By 2050, population growth and climate change will lead to increased demand for food and water. Nanoparticles (NPs), an advanced technology, can be applied to many areas of agriculture, including crop protection and growth enhancement, to build sustainable agricultural production. Ionic gelation method is a synthesis of microparticles or NPs, based on an electrostatic interaction between opposite charge types that contains at least one polymer under mechanical stirring conditions. 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. Many crops have been evaluated in in vivo or in greenhouse conditions but only maize (CS-NP-loaded Cu, Zn, SA, and silicon) and soybean (CS-NP-loaded Cu) were tested for manage post flowering stalk rot, Curvularia leaf spot, and bacterial pustule disease in field condition. Since 2019, five of eight studies have been performed in field conditions that have shown interest in CS-NPs synthesized by the ionic gelation method. In this review, we summarized the current state of research and provided a forward-looking view of the use of CS-NPs in plant disease management.
The objective of this study was to identify the causal agent of anthracnose disease of cassava in Thailand. The study was carried out by collecting cassava samples with anthracnose symptoms from various planting areas including 10 districts of eight provinces in Thailand. One hundred and thirty‐six Colletotrichum samples were isolated from cassava anthracnose lesions on leaves, petioles and stems. Thirty‐eight single‐spore isolates were subsequently obtained and cultured on half potato dextrose agar for morphological and molecular characterizations. All 38 isolates were pathogenic with varying degrees of virulence when tested on detached leaves of Kasetsart 50, a susceptible cassava cultivar. Based on their growth habit, colony morphology, conidial morphology and the internal transcribed spacer sequences similarity to that of Colletotrichum accessions in the GenBank, one isolate was identified as C. capsici, one as C. lindemuthianum, two as C. aeschynomene, four as C. boninense and 28 C. gloeosporioides species complex. Geographically, the cosmopolitan C. gloeosporioides species complex was found in all regions, but other species were found only in particular regions. This is, so far, the first report of Colletotrichum complex species associated with cassava anthracnose in Thailand.
This study was to investigate defense mechanisms on cassava induced by salicylic acid formulation (SA) against anthracnose disease. Our results indicated that the SA could reduce anthracnose severity in cassava plants up to 33.3% under the greenhouse condition. The β-1,3-glucanase and chitinase enzyme activities were significantly increased at 24 hours after inoculation (HAI) and decrease at 48 HAI after Colletotrichum gloeosporioides challenge inoculation, respectively, for cassava treated with SA formulation. Synchrotron radiation–based Fourier-transform infrared microspectroscopy spectra revealed changes of the C=H stretching vibration (3,000-2,800 cm−1), pectin (1,740-1,700 cm−1), amide I protein (1,700-1,600 cm−1), amide II protein (1,600-1,500 cm−1), lignin (1,515 cm−1) as well as mainly C–O–C of polysaccharides (1,300-1,100 cm−1) in the leaf epidermal and mesophyll tissues treated with SA formulations, compared to those treated with fungicide carbendazim and distilled water after the challenged inoculation with C. gloeosporioides. The results indicate that biochemical changes in cassava leaf treated with SA played an important role in the enhancement of structural and chemical defense mechanisms leading to reduced anthracnose severity.
In Asia, one of the most important cereal crops is rice. Presently, a fungal pathogen called rice blast (Magnaporthe grisea) is the most devastating diseases affecting this valuable human staple. One of the ways growers can control rice blast is by chemical fungicides; however, the down side to using chemicals is the increase of production cost, environmental contamination, and loss of chemical efficacy over time. The use of resistant rice cultivars provide fungal suppression and have a positive impact on the environment. The objective of this study was to screened rice blast-resistant cultivars via SR-FTIR microspectroscopy and compare it to the traditional method. At 14 days after pathogens inoculation (DAPI) of 80 cultivars and two reference cultivars, the leaves of inoculated plants showed elliptical or spindle-shaped lesions with pointed ends, gray or white centers, and dark-green to reddish-brown margins, with an occasional yellow halo. The results of disease severity were classified as susceptible (17 cultivars), moderately susceptible (28 cultivars), and resistant group (35 cultivars) of all 80 varieties of rice. Rice cultivar no. 34 had the lowest level of disease severity, which was 6.66 ± 11.54%. Furthermore, we evaluated the accumulation of salicylic acid (SA) in rice at 24 DAPI compared with uninoculated plants. The results of the resistant group showed an increase of SA level at 24 DAPI as well as reference resistant cultivars. Rice cultivar no. 34 had SA level of 15.19 68 μg g-1 fresh weight and all other reference-resistant cultivars had a SA level at 14.70 μg g-1 fresh weight, respectively. Additionally, screening rice blast-resistant cultivars via SR-FTIR microspectroscopy revealed altered variation in biochemical components of the plants after infection. A comparison of the susceptible, moderately susceptible, and resistant cultivars revealed differences in the biochemical components of rice tissues, which may be correlated with plant defense responses to disease. These outcomes could help breeding programs in terms of the selection of resistant-rice cultivars. Keywords: biochemical change; rice; rice blast disease; salicylic acid; SR-FTIR
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