Bacillus Spp.: Efficient Biotic Strategy to Control Postharvest Diseases of Fruits and Vegetables

Abstract

: Postharvest diseases significantly reduce the shelf-life of harvested fruits/vegetables worldwide. Bacillus spp. are considered to be an eco-friendly and bio-safe alternative to traditional chemical fungicides/bactericides due to their intrinsic ability to induce native anti-stress pathways in plants. This review compiles information from multiple scientific databases (Scopus, ScienceDirect, GoogleScholar, ResearchGate, etc.) using the keywords “postharvest diseases”, “Bacillus”, “Bacillus subtilis”, “biocontrol”, “storage”, “losses”, and “fruits/vegetables”. To date, numerous examples of successful Bacillus spp. application in controlling various postharvest-emerged pathogens of different fruits/vegetables during handling, transportation, and storage have been described in the literature. The mechanism/s of such action is/are still largely unknown; however, it is suggested that they include: i) competition for space/nutrients with pathogens; ii) production of various bio-active substances with antibiotic activity and cell wall-degrading compounds; and iii) induction of systemic resistance. With that, Bacillus efficiency may depend on various factors including strain characteristics (epiphytes or endophytes), application methods (before or after harvest/storage), type of pathogens/hosts, etc. Endophytic B. subtilis-based products can be more effective because they colonize internal plant tissues and are less dependent on external environmental factors while protecting cells inside. Nevertheless, the mechanism/s of Bacillus action on harvested fruits/vegetables is largely unknown and requires further detailed investigations to fully realize their potential in agricultural/food industries.

Effects of Endophytic Bacillus Subtilis and Salicylic Acid on Postharvest Diseases (Phytophthora infestans, Fusarium oxysporum) Development in Stored Potato Tubers

“…This was quite expected due to two know an phenomenon (i) the environmental and physical changes before and after harvest induced the production of reactive oxygen species (ROS), which in turn cause oxidative damage during the postharvest stages of immature fruits and vegetables, inducing decay of the product and loss of quality; (ii) the formation of ROS (hydrogen peroxide (H 2 O 2 ), superoxide radicals, etc. ), one of the earliest responses of plant cells to pathogens infection, which induce range of defense responses in plants, including the synthesis of a whole spectrum of protective compounds [13,19,39,44,45,47]. If ROS production increases dramatically, as occurs under environmental stresses, hydroxyl radical reacts with membrane lipids, inducing their peroxidation-the final product of which is MDA [13,25,53].…”

“…), one of the earliest responses of plant cells to pathogens infection, which induce range of defense responses in plants, including the synthesis of a whole spectrum of protective compounds [13,19,39,44,45,47]. If ROS production increases dramatically, as occurs under environmental stresses, hydroxyl radical reacts with membrane lipids, inducing their peroxidation-the final product of which is MDA [13,25,53]. Thus, the development of the protective reactions of a plant organism to pathogens can be assayed by the degree of MDA accumulation.…”

“…peroxidation-the final product of which is MDA [13,25,53]. Thus, the development of the protective reactions of a plant organism to pathogens can be assayed by the degree of MDA accumulation.…”

“…It can be assumed that the mechanisms of action differ between strains 10-4 and 26D and that in the compositions with SA, the protective effect against late blight is enhanced in one case (strain 10-4 + SA), and not the other (strain 26D + SA) ( Figure 3). This finding allows for the possibility that this effect may be associated with the ability of the strains to produce their own phytohormones [13]. It is likely that if strain 10-4 produces SA, then the addition of exogenous SA can enhance its protective effect; if strain 26D produces jasmonic acid (JA), the addition of SA to the composition may have the opposite effect, since JA and SA are antagonists.…”

“…Moreover, as was mentioned above, endophytes have a significant advantage over epiphytic (surface) organisms living in the rhizosphere and phyllosphere due to the stable pH, humidity, nutrients and the lack of competition from a large number of microorganisms. It is believed that endophytic bacteria, once embedded in plant tissue, establish their long-term protection against environmental factors over a period of time, which, in particular, can be manifested in better preservation of fruits and vegetables during storage [13,21,50,52]. So, the observed protective effect of the studied endophytic B. subtilis (strains 10-4 and 26D) and SA on potato tubers during storage against late blight and fusariosis for a long time may be associated both with their ability to penetrate into internal tissues and with their internal regulation of physiological processes responsible for inducing defense mechanisms against pathogens.…”