Revisão bibliográfica sobre proteínas inseticidas e indução de brotos em capim-elefante [Cenchrus purpureus syn Pennisetum purpureum (Schumach) Morrone], visando resistência à cigarrinha-das-pastagens

Abstract

Elephant grass is a forage used to feed the cattle. It has multiple cultivars and one of them that calls attention is the BRS Capiaçu, which has high livestock production, hydrical stress, and drought resistance however it does not show resistance to pest insects. Among the insects that ravage elephant grass plantations, it is possible to highlight the spittlebug, an amount of insects from Hemiptera order. Those animals feed on sap and release salivary secretions which directly impact livestock production once it decreases the chlorophyll production. Hence it is important to develop an elephant grass that shows resistance to spittlebug. Therefore, this project aims to research insecticidal proteins and to develop an in vitro elephant grass shoot induction protocol to genetic transformation. Thereunto, the grass samples were brought to have their lateral meristems withdrawn and induced. The samples were cut and cleaned using water and detergent. Then they were bathed in alcohol 70% for two minutes and transferred to sodium hypochlorite 2% for 15 minutes. Finally they were washed in water with PPM 0,1% so the meristems could be withdrawn. Thus we developed Murashige-Skoog growth mediums with different concentrations of BAP, TDZ, and 2,4-D to analyse the meristem development. The results appointed the best growth medium as the one with 0,1 mg.L-1 of TDZ and 0,5 mg.L-1 of BAP (MIB2). For the selection curve we tested different concentrations of kanamycin until 150 mg.L although the best concentration was 50 mg.L-1. Thereby in order to test the transformation we co-cultured the meristems with Agrobacterium, which had the GFP gene for fluorescence. The bacteria grew for two days in Luria Bertani growth medium and the sample had 0.828 of absorbance. The meristems were cut in the middle and rested in contact with the Agrobacterium for 40 minutes. Posteriorly, they were washed in water with 0.1% PPM and then inoculated in MIB2 with no Kanamycin. Three days later those meristems were transferred to MIB2 with 50 mg.L-1 of Kanamycin and the Petri dishes were swapped whenever there were signs of contamination. One week later the samples were observed at the inverted microscope and the signs of transformation were seen in 14 out of 45 induced meristems.