Encyclopedia
Please note this is a comparison between Version 1 by Nguyen Hoang and Version 3 by Catherine Yang.
Nanoparticles (NPs), which are commonly based on chitosan (CS), have been applied to many agricultural fields, including nanopesticides, nanofertilizers, and nanoherbicides. The CS-NP or CS-NPs-loaded active ingredients (Cu, saponin, harpin, Zn, hexaconazole, salicylic acid (SA), NPK, thiamine, silicon, and silver (Ag)) are effective in controlling plant diseases and enhancing plant growth, depending on the concentration and application method by direct and indirect mechanisms, and have attracted much attention in the last five years.
- chitosan
- plant disease
1. Chitosan Nanoparticles (CS-NPs)
1.1. Directly
Under in vitro conditions, the authors of [1][52] determined that the minimum inhibitory concentration of CS-NPs prepared by centrifuge and pH change method at 0.05 and 0.09% could inhibit growth of F. graminearum at 31.97% and 29.67%, respectively. Furthermore, the authors of [1][52] also showed that CS-NPs were originated from CS low molecular weight, which has a higher inhibitory effect than CS height molecular weight at the same concentration. CS-NPs may or may not inhibit pathogens. CS-NPs may inhibit mycelial growth of Pyricularia grisea (65%) at 0.1% [2][71], Colletotrichum gloeosporioides (85.7%) [3][56], C. gloeosporioides (37.8%), Phytophthora capsica (50.7%), Sclerotinia sclerotiorum (39.5%), Fusarium oxysporum (50.3%), Gibberella fujikuori (56.3%) at 0.5% [4][54], P. grisea (92%), Alternaria solani (87%), F. oxysporum (72%) with amount of 100 µg [5][63], A. alternata (80.1–82.2%), R. solani (32.2–34.4%) at 0.06–0.1%, M. phaseolina (84%) at 0.1% [6][51], A. solani (10, 70%) at 0.03, 0.04% [7][72], Alternaria tenuis (67.67%), Aspergillus niger (62.75%), Aspergillus terreus (74.67%), Baeuvaria bassiana (76.08%), F. graminearum (60.37%), F. oxysporum (66.60%), Sclerotium rolfsii (37.41%) at 800 ppm, and the zearalenone produced by F. graminearum [8][73]. Furthermore, CS-NPs were 0.014% (in acetate buffer), the lysis zone diameter of Clavibacter michiganensis and Fusarium graminearum were 29.5 and 20.0 mm, and CS was 22.5 and 18.0 mm, respectively [7][72]. Moreover, 0.2 mL of CS-NP at 125 ppm could inhibit mycelium of F. graminearum by 44.3%, higher than fungicide (8-hydroxy quinoline) at 42.33% [8][73]. In addition, CS-NPs also inhibited spore germination of C. gloeosporioides (61.2%) [3][56] and A. alternata (84.4–87.1%) at 0.06–0.1% [6][51]. On the other hand, CS-NPs do not inhibit mycelial growth, spore germination, and sporulation of P. grisea, even at a concentration of 0.1% [9][2][59,71]. A study by [4][54] showed that OD600 nm of Erwinia carotovora subsp. carotovora strains 113114, 113154, and YKB133061, and Xanthomonas campestris pv. vesicatoria strain 11,154, were reduced by 41.3, 55.5, 48.5, and 52.1% when treated with CS-NPs at 0.5%; interestingly, they were also reduced by 64.7, 76.3, 78.0, and 73.8% when CS-NPs were treated at 0.05%, respectively. Furthermore, CS-NPs at 2 mL/L inhibited anthracnose disease at 87.5 and 75% for chili and at 50 and 10% for papaya, by using the preventative and curative treatments under in vivo conditions, respectively [3][56].
1.2. Indirectly
Pre-treatment of CS-NPs at 0.1% reduced sheath blight and blast in rice caused by R. solani and P. grisea by 92.78% and 100% under detach leaves assay, respectively [9][10][59,74].
In the greenhouse trial, CS-NPs are capable of protecting plants of rice, finger millet, and wheat from pathogens attacks [1][2][10][52,71,74]. The sheath blight disease was reduced by 75.01% compared with CS at 44.82%, and the peroxidase, phenylalanine ammonia-lyase, and chitinases activity also increased by 19-, 1.5-, and 1.9-fold, respectively [10][74]. In the study of [2][71], the symptom and disease incidence of blast was delayed by 10 days and decreased 2.8-fold, respectively, influenced by peroxidase activity (which increased 1.6-fold) and reactive oxygen species activity. Spray of CS-NPs at 0.05% after infection of F. graminearum leads to reduce AUPDC at 28 days after inoculation (DAI) by 2.2-fold compared to the water control. The NPs caused structural damage in mycelium and cell pathogen but also increased superoxide and H2O2 content [1][52].
2. Chitosan-Nanoparticles-Loaded Active Ingredients
2.1. Directly
The effect of controlling or enhancing the immunity of plants is different, depending on the same CS-NPs and the type of active ingredient. The EC50 of four formulate CS-NPs-loaded hexaconazole to control Ganoderma boninense is 8.0–18.4 ppb, which is 21.4 and 1534.5 ppb lower than hexaconazole and CS-NPs, respectively. Similarly, fiducial limit (lower-upper) was 6.0–10.9 to 13.0–32.8 ppb, while hexaconazole and CS-NPs were 16.7–27.3 and 494.0–13280.4 ppb [11][58].
CS-NPs-loaded Cu could inhibit mycelial growth of Curvularia lunata by 50.0 and 52.7% at 0.12 and 0.16% [12][75], A. solani and F. oxysporum by 84.2 and 60.1% at 0.1% [13][76], A. alternata and R. solani by 82.1–89.5% and 62.5–63.0% at 0.06–0.1%, and M. phaseolina by 60.1% at 0.1% [6][51], respectively. These NPs also inhibited spore germination of A. solani and F. oxysporum by 73.3 and 79.9% at 0.1% [12][75] and A. alternata by 83.3–87.4% at 0.06–0.1% [6][51]. CS-NPs-loaded Zn inhibited mycelial growth and spore germination of C. lunata by 47.7–65.2% and 50.5–73.3% at 0.08–0.16% [14][77]. In addition, the mixture of CS-NPs (ionic gelation) and Cu-NPs (chemical reduction) inhibited the mycelial growth of F. oxysporum by 61.94–100% at 0.05–0.2% [15][57]. CS-NPs-loaded SA evaded mycelial growth by 62.2–100% and spore germination of Fusarium verticillioides by 48.3–60.5% at 0.08–0.16% [16][65]. CS-NPs-loaded saponin inhibited mycelial growth of A. alternata by 78.3–80.9% and R. solani by 27.7% at 0.06–0.1% and spore germination of A. alternata by 78.3–82.9% at 0.1% [6][51]. On the other hand, CS-NPs-loaded thiamine did not inhibit F. oxysporum, even at a concentration of 0.1% [17][66].
Under greenhouse conditions, at 3 DAI, A. solani and F. oxysporum, CS-NPs-loaded Cu (0.1 and 0.12%) was foliar sprayed and applied to soil lead to reduced early blight (84.2 and 87.7%) and fusarium wilt (49.9 and 61.1%), respectively [12][75]. Furthermore, priming maize seeds into these NPs (0.02–0.14%) for 4 and 8 h combined with foliar spraying after F. verticillioides infected reduced post-flowering stalk rot disease by 38.2–48.1% and 24.8–49.6%, respectively [18][78]. Moreover, these treatments reduced disease severity by 23.5–33.9% and 2.55–15.8% for 4 and 8 h priming under field conditions.
2.2. Indirectly
Previously, Harpin protein (from Erwinia amylovora) was known for its ability to induce systemic acquired resistance in plants [19][79]. With the same amount (20 µg), CS-NPs-loaded Harpin protein (from P. syringae pv. syringae) enhanced cell death, necrotic lesions, and H2O2 accumulation faster and stronger than Harpin protein only [20][60]. Furthermore, treatment of these NPs reduced fungal biomass (5-fold) and lesion diameter (12-fold) and caused failing colonization of R. solani in tomato leaves compared with the control. Peroxidase and phenylalanine ammonia-lyase activity also steadily increased up to 72 h. Interestingly, the transcriptome changes, including defense response, signal transduction, transport, transcription, photosynthesis, housekeeping, and aromatic biosynthesis, were enhanced more than 2-fold at 24, 48, and 72 h after spraying.
Under greenhouse conditions, pre-treated CS-NPs-loaded Cu (0.04–0.16%) reduced leaf spot disease (C. lunata) in maize by 43.86–48.48%. Moreover, this treatment increased superoxide dismutases (1.8–2.2 folds), peroxidase (1.5–2.1 folds), phenylalanine ammonia-lyase (1.3–2.0 folds), and polyphenol oxidase (1.1–1.2 folds) [12][75]. Furthermore, CS-NPs-loaded Zn also induced superoxide dismutases, phenylalanine ammonia-lyase, polyphenol oxidase, and H2O2 activity by 1.2–2.0-, 2.0–3.0-, 17.24–49.37-, and 1.5–2.6-fold when compared with the control, respectively. The H2O2 and lignin localization also increased, leading to maize leaf spot (C. lunata) reduction by 32.3–50.77% [14][77].
A hormone-elicitor is an SA that has been loaded into CS-NPs. Maize was pre-treated with these NPs at 0.01–0.16% and suppressed post-flowering stalk rot disease (37.33–49.5%) caused by F. verticillioides. Furthermore, at 2 and 3 days after spraying NPs, superoxide dismutases (1.8- and 3.2-fold), peroxidase (7.0- and 4.6-fold), catalase (3.1- and 2.6-fold), phenylalanine ammonia-lyase (2.0- and 1.7-fold), polyphenol oxidase (1.7- and 2.0-fold), O2− (1.1- and 1.1-fold), H2O2 (17.5- and 37.0-fold), and lignin accumulation increased [16][65]. Pre-treated CS-NP-loaded SA at 400 ppm and CS-NP-loaded Ag at 200, 400, and 800 ppm by stalk-soaking and foliar spraying reduced cassava leaf spot disease by 68.9–73.6% at 56 DAP (first inoculate with fungal density 104 conidia per mL) and 37.0–37.7% at 75 DAP (second inoculate with fungal density 105 conidia per mL) [21][69].
Although CS-NPs-loaded thiamine did not inhibit fungi in vitro condition, pre-treatment of these NPs (0.1%) at 3 days before infection of F. oxysporum on chickpea reduced cell death in 2 DAI compared with control. Furthermore, polyphenol oxidase, peroxidase, β-1,3-glucanase, chitinase, chitosanase, and protease were increased by 2.1-, 2.0-, 1.4-, 1.4-, 1.4-, and 1.1-fold in leaves and 2.0-, 1.3-, 1.1-, 1.3-, 1.3-, and 1.1-fold in roots, respectively [17][66].
On the other hand, in the study of [22][80], CS-NPs-loaded Cu at 0.12–0.06% was treated before and after an infection of Xanthomonas axonopodis pv. glycine could reduce bacterial pustule disease in soybean by 40.6–49.7%, respectively. Interestingly, the low concentration is more effective. In addition, application of the mixture of CS-NPs (ionic gelation) and Cu-NPs (chemical reduction) to date palm root zone increased plant immunomodulatory, including total phenols (1.1–1.5 folds), phenoloxidases (1.1–2.0 folds), and peroxidase (1.6–3.0 folds), which led to a reduction in disease by 16.2–59.3% [15][57].
Under field conditions, CS-NPs-loaded Cu, Zn, and SA are effective in reducing disease by inducing plant defense system in maize and soybean [16][12][14][22][65,75,77,80]. Treatment CS-NPs-loaded Cu (0.06%) reduced bacterial pustule disease by 51.3%. In addition, these NPs at 0.01–0.08% reduced maize leaf spot disease by 27.72–28.53% while at 0.12–0.16% they reduced it by 30.42–33.8% [12][75]. On the other hand, CS-NPs-loaded Zn at 0.01–0.16% reduced this disease by 25.42–39.67% [14][77]. CS-NPs-loaded SA at 0.01–0.16% reduced post-flowering stalk rot by 40.5–59.47% [16][65].
3. Plant Growth Promotion
A concern for any agrochemical is the safety of plants, environment, farmers, and consumers. In recent reviews, NP is a biosafety solution. However, nanotoxicology still remains to be noticed [23][24][81,82]. When applying NPs to plants, they will enter the tissues and cause positive and negative impacts depending on their size, shape, and concentration. NPs usually enhance shoot elongation, root elongation, seed germination at low concentration, and in contrast at high concentration [25][17]. The effective concentration varies between NPs and crops. In the study by the authors of [21][69], the CS-NP-loaded SA and silver were tested for phytotoxicity with the cassava by leaf disk assay method before being applied to cassava plants at net house condition. Results showed that these formulations did not cause damage in leaf disk up to 800 ppm. Then, researchers varied concentrations of 25–800 ppm for stalk-soaking and foliar spraying to enhance cassava growth and reduce leaf spot disease. This is an easy way to know what “safe” concentrations are for the plant. When applied to soil, NPs can cause negative impacts on soil microflora but will be less damaging than agrochemical applications [26][83]. On the other hand, the amount of agrochemical and fertilizer applied to agriculture is reduced if they are replaced by NPs, which leads to a reduction in their toxicity. Usually, the safety-by-design principle is applied to screen potential risks from materials and methods synthesis to NP formulation [27][84]. As mentioned above, ionic gelation method and CS—a natural polymer—are friendly, safe, and biodegradable solutions.
In addition to its ability to directly inhibit pathogens or induce plant defense system against diseases, CS-NPs or CS-NPs-loaded active ingredients have the ability to stimulate plant growth. At this time, they act as fertilizers or nutrients, affecting plant physiological processes, including nutrient uptake, cell division, cell elongation, enzymatic activation, and the synthesis of protein that leads to increase yield [28][43]. Efficiency depends on both the CS-NPs and the active ingredient, even when it releases all the active ingredients because the main component of CS is nitrogen, which takes 9–10% [29][46]. Furthermore, the rich positive charge of CS leads to increased affinity toward the plant cell membrane, which enhances reactivity in the plant system [30][49].
In the seeding stage, CS-NPs increased the seeding vigor index (57.1%), the number of lateral root (133.3%), and dry weight (200%) of chickpeas [5][63]. Additionally, the chickpea seeds were soaked with CS-NPs-loaded thiamine at 0.1% overnight, leading to the seeding vigor index increasing by 64.2%, with Indole-3-acetic acid content increased 10-fold [17][66]. Treatment with CS-NPs-loaded Cu at 0.08, 0.1, and 0.12% increased seedling vigor index (33.9, 33.7, and 24.3%), fresh weight (18.9, 21.6, and 16.2%), and dry weight (20.0, 26.7, and 13.3%) in tomato, respectively [12][75]. Additionally, CS-NPs-loaded Cu at 0.01–0.16% increased seeding vigor index (15.6–48.6%), fresh weight (7.1–11.4%), and dry weight (21.4–57.1%) in maize seedings, which were related to increasing α-amylase and proteases at days 5 and 7, respectively [31][85].
Under greenhouse conditions, the dry weight and yield of finger millet increased by 148.8% and 93.2% when treated with CS-NPs, respectively [2][71]. The plant height, stem height, and root length of maize increased by 30.3–60.3, 66.3–237.5, and 2.7–61.1% when treated with CS-NPs-loaded Zn at 0.01–0.16%, respectively [14][77]. In chickpea, the shoot length, number of leaves per plant, fresh weight, dry weight, and number of secondary roots per plant increased by 15.3, 14.4, 37.7, 20.0, and 52.8% when sprayed with CS-NPs-loaded thiamine at 0.1%, respectively [17][66]. In present year, pre-treated CS-NP-loaded SA at 400 ppm and CS-NP-loaded Ag at 200, 400, 800 ppm by stalk-soaking for 5 min and foliar spraying at 28, 42 DAP could increase the number of leaves (45.1–82.4%), the number of shoots (38.5–46.2%), the largest leaf area (29.6–41.9%), root length (11.6–29.9%), and root weight (27.6–82.8%) of cassava, at 75 DAP in net house condition [21][69]. In addition, CS-NPs-loaded Cu at 0.06% could increase plant height (56.8%), root length (40.3%), and pod number (7.2%). NPs treatment at 0.02% could increase root weight (46.8%), nodule number (44.2%), nodule weight (125.8%) under greenhouse conditions and also increase root length (60.9%), root weight (46.8%), and pod number (29.7%), in soybean under field conditions [22][80]. Furthermore, NPs at 0.01–0.08% increased plant height (15.9–47.0%), stem diameter (82.9–102.9%), root length (9.5–15.8%), root number (20.9–46.3%), and chlorophyll content (67.3–182.6%) under greenhouse conditions and increased grain yield (25.4–29.3%), 100 grain weight (14.4–16.9%) in maize under field conditions [12][75]. However, the treatment at 0.16% reduced root length (9.8%) and chlorophyll content (4.6–9.7%), although the difference was not significance. The CS-NPs-loaded SA at 0.01–0.16% increased leaf area (160.6–224.7%), shoot length (38.5–76.9%), root length (66.9–111.5%), root number (59.6–91.8%), stem diameter (22.8–53.9%), and total chlorophyll (54.2–141.4%) in maize under greenhouse conditions. Moreover, the treatment of these NPs at 0.08%, days to 50% tasselling was early by 4 days under field conditions. Moreover, the plant height (25.5%), ear height (12.1%), cob length (44.8%), test weight (71.1%), and grain yield (48.3%) also increased [16][65]. The authors of [32][86] synthesized CS-NPs-loaded NPK (ionic gelation) with slow-release N (66.7%), P (3.1%), and K (57.7%) for 240 h. The leaf number, leaf area, plant height, and stem diameter of coffee increased 22.8, 46.9, 12.7, and 28.3% when these NPs were treated at 30 ppm, respectively. This synthesized CS-NPs-loaded NPK improved N (17.04%), P (13.1%), K (67.5%), chlorophyll (30.68%), carotenoid (21.4%) content, and photosynthesis rate (71.7%) in the coffee leaves. Another nano fertilizer, CS-NPs-loaded silicon at 0.04–0.12%, increased the seeding vigor index in maize seeding by 167.5–285.2%. Furthermore, foliar spraying induced antioxidant defense enzyme activity; equilibrated cellular redox; and balanced O2− and H2O2 in leaf, leading to homeostasis. In the field trial, the yield and test weight of maize was increased by 186.6 and 77.1% by treated CS-NPs-loaded silicon at 0.08 and 0.04%, respectively [33] (Figure 1)[87].
Figure 14. The application of CS-NPs and CS-NPs-loaded active ingredients synthesized by ionic gelation method in plant disease management and enhancing plant growth. Note: 1 Mixture of CS-NP (ionic gelation method) and Cu-NP (chemical reduction method). Saharan et al. 2013 [6][51], Sathiyabama et al. 2016 [5][63], Sathiyabama et al. 2016 [2][71], Manikandan et al. 2016 [9][59], Kheiri et al. 2017 [1][52], Suryadi et al. 2019 [3][56], Oh et al. 2019 [4][54], Abdel-Aliem et al. 2019 [8][73], Popova et al. 2020 [7][72], Divya et al. 2020 [10][74], Saharan et al. 2015 [13][76], Choudhary et al. 2017 [12][75], Choudhary et al. 2017 [18][78], Choudhary et al. 2017 [31][85], Mohamed et al. 2018 [15][57], Nadendla et al. 2018 [20][60], Choudhary et al. 2019 [14][77], Kumaraswamy et al. 2019 [16][65], Maluin et al. 2019 [11][58], Ha et al. 2019 [32][86], Muthukrishnan et al. 2019 [17][66], Swati et al. 2020 [22][80], Kumaraswamy et al. 2021 [33][87], Hoang et al. 2022 [21][69].
