Antisense inhibition of pectate lyase gene expression in strawberry fruit: Characteristics of fruits processed into jam

We have analyzed several quality parameters of strawberry jam prepared from transgenic fruits with reduced expression of a pectate lyase gene. Two independent lines showing a reduction in pectate lyase mRNA transcript level of 90% (Apel 14) and 99% (Apel 23) have been studied. At harvest, ripen fruits from these two lines were significantly firmer than control. Soluble solid content was similar in all genotypes. Control and transgenic fruits were processed into jam and the textural properties of jam berries and medium were analyzed separately using a back extrusion test. Transgenic fruits resisted the cooking process better than control, as reflected by the higher weight of berries in these jams. The back extrusion test of jam berries showed that cooked fruits from both transgenic lines were firmer than control, and the firmness values correlated positively with the degree of pectate lyase silencing. By contrast, jam mediums of these lines were similar in firmness but slightly less viscous than control. Overall, the results obtained indicate that inhibition of pectate lyase gene expression can improve several quality traits of strawberry jam, such as texture and content of whole berries.