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. Rodríguez-Burruezo, J. Prohens and F. Nuez
Twenty-six clones of pepino (Solanum muricatum Aiton) were evaluated for yield, fruit weight, fruit shape (length to width ratio), soluble solids concentration (SSC), titratable acidity (TA), and ascorbic acid concentration (AAC) over two growing seasons: autumn-winter (AW) and spring-summer (SS). Significant differences were found for the effects of clone, season, and clon× season interaction for all traits, except in the case of season for fruit shape. Mean values for yield, SSC, and AAC were higher in the AW than in the SS season, while mean fruit weight and TA were lower. Many clones (13 in AW and six in SS) had a yield higher than 30 t·ha-1. Substantial genotypic variation was found for all traits studied except for SSC. Clones stable for all traits were detected over both seasons, except for SSC, where the differences between seasons were very high. The significant clone × season interaction for all traits indicates that selection of genotypes adapted specifically to either AW or SS seasons would maximize the response to selection. Broad sense heritabilities were highest for fruit shape and yield (>0.70), while SSC had the lowest values (0.39 in AW, 0.17 in SS, and almost 0 when considering both seasons combined). For the AW season, significant fruit weight-SSC and fruit weight-AAC genotypic correlations were detected; for the SS season the significant genotypic correlations were yield-SSC, fruit weight-TA, fruit shape-TA, and SSC-TA. Results suggest there are ample opportunities for improving several traits in this crop using intraspecific variation for adaptation to specific environments.
L. Bosch, F. Casañas, E. Sánchez, M. Pujolà and F. Nuez
Salvador Soler-Aleixandre, C. López, J. Cebolla-Cornejo and F. Nuez
The disease incited by Pepino mosaic virus (PepMV) is currently a serious problem for tomato (Solanum lycopersicum L.) crops in several European countries. A collection of accessions from different Solanum species was screened to find sources of resistance to PepMV. All plants of S. lycopersicum, S. lycopersicum var. cerasiforme, S. pennellii Correll, S. cheesmaniae (L. Riley) Fosberg, S. habrochaites S. Knapp & D.M. Spooner, S. neorickii D.M. Spooner, G.J. Anderson & R.K. Jansen, S. pimpinellifolium L., S. basendopogon Bitter, S. canense Rydb., S. caripense Humb. & Bonpl. ex Dunal, and S. muricatum Aiton accessions showed a 100% systemic infection rate, high viral accumulation, and apparent symptoms. In some accessions of the species S. chilense (Dunal) Reiche and S. peruvianum L., a variable percentage of plants without systemic infection was observed. Although all plants of ECU-335 accession of S. ochranthum Dunal showed systemic infection by PepMV, the symptoms were mild and the levels of viral accumulation were low. PepMV was not detected in plants of AN-CA-214 accession of S. pseudocapsicum L. No symptoms were observed either on inoculated leaves or on growing leaves. The use of the latter two species is limited considering that they cannot be sexually crossed with cultivated tomato. As a result, S. chilense and S. peruvianum are the most promising species in the search for sources of resistance to PepMV.
M.J. Díez, S. Roselló, F. Nuez, J. Costa, M.S. Catalá and A. Lacasa
Seedlings of three tomato (Lycopersicon esculentum Mill.) cultivars [`RDD', carrier of the Sw5 gene, which confers resistance to tomato spotted wilt virus (TSWV); `Pitihué', tolerant to the virus; and the susceptible cultivar Rutgers] were placed at the four- to five-leaf stage in cages containing a population of viruliferous thrips (Frankliniella occidentalis Perg.), and remained there for 0, 7, or 15 days. Plants were subsequently transplanted either into the open field or in tunnels protected with a mesh of 14 × 10 threads/cm. Systemic symptoms and number of dead plants were recorded and enzymelinked immunosorbent assays (ELISA) were performed. `Rutgers' exhibited severe systemic symptoms regardless of treatment and a high number of plants died. The level of infected plants remained low when protective measures were applied to seedlings of `Pitihué' and acceptable yields were obtained. In open air cultivation, where seedling infection was severe, <20% of `RDD' plants became infected and high yields were obtained; protected cultivation did not reduce yield. Although the percentage of infected plants was higher when cultivated under mesh, the yield of all three cultivars was greater than in the open field. The environment created under mesh stimulated growth, neutralizing the effect of the infection.
V. Fernández-Ruiz, M.C. Sánchez-Mata, M. Cámara, M.E. Torija, C. Chaya, L. Galiana-Balaguer, S. Roselló and F. Nuez
The characterization of Lycopersicon germplasm for internal quality properties is essential to choose suitable donor parents for breeding programs. When donor parents belong to species of subgenus Eulycopersicon, which are phyletically closer to L. esculentum Mill., the recovery of agronomic traits is faster. When using these materials, a careful selection of donor parents which could improve several internal quality properties allows the acceleration of these breeding programs. In this work, we combine general determinations, such as soluble solid content, titratable acidity, pH, total sugars, pectic substances and total protein contents with precise high-performance liquid chromatography (HPLC), quantitations of individual compounds (vitamin C; citric, malic, fumaric and oxalic acids; glucose, fructose, and sucrose), in order to obtain a more complete characterization of flavor intensity and nutritional properties in Lycopersicon germplasm. The multidimensional analysis of all these variables allows classification of several accessions of L. esculentum Mill. and L. pimpinellifolium (Jusl.) Mill., according to their usefulness for internal quality breeding programs of fresh tomato. The classification obtained and the comparison of accessions quality characteristics with selected controls show that five of the L. pimpinellifolium (Jusl.) Mill. accessions tested can be of great usefulness for being used in breeding for internal quality characteristics. A flavor intensity ≈625% higher than commercial hybrids was obtained in the best accession tested. Some of these L. pimpinellifolium (Jusl.) Mill. accessions showed better flavor intensity properties than a high SSC L. cheesmanii Riley control, traditionally used in internal quality breeding. In addition, three of the L. esculentum Mill. accessions tested with medium-to-high flavor intensity value could be useful in advanced stages of breeding programs.