Surface sterilization of English oak (Quercus robur L.) acorns using wet water steam

Abstract

Effective and environmentally friendly methods of protection to reduce seed contamination from fungi are constantly sought. The use of thermal impulses of 100 °C wet water steam to reduce fungal contamination has not been sufficiently investigated, and the potential of this physical approach has not been estimated.The aim of the study was to investigate what impact 100 °C wet water steam with different time durations had on acorn contamination with fungi, acorn germination and biometric indicators of English oak (Quercus robur) seedlings during the first year of growth. Different treatment durations with wet water steam were used: 2, 4, 6, 8, 10, 12 and 14 s.Research showed that 6 seconds impact of wet steam on the surface of the oak acorn destroyed Alternaria spp., 8 seconds impact destroyed Penicillium spp. and 14 seconds impact destroyed Mucor spp. Using 14 seconds water steam treatment Penicillium, Alternaria and Mucor spp. fungi were eliminated.Wet water steam treatment for 2 - 4 seconds not only stimulated the acorns germination by 4.0 - 7.6%, but also had positive influence on the root collar diameter of seedlings. Wet water steam treatment for 2 - 12 seconds had a positive effect on the root development of oak seedlings, however, high temperature environment had a suppressive effect on the oak seedling height.
 Keywords: biological control, wet water steam, fungi, oak acorns, seedling production

Impact of Thermotherapy and Short-Term Storage on Quercus robur L. Acorn Mycobiota and Germination

“…Since the commonly performed thermotherapy treatment (at 41 • C for 2.5 h) can lead to the proliferation of ubiquitous fungal species during acorn storage [39,41,44,45], the second part of this study focused on the impact of different thermotherapy and short-term storage conditions on the internal acorn mycobiota. Generally, among the ten most frequently isolated species were Penicillim glandicola, P. glabrum, Fusarium solani, F. avenaceum, and Alternaria alternata, which was not surprising as members of these genera were reported to be the most common potentially harmful fungi inhabiting Quercus robur acorns in similar studies [11,27,32,33,66]. Several other frequently isolated species in this research were reported as plant pathogens by other authors, although not on oak acorns.…”

Effect of Acorn Thermotherapy and Short-Term Storage on Morphological Characteristics of Related Quercus Robur L. Seedlings

“…Other studies on Quercus spp. confirmed the association of the exposure of acorns to thermotherapy with higher acorn viability, germination rates, and the earlier and more uniform germination [29,30,32,36]. The latter was also noticed in this research (personal observation, data not shown).…”

“…Fungal infections can also be successfully prevented or controlled by storing the acorns under the adequate conditions and by applying eradicative treatments which target harmful pathogens prior to storage. Detrimental fungi can be inhibited or eliminated from the acorns with the use of fungicides, biological control agents (antagonistic fungi or bacteria), disinfectants, steam or hot water [28][29][30]. The use of the latter two is referred to as a thermotherapy.…”

“…Still, thermotherapy is considered to be an efficient method for the control of acorn mycobiota, as the ubiquitous proliferating fungi which can be induced by its application have not yet been proven to reduce the acorn germination after short-term storage [30,33]. Moreover, thermotherapy has been associated with higher acorn viability and germination rates, indicating it does not adversely affect the quality of acorns if combined with the appropriate storage conditions [29,30,33,36]. However, still little is known about the effect of acorn thermotherapy and storage on the characteristics of related seedlings, as there are not many available studies on this topic and most of them are primarily focused on the storage alone [29,[37][38][39][40].…”

“…Moreover, thermotherapy has been associated with higher acorn viability and germination rates, indicating it does not adversely affect the quality of acorns if combined with the appropriate storage conditions [29,30,33,36]. However, still little is known about the effect of acorn thermotherapy and storage on the characteristics of related seedlings, as there are not many available studies on this topic and most of them are primarily focused on the storage alone [29,[37][38][39][40].…”