PERAKITAN KEDELAI UNGGUL BARU BERDAYA HASIL TINGGI, BERUMUR GENJAH, DAN TAHAN HAMA UTAMA KEDELAI (ULAT GRAYAK) IMPROVEMENT OF SOYBEAN CULTIVARS FOR HIGH YIELD, EARLY MATURITY, AND RESISTANCE TO MAIN PEST (ARMYWORM) Mohammad Setyo Poerwoko 1), Titik Sundari 2), Dyah Nuning Erawati 3) 1) Universitas Jember 2) Badan Penelitian dan Pengembangan Pertanian 3) Politeknik Negeri Jember ABSTRAK Ulat grayak (Spodoptera litura) adalah salah satu hama pemakan daun yang menyebabkan kerusakan berat pada tanaman kedelai. Hama ini bersifat polifag, dengan kisaran inang yang luas, tidak hanya tanaman pangan, tetapi juga tanaman perkebunan, sayuran, dan buahbuahan. Hama tersebut umumnya dikendalikan dengan menggunakan insektisida kimia sehingga dapat memicu terbentuknya strain-strain baru yang tahan terhadap pestisida. Penelitian bertujuan untuk merakit varietas kedelai berdaya hasil tinggi, berumur genjah, dan tahan hama ulat grayak. Tetua persilangan adalah dua adapted cultivar NSP (GHJ-7) dan GHJ-6 (UNEJ-2) dengan tiga tetua donor tahan ulat grayak, yaitu W/80-2-4-20, IAC- 80, dan IAC-100. Persilangan menghasilkan 12 hibrida
dan lima tetua hasil selfing, yaitu (1) 1x3 = NSP x W/80-2-4-20, (2) 1x4 = NSP x IAC-80, (3) 1x5 = NSP x IAC- 100, (4) 2x3 = GHJ-6 x W/80-2-4-20, (5) 2x4 = GHJ-6 x IAC-80, (6) 2x5 = GHJ-6 x IAC-100, (7) 3x1 = W/80-2-4-20 xnsp, (8)3x2 = W/8-2-4-20 x GHJ-6, (9) 4x1 = IAC- 80 x NSP, (10) 4x2 = IAC-80 x GHJ-6, (11) 5x1 = IAC- 100 x NSP, dan(12) 5x2 = IAC-100 x GHJ-6. Selanjutnya 17 genotipe tersebut ditanam di lapangan menggunakan rancangan acak kelompok dan diulang tiga kali. Pemaparan tanaman terhadap ulat grayak instar tiga diberikan pada dua percobaan lapangan, yaitu tanpa pilihan dan dengan pilihan. Berdasarkan tiga parameter yang diamati, yaitu ketahanan, jumlah polong sehat per tanaman, dan berat 100 biji, peringkat pertama genotipe terseleksi adalah 1x5 (GHJ-6/UNEJ-2 x IAC-100) dengan kategori ketahanan sangat tahan (ST), jumlah polong sehat per tanaman 146,33, dan berat 100 biji 10,57 g. Urutan kedua ialah 1x4 = GHJ-6/UNEJ-2 x IAC-80 dengan kategori ketahanan agak tahan, jumlah polong sehat per tanaman rata-rata 57,17, dan berat 100 biji 11,40 g. Urutan ketiga ialah 1x3 = GHJ-6/UNEJ-2 x W/80-2-4-20, dengan kategori ketahanan agak tahan, jumlah polong sehat rata-rata 89,50, dan berat biji per tanaman 9,40 g. Biji-biji F2 dari tiga genotipe terpilih selanjutnya akan disilang-balik dengan adapted cultivar, GHJ-6 (UNEJ-2) untuk meningkatkan daya hasil dan memperpendek umur masak polong. Kata kunci: Kedelai, perakitan varietas, hasil, umur genjah, tahan hama, ulat grayak.
ABSTRACT Armyworm (Spodoptera litura) is one of leaf-eating pests that cause serious damage on soybean. This pest is polifag, which has a broad-range of hosts, not only on food crops, but also estate crops, vegetables and fruits. This pest is commonly controlled by using pesticide which potentially form new strains that are more resistant to pesticide. The study aimed to improve soybean cultivars for high yield, early maturity and resistant to armyworm. Parents for the crosses were two cultivars of adapted NSP (GHJ-7) and GHJ-6 (UNEJ-2) with three armyworm resistant donors based on the results of previous research, i.e. W/80-2-4-20, IAC -80 and IAC-100. Crosses resulted in 12 hybrids and five selfing of parents, namely (1) 1x3 = NSP x W/80-2-4-20, (2) 1x4 = NSP x IAC - 80, (3) 1x5 = NSP x IAC-100, (4) 2x3 = 6 x W/80-2-4-20 GHJ, (5) 2x4 = 6 x GHJ-IAC-80, (6) 2x5 = 6 x GHJ-IAC- 100, (7) 3x1 = W/80-2-4-20 x NSP, (8) 3x2 = W/8-2-4-20 x GHJ-6, (9) 4x1 = IAC-80 x NSP, (10) 4x2 = IAC -80 x GHJ-6, (11) 5x1 = IAC -100 x NSP, and (12) 5x2 = IAC - 100 x GHJ-6. The 17 genotypes were grown in the field using a randomized block design (RBD) repeated three times. Exposes to instar 3 of armyworm larvae were given toward two field trials, i.e. with and without choices. Based on three parameters, namely plant resistance, average number of healthy pods per plant, and weight of 100 seeds, the ranks of the selected genotypes were (1) = 1x5 (GHJ-6/UNEJ-2 x IAC-100) categorized as very resistant, average number of healthy pods per plant was 146.33, and weight of 100 seeds was 10.57g; (2) 1x4 =
GHJ-6/UNEJ-2 x IAC-80 categorized as moderately resistant and had the average number of healthy pods per plant 57.17 and weight of 100 seeds 11.40 g; and (3) 1 x 3 = GHJ-6/UNEJ-2 x W/80-2-4-20, categorized as moderately resistant with the average number of healthy pods 89.50 and weight of 100 seeds 9.40 g. F2 seeds of the three selected genotypes would be subsequently back-crossed with adapted cultivars, GHJ-6 (UNEJ-2) to recover the good properties of adapted cultivars, to improve yields and shorten pods maturity. Keywords: Soybeans, varietal improvement, yields, early maturity, pest resistance. Gambar 1. Hasil persilangan 3 x 5
Gambar 2. Kedelai varietas Sumbersari