2.4.5.2. Chemical treatment
The most effective strategy to control potato dry rot is the combination of pre-and post-harvest treatment. Firstly, it is necessary to disinfect the seed tuber before planting, chemical treatments to the harvested tubers also play an important role before storage. Thiabendazole is currently considered as the most widely used chemical fungicide to manage
Fusarium dry rot of potato [
88]. Thiophanate-methyl (benzimidazole group) was reported that is extensively applied to manage seed tuber piece disease in Canada. Nevertheless, the employment of thiabendazole has resulted in the occurrence of the drug-resistant strains against the pathogen of
F. sambucinum, it is fortunate that the rest of the
Fusarium species viz.
F. solani,
F. culmorum,
F. equiseti,
F. acuminatum and
F. avenaceum are still sensitive to the fungicide of thiabendazole [72, 89]. Some alternative fungicides with high-efficiency and low-toxicity (such as fludioxonil) also have incomparable effects to manage dry rot. For instance, fludioxonil was used to effectively control tuber seed disease and sprout rot [
90]. The application of azoxystrobin and fludioxonil effectively managed dry rot, the disease incidence decreased to 50% comparing with the control after 21 days of storage [
15]. However, with the extensive application of synthesis chemical fungicide, the inevitable problems of drug-resistance, environmental pollution, as well as food safety are becoming more and more prominent. Therefore, it is urgent to develop more safer and efficient fungicides to control Fusarium dry rot of potato.
Accordingly, the generally recognized as safe (GRAS) substances, such as inorganic acid, organic acid, inorganic salts, organic salts, essential oils and phytohormones, all display excellent effects in sustainably controlling the dry rot of potato. Raigond et al. [
91] indicated that chitosan application significantly managed dry rot in potato, and he also found that chitosan coating significantly reduced the
Fusarium incidence by inhibiting
Fusarium growth. Xue et al. [
7] suggested chitosan, sodium silicate and β-aminobutyric acid treatments markedly inhibited the expansion of lesion diameter in tuber infected with
F. sulphureum, interestedly, trichothecenes concentration was also decreased, the involved action mechanism was attributed to the up-regulation of enzyme activities involved in defense reaction, and down-regulated genes related with trichothecenes biosynthesis pathway. Afterwards, Xue research group found an interesting result that T-2 toxin, as a kind of trichothecenes A, suppressed the expansion of dry rot of potato at a low concentration [
92]. Later, Han found the treatments of sodium silicate and brassinosteroid promoted wound healing of potato and accelerating suberin deposit, ultimately enhanced the resistance against dry rot of potato [78-79]. Jiang adopted BTH to treat potato and also observed the similar control effect on potato dry rot by accelerating wound healing [
80]. Ma et al. [
93] found the gene of
StCDPK23 played an important role on wound healing of potato and suberin deposition, and constructed
StCDPK23-overexpressing plants to conformed
StCDPK23 participated in the tuber wound healing and contributed the resistance against dry rot of potato.
In addition, essential oils and extracts from plants displayed an excellent effect in suppressing the development of
Fusarium dry rot by soaking or fumigation treatment [
94]. Essential oil from
Zanthoxylum bungeanum was found to be efficient in inhibiting the expansion of dry rot disease resulted from
F. sulphureum [
11]. The cinnamaldehyde, a major component of cinnamon essential oil, displayed a better control effect on potato dry rot resulted from
F. sambucinum, the underlying mechanism revealed that cinnamaldehyde suppressed spore germination by impacting the biosynthetic pathway of ergosterol, improving ROS accumulation, ultimately resulting in a breakdown of cell membrane integrity [
12]. Similarly, the essential oils from peppermint and fennel also remarkedly suppressed the
F. oxysporum growing and reduced the Fusarium dry rot developing when treated with a protective emulsifiable concentrate [
95]. It is interesting that some essential oils directly influenced mycotoxin metabolism by impacting the biosynthetic pathway of mycotoxins, for instance, the essential oils from palmarose and clove reduced DON and ZEA accumulation by down-regulating the expression of genes involved in mycotoxin the biosynthetic pathway of DON and ZEA [
96]. Essential oils from plant, as a sustainable alternative to chemical synthetic fungicides, needs to be studied in-depth in the future [1, 97]. The extract from plant also displays excellent effect on plant disease [
98]. The extract from black spruce revealed antifungal and suppressive potential to prevent the development of potato dry rot [
99]. The extract from cinnamon also significantly inhibited
F. sambucinum spore growth
in vitro and reduced dry rot development
in vivo [
100]. Chlorogenic acid, as a kind of polyphenols with antioxidative activity, is mainly from the methanol extract, and also displayed a better inhibitory activity on the development of
Fusarium dry rot of potato. The possible action mechanism is attributed to chlorogenic acid application modified morphological structure of
F. sambucinum, the phenomenon of curling, twisting and collapse was observed after exposure of chlorogenic acid [
1].
Additionally, chlorine dioxide and ozone, as the two strong oxidants, also perform an important and crucial role in controlling the
Fusarium dry rot. Chlorine dioxide (ClO
2) acts as a water-soluble strong oxidant, whose oxidation ability is 2.5 times higher than that of chlorine. ClO
2 can be applied in both gaseous and aqueous solution form to control the postharvest disease on fruits and vegetables. For instance, Li et al [
101] suggested that 0.75 ug/mL ClO
2 solution application significantly reduced the incidence of
Fusarium dry rot of potato and suppressed the expansion of the lesion diameter by damaging the morphology and ultrastructure of
F. sulphureun hyphae. Ozone, as another high efficiency and non-toxic, strong oxidant, also display an important role to control potato dry rot, on the one hand, ozone inhibited the growth of
F. sulphureum spore, destroyed the structure of
F. sulphureum [
102], on the other hand, ozone treatment activated ROS metabolism of the potato tuber, and induced the resistance against dry rot [
103].
2.4.5.3. Biological treatment
Biocontrol is regarded as a greener and safer strategy for the food safety and human health, comparing with the traditional chemical synthetic fungicides. Presently, scientists have been focusing on the research on antagonistic microorganisms to manage plant diseases. Antagonistic microorganism is currently regarded as the most potential alternative option to manage postharvest diseases. For instance, antagonistic microorganisms effectively controlled
Fusarium dry rot during the potato wounds healing process when the tubers are at their most vulnerable. Schisler’s group firstly reported the strains of
Pseudomonas Migula spp.,
Enterobacter Hormaeche &
Edwards spp., and
Pantoea Gavini. spp. remarkedly decreased the incidence of potato dry rot resulted from
F. sambucinum [
104]. Later, the group found the mixtures of various antagonist strains had more efficient to control potato dry rot than that of single strain [
105]. Gözdenur and Elif [
106] screened 12 bacterial and fungal isolates and found that
Pantoea agglomerans manifested the most efficacy to suppress the growth of
F. oxysporum and control the occurrence of potato dry rot.
Trichoderma harzianum and
Bacillus subtilis, as the two most important biological control agents, were registered to manage potato disease. The two agents were the most studied mycoparasitic species for their antagonistic function against a broad spectrum of pathogenic fungus, as well as recognized as a most promising strategy to inhibit different kinds of pathogenic fungi growth and control both preharvest and postharvest plant diseases occurrence. Daami-Remadi et al. [
107] suggested
T. harzianum and
T. viride manifested a greater antagonistic activity against Fusarium dry rot in potato in Tunisia. El-Kot [
108] compared four strains of fungal, bacterial and bioagents actinomycetes, and suggested that
T. harzianum displayed the most efficient to inhibit the radial development of
F. sambucinum and controlling the occurrence of dry rot under green house. Paul et al. [
109] also observed
T. harzianum strains CMML20-26 and CMML20-27 significantly decreased the postharvest disease in sweet potato
. B. subtilis also plays a vital role to reduce potato disease. Wharton and Kirk [
110] used the bioagent of
B. subtilis in combination with excellent management practices to significantly reduce seed piece decay by 94.3% in 2007. Hussain et al [
111] compared the biosurfactant extract, culture filtrate and bacterial cell suspension from
B. subtilis
HussainT-AMU and found bacterial cell suspension (49%) and biosurfactant extract (70%) had the most control effects on the net house and field, respectively.
In recent years,
Trichothecium roseum was also reported to act as an elicitor to induce resistance against dry rot in potato tuber infected by
F. sulphureum. During the defense responses induced by elicitor, the genes involved in resistant-reaction were up-regulated, accordingly, the enzymes activities and antifungal compounds contents were also significantly decreased after
T. roseum application [
112]. The possible mode of action for bioagent include mycoparasitism, competition for nutrients, and the production of extracellular enzymes and/or secondary metabolites [
113]. For instance, Xue et al. research group [
92] indicated that T-2 toxin (secondary metabolites from
F. sulphureum) at the concentration of 1µg/mL could be act as an elicitor to induce resistance against dry rot by activating ROS metabolism and phenylpropane metabolism in potato.