Kajian Ketahanan Cabai terhadap Infestasi Kutudaun Aphis gossypii Berdasarkan Fenotipik, Metabolomik dan Molekuler

Abstract

Produksi cabai di Indonesia terkendala oleh tingginya serangan hama penyakit. Kutudaun A. gossypii menyerang cabai di dataran rendah dan menjadi vektor berbagai jenis virus tanaman. Pengendalian kutudaun secara kimiawi sudah tidak efektif dikarenakan ketahanannya terhadap beberapa bahan aktif insektisida. Penggunaan varietas tahan kutudaun pada tanaman cabai diharapkan mampu meningkatkan kualitas dari produksi cabai, menurunkan transmisi virus, serta mengurangi beban penggunaan insektisida bagi petani dan lingkungan. Adapun tujuan dari penelitian ini adalah untuk mengkaji kendali genetik ketahanan cabai terhadap infestasi kutudaun A. gossypii dari aspek fenotipik, metabolomik, serta molekuler. Tahapan penelitian terdiri atas: 1) Pengembangan metode skrining cabai terhadap infestasi hama A. gossypii; 2) Evaluasi ketahanan cabai terhadap infestasi kutudaun pada populasi bersegregasi hasil persilangan genotipe tahan dan rentan; 3) Senyawa kimia (metabolit sekunder) cabai yang terkait dengan ketahanan terhadap infestasi kutudaun melalui teknik metabolomik pada populasi bersegregasi; serta 4) Pengembangkan marka molekuler yang dapat digunakan sebagai marker assisted selection (MAS) dalam proses pemuliaan tanaman cabai ketahananterhadap infestasi kutudaun A. gossypii. Hasil penelitian menunjukkan bahwa: 1) Semua metode skrining yang digunakan efektif dan metode uji clip cage terpilih sebagai metode pengujian yang handal dan praktis dalam uji ketahanan cabai terhadap infestasi A. gossypii; 2) Genotipe cabai IPB C367 dan IPB C20 memiliki ketahanan antibiosis terhadap kutudaun A. gossypii; 3) Ketahanan cabai dikendalikan secara resesif oleh banyak gen dengan aksi gen pengendali ketahanan hama kutudaun adalah aditif-epistasis duplikat; 4) senyawa 2,4-difluorobenzoic (fluorobenzoic acid) dan senyawa 2,5- octadecadiynoic acid (fatty acid) menjadi senyawa antibiosis tanaman cabai dalam menekan populasi koloni kutudaun A. gossypii.; dan 5) Terdapat tiga perubahan basa non-synonymous yang berpotensi untuk membedakan genotipe tahan dan genotipe rentan secara molekuler terhadap infestasi kutudaun A. gossypii. Belum adanya asosiasi yang kuat antara marka molekuler dengan fenotipe tanaman dalam mengidentifikasi gen ketahanan cabai terhadap kutudaun disebabkan oleh sifat ketahanan ini memiliki kompleksitas yang tinggi karena dikendalikan oleh banyak gen (poligen) secara resesif serta terdapat peran dari aksi gen epistasis duplikat.

Chili pepper production in Indonesia is constrained by high pest attacks. The cotton aphid (CA), Aphis gossypii, attachesto chilies in the lowland and is a vector for various types of plant viruses. Chemical control of aphids is no longer effective due to their resistance to several insecticidal active ingredients. The use of aphid resistant varieties on chili peppers is expected to improve the quality of chili pepper production, reduce virus transmission, and reduce the cost of using insecticides for farmers and the environment. The purpose of this study was to examine the genetic control of chili pepper resistance to CA infestation from phenotypic, metabolomic, and molecular aspects. The stages of the research consisted of: 1) the development of a chili pepper screening method for CA infestation; 2) the evaluation of chili pepper resistance to aphids in segregated populations resulting from crosses of resistant with susceptible chili genotypes; 3) the identification of chemical compounds (secondary metabolites) of chili that are related to resistance to CA through metabolomic techniques in segregated populations; and 4) the development of moleculer markers that can be used as market assisted selection (MAS) in the chili pepper breeding program for resistance to CA. The results showed that: 1) All of the screening methods used were effective, and the clip cage test method was chosen as a practical and reliable method for screening resistance to CA infestation; 2) The chili pepper genotypes IPB C367 and IPB C20 had antibiosis resistance against CA; 3) Chili pepper resistance was controlled recessively by polygenes with additive-epistatic duplicate gene action; 40 2,4-diflorobenzoic (fluorobenzoic acid) and 2,5-octadecadiynoic acid (fatty acid) were antibiosis compounds in chili pepper that suppressed the aphid colonies, and 5) there were three non-synonymous base changes that had the potential to differentiate resistant genotypes and susceptible genotypes molecularly to aphid infestation. There was no strong association between molecular markers and plant phenotypes in identifying chili pepper resistance genes to A. gossypii. This resistance trait had high complexity because it was controlled by many genes (polygenes) in a recessive manner and the gene action that controls was duplicated epistasis.