Fruit misshapen in strawberry cultivars (Fragaria×ananassa) is related to achenes functionality

Abstract

Fruit deformation is a phenomenon commonly observed in commercial strawberry cultivars (Fragaria × ananassa) with a negative impact on the economic benefit of crop production. To better understand this physiopathy, we evaluated fruit size and the relative amount of 'small' (<0.4 mm) and 'big' achenes (>0.6 mm) in misshapen (MF) and well-formed (WF) fruits from 'Camarosa', 'Ventana' and 'Medina' strawberry cultivars growing in the field. In 'Camarosa', size-dependent achenes functionality was assessed by analysing achenes germinability and differences in time to ripening between MF and WF. We found that the occurrence of fruit deformation was not only strongly dependent on the cultivar (i.e. genetic factor) but also was promoted by low temperatures (i.e. environmental factor). Regardless of the cultivar, MF showed higher percentage of 'small' non-functional achenes than WF, indicating a failure in achene development, which could be related to the functional integrity of reproductive structures. To test this hypothesis, we performed an experiment by pollinating strawberry flowers with pollen developed under low and mild temperatures. Low temperatures reduced pollen viability, and flowers pollinated with low quality pollen led to a higher amount of MF. However, fruit deformation was not completely explained by differences in pollen quality, neither by differences in pistil maturity and receptivity nor ovule viability, suggesting that non-functional achenes might result from a disruption in postfertilisation processes such as embryo abortion as a consequence of low temperatures.

Enhancing crop shelf life with pollination

“…Unfertilized achenes are a result of pollination limitation [28] and have no physiological functionality [29]. Aggregations of unfertilized achenes usually lead to deformations in strawberry fruits [17,30] and thus deformations can be directly linked to insufficient pollination.…”

“…Deformations in strawberry fruits are a result of pollination limitation, mainly due to the absence of insect pollinators [28]. The mechanism is based on the amount of fertilized achenes [17], the true 'nut'-fruits of strawberry being an aggregated fruit [18]. Unfertilized achenes are a result of pollination limitation [28] and have no physiological functionality [29].…”

“…Almost 90% of fruits are lost after only four days in storage [16]. Thus, shelf life is an important determinant of postharvest quality in strawberries [17]. We analysed the impact of pollination on the shelf life of strawberries based on the degree of fruit deformation, which is another important reason for quality loss in strawberries.…”

“…We analysed the impact of pollination on the shelf life of strawberries based on the degree of fruit deformation, which is another important reason for quality loss in strawberries. Deformations are caused by pollination limitation, which leads to achenes, the true nut-fruits of the strawberry, being unfertilized and thereby unable to build tissue [17]. Firmness, fruit weight and decay were used as fruit quality parameters determining shelf life [16].…”

“…We expected fruit quality to decline during storage due to decreasing firmness and fruit weight and increasing decay of the fruits. The degradation was expected to vary in relation to the degree of deformation, which is directly related to pollination limitation [17][18][19].…”