Abstract
The objective of this study was to determine the elicitor potential of plant extracts from Caatinga biome by enzyme activity and epidemiological components of Alternaria brown spot (Alternaria alternate f. spp. citri). These were prepared ethanolic, dichloromethanic, and aqueous extracts from 14 plants (Anadenanthera macrocarpa, Schinopsis brasiliensis, Maytenus rigida, Caesalpinia pyramidalis, C. ferrea, Peltophorum dubium, Capariscyn ophallophora, Ziziphus joazeiro, Mimosa hostilis, Momordica charantia, Erythrina velutina, Cleome hassleriana, Sideroxylum obtusifolium Spondias tuberosa) after dilution, (1mg/mL) they were sprayed on Citrus reticulate ‘Ponkan’seedlings and after 0, 24, 48, 72 and 96 h the leaves were collected for determination of polyphenol oxidase and peroxidase activity. For epidemiological disease components, leaves were collected 72 h after spraying, deposited on Petri dishes with moist paper, inoculated with a spore suspension of A. alternata f. spp. citri (2x105 conidia mL-1) and evaluated for 12 days initial and final severity, area below the progress curve of disease and protection. The extracts of A. macrocarpa and M. rigida potentiated the polyphenol oxidase and peroxidase activity which had great potential in the management of the disease, reducing the final severity and area under the disease progress curve, providing high levels of control. Key words: Citrus reticulata, alternaria brown spot, elicitor.  
Highlights
The national citrus production places Brazil was in a prominent status in world market, being the top producer with 19 million tons of oranges harvested in 2011/2012(Agrianual, 2012)
The objective of this study was to determine the elicitor potential of plant extracts from Caatinga biome by enzyme activity and epidemiological components of Alternaria brown spot (Alternaria alternate f. spp. citri). These were prepared ethanolic, dichloromethanic, and aqueous extracts from 14 plants (Anadenanthera macrocarpa, Schinopsis brasiliensis, Maytenus rigida, Caesalpinia pyramidalis, C. ferrea, Peltophorum dubium, Capariscyn ophallophora, Ziziphus joazeiro, Mimosa hostilis, Momordica charantia, Erythrina velutina, Cleome hassleriana, Sideroxylum obtusifolium Spondias tuberosa) after dilution, (1mg/mL) they were sprayed on Citrus reticulate ‘Ponkan’seedlings and after 0, 24, 48, 72 and 96 h the leaves were collected for determination of polyphenol oxidase and peroxidase activity
Despite having sweet orange [Citrus sinensis (L.) Osbeck] as the main spp produced, several spp of tangerines and some of their hybrids such as tangelos, willow leaf and tangors stands out in Brazilian orchards when the target is the National fruit market in natura (Azevedo et al, 2010). These orchards are constantly targets of Alternaria brown spot (ABS) infections, initiated by A. alternate f. spp. citri. which considered the main fungal disease of this specie (Peres et al, 2003), and caused serious damage in the Brazilian orchards resulting in the reduction of some susceptible varieties planted, mainly in the state of Sao Paulo, where many growers are eradicating their orchards due to the drastic increase on production costs, as a consequence of the high number of fungicide applications, discouraging planting in new areas (Azevedo et al, 2010)
Summary
The national citrus production places Brazil was in a prominent status in world market, being the top producer with 19 million tons of oranges harvested in 2011/2012(Agrianual, 2012). Despite having sweet orange [Citrus sinensis (L.) Osbeck] as the main spp produced, several spp of tangerines and some of their hybrids such as tangelos, willow leaf and tangors stands out in Brazilian orchards when the target is the National fruit market in natura (Azevedo et al, 2010). These orchards are constantly targets of Alternaria brown spot (ABS) infections, initiated by A. alternate f. In other to do that, the use of medicinal plants represent a rich source of natural compounds to be explored for the identification of new defense principles (Belting, 2009)
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