Resistance of Transgenic Betula platyphylla to the Defoliator Lymantria dispar Study on Transformation of Insecticidal Bacillus thuringiensis cryIAc Gene in Pepper Maize Transformation of cry1Ac3 Gene and Insect Resistance of Their Transgenic Plants Obtaining a Transgenic Upland Cotton Harboring Two Insecticidal Genes