Tamarillo [Cyphomandra betacea (Cav.) Sendt., Solanaceae] dark-red-, red-, and yellow-type fruit were sorted into two maturity stages (green and turning); dipped in ethephon at 0, 250, 500, or 750 mg·liter–1; and kept at 18 or 28C. Seven days later, fruit dipped in ethephon at 500 or 750 mg·liter–1 and stored at 28C showed a color score, maturity index, and ascorbic acid content similar to those tree-ripened, thus making it possible for harvesting to be advanced 36 days. Under these conditions, weight loss was always lower than 8.5%, resulting in only slight symptoms of shriveling that did not affect commercial quality. Postharvest ripening reduces the risk of crop failure, increases earliness, and concentrates harvesting. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
J. Prohens, J.J. Ruiz and F. Nuez
A. Belakbir, J.M. Ruiz and L. Romero
To test the effectiveness of different bioregulators in enhancing bell pepper (Capsicum annuum L.) yield and fruit quality, the commercial bioregulators CCC, NAA, GA3, and Biozyme® were sprayed on plants at flower initiation, followed by two additional applications at 30-day intervals. Biozyme produced a significant increase in total yield but ≈40% of the fruit were not marketable. Treatment with NAA produced the highest yield of marketable fruit. Treatments did not affect fruit firmness compared to the control. Gibberellic acid increased fruit ascorbic acid and citric acid concentrations and Biozyme, GA3, and CCC increased fruit soluble solids content. Biozyme treatment increased fruit fructose, sucrose, carotenoid, and lycopene concentration. Treatments had no effect on fruit calcium concentration or pH. Chemical names used: chlormequat chloride (CCC); naphthaleneacetic acid (NAA), gibberellic acid (GA3); GA3 + IAA (indoIe-3-acetic acid) + zeatine + micronutrients (Biozyme®).
J. Egea, D. Ruiz and L. Burgos
Juan J. Ruiz, Jaime Prohens and Fernando Nuez
Jaime Prohens, Juan J. Ruiz and Fernando Nuez
Parthenocarpy in pepino (Solanum muricatum Aiton) can overcome poor fruit set caused by pollination deficiencies. In two families involving a parthenocarpic parent (Pp), a nonparthenocarpic parent (Pnp), and the generations Pp⊗, Pnp⊗, F1, BCp, BCnp, and F2, we studied three traits that are often confused: parthenocarpy, efficiency of parthenocarpy over seeded fruit set, and the degree of facultative parthenocarpy. Plants were trained to two stems (A and B). On stem A we emasculated six flowers per truss; three were pollinated and the other three were left unpollinated. We considered that a plant was parthenocarpic if it set one or more seedless fruit similar in size and shape to those seeded, and nonparthenocarpic if it only set seeded fruit. The efficiency of parthenocarpy over seeded fruit set was measured with a parthenocarpic fruit set index (PFSI), defined as twice the ratio of seedless to total fruit on stem A. In stem B all flowers were left to self-pollinate naturally. We quantified the degree of facultative parthenocarpy as the percentage of seedless fruit of the total. Parthenocarpy is controlled by one dominant gene for which we propose the symbol P. Parthenocarpic fruit set in the homozygote PP was as efficient as the seeded one (PFSI ≈ 1); in the heterozygote Pp it was less efficient (PFSI ≈ 0.6). The dose of gene P explained the differences found between generations for the PFSI and made it possible to predict the PFSI of a given generation from the proportions of PP and Pp genotypes. Although for the Pp hybrids parthenocarpic fruit set was less efficient than the seeded one, their ability to set seedless fruit in conditions of deficient pollination, together with their high degree of heterosis, makes them agronomically useful. The degree of facultative parthenocarpy seemed to be a complex trait with low heritability. In environments unfavorable for pollination, parthenocarpic genotypes set seedless fruit, thus ensuring crop production and yield stability. Using the degree of facultative parthenocarpy to classify plants for parthenocarpy is not recommended. Developing parthenocarpic cultivars can help spread this crop and stabilize yields.
J. Egea, D. Ruiz, F. Dicenta and L. Burgos
Juan J. Ruiz, Santiago García-Martínez, Belén Picó, Muquiang Gao and Carlos F. Quiros
We studied the genetic variability of some traditional tomato (Lycopersicon esculentum L. Mill.) cultivars of Spain, and established their relationships using both simple sequence repeats (SSR) and sequence related amplified polymorphism (SRAP) markers. These included cultivars from different locations of three main types, Muchamiel, De la pera, and Moruno. Additionally we tested two other local cultivars, `Valenciano' and `Flor de Baladre', plus a small sample of commercial cultivars and a few wild species. Both types of markers resolved the cultivars from different groups, but SSR failed to distinguish some of those classified under the same group. All the De la pera cultivars clustered together by genetic similarity with the SRAP markers. The other traditional cultivars, which are grown in a wider geographic range, formed a more diffuse group, which included the commercial cultivar Roma. The Mexican cultivar Zapotec, a breeding line, and the virus-resistant commercial hybrid `Anastasia' were the most distant of all the cultivars. The latter hybrid had higher similarity to the wild species due to introgressed segments from them carrying the resistance genes. Similar results were observed for SSR markers but with a lower level of resolution. This information would be useful to facilitate tomato germplasm conservation and management efforts.
Timothy S. Prather, James J. Stapleton, Susan B. Mallek, Tarcisio S. Ruiz and Clyde L. Elmore
A double-tent solarization technique, which accumulates higher soil temperatures than solarization of open fields, was recently approved by the California Department of Food and Agriculture (CDFA) as a nematicidal treatment for container nurseries. Due to the need for broad-spectrum pest control in container nursery settings, this technique was tested to determine its usefulness as an herbicidal treatment. Laboratory-derived thermal death dosages (temperatur × time) for several weed species important in California, including common purslane (Portulaca oleracea), tumble pigweed (Amaranthus albus), and black nightshade (Solanum nigrum), were previously determined and the data were used as guidelines for devising treatment duration in this study. In two field experiments conducted in 1999 and 2000 to validate the laboratory data, moist soil was placed in black polyethylene planting bags [3.8 L (1 gal) volume], artificially infested with seeds of the three test species, and subjected to 0 to 24 hours of double-tent solarization after reaching a threshold temperature of 60 °C (140 °F) (about 1.5 to 2.0 h after initiation of the experiment). In 1999, samples were removed at 2, 4, 20, and 24 hours after reaching the 60 °C threshold, then incubated to ameliorate possible secondary dormancy effects. Seeds failed to germinate in any of the solarized treatments. In 2000, samples were removed at 0, 1, 2, and 6 h after reaching 60 °C. Again, apart from the nonsolarized control treatment, all weed seeds failed to germinate at any of the sampling periods, in accordance with prior laboratory thermal death results. Reference tests to estimate effects of container size on soil heating showed that soil in smaller container sizes (soil volume) reached higher temperatures, and were maintained at high temperature [above 60 °C (140 °F)] for a longer period of time, than larger container sizes. The double-tent solarization technique can be used by commercial growers and household gardeners to effectively and inexpensively produce weed-free soil and potting mixes in warmer climatic areas.