Iradiasi Sinar Gamma pada Genotipe Koro Pedang (Canavalia ensiformis L.) Koleksi IPB

Abstract

Koro pedang (Canavalia ensiformis L.) memiliki potensi sebagai alternatif kedelai karena memiliki kandungan protein tinggi (21,42-38,50%) dan mampu beradaptasi di lahan marginal. Namun, kendala utama pengembangannya terletak pada masa panen yang panjang dan produktivitas yang masih rendah. Pemuliaan menggunakan metode iradiasi sinar gamma diharapkan mampu meningkatkan keragaman koro pedang. Perlakuan iradiasi pada benih koro pedang dapat menyebabkan gangguan fisiologis pada generasi M1. Sementara itu, pada populasi M2 dapat diperoleh keragaman yang tinggi dan potensial untuk dilakukan seleksi. Karakter seleksi didasarkan pada potensi hasil yang tinggi, tinggi tanaman yang relatif rendah, dan umur panen yang genjah. Penelitian ini bertujuan untuk mendapatkan nilai lethal dose 50% (LD50) iradiasi sinar gamma pada koro pedang, mengetahui pengaruh iradiasi sinar gamma terhadap morfologi koro pedang generasi M1, serta memperoleh keragaman genetik pada generasi M2 koro pedang koleksi IPB. Penelitian dilaksanakan dalam dua tahap di Dramaga, Bogor, pada periode 2024 hingga 2026. Percobaan pertama menggunakan benih koro pedang genotipe IPBFA KP01(SB) koleksi IPB yang telah diinduksi sinar gamma dengan rentang dosis 0–1.000 Gy menggunakan rancangan acak lengkap (RAL) dengan tiga ulangan. Percobaan kedua mengevaluasi seluruh populasi M2 hasil selfing generasi sebelumnya menggunakan rancangan percobaan untuk populasi bersegregasi. Data percobaan pertama dianalisis menggunakan curve fit analysis dan sidik ragam (ANOVA) yang dilanjutkan dengan uji DMRT, sedangkan data pada percobaan kedua dianalisis menggunakan uji T dua populasi. Selain itu, pada populasi M2 dilakukan perhitungan indeks panen serempak (IPS), derajat indeterminasi, komponen ragam, heritabilitas, koefisien keragaman genetik, serta analisis korelasi. Iradiasi sinar gamma pada koro pedang menghasilkan LD50 sebesar 355,91 Gy dengan ambang toleransi maksimum 400 Gy. Pada generasi M1, dosis rendah (100–200 Gy) memicu efek hormesis yang merangsang tinggi tanaman dan panjang daun, sementara dosis tinggi (300–400 Gy) menyebabkan inhibisi vegetatif, keterlambatan generatif, serta penurunan hasil akibat kerusakan DNA dan sterilitas tanaman. Iradiasi sinar gamma meningkatkan keragaman genetik pada populasi M2 koro pedang dan umumnya memengaruhi nilai rataan karakter pertumbuhan, namun tidak berpengaruh nyata pada komponen hasil dan kegenjahan. Umur panen menunjukkan heritabilitas tinggi dengan KKG sedang. Seleksi indeks terboboti dengan intensitas 10% menghasilkan 50 genotipe mutan putatif potensial dan efektif meningkatkan bobot biji serta menurunkan tinggi tanaman, meskipun demikian perubahan pada umur panen belum signifikan.

Jack bean (Canavalia ensiformis L.) has the potential to serve as an alternative to soybeans because it has a high protein content (21.42–38.50%) and can adapt to marginal lands. However, the main constraints to its development lie in its long harvest period and still-low productivity. Breeding using gamma-ray irradiation is expected to increase the diversity of jack bean. Irradiation treatment of jack bean seeds can cause physiological disturbances in the M1 generation. Meanwhile, the M2 population exhibits high diversity and has potential for selection. Selection criteria are based on high yield potential, relatively short plant height, and an early harvest period. This study aims to determine the lethal dose 50% (LD50) of gamma-ray irradiation on jack bean, to investigate the effect of gamma-ray irradiation on the morphology of M1-generation jack bean, and to assess the genetic diversity of the M2 generation of jack bean from the IPB collection. The study was conducted in two phases in Dramaga, Bogor, during the period from 2024 to 2026. The first experiment used seeds from the jack bean IPBFA KP01(SB) genotype IPB collection that had been gamma-irradiated at doses ranging from 0 to 1,000 Gy using a completely randomized design with three replicates. The second experiment evaluated the entire M2 population resulting from self-pollination of the previous generation using an experimental design for segregating populations. Data from the first experiment were analyzed using curve fit analysis and analysis of variance, followed by the DMRT test, while data from the second experiment were analyzed using a two-population T test. In addition, for the M2 population, calculations were performed for the simultaneous harvest index, degree of indeterminacy, components of variance, heritability, coefficient of genetic variation, and correlation analysis. Gamma-ray irradiation of jack bean resulted in an LD50 of 355.91 Gy with a maximum tolerance threshold of 400 Gy. In the M1 generation, low doses (100–200 Gy) triggered a hormetic effect that stimulated plant height and leaf length, while high doses (300–400 Gy) caused vegetative inhibition, delayed generative development, and reduced yield due to DNA damage and plant sterility. Gamma-ray irradiation increased genetic diversity in the M2 population of jack bean and generally affected the mean values of growth traits, but had no significant effect on yield components and maturity. Maturity showed high heritability with moderate heritability coefficient. Weighted index selection at an intensity of 10% yielded 50 potential putative mutant genotypes and effectively increased seed weight and reduced plant height. However, changes in maturity were not yet significant.