Involvement of bacterial endophytes in storage rots of buttercup squash (Cucurbita maxima D. hybrid ‘Delica’)

Abstract

The incidence and numbers of bacteria were studied in internal tissues of fruits of buttercup squash (Cucurbita maxima Duchesne hybrid ‘Delica’) of various maturities and susceptibilities to storage rotting. Overall, 70% of 55 apparently healthy squash fruit were found to contain bacteria within the internal mesocarp tissues, when sampled within 2 days after harvest. Bacteria with a range of morphology and growth habit (mostly facultative anaerobes) were found to be present. Bacterial populations within the squash mesocarp tissue were typically low (c. 10²/g), and did not change significantly during fruit growth and storage, provided the tissue remained sound. Predisposition to decay in storage, through harvesting when either under- or over-mature, was associated with fewer fruit containing detectable levels of internal bacteria when compared with fruit harvested at the optimum maturity for prolonged storage life. A negative correlation was found between the percentage of fruit containing detectable levels of endogenous bacteria and fruit proneness to rot in storage. These findings suggest that the natural bacterial endoflora of squash is not directly responsible for storage rots of the fruit.

Keywords:

• buttercup squash
• Cucurbita maxima
• endophytes
• facultative anaerobes
• fruit protection
• fruit storage rots
• internal bacteria
• susceptibility to fungal decay