Strawberry (Fragaria ϫ ananassa, Duch., cv Chandler) is a soft fruit with a short postharvest life, mainly due to a rapid lost of firm texture. To control the strawberry fruit softening, we obtained transgenic plants that incorporate an antisense sequence of a strawberry pectate lyase gene under the control of the 35S promoter. Forty-one independent transgenic lines (Apel lines) were obtained, propagated in the greenhouse for agronomical analysis, and compared with control plants, non-transformed plants, and transgenic lines transformed with the pGUSINT plasmid. Total yield was significantly reduced in 33 of the 41 Apel lines. At the stage of full ripen, no differences in color, size, shape, and weight were observed between Apel and control fruit. However, in most of the Apel lines, ripened fruits were significantly firmer than controls. Six Apel lines were selected for further analysis. In all these lines, the pectate lyase gene expression in ripened fruit was 30% lower than in control, being totally suppressed in three of them. Cell wall material isolated from ripened Apel fruit showed a lower degree of in vitro swelling and a lower amount of ionically bound pectins than control fruit. An analysis of firmness at three different stages of fruit development (green, white, and red) showed that the highest reduction of softening in Apel fruit occurred during the transition from the white to the red stage. The postharvest softening of Apel fruit was also diminished. Our results indicate that pectate lyase gene is an excellent candidate for biotechnological improvement of fruit softening in strawberry.Temperate fruits can be classified into two categories according to their softening behavior and textural properties (Bourne, 1979). One group includes those fruits that soften greatly during ripening, acquiring a melting texture, whereas the other group comprises fruits that soften moderately and display a crisp fracturable texture. Strawberry (Fragaria ϫ ananassa, Duch., cv Chandler) is included in the first group, joint to other economically important crops such as tomato (Lycopersicon esculentum) and avocado (Persea americana). Rapid softening during ripening is one of the main causes of the short postharvest shelf life of these fruits; therefore, any improvement of softening behavior could have a significant commercial importance.Softening of ripe strawberry fruit occurs mainly by degradation of the middle lammella of cortical parenchyma cells (Perkins-Veazie, 1995). Histological analysis of ripe fruit showed a cell wall thinner than unripe fruit and the lost of intercellular material, the cells being with little contact and separated by considerable intercellular space (Redgwell et al., 1997). The underlying biochemical mechanism of strawberry softening is unclear. The largest changes in the plant cell wall during ripening occur in the pectin component. The percentage of water-soluble pectins increases during ripening but total quantity of polyuronide residues (Woodward, 1972; Knee et al., 1977; Huber, 1984;Redg...

Cryopreservation is the conservation at very low temperature (

Unlike other important crops analyzed so far for genetic diversity and population structure, the brief history and particularities of the genetics of the cultivated strawberry (Fragaria ×ananassa Duchesne) have limited its genetic characterization. The genomic composition and the pattern of inheritance have not been fully elucidated, although a number of studies have suggested a highly diploidized genome. In this study, the similarity relationships and structure of 92 selected strawberry cultivars with widely diverse origins have been established using simple sequence repeat (SSR) markers derived from expressed sequence tags (EST-SSR markers). Genetic analysis performed by the unweighted pair group method with arithmetic mean clustering revealed a distribution according to both date of cultivar release and breeding for a specific climatic adaptation. Additionally, a model-based clustering approach identified three populations among the strawberry cultivars with an overall FST value of 0.15 to 0.16. Both analyses support a limited differentiation of modern cultivars, most probably as a consequence of the methodology of strawberry breeding. Interestingly, the collection of strawberry cultivars here analyzed showed comparable genetic differentiation to that observed in natural populations of Fragaria chiloensis (L.) Mill., one of its wild ancestors. Our results suggest that breeding has produced a small but significant reduction on the genetic diversity of F. ×ananassa. The panel of 10 EST-SSRs described in this work provided an extremely low probability of confusion (less than 10−11), offering an efficient and accurate method for cultivar identification.

Strawberry is a high value crop worth 315.6 million euros in 2013 in Spain. Strawberry diseases are commonly controlled by soil fumigation with toxic chemicals. However, since 2007, the methyl bromide fumigant is banned for strawberry cultivation. Moreover, European policies are progressively restricting the use of other toxic fumigants such as dichloropropene. Alternative control techniques are thus needed. Therefore, we have tested soil biosolarization, a new technique combining soil biofumigation and soil solarization, to cultivate the Camarosa strawberry in 2010-12 at Huelva in the southwestern coast of Spain. Soil was biofumigated by amendment of fresh chicken manure at 12,500 kg/ha with or without Trichoderma at 3.5 kg/ha; chicken manure at 25,000 kg/ha; Brassica juncea pellets at 2,000 kg/ha; sugar beet vinasse at 15,000 kg/ha; or dried olive pomace at 12,500 kg/ha. Soil was then solarized for 30 days by covering with a clear plastic mulch. A control that received fermented manure remained uncovered. Our results show that the highest yield averaging 70,543 kg/ha and the lowest percentage of 12.6 % of second-class fruits were obtained by amendment of fresh chicken manure. Yields were also similar to the higher yields previously reported for chemical fumigation with 1,3dichloropropene and chloropicrin. In addition, biosolarization is about 20 % cheaper than treatment with 1,3-dichloropropene and chloropicrin. Biosolarization with chicken manure is, therefore, a promising sustainable option for strawberry production.