Prospecção fitoquímica e efeito de extratos da folha da algarobeira (Prosopis juliflora (Sw)) no controle do Colletotrichum gloeosporioides (Penz.) Penz & Sacc do cajueiro (Anacardium occidentale L.)

Abstract

The cashew culture (Anacardium Occidentale L.) is an important agribusiness responsible for the Brazilian economic movement. However, the decline of the cashew nut almond crop in recent years has made Brazil the 14th place in the world production ranking in 2016. The weakening of cashew cultivation is attributed to the spread of diseases and pests, lack of management, anthracnose is the most worrying disease because it attacks the host at any stage of its development and is enhanced by the action of environmental factors. Continuous use of synthetic chemicals for the control and management results in selectivity and resistance to pathogens and thus alternative methods of natural source are an effective solution for the treatment of such plant diseases, while minimizing the environmental impact and reducing the risk to human health. In this way, the present work aims to evaluate the antifungal potential of leaf extracts of Prosopis juliflora (Sw) in the control of Colletotrichum gloeosporioides, phytopathogenic agent of anthracnose. P. juliflora leaves were collected in the city of Juru-PB, and after drying and crushing of the plant material, the phytochemical prospection of the aqueous and ethanolic extracts was carried out, proving the presence of phenolic, tannic, flavonoid and alkaloid compounds. Then it was performed to obtain the fraction of total alkaloids by acidbase extraction from the plant under study. After harvesting leaves, fruits and branches with symptomatic features typical of anthracnose, in Fátima, District of Flores-PE, the pathogen was identified by macroscopic and microscopic method after being cultured in petri dishes discharged with BDA (Potato-Dextrose-Agar ) for seven days of cultivation at room temperature and photoperiod of 12 hours. Aqueous, ethanolic and alkaloidal extracts were prepared and submitted to antifungal evaluation. Pre-tests were carried out in wells and disks with better results for the ethanolic extract and later with reproduction of the diffusion method in wells with alkaloidal extract. In the methodology of mycelial growth by plate dilution the dose of 13.6 mg.mL-1 of the FAT extract and 100% of the ethanolic extract resulted in a PIC of 100% and with the dose of 6.8 mg.mL-1 of the extract of FAT and the ethanolic extract diluted to 50% resulted in a PIC of 75% and 81%, respectively. Thus, all leaf extracts of P. juliflora tested in this work, proof of presence of alkaloids having potential antifungal about C. gloeospoioides.