Repellent compositions and genetic approaches for controlling huanglongbing
The invention provides a method for controlling Huanglongbing (HLB) disease of citrus plants through expressing genes encoding synthases for sesquiterpenes such as β-caryophyllene, and α-copaene, and combinations thereof, in citrus plants. Methods of controlling HLB comprising applying at least one purified sesquiterpene, which repels Diaphorina citri and/or Tryoza erytrae psyllid insects, so as to control the HLB disease of citrus plants, are also disclosed.
1. A method for controlling Huanglongbing (HLB) in citrus plants comprising expressing at least one gene encoding a polypeptide, wherein the polypeptide has β-caryophyllene synthase or α-copaene synthase activity in citrus plants to produce an increased amount of β-caryophyllene, α-copaene, or combinations thereof which amount is sufficient to repel Diaphorina citri and/or Tryoza erytrae psyllid insects so as to control HLB.
2. The method of claim 1 , wherein the expression of the at least one gene is driven by a constitutive promoter and terminator regions.
3. The method of claim 1 , wherein the expression of the at least one gene is driven by a heterologous regulator region providing strong constitutive, tissue-specific or inducible expression.
4. The method of claim 3 , wherein the heterologous regulator region provides strong expression in the cytosol, chloroplasts or mitochondria.
5. The method of claim 1 , which further comprises expressing a gene encoding a polypeptide, wherein the polypeptide has farnesyl pyrophophase synthase activity in citrus plants, to enhance the accumulation of the increased amount of β-caryophyllene, α-copaene, or combinations thereof produced by the polypeptides having β-caryophyllene or α-copaene synthase activity.
6. A method for controlling Huanglongbing (HLB) disease of citrus plants comprising applying an amount of purified β-caryophyllene, α-copaene, or combinations thereof to citrus plants which amount is sufficient to repel Diaphorina citri and/or Tryoza erytrae psyllid insects, so as to control the HLB disease of citrus plants.
7. The method of claim 6 , wherein the purified β-caryophyllene, α-copaene, or combinations thereof is purified from an organism selected from the group consisting of plants, genetically modified plants, genetically modified bacteria, and genetically modified yeasts; wherein the genetically modified plants, the genetically modified bacteria, and the genetically modified yeasts are able to overproduce β-caryophyllene, α-copaene, or combinations thereof.
8. The method of claim 7 , wherein the purified β-caryophyllene, α-copaene, or combinations thereof is purified from a guava plant.
9. The method of claim 8 , wherein the purified β-caryophyllene, α-copaene, or combinations thereof is purified from leaf, fruit or stem extracts of the guava plant.
10. The method of claim 6 , wherein the purified β-caryophyllene, α-copaene, or combinations thereof is applied to the citrus plants through slow delivery systems.