Peningkatan Hasil Kedelai di Tanah Salin dengan Penggunaan Genotipa Tahan, Asam Askorbat, dan Fungi Mikoriza Arbuskular

Abstract

Upaya peningkatan produksi kedelai dalam negeri diarahkan melalui strategi perluasan areal tanam dan penerapan teknologi spesifik lokasi. Lahan salin merupakan lahan marjinal yang belum dimanfaatkan secara optimal untuk budidaya tanaman, termasuk kedelai. Produksi kedelai di lahan salin masih sangat rendah disebabkan cekaman osmotik, cekaman oksidatif dan keracunan ion, dan kekurangan hara. Tujuan penelitian ini adalah meningkatkan produksi kedelai di lahan salin melalui penggunaan genotipa kedelai tahan cekaman salintas, aplikasi asam askorbat dan inokulasi fungi mikoriza arbuskular indigenous. Penelitian terdiri atas tiga tahap. Penelitian tahap pertama yaitu seleksi massa sampai dengan generasi keempat (F4) untuk mendapatkan genotipa tahan salinitas dan uji molekular dilaksanakan di lahan salin Desa Paluh Merbau Kecamatan Percut Sei Tuan Kabupaten Deli Serdang dengan DHL 5 – 6 mmhos/cm dan laboratorium Molecular Biotechnology Center of Molecular Biosciences (COMB) University of the Ryukyus, Okinawa, Jepang, Penelitian kedua yaitu eksplorasi fungi mikoriza arbuskular indigenous melalui tahap ekstraksi dan indentifikasi fungi mikoriza arbuskular, pemerangkapan dan kultur spora berdasarkan genus di laksanakan di Laboratorium Biologi Tanah dan rumah kassa Fakultas Pertanian USU. Penelitian tahap ketiga yaitu pengujian efektivitas fungi mikoriza arbuskular dan aplikasi asam askorbat pada genotipa kedelai tahan salinitas dilaksanakan di lahan salin Desa Paluh Merbau Kecamatan Percut Sei Tuan Kabupaten Deli Serdang dengan 3 seri percobaan dengan perbedaan tingkat salinitas yaitu lokasi 1 dengan DHL 4 – 5 mmhos/cm, lokasi 2 dengan DHL 5 – 6 mmhos/cm dan lokasi 3 dengan DHL 6 – 7 mmhos/cm. Rancangan yang digunakan yaitu Rancangan Petak Petak Terpisah dengan 3 petak dan 3 ulangan. Petak utama yaitu genotipa kedelai (kedelai varietas grobogan non-seleksi dan kedelai hasil seleksi tahan salinitas generasi keempat - F4). Anak petak yaitu aplikasi asam askorbat (tanpa aplikasi asam askorbat dan aplikasi asam askorbat dengan dosis 500 ppm). Anak-anak petak yaitu isolat fungi mikoriza arbuskular indigenous (tanpa pemberian isolat mikoriza, Glomus sp.1, Glomus sp.2, Glomus sp.3, Glomus sp.4, Glomus sp.5, dan isolat campuran kelima jenis mikoriza). Hasil seleksi menunjukkan kemajuan seleksi, produksi tanaman dan nilai heritabilitas belum stabil disebabkan pengaruh salinitas tanah tanah yang selalu berubah pada setiap tahap seleksi. Uji molekuler gen toleran salinitas pada generasi ketiga menunjukkan ekspresi gen Dehydration Responsive Element Binding Protein 5 (DREB5), Glycine and Proline Rich Proteins 3 (GPRP3), ∆1-Pyrroline-5-Carboxylate Synthetase (P5CS), bZIP Transcription Factor (ZIP), EREBP/AP2 Transcription Factor (ERF) dan Gm Putative Na+/H+ Antiporter (NHX1) lebih tinggi pada kedelai terseleksi tahan salinitas F3 yang mendapat cekaman salinitas dibandingkan dengan perlakuan tanpa cekaman salinitas, sedangkan tingkat ekspresi gen Gm Chloride Channel 1(GmCLC1) dan Purple Acid Phosphatases 3 (PAP3) lebih rendah dibandingkan perlakuan tanpa cekaman salinitas. Hasil eksplorasi dan identifikasi fungi mikoriza arbuskular indigenous dari lahan salin menunjukkan ada 5 genus dengan karakteristik berbeda yaitu Glomus sp.1, Glomus sp.2, Glomus sp.3, Glomus sp.4, Glomus sp.5. 2. Peningkatan salinitas tanah berpengaruh negatif keberadaan FMA, di mana jumlah spora dan kemampuan FMA dalam menginfeksi tanaman inang menurun dengan semakin meningkatnya salinitas tanah. Hasil penelitian menunjukkan kedelai terseleksi tahan salinitas mampu tumbuh dan berproduksi lebih baik dibandingkan kedelai varietas Grobogan dengan adanya perubahan karakter morfologi, fisiologi dan biokimia. Aplikasi asam askorbat mampu membantu kedelai untuk tumbuh dan berproduksi lebih baik di tanah salin dengan berbagai tingkat salinitas dengan adanya perubahan karakter morfologi, fisiologi dan biokimia terkait dengan perannya sebagai antioksidan untuk mengatasi stres oksidatif. Inokulasi FMA dapat meningkatkan pertumbuhan dan produksi kedelai di tanah salin dengan berbagai tingkat salinitas dengan adanya perubahan karakter morfologi, fisiologi dan biokimia yang disebabkan peran FMA untuk meningkatkan serapan air dan hara. Berdasarkan hasil penelitian dapat disimpulkan bahwa peningkatan salinitas tanah menyebabkan pertumbuhan dan produksi kedelai semakin tertekan. Penggunaan kedelai terseleksi tahan salinitas, aplikasi asam askorbat dan inokulasi campuran isolat FMA menghasilkan produksi kedelai tertinggi pada berbagai tingkat salinitas tanah.

Efforts to increase domestic soybean production are directed through strategies of expansion of cultivation area under the application of specific technologies. Saline soil in marginal land that is not optimally used for the cultivation of crops, including soybeans. Soybean production in saline soil is still very low due to osmotic stress, oxidative stress and ion toxicity, and nutrient deficiencies. The purpose of this study is to increase soybean production in saline soil through the utilization of stress salinity-resistance soybean genotypes, ascorbic acid application and indigenous arbuscular mycorrhiza fungi inoculation. The study consisted of three phases. The first phase of research was mass selection until the fourth generation (F4) to obtain salinity resistance genotypes and molecular tests carried out in the village of saline soil Paluh Merbau, Percut Sei Tuan, Regency of Deli Serdang with DHL 5-6 mmhos/cm and Laboratory Molecular Biotechnology Center of Molecular Biosciences (COMB)’s University of The Ryukyus, Okinawa, Japan. The second phase was the exploration of indigenous arbuscular mycorrhizal fungi through the extraction stages and identification of arbuscular mycorrhiza fungi, trapping and spores culture done in Soil Biology Laboratory of Faculty of Agriculture. The third phase of research was tests of the effectiveness of arbuscular mycorrhiza fungi and application of ascorbic acid in soybean genotypes resistant salinity saline soil, held in Paluh Merbau Village, Percut Sei Tuan District of Deli Serdang with three series of tests and different levels of salinity, location one with DHL 4-5 mmhos / cm, location 2 with DHL 5-6 mmhos / cm and 3 locations with DHL 6-7 mmhos / cm. The design used was separated plots design with 3 plots and 3 replications. The main plot was soybean genotype (non selection Grobogan soybean variety and the fourth generation of soybeans salinity resistant selection results (F4). The subplots were ascorbic acid application (without application of ascorbic acid and ascorbic acid application at 500 ppm dose). Sub-sub plot was indigenous arbuscular mycorrhiza fungi isolate (without mycorrhizal isolates, Glomus sp.1, Glomus sp.2, Glomus sp.3, Glomus sp.4, Glomus sp.5, and the mixture of five types of mycorrhizal isolates). Selection results showed the progress of selection, crop production and value of heritability were not stable due to the influence of soil salinity changes at every stage of the selection. Molecular test on in the third generation of salinity tolerant gene showed that the mRNA expressions of Dehydration Responsive Element Binding Protein 5 (DREB5), Glycine and Proline Rich Proteins 3 (GPRP3), ∆1-Pyrroline-5-carboxylate synthetase (P5CS), bzip Transcription Factor (ZIP), EREBP / AP2 Transcription Factor (ERF) and Gm putative Na+ /H+ antiporter (NHX1) were higher in F3 selected salinity resistance soybean of salt stressed compared to without salinity stress, whereas the mRNA expression Gm Chloride Channel 1 (GmCLC1 ) and Purple acid phosphatases 3 (PAP3) gene were lower than those of control. Exploration and the identification of indigenous arbuscular mycorrhizal fungi of saline soil shows that there are five distinct characteristic types, namely Glomus sp.1, Glomus sp.2, Glomus sp.3, Glomus sp.4, Glomus sp.5. The increase of soil salinity negatively affected the existence of the FMA, where the number of spores and the ability of AMF to infect the host plant decreased with increasing of soil salinity. The research showed that selected salinity resistance of soybean grown and produced better than Grobogan soybean varieties through the change of morphological, physiological and biochemical characters. Application of ascorbic acid increase the growth and production of soybean in saline soil with different levels of salinity through the change of morphological, physiological and biochemical characters associated to its role as an antioxidant to cope the oxidative stress. AMF inoculation increase growth and soybean production in saline soils with different levels of salinity through the change of morphological, physiological and biochemical characters caused by AMF role to increase the uptake of water and nutrients. This research concluded that the increase in soil salinity led to attenvation of the growth and production of soybean. The application of selected resistant salinity soybean, ascorbic acid and inoculation of mixture of AMF isolates produced the highest soybean production at various levels of soil salinity.