The Effect of Different Phosphite Spray Formulas on Phytotoxicity and Phosphite Uptake of Avocado and Control Efficacy against Phytophthora Root Rot

Phytophthora root rot (PRR) caused by Phytophthora cinnamomi is one of the most important avocado diseases in Taiwan. Though foliar sprays of phosphonate fungicides have been used to manage this disease in other countries, the most effective application dosage and techniques have not been determined for avocado cultivars planted in Taiwan. To provide information for optimizing phosphite application strategies, this study investigated the effects of different phosphite spray formulas on avocado seedlings of various cultivars, focusing on phytotoxicity and phosphite uptake. The results showed that 0.1% and 0.2% phosphite caused mild (phytotoxicity score < 2) or no phytotoxic damage on seedlings of 6 avocado cultivars tested, including ‘Choquette’, ‘Changan’, ‘Hung Shin Yuan’, ‘Zongpu Green Skin’, ‘Hall’, and ‘CAES3’, while 0.5% phosphite could cause severe phytotoxic damage (phytotoxicity score ≥ 2) on ‘Choquette’, ‘Changan’, and ‘Hall’ under high temperature. In addition, pH had no obvious effect on phytotoxicity when the solutions were buffered to a pH ranging from 6.5 to 7.5. A detached root bioassay showed that, compared with the control, the colonization rates of P. cinnamomi were significantly lower in ‘Changan’ seedlings treated with phosphite and an adjuvant (0.2% phosphite plus Jia-Shou-Huo-Jhan (加收活展, JSHJ), 0.5% phosphite plus JSHJ, or 0.5% phosphite plus S-408), and the root phosphite concentrations were above 180 μg g-1 for all these three treatments. Moreover, adding an adjuvant (JSHJ or S-408) to the phosphite solution reduced phytotoxic damage and increased the uptake of phosphite into the roots. The results generated from in this study will be helpful for the optimization of phosphite application strategies for the avocado industry. 由Phytophthora cinnamomi 造成之根腐病 (Phytophthora root rot) 為台灣酪梨最重要之病害。雖然在國外，以葉面噴施亞磷酸防治酪梨根腐病由來已久，但針對國內酪梨品種，至今仍缺乏有效施用亞磷酸劑量及技術之研究。為優化亞磷酸防治酪梨根腐病施用策略所需資訊，本研究以國內常見品種之酪梨苗測試不同亞磷酸配方對酪梨葉片藥害及亞磷酸吸收之影響。實驗結果顯示，於測試的6 個品種 (「秋殼」、「章安」、「紅心圓」、「中埔青皮」、「厚兒」及「嘉選三號」) 上，葉面噴施0.1% 及0.2% 之亞磷酸於酪梨苗造成之藥害均極輕微 (藥害級數 < 2)，而0.5% 亞磷酸則可能於高溫下對「秋殼」、「章安」及「厚兒」造成嚴重藥害 (藥害級數 ≥ 2)。若亞磷酸已中和至pH 值介於6.5–7.5 之間，則pH 值對藥害程度影響無顯著差異。於「章安」之離根接種實驗結果顯示，噴施0.2% 亞磷酸 + 加收活展、0.5% 亞磷酸 + 加收活展，或0.5% 亞磷酸 + S-408 處理之根系P. cinnamomi 感染率均顯著低於對照組，且此些處理酪梨根系之亞磷酸濃度均大於180 μg g-1。此外，於亞磷酸溶液中添加展著劑 (加收活展或S-408) 可減少藥害並增加根部對亞磷酸之吸收。本研究結果有助於優化亞磷酸在酪梨產業的應用策略。

Subjects

avocado

adjuvant

Phosphite

Phytophthora root rot

phytotoxicity

酪梨

展著劑

亞磷酸

根腐病

藥害

Publisher

農業試驗所

Type

journal article

File(s)

Name

72-2-1.pdf

Size

2.58 MB

Format

Adobe PDF

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