Abstract
In order to investigate the effect of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) on the resistance of tea plants (Camellia sinensis) to tea geometrid (Ectropis obliqua), three levels each of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) were sprayed on 10-year-old tea plants. Generally PPO and PAL activities increased with low concentrations of BTH and BABA treatments. Quantitative RT-PCR revealed a 1.43 and 2.72-fold increase in PPO gene expression, and 3.26 and 3.99-fold increase in PAL gene expression with 75 mg/L BTH and 400 mg/L BABA respectively. Analysis of hydrolysis of synthetic substrates also revealed that chymotrypsin-like enzyme activity present in larval midgut extracts was not significantly inhibited by BTH and BABA. However, proteinase activity was found to be inversely proportional to the age of tea geometrid. Larvae pupation rate decreased by 8.10, 10.81 and 21.62% when tea geometrid were fed with leaves treated with 25, 50 and 75 mg/L BTH solutions, while 100, 200 and 400 mg/L BABA solutions decreased same by 8.10, 16.21 and 13.51% respectively. Also, larvae development period delayed to 23.33 and 26.33 days with 75 mg/L BTH and 400 mg/L BABA treatments respectively. The results in this study; therefore, suggest that benzothiadiazole (BTH) and β-aminobutyric acid (BABA) play a role in inducing resistance in tea plants to tea geometrid, with the optimal effect achieved at BTH-3 (75 mg/L) and BABA-3 (400 mg/L), respectively.
Highlights
Tea (Camellia sinensis) is a popular plant which originated in the southwest of China
The order of PAL gene expression levels in BTH and BABA treatment groups was observed as BTH-3 > BTH-2 > BTH-1, and BABA-3 > BABA-2 >
Inhibited growth, development and performance of geometrid larvae as characterized by decreased body weight, prolonged development duration, and lower rates of survival, pupation and emergence of tea geometrid larvae relative to the control
Summary
Tea (Camellia sinensis) is a popular plant which originated in the southwest of China. Tea is cultivated in more than hundred countries worldwide [1].Leaves of tea plants are brewed into tea which is the most popular non-alcoholic beverage in the world. Tea cultivation in China is faced with several biotic stressors, of which tea geometrid (Ectropis obliqua) is the most significant [2]. Tea geometrid feeds on tea shoots and causes serious hindrances to tea production and quality, resulting in huge economic losses [3]. Several methods have been developed to control tea geometrid, yet pesticide use has been the primary technique [4]. Pesticide use may result in severe ecological and environmental issues. Residues from pesticides pose serious health hazards to Molecules 2018, 23, 1290; doi:10.3390/molecules23061290 www.mdpi.com/journal/molecules
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