Biochar addition to soil not only sequesters carbon for the long-term but enhances agricultural productivity. Several well-known benefits arise from biochar amendment, including constant provision of nutrients, increased soil moisture retention, decreased soil bulk density, and sometimes the induction of systemic resistance against foliar and soil borne plant pathogens. However, no research has investigated the potential of biochar to increase resistance against herbivory. The white-backed plant hopper (WBPH) (Sogatella furcifera Horváth) is a serious agricultural pest that targets rice (Oryza sativa L.), a staple crop that feeds half of the world’s human population. Therefore, we investigated the (1) optimization of biochar amendment levels for two rice varieties (‘Cheongcheong’ and ‘Nagdong’) and (2) subsequent effects of different biochar amendments on resistance and susceptibility of these two varieties to WBPH infestation. Initial screening results for the optimization level revealed that the application of biochar 10% (w/w) to the rooting media significantly improved plant physiological characteristics of both rice varieties. However, levels of biochar amendment, mainly 1, 2, 3, and 20%, resulted in negative effects on plant growth characteristics. Cheongcheong and Nagdong rice plants grown with the optimum biochar level showed contrasting reactions to WBPH infestation. Specifically, biochar application significantly increased plant growth characteristics of Nagdong when exposed to WBPH infestation and significantly decreased these characteristics in Cheongcheong. The amount of WBPH-induced damage to plants was significantly lower and higher in Nagdong and Cheongcheong, respectively, compared to that in the controls. Higher levels of jasmonic acid caused by the biochar priming effect could have accumulated in response to WBPH infestation, resulting in a maladaptive response to stress, negatively affecting growth and resistance to WBPH in Cheongcheong. This study highlights the importance of investigating the effects of biochar on different rice varieties before application on a commercial scale to avoid potential crop losses.
Brown planthopper (BPH, Nilaparvata lugens Stal.) is the most damaging rice pest affecting stable rice yields worldwide. Currently, methods for controlling BPH include breeding a BPH-resistant cultivar and using synthetic pesticides. Nevertheless, the continuous cultivation of resistant cultivars allows for the emergence of various resistant races, and the use of synthetic pesticides can induce environmental pollution as well as the emergence of unpredictable new pest species. As plants cannot migrate to other locations on their own to combat various stresses, the production of secondary metabolites allows plants to protect themselves from stress and tolerate their reproduction. Pesticides using natural products are currently being developed to prevent environmental pollution and ecosystem disturbance caused by synthetic pesticides. In this study, after BPH infection in rice, chrysoeriol7 (C7), a secondary metabolite that induces resistance against BPH, was assessed. After C7 treatment and BPH infection, relative expression levels of the flavonoid-related genes were elevated, suggesting that in plants subjected to BPH, compounds related to flavonoids, among the secondary metabolites, play an important role in inducing resistance. The plant-derived natural compound chrysoeriol7 can potentially thus be used to develop environmentally friendly pesticides. The suggested control of BPH can be effectively used to alleviate concerns regarding environmental pollution and to construct a relatively safe rice breeding environment.
The brown planthopper (BPH) is a major pest that causes serious damage to rice in countries with mild climates, including Korea, Japan, China, and Vietnam. Although a large number of BPH-resistant genes have been reported, BPH has recently evolved rapidly and in a variable manner due to rapid climate change and an unpredictable environment. The synthesis of secondary metabolites in plants is essential, as it provides resistance to various stressors, including pests such as BPH. For QTL mapping, a Samgang/Nagdong double haploid (SNDH) 113 population was used. The BPH resistance gene was screening by measure the resistance score using the phenotype that appeared after BPH inoculation in the 113 SNDH population. QTL mapping was used, and SSR marker RM584-RM225 of chromosome 6 and SSR marker RM331-S8024 of chromosome 8 were commonly identified. These locations contained transcription factors, phytohormones, signaling molecules, kinases, and secondary metabolites that defend plants from stressors in the environment. This region of chromosome 8 also contained a sequence similar to that of rice Choristmate mutase (OsCM9). CM is a gene that is not only found in rice, but also in thale cress (Arabidopsis thaliana (L.) Heynh.), maize (Zea mays L.), and soybean (Glycine max (L.) Merr.). After inoculation with BPH, the relative expression levels of OsCM9 were greater in the line resistant to BPH than in the line susceptible to BPH. The newly identified BPH-resistant gene OsCM9 can be used for the development of rice varieties that are capable of resisting sudden damage due to BPH, as the evolution of BPH due to climate change has had negative impacts on rice crops.
Whitebacked planthopper (WBPH) is a pest that causes serious damage to rice in Asian countries with a mild climate. WBPH causes severely rice yield losses and grain poor quality each year so needs biological control. Plants resist biotic and abiotic stress using expressing variety genes, such as kinase, phytohormones, transcription factors, and especially secondary metabolites. In this research, quantitative trait locus (QTL) mapping was performed by assigning the WBPH resistance score in the Cheongcheong/Nagdong doubled haploid (CNDH) line in 2018 and 2019. The RM280-RM6909 on chromosome 4 was detected as a duplicate in 2018, 2019, and derived from Cheongcheong. This region includes cell function, kinase, signaling, transcription factors, and secondary metabolites that protect plants from the stress of WBPH. The RM280-RM6909 on chromosome 4 contains candidate genes that are similar to the flavanone 3-hydroxylase (F3H) of rice. The F3H are homologous genes, which play an important role in biosynthesis defending against biotic stress in plants. After WBPH inoculation, the relative expression level of F3H was higher in resistant line than in a susceptible line. The newly identified WBPH resistance gene F3H by QTL mapping can be used for the breeding of rice cultivars that are resistant against WBPH.
Whitebacked Planthopper is a sucking phloem sap insect which can greatly affect quality of the grain and yield losses. Determination of the resistance and susceptibility to WBPH is very important to accurate QTL analysis. The main objective of the study was to examine the level of resistance to determine optimum screening time using 120 doubled haploid lines. CNDH populations were developed from anther culture of F1, which was derived after a crossing WBPH, Sogatella furcifera resistance 'Cheongcheong' and susceptible 'Nagdong' lines. The genetic map with average 9.6 CM between markers was constructed from 120 CNDH populations, which included 217 SSR markers. Four QTLs were detected at different time and points based on the rate of seedling mortality after WBPH infestation. The markers were found to be comprehensive in identification of genotype and phenotype at coincident rate of 95% 14 days after infestation. These markers are efficiently very useful for MAS and develop new varieties in rice breeding program.
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