β-Aminobutyric Acid Induced Resistance against Alternaria Fruit Rot in Apple Fruits.

Lior Gur,Yigal Cohen,Moshe Reuveni

doi:10.3390/jof7070564

Lior Gur, Yigal Cohen + Show 1 more

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https://doi.org/10.3390/jof7070564

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Abstract

Fruit body rot and calyx rot caused by Alternaria alternata f. sp. mali is an important disease of apple worldwide. The disease has recently become severe in cv. Pink Lady apple in Israel to an extent that has never been reported elsewhere in the world. No alternative control measures of the disease except fungicides are known. Here, we show for the first time that dl-β-aminobutyric acid (BABA) induces resistance against Alternaria fruit rot (AFR) in apple fruits in the laboratory and in the orchard. AFR was inhibited in fruits treated with BABA of 1000 μg/mL. BABA did not inhibit spore germination or mycelial growth of the pathogen in vitro (up to 2000 μg/mL). It was most inhibitory when applied 4 days prior to inoculation of detached fruits. BABA inhibited AFR also curatively when applied at 24 h post inoculation. Five other isomers of aminobutyric acid failed to protect the fruits from rot formation. Three field trials in commercial apple orchards proved that BABA was as protective against AFR as the commercial standard fungicidal mixture of azoxystrobin and difenoconazole. This research suggests that BABA may serve as a resistance inducer in apple against AFR. It can be used as an adequate alternative to the currently used fungicides or integrated in disease management programs to reduce fungicide load and buildup of fungicide resistance.

Highlights

Alternaria leaf blotch and fruit spot of apple (Malus domestica Borkh), caused by the fungus Alternaria alternata f. sp. mali
The efficacy of BABA in controlling Alternaria fruit rot in apple fruits in the field was compared to that of the commercial pre-mixed fungicide
Conidial germination was insensitive to BABA: percent germination in BABA of 10, 100, 1000 and 2000 μg/mL at 20 h ranged between 88.6–96.2% (Table 1)

Summary

Introduction

Alternaria leaf blotch and fruit spot of apple (Malus domestica Borkh), caused by the fungus Alternaria alternata f. sp. mali Alternaria leaf blotch and fruit spot of apple (Malus domestica Borkh), caused by the fungus Alternaria alternata f. Alternaria mali Roberts, or Alternaria alternata apple pathotype) [1,2,3], is an important disease of apple in many countries [4,5,6,7,8,9,10], including. The disease affects cultivars such as Golden Delicious, Starking Delicious, Gala and Pink Lady [5,8,11,12,13]. The pathogen may cause soft rot, when the skin is wounded by mechanical damage or insects [14,15,16] or has cracks around the fruit calyx [17]. Severe outbreaks of apple fruit rot were observed in cv

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