Respons Seleksi Tunggal dan Multikarakter terhadap Hasil Biomassa dan Nira Galur-Galur Sorgum (Sorghum Bicolor [L.] Moench)

Abstract

Sorgum (Sorghum bicolor [L.] Moench) merupakan tanaman yang berpotensi dikembangkan sebagai bahan baku bioenergi karena mampu menghasilkan biomassa dan nira dalam jumlah besar serta memiliki kemampuan meratun. Kemampuan tersebut memungkinkan tanaman tumbuh kembali setelah panen tanpa penanaman ulang sehingga dapat meningkatkan efisiensi budidaya. Oleh karena itu, diperlukan galur sorgum yang memiliki produktivitas biomassa dan nira tinggi serta kemampuan meratun yang baik. Penelitian ini terdiri atas dua percobaan. Percobaan pertama mengevaluasi keragaan tanaman ratun F9 hasil persilangan Numbu × Samurai 2 dan melakukan seleksi galur menggunakan metode seleksi tunggal berdasarkan total bobot biomassa serta seleksi multikarakter berbasis Multi-Trait Genotype-Ideotype Distance Index (MGIDI). Percobaan kedua mengevaluasi sepuluh galur hasil seleksi untuk mengetahui keragaan agronomi, biomassa, dan nira serta respons seleksi yang dihasilkan. Hasil penelitian menunjukkan bahwa populasi ratun F9 hasil persilangan Numbu × Samurai 2 memiliki keragaman yang besar pada beberapa karakter agronomi, biomassa, dan nilai Brix. Tanaman ratun memiliki nilai yang lebih tinggi pada karakter diameter batang, jumlah daun, bobot batang kering, dan volume nira dibandingkan tanaman utama, tetapi lebih rendah pada sebagian besar karakter pertumbuhan dan nilai Brix. Meskipun demikian, biomassa yang dihasilkan tanaman ratun relatif setara dengan tanaman utama. Seleksi tunggal menghasilkan galur NS2-108, NS2-022, NS2-122, NS2-161, dan NS2-168, sedangkan seleksi multikarakter berbasis MGIDI menghasilkan galur NS2-010, NS2-109, NS2-121, NS2-013, dan NS2-101. Evaluasi galur terseleksi menunjukkan bahwa NS2-010 unggul pada karakter biomassa kering, sedangkan NS2-168 memiliki kombinasi biomassa dan volume nira yang baik. Analisis korelasi dan PCA menunjukkan bahwa karakter biomassa dan volume nira menjadi faktor utama yang membedakan genotipe yang diuji. Respons seleksi menunjukkan bahwa seleksi tunggal berdasarkan total bobot biomassa menghasilkan kemajuan seleksi yang lebih tinggi dibandingkan seleksi multikarakter berbasis MGIDI, terutama pada karakter biomassa dan volume nira. Hasil tersebut menunjukkan bahwa seleksi berdasarkan total bobot biomassa lebih efektif untuk meningkatkan potensi biomassa dan produksi nira pada populasi sorgum hasil persilangan Numbu × Samurai 2.

Sorghum (Sorghum bicolor [L.] Moench) is a crop with considerable potential as a bioenergy feedstock due to its high biomass and juice production as well as its ratooning ability. This characteristic enables the crop to regrow after harvest without replanting, thereby improving cultivation efficiency. Therefore, the development of sorghum lines with high biomass and juice productivity and good ratooning ability is essential for bioenergy breeding programs. This study consisted of two experiments. The first experiment evaluated the performance of the F9 ratoon population derived from the cross between Numbu and Samurai 2 and selected superior lines using single-trait selection based on total biomass weight and multi-trait selection based on the Multi-Trait Genotype-Ideotype Distance Index (MGIDI). The second experiment evaluated ten selected lines to assess their agronomic performance, biomass production, juice yield, and selection response. The results showed that the F9 ratoon population from the Numbu × Samurai 2 cross exhibited significant variation in several agronomic, biomass, and Brix-related traits. Compared with the main crop, ratoon plants showed higher values for stem diameter, number of leaves, dry stem weight, and juice volume, but lower values for most growth traits and Brix content. Nevertheless, biomass production of ratoon plants was relatively comparable to that of the main crop. Single-trait selection identified five superior lines, namely NS2-108, NS2-022, NS2-122, NS2-161, and NS2-168, whereas MGIDI-based multi-trait selection identified NS2-010, NS2-109, NS2-121, NS2-013, and NS2-101. Evaluation of the selected lines revealed that NS2-010 was superior for dry biomass production, while NS2-168 exhibited a favorable combination of biomass yield and juice volume. Correlation and principal component analyses indicated that biomass and juice-related traits were the major factors differentiating the evaluated genotypes. Selection response analysis showed that single-trait selection based on total biomass weight resulted in greater selection gain than MGIDI-based multi-trait selection, particularly for biomass and juice-related traits. These findings indicate that selection based on total biomass weight is a more effective approach for improving biomass potential and juice production in sorghum populations derived from the Numbu × Samurai 2 cross.