2.05 DISEASE: POST-HARVEST

The fungal organisms Botrytis cinerea, Fusarium spp., Penicillium spp. and Phoma betae are generally recognised as the major damage causing pathogens in post-harvest storage of sugar beet (Bugbee, 1975; Bugbee & Cole, 1975; Legrand & Wauters, 2012; Liebe, 2016; Liebe & Varrelmann, 2016). From the work of Liebe and Varrelmann (2016), the conclusion can be draw that the presence of these pathogen is very widespread in the fields of northern Europe were sugar beet is grown, possibly with the exception of Phoma betae. Leuconostoc mesenteroides subsp. dextranicum is a bacteria commonly found to populate damaged cells of sugar beet roots, particularly after roots have been allowed to freeze and thaw. The presence of a post-harvest disease leads to rots. Regions of rotten cells will either be washed away at processing, or will likely have higher concentrations of non-sucrose components. For example, dextran and levan are not present in healthy sugar beet roots, only forming in the presence of rot forming micro-organisms (Harvey & Dutton, 1993), and invert sugars concentrations have repeatedly been shown to increase with rates of mould growth during post-harvest storage (Campbell et al., 2011; Kenter et al., 2006).

The presence of fungal or bacterial organisms does not necessarily mean a root will become unhealthy. Strausbaugh et al. (2011) notes that many of the common bacteria found with sugar beet roots slow the development of Leuconostoc. Ongoing work presented at the 78th Congress of the International Institute for Sugar Beet Research (IIRB) – Molin (2022) – has found that the fungal and bacterial communities in the soil and on the root post-harvest varied between varieties, and this correlated with their storability. The bacteria ASV-649 was associated with good storability.