill.) D.A. Webb], a high flower density and fruit set rate is important, because yield increases with higher fruit set ratio. Furthermore, because the ovule of some cultivars mature at anthesis, rapid pollination and pollen tube growth along the style are essential to ensure fertilization of a viable ovule. In this work, we studied the effective pollination period (EPP) of four almond cultivars of different bloom time by studying pollen tube growth and fruit set. EPP in almond was longer than in other fruit trees, and its duration was determined by stigma receptivity, which decreased with high temperature. An acceptable fruit set for all cultivars was obtained following pollination from day 0 to day 4 after emasculation.

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J. Ordovás, E. Carmona, M.T. Moreno, and M.C. Ortega

The structure of cork (Quercus suber L.) bark presents a series of characteristics, suggesting that internal porosity is partly occluded. This study determined the porosity in the waste cork industry (C) and when such waste product had been composted during 4 (CC-4), 7 (CC-7), and 10.5 months (CC-10.5). The particle density of the intact and finely ground material differed significantly in all particle size ranges larger than 0.5 mm. The porosity of the cork substrates ranged from 80% to 94% of the total volume, according to granulometry and the degree of decomposition. However, large particles and less decomposed material with a high porosity had up to 10% of the total volume as occluded pores. The material's effective porosity varied slightly between the various particle sizes and degrees of decomposition, which ranged between 80% and 89%, having an average value of 85%. The ash content was highly correlated with the particle density of the finely ground material. Nevertheless, and due to occluded porosity, we cannot estimate the “effective porosity” from the ashes; therefore, we must resort to techniques that involve the displacement of a fluid, such as liquids or gas pycnometry or submersion.

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P. Martínez-Gómez, T.M. Gradziel, E. Ortega, and F. Dicenta

Almond [Prunus dulcis (Mill.) D.A. Webb] breeding programs require successful techniques for pollen storage. We studied the pollen viability of two almond cultivars, `Ramillete' and `Desmayo Largueta', during 8 weeks of storage, in conditions that simulated standard situations including storage at 4, 22, and 4 °C alternating with 22 °C (4 °C/22 °C). Viability remained at 60% or more for 2 weeks under all three conditions. After the second week, germination capacity decreased rapidly at 22 °C, but remained above 50% for as long as 8 weeks at 4 °C or 4 °C/22 °C.

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F. Dicenta, P. Martínez-Gómez, E. Ortega, and H. Duval

The effect of pollinizer on sweet or bitter almond flavor was studied by tasting the seeds obtained from 32 crosses between sweet, bitter, and slightly bitter parents. Out of eight female parents, two were homozygous sweet (`Del Cid' and `Aï'); two were heterozygous sweet (`Marcona' and `Nonpareil'); one heterozygous with an almost undetectable slightly bitter flavor (`Ferrastar'); two heterozygous slightly bitter (`Garrigues' and `Marie Dupuy'); and one bitter homozygous (`S3067', self-compatible clone obtained in CEBAS). Each cultivar was hand-pollinated with four male cultivars: one homozygous sweet (`Ramillete'), one heterozygous sweet (`Atocha'), one heterozygous slightly bitter (`Garrigues'), and one homozygous (`S3067'). Since `Garrigues' is self-incompatible, the cross `Garrigues' × `Garrigues' was replaced by `Garrigues' × `S3065' (slightly bitter clone obtained in CEBAS). Tasting of the seeds resulting from each cross resulted in the complete absence of any influence of pollinizer on flavor, which only depended on the female parent.

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P. Martínez-Gómez, T.M. Gradziel, E. Ortega, and F. Dicenta

Pollen of the California almond cultivars Nonpareil, Ne Plus Ultra, Sonora, and Peerless was evaluated for viability following storage over 12 months at 4, 0, -20, and -80 °C. The proportion of viable pollen exceeded 80% for all cultivars and for all temperatures evaluated after 2 months of storage. Following 12 months of storage at 4 °C, germination decreased to 8% for `Nonpareil', 10% for `Ne Plus Ultra', 50% for `Sonora', with no germination observed for `Peerless'. Storage at sub-freezing temperatures maintained pollen viability above 70% in `Nonpareil', `Ne Plus Ultra', and `Sonora' and above 40% in `Peerless'. Cultivars differed significantly in their tolerance to low temperature pollen storage. Within cultivars, differences in pollen germination following storage at 0, -20, or -80 °C were nonsignificant.

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Rosalía Servín, Jos L. Martínez, E. Troyo-Diguez, and A. Ortega

The sweetpotato whitefly [Bemisia tabaci (Gennadius)] has become a high-risk insect pest in Mexico as well as in other countries, causing serious damage to several crops. Control of whitefly in Baja California Sur, ,Mexico, is usually done by intense insecticides applications, either alone or in mixtures of several kinds. The aim in this work was to determine its susceptibility to cypermethrin, endosulfan, methamidophos, and methyl-parathion. LC50 was obtained to identify the resistant and susceptible populations. A group of 20 whiteflies were introduced in a 20-ml scintillation vial coated in the inner surface with a known concentration of the insecticide. Mortality readings were obtained 3 h after exposing the insects to the residual activity at five concentrations. Five replications and control were run in different consecutive days for each bioassay. Results indicated that cypermethrin was the most toxic to B. tabaci and metamidophos the least. Data will be considered for further evaluations.

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J.L. Garcia-Hernandez, E. Troyo-Dieguez, H. Nolasco, H.G. Jones, and A. Ortega-Rubio

The phytotoxic effects on the physiology of chili (Capsicum annum L. cv. Ancho San Luis) caused by four different insecticides were evaluated. Three commercial mixes (methyl azinfos, methyl parathion CE720, and metamidophos 600 LM), and an active ingredient alone (methamidophos) were assayed; water was used as the control. The main goal was to evaluate the insecticide effects on chili using four different doses; the mean dose, recommended on the label of the product (R), a half one (1/2R), 1.5 times (1.5R) and twice the recommended dose (2R). Three frequencies of application were applied; once a week, twice a week, and once every other week, for 6 weeks from the beginning of flowering. Phytotoxicity was evaluated measuring the response of some physiological traits, Chlorophyll Fluorescence (CF), Leaf Temperature (LT), Transpiration (Tr), and Stomatal Resistance (SR). CF was measured by means of a portable chorophyll fluorscence meter; LT, Tr, and SR were measured using a LI-Cor Porometer. The doses and frequencies used are all common in commercial chili fields in Mexico. Results showed that phytotoxicity caused by insecticides can be an important damage factor to the plants, something that can cause reduction of yields. CF was shown to be the most sensitive variable to evaluate the phytotoxicity caused by insecticides. Fruit malformation was observed in all treatments. Chlorophyll content was reduced up to 25%, on average. The phosphorate insecticides affected the physiological parameters more drastically than the others. Results evidence the irreversible crop damage caused by excessive insecticide applications.

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E. Carmona, J. Ordovás, M.T. Moreno, M. Avilés, M.T. Aguado, and M.C. Ortega

Static hydrological properties [aeration capacity, easily available water, reserve water, water release curves: θvm), and specific humidity curves] and dynamic hydrological properties (saturated and unsaturated hydraulic conductivity) of sub strates based on industrial cork residue (the bark of Quercus suber L.) and cork compost were studied. Samples of similar granulometry have been used to establish the effect of cork composting on the afore mentioned physical properties. Different models were tested to describe the mechanism of water release from these materials. Van Genuchtens model (Van Genuchten, 1978) was the best fit and produced specific humidity curves that revealed slight differences in the ratio of water capacity function. When cork residues were composted for 7 months, important changes occurred in hydrological properties of the material as it became more wettable. Water retention significantly increased from 45% to 54%, at a potential of 5 kPa, although this did not necessarily result in increased water available to plants. A study of the unsaturated hydraulic conductivity (Kunsat) of these materials revealed a significant de crease in the Kunsat water potential at 0-5 kPa, which corresponds to the range in which the irrigation with these substrates was usually carried out. The long composting process resulted in increased Kunsat between 4 and 5 times that of uncomposted material, which would improve the water supply to the plant.

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E. Carmona, J. Ordovás, M.T. Moreno, M. Avilés, M.T. Aguado, and M.C. Ortega

This work describes the granulometry of industrial cork residue (bark of Quercus suber L.) and its possible alteration during composting to eliminate the high content of phytotoxic substances. Because of the differences in density of the different-sized cork particles, expression of the granulometric distribution in relation to volume reflected the size distribution more accurately than its expression in relation to weight. As a consequence, predictions of the physical and hydrological behavior of the substrate, deduced from its granulometry, were more accurate when this was calculated in relation to volume. Objective parameters used for textural comparison, such as the geometric mean (dg) and standard deviation of particle size (σg), which were previously used in soils, were tested. These permit the estimation of small differences in the particle size of different lots or the granulometric alteration occurring during composting. With the same purpose, a new diagram of textures for the classification of granular substrates was also studied.