Abstract
Leaf spot disease caused by Lasiodiplodia theobromae is one of the most serious fungal diseases of kiwifruit production. In this work, the co-application of isopyrazam·azoxystrobin and chitosan against leaf spot disease in kiwifruit and its effects on disease resistance, photosynthesis, yield, quality, and amino acids of kiwifruit were investigated. The results show that isopyrazam·azoxystrobin exhibited a superior bioactivity against L. theobromae with an EC50 value of 0.1826 mg kg−1. The foliar application of chitosan could effectively enhance isopyrazam·azoxystrobin against leaf spot disease with a field control efficacy of 86.83% by spraying 29% isopyrazam·azoxystrobin suspension concentrate (SC) 1500 time + chitosan 100-time liquid, which was significantly (p < 0.05) higher than 78.70% of 29% isopyrazam·azoxystrobin SC 1000-time liquid. The co-application of isopyrazam·azoxystrobin and chitosan effectively enhanced soluble protein, resistance enzymes’ activity in kiwifruit leaves, and reduced their malonaldehyde (MDA), as well as reliably improved their photosynthetic characteristics. Simultaneously, their co-application was more effective in promoting growth, quality, and amino acids of kiwifruit fruits compared to isopyrazam·azoxystrobin or chitosan alone. This study highlights that the co-application of isopyrazam·azoxystrobin and chitosan can be used as a green, safe, and efficient approach for controlling leaf spot disease of kiwifruit and reducing the application of chemical fungicides.
Highlights
Kiwifruit (Actinidia chinensis), an edible and medicinal third-generation fruit rich in vitamin C, essential amino acids for humans and various minerals, has high nutritional, medicinal, and economical values [1–3]
Shi et al [8] reported that leaf spot disease caused by L. theobromae is one of the most serious fungal diseases of the kiwifruit production area in Guizhou Province; the initial stage is in late June and the peak stage is from July to August, and its spots are round or irregularly shaped brown necrosis
L. theobromae with an EC50 value of 0.1826 mg kg−1, which was 12.98, 19.55, 19.88, 19.93, 151.81, 211.72, 346.88, 889.98, and 2658.32-fold higher compared to 0.3% Tetramycin aqueous solutions (AS), 48%
Summary
Kiwifruit (Actinidia chinensis), an edible and medicinal third-generation fruit rich in vitamin C, essential amino acids for humans and various minerals, has high nutritional, medicinal, and economical values [1–3]. Shi et al [8] reported that leaf spot disease caused by L. theobromae is one of the most serious fungal diseases of the kiwifruit production area in Guizhou Province; the initial stage is in late June and the peak stage is from July to August, and its spots are round or irregularly shaped brown necrosis. It seriously affects the growth and photosynthesis of kiwifruit plants, resulting in a reduction in kiwifruit yield and quality, as well as major economic losses.
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