Studi Genetik Senyawa Fungsional pada Okra (Abelmoschus esculentus L. Moench)

Abstract

Okra (Abelmoschus esculentus L. Moench) termasuk dalam famili Malvaceae, merupakan tanaman hortikultura yang memiliki nilai ekonomi dan farmakologis tinggi. Selain dikonsumsi sebagai sayuran, okra dikenal sebagai sumber senyawa bioaktif seperti flavonoid, fenolik, dan senyawa antioksidan lainnya yang mempunyai fungsi fisiologis dan bermanfaat bagi kesehatan. Oleh sebab itu selain produktivitas tinggi, program pemuliaan tanaman okra diarahkan untuk tujuan senyawa fungsional tinggi. Studi genetik senyawa fungsional pada okra perlu dipelajari sebagai landasan awal program pemuliaan tersebut. Penelitian terdiri atas lima percobaan, yaitu: Percobaan pertama adalah karakterisasi kandungan biokimia, karakter kuantitatif dan kualitatif genotipe okra yang bertujuan untuk memperoleh informasi keragaman pada genotipe okra yang akan dijadikan sebagai calon tetua dalam kegiatan pembentukan populasi untuk kegiatan penelitian selanjutnya. Percobaan kedua yaitu uji kandungan biokimia pada beberapa fase panen muda buah okra yang bertujuan untuk memperoleh fase panen muda yang tepat untuk kandungan biokimia tertinggi. Percobaan ketiga yaitu studi pewarisan sifat kandungan biokimia dan karakter kuantitatif pada okra yang bertujuan untuk memperoleh informasi studi pewarisan sifat. Percobaan keempat yaitu analisis daya gabung umum dan khusus kandungan biokimia dan karakter kuantitatif pada genotipe tetua dan hasil persilangan okra yang bertujuan untuk memperoleh informasi daya gabung kandungan biokimia dan karakter kuantitatif. Percobaan kelima yaitu keragaan calon varietas unggul hibrida okra yang bertujuan memperoleh informasi keragaan hibrida genotipe okra hasil persilangan. Percobaan pertama menghasilkan perbedaan baik pada kandungan biokimia, karakter kuantitatif dan kualitatif. Karakter buah merupakan karakter kuantitatif yang paling beragam. Berdasarkan hasil analisis cluster menunjukkan bahwa genotipe okra dikelompokkan menjadi 3 cluster baik untuk kandungan biokimia maupuk karakter kuantitatif dan kualitatif. Berdasarkan hasil analisis ini terpilih 8 genotipe yaitu Naila IPB dengan keunggulan tinggi kandungan flavonoid dan antioksidan DPPH, Green Velvet unggul pada keragaan vegetative, Clemson memiliki keunggulan pada panjang buah, F7 ClemsonxStripe-3-23-4 27-50 unggul pada karakter jumlah lokul. Genotipe okra merah unggul pada aktivitas antioksidan DPPH, C127 memiliki keunggulan pada umur panen yang genjah serta Red Hill Country unggul pada karakter inhibisi enzim alfaglukosidase, bobot dan diameter buah. Tidak ada keterkaitan antara komponen produksi dengan karakter biokimia kecuali umur berbunga dan umur panen. Percobaan kedua menunjukan bahwa genotipe dan fase panen menunjukkan interaksi sehingga respon delapan genotipe uji berbeda-beda pada masing-masing fase terhadap kandungan biokimia. Karakter kandungan total fenolik, flavonoid dan aktivitas antioksidan metode FRAP menyatakan fase panen 6 HSA paling tinggi menghasilkan kandungan biokimia tersebut. Sedangkan pada aktivitas antioksidan metode DPPH fase 6 dan 9 HSA menghasilkan kandungan yang hampir sama. Selanjutnya untuk karakter inhibisi enzim alfaglukosidase maksimal dihasilkan oleh okra dengan fase panen 9 HSA. Genotipe Okra Merah unggul pada karakter fenolik dan antioksidan FRAP. Genotipe Red Hill Country unggul pada karakter flavonoid, antioksidan DPPH dan FRAP. Naila IPB unggul pada karakter antioksidan DPPH, serta F7 ClemsonxStripe-3-23-4-27-50 unggul pada karakter fenolik, antioksidan DPPH, dan inhibisi enzim alfaglukosidase. Hasil penelitian ini memperkuat bukti bahwa pemilihan waktu panen dapat dioptimalkan untuk tujuan tertentu, baik untuk potensi antioksidan maupun antidiabetik. Percobaan ketiga menunjukkan bahwa semua karakter komponen hasil dan hasil tidak memiliki peranan interaksi gen kecuali jumlah buah dan umur panen. Karakter antioksidan metode DPPH dan FRAP serta inhibisi enzim alfaglukosidase tidak memiliki peranan interaksi gen. Terdapat pengaruh aksi gen aditif dan dominan pada jumlah cabang, diameter buah, jumlah buah dan umur panen. Pengaruh over dominansi dihasilkan oleh karakter jumlah buku, jumlah cabang, jumlah buah, umur panen, produktivitas, total fenolik, total flavonoid, aktivitas antioksidan DPPH dan FRAP. Semua karakter komponen hasil dan hasil dikendalikan oleh satu kelompok gen kecuali karakter panjang buah. Selain itu, semua karakter kandungan biokimia dikendalikan oleh dua kelompok gen. Nilai duga heritabilitas arti luas (h2bs) pada karakter komponen hasil, hasil dan kandungan biokimia menunjukkan kategori luas. Nilai duga heritabilitas arti sempit (h2ns) kategori tinggi dihasilkan oleh karakter bobot per buah, panjang buah dan diameter buah serta semua karakter kandungan biokimia. Percobaan keempat menunjukkan bahwa Tetua F7 memiliki daya gabung umum terbaik pada karakter jumlah buku, jumlah cabang, jumlah buah, dan inhibisi enzim alfaglukosidase. Tetua RHC memiliki daya gabung umum terbaik pada karakter bobot per buah, diameter buah, dan aktivitas antioksidan FRAP. GV merupakan tetua dengan nilai DGU terbaik pada panjang buah dan umur panen. Selanjutnya tetua OKM merupakan tetua dengan nilai daya gabung umum terbaik untuk total fenolik dan flavonoid serta aktivitas antioksidan DPPH. Hibrida F7 x Nai menghasilkan nilai daya gabung khusus tinggi pada karakter jumlah buah dan produktivitas, kombinasi persilangan OKM x Nai menghasilkan daya gabung khusus terbaik pada karakter panjang buah dan bobot buah. Hibrida GV x F7 menghasilkan nilai daya gabung khusus tinggi pada umur panen dan inhibisi enzim alfaglukosidase serta kombinasi RHC x OKM menghasilkan daya gabung khusus tinggi pada total fenolik dan antioksidan DPPH. Percobaan kelima menunjukkan bahwa Hibrida F7xNai memiliki keunggulan pada jumlah buku, jumlah cabang, jumlah buah, produktivitas dan inhibisi enzim alfaglukosidase tinggi. Sehingga hibrida F7xNai direkomendasikan sebagai hibrida dengan produktivitas dan memiliki efek antidiabetes tinggi, sedangkan hibrida RHCxOKM dan resiprokalnya direkomendasikan menjadi hibrida dengan kandungan polifenol dan kapasitas antioksidan paling baik dibandingkan hibrida lainnya. Keragaan warna buah dari hibrida menunjukkan warna ungu lebih dominan dibandingkan warna hijau. Karakter warna buah pada generasi F1 menjadikan warna sebagai penanda visual (visual marker) yang sangat berguna dalam proses seleksi awal pemuliaan.

Okra (Abelmoschus esculentus L. Moench) is a horticultural crop belonging to the Malvaceae family with high economic and pharmacological value. Okra is consumed as a vegetable and is known as a source of bioactive compounds, such as flavonoids and phenolic compounds, which have physiological functions and health benefits. Therefore, okra breeding programs focus on biofortification in addition to high productivity. Conducting genetic studies of functional compounds in okra is necessary to establish a foundation for such breeding programs. The study consisted of five experiments. The first experiment involved characterizing the biochemical content and quantitative and qualitative characteristics of okra genotypes. This experiment aimed to obtain information on the diversity of okra genotypes that would be used to form populations for further research activities. The second experiment tested the biochemical content at various stages of young okra fruit harvest to identify the optimal harvest stage with the highest biochemical content. The third experiment studied the inheritance of biochemical content and quantitative characteristics in okra to obtain information on how these traits were inherited. The fourth experiment analyzed the general and specific combining abilities of the biochemical content and quantitative characteristics of the parent genotypes and okra crossbreeds to obtain information about their combining abilities. The fifth experiment examined the performance of superior okra hybrid candidate varieties. The first experiment revealed differences in biochemical content and quantitative and qualitative characteristics. Fruit characteristics were the most diverse quantitative traits. Based on the results of the cluster analysis, the okra genotypes were grouped into three clusters according to their biochemical content, as well as their quantitative and qualitative characteristics. Based on the results of this analysis, eight genotypes were selected, namely Naila IPB with high flavonoid content and DPPH antioxidants; Green Velvet, which was superior in vegetative performance; Clemson, which had an advantage in fruit length; F7 ClemsonxStripe-3-23-4-27-50, which was superior in the number of locules. Red okra genotypes were superior in DPPH antioxidant activity; C127 had an advantage in early harvest age; and Red Hill Country was superior in alphaglucosidase enzyme inhibition, weight, and fruit diameter. No association was found between yield components and biochemical characters, except for flowering and harvesting time. The second experiment revealed that an interaction was observed between genotype and harvest phase, resulting in different responses to biochemical content at each phase for the eight genotypes. The 6 days after anthesis (DAA) harvest phase produced the highest levels of total phenolic content, flavonoid content, and antioxidant activity, as determined by the FRAP method. However, antioxidant activity measured by the DPPH method revealed similar levels in the 6 and 9 DAA phases. Additionally, okra with a 9 DAA harvest phase produced the maximum alpha-glucosidase enzyme inhibition. The Red Okra genotype demonstrated superior phenolic content and FRAP antioxidant activity. The Red Hill Country genotype excelled in flavonoid, DPPH, and FRAP antioxidant activity. Naila IPB was superior in DPPH antioxidant activity, and F7 ClemsonxStripe-3-23-4-27-50 was superior in phenolic content, DPPH antioxidant activity, and alpha-glucosidase enzyme inhibition. These results reinforced the idea that harvest timing could be optimized for specific purposes, such as antioxidant or antidiabetic potential. The third experiment demonstrated that the role of gene interaction was not evident in all yield and yield component characters, with the exception of fruit number and harvest age. The antioxidant traits measured by the DPPH and FRAP methods, as well as alpha-glucosidase enzyme inhibition, did not demonstrate a gene interaction effect. The findings of this study indicated additive and dominant gene action effects on several key parameters, including branch number, fruit diameter, fruit number, and harvest time. Overdominance effects were observed in the traits of number of nodes, number of branches, number of fruits, harvest time, productivity, total phenolics, total flavonoids, DPPH, and FRAP antioxidant activity. It was observed that all yield components and yield traits were controlled by a single group of genes, with the exception of fruit length. Furthermore, the expression of all biochemical content traits was governed by the activity of two distinct gene groups. The broad-sense heritability estimates (h²bs) for yield components, yield, and biochemical content traits indicated a broad category. The narrow-sense heritability estimates (h²ns) in the high category were produced by fruit weight, fruit length, fruit diameter, and all biochemical content traits.. The fourth experiment demonstrated that parents F7 exhibited the optimal overall combining ability for the traits of number of nodes, number of branches, number of fruits, and alpha-glucosidase enzyme inhibition. A comparison of the overall combining ability for the traits of weight per fruit, fruit diameter, and FRAP antioxidant activity revealed that parents RHC exhibited the most optimal performance. GV was identified as the parent with the optimal DGU value for fruit length and harvest age. In addition, OKM demonstrated the most optimal overall combining ability for total phenolics and flavonoids, as well as DPPH antioxidant activity. The F7 × Nai combination produced high specific combining ability values for the number of fruits and productivity. In contrast, the OKM × Nai cross combination produced the best specific combining ability for fruit length and fruit weight. The GV × F7 combination exhibited elevated specific combining ability values for harvest age and alpha-glucosidase inhibition, while the RHC × OKM combination demonstrated high specific combining ability for total phenolics and DPPH antioxidant activity. It was not possible to prove the relationship between genetic distance and genetic parameters, particularly heterosis, in this population. The fifth experiment demonstrated that the F7xNai hybrid exhibited superiority in terms of the number of nodes, number of branches, number of fruits, productivity, and high alpha-glucosidase enzyme inhibition. Consequently, the F7xNai hybrid was recommended as a hybrid with high productivity and strong antidiabetic effects, while the RHCxOKM hybrid was recommended as the hybrid with the highest polyphenol content and antioxidant capacity. The fruit color characteristics of the hybrids manifested as a more pronounced purple hue in comparison to the green coloration observed in their parental species. The fruit color characteristics exhibited in the F1 generation served as highly effective visual markers during the preliminary selection process of breeding.