Genetika ketahanan dan pemuliaan kedelai (Glycine max L.) terhadap virus kerdil (Soybean stunt virus)

ASADI, Promotor Prof.Dr.Ir. Soemartono

2005 | Disertasi | S3 Ilmu Pertanian

Penelitian genetika ketahanan terhadap virus kerdil (Soybean stunt virus) dan pemuliaan kedelai (Glycine max L.) terdiri atas tiga sub penelitian. Penelitian pertama bertujuan untuk memperoleh genotipe kedelai tahan SSV. Penelitian ke dua untuk mengetahui genetika pewarisan sifat tahan SSV dari tiga genotipe tahan yang meliputi pengaruh tetua betina, jumlah dan jenis gen tahan yang berperan, model pewarisan sifat tahan. serta heritabilitasnya. Penelitian ke tiga bertujuan untuk : (1) memperoleh ga lurgalur harapan tahan SSV yang berdaya hasil tinggi melalui metode seleksi bulk yang dimodifikasi dan metode pedigri, (2) mengetahui efektifivas kedua metode seleksi, dan mengetahui pengaruh langsung atau tidak langsung karakter-karakter agronomi dan ketahanan terhadap SSV pada galur-galur F7 kedelai. Pada penelitian pertama dievaluasi 900 asesi dan genotipe pilihan diuji kembali hingga diperoleh genotipe tahan. Pada penelitian ke-dua, tiga tetua tahan disilangkan dengan dua tetua rentan. Model pewarisan dan banyaknya gen pengendali sifat tahan SSV serta nilai heritabilitas dalam arti luas dianalisis berdasarkan hasil skoring dari setiap tanaman pada populasi P1, P2, segregan F1 dan F2. Penelitian ke-tiga terdiri dari 3 kegiatan yaitu (a) hibridisasi da n produksi biji F2, (b) pembentukan galur-galur F7 tahan SSV dan hasil tinggi melalui metode seleksi bulk yang dimodifikasi dan metode pedigri, (c) efektifivas metode bulk dan metode pedigri untuk seleksi ketahanan terhadap SSV pada galur F7. Pada kegiatan (c), 30 galur F7 bulk, 30 galur pedigri, dan 5 tetua asalnya ditanam di lapangan dengan menggunakan rancangan acak kelompok dan 3 ulangan. Efektifivas metode seleksi diuji dengan uji t. Pengaruh langsung dan tidak langsung antar hasil dengan karakter agronomi dan intensitas penyakit SSV diketahui berdasarkan analisis lintasan. Evaluasi plasma nutfah kedelai memperoleh tiga genotipe tahan SSV, yaitu Mlg2521, B3570 dan Taichung. Pengaruh tetua betina terhadap ketahanan SSV tidak ditemukan. Ketahanan genotipe B3570 bersifat dominan dan dikendalikan oleh gen tunggal (AA). Ketahanan genotpe Mlg2521 bersifat dominan, dikendalikan oleh dua gen (BBCC) yang terletak pada lokus berbeda dan berinteraksi epistatik duplikat resesif. Ketahanan varietas Taichung bersifat resesif, dikendalikan oleh dua gen (ddee) yang terletak pada lokus berbeda dan berinteraksi epistatik duplikat resesif. Faktor genetik lebih berperan dalam mewariskan sifat ketahanan SSV. Seleksi dengan metode bulk yang dimodifikasi lebih efektif diband ing seleksi dengan metode pedigri, Seleksi galur F7 menghasilkan dua galur F8 yang terbaik, yaitu B(P/M-b-7-7) dan B(P/M-b-7-10).

Research of genetic resistance and breeding of soybean to Soybean stunt virus (SSV) was done in three experiments. The first experiment was aimed to find resistance of soybean germplasm to SSV. The second experiment was aimed to understand the maternal effect, number and model of gene governing resistance to SSV, and heritability of the resistance. The third experiment was done: (a) to develop soybean lines that were high yielding and resistant to SSV, (b) to compare effectiveness of modified bulk technique and pedigree technique for selection of F7 soybean lines that were resistant to SSV, and (3) to identify the direct and indirect effect of agronomic characters and SSV resistance on yields of F7 soybean lines. In the first experiment nine hundred genotypes were evaluated for their resistance to SSV, the selected genotypes were reevaluated for their resistance. In the second experiment, three resistant genotypes were crossed with two susceptible ones. The genetic inheritance of genes governing the resistance to SSV were determined based on scores of resistance of the P1, P2, F1 and F2 plants. The third experiment consisted of three trials, i.e., (a) hybridization and F2 seed production, (b) development of F7 lines, which were resistant to SSV and high yielding, using the bulk and the pedigree selection techniques, and (c) study on effectiveness of the bulk and the pedigree selection techniques on F7 soybean lines. In the step (c), two groups of F7 soybean lines consisted of 30 F7 bulk lines and 30 F7 pedigree lines along with their five parental genotypes were grown in the field. These trials were set up in a randomized block design with three replications. Effectiveness of the two selection techniques was compared using the t-test. Direct and indirect effect of the selection techniques on agronomic characters and seed yields were identified using the path analysis. Threesoybean genotypes were found resistant to SSV, i.e., Mlg 2521, B3570, and Taichung. No maternal effect was found on the inheritance of resistance to SSV. A dominant gene (AA) controlled resistance to SSV in B3570. The resistance to SSV in Mlg2521 was controlled by two dominant genes (BBDD) located at different loci with a duplicate recessive epistatic interaction. The resistance in Taichung, however, was controlled by two recessive genes (ddee) located at difference loci with a duplicate recessive epistatic interaction. Genetic factors have significant roles in governing the resistance to SSV. Study on effectiveness of the selection methods showed that the modified bulk method was better then the pedigree method. The path analysis indicated that the number of pods per plant directly affected the seed yields. B(P/M-b-7-7) and B(P/M-b-7-10) were the best lines obtained from the selection based on their resistance to SSV as well as on their agronomic characters.

Kata Kunci : Virus Kerdil,Tanaman Kedelai,Genetika Ketahanan dan Pemuliaan