Productivity of swampy land rice varieties in Indonesia remains low due to abiotic and biotic stresses. Iron toxicity, submergence and long-term flooding are common problems that affect plant growth, sometimes leading to total crop loss. Meanwhile, rice blast, rice tungro virus (RTV), and bacterial leaf blight (BLB) can also lead to severe yield loss. These stresses could be overcome by an integrative approach of cultural practices and planting multi-stress tolerant rice. Here we describe the development of new high-yielding varieties that are adapted to the swampy land environments in Indonesia with multi-stress tolerance to diverse abiotic and biotic stresses. Multi-environmental trials were performed in nine locations to screen for several abiotic and biotic stresses in the field and greenhouse in 2012 and 2013. This study identified promising rice lines that had high grain yield as well as tolerance to iron toxicity and submergence, resistance to BLB and RTV, and good grain quality. The best line was B11377F-MR-34-2, derived from a double cross among Cinglonik, IRBB7, Mamberamo and IR64. It was confirmed that this advanced breeding line carries the submergence tolerance gene, SUB1, through expression analysis of the SUB1A gene. Another promising line was B11586F-MR-11-2-2, having iron toxicity tolerance, resistance to RTV, and high milling recovery. Moreover, these lines have passed the Indonesian national variety release committee and have been named as Inpara8 and Inpara9, and are targeted for dissemination and adoption in the swampy areas.
Drought is an important constraint for rice production in rainfed lowland and shallow freshwater swamp. The area often experiences drought stress at the generative stage of the plants. This study aimed at selecting adaptive lines to terminal drought and formulating a multiple regression model to estimate the productivity under drought stress conditions at the generative stage. The experiment was conducted in a greenhouse of the Indonesian Center for Rice Research, Subang, West Java, using an augmented design with five blocks. The genetic material used was ninety-nine lines and four checks varieties, namely Inpari 30, Limboto, Salumpikit, and IR 20. The model was formulated using stepwise regression analysis. Based on this study, ten lines were adapted to drought stress at the generative stage, namely B13983E-KA-12-2, B13926E-KA-13, B13507E-MR-19, B14366E-KY-50, B14366E-KY-37, IR86384- 46-3-1-B, BP20452e-PWK-0-SKI-1-1, BP20452e-PWK-0-SKI-2-4, BP20452e-PWK-0-SKI-3-3, and BP29790d-PWK-3 -SKI-1-5. The B13507E-MR-19 had the highest productivity (4.02 ton ha-1) under drought stress conditions. Yield under drought stress in the greenhouse could be predicted using a linear regression model involving plant height at early vegetative stage, plant height up to the panicle, tiller number at early vegetative stage, tiller number at late vegetative stage, tiller number at flowering, heading time, number of filled grain, and panicle exsertion length. This model was able to explain 75.92% of yield variation. Potential rice lines and the regression model obtained are expected to contribute to the development of rice varieties adaptive to drought. Keywords: drought tolerant, freshwater swamp, rainfed, regression model
ABSTRAKSeleksi Ketahanan Aksesi Plasma Nutfah Padi terhadap Hawar Daun Bakteri. Dini Yuliani, Rina H. Wening, dan Sudir. Usaha budi daya tanaman padi di Indonesia selalu dihadapkan pada berbagai kendala, di antaranya serangan penyakit hawar daun bakteri (HDB) yang disebabkan oleh bakteri Xanthomonas oryzae pv. oryzae (Xoo). Pengendalian penyakit HDB dengan varietas tahan merupakan salah satu teknik yang murah dan mudah dilakukan oleh petani padi. Aksesi plasma nutfah sebagai sumber tetua untuk perakitan varietas tahan perlu diketahui reaksi ketahanannya terhadap penyakit HDB. Penelitian ini bertujuan untuk menyeleksi ketahanan aksesi plasma nutfah terhadap penyakit HDB patotipe III, IV, dan VIII. Penelitian dilaksanakan di Kebun Percobaan Balai Besar Penelitian Tanaman Padi di Sukamandi, Subang, Jawa Barat pada Musim Hujan 2012/2013 dan Musim Kemarau 2013 dengan Rancangan Acak Terpisah. Petak utama adalah tiga patotipe Xoo, yaitu patotipe III, IV, dan VIII. Sedangkan anak petak adalah materi yang diuji, yaitu 20 aksesi plasma nutfah dan tiga varietas pembanding. Sebanyak 20 rumpun tanaman per petak diinokulasi Xoo dengan metode pengguntingan. Inokulasi dilakukan pada saat pertanaman menjelang stadium primordia. Ujung-ujung daun digunting sepanjang kira-kira 10 cm dari ujung daun dengan gunting inokulasi yang berisi suspensi bakteri Xoo umur 48 jam dengan kepekatan 10 8 cfu. Pengamatan keparahan penyakit HDB dilakukan dengan mengukur panjang gejala terpanjang pada umur dua, tiga, dan empat minggu setelah inokulasi. Hasil pengujian ketahanan terhadap HDB patotipe III, IV, dan VIII diperoleh tiga aksesi plasma nutfah yang berasal dari galur isogenik menunjukkan keparahan penyakit HDB tidak berbeda nyata dengan varietas pembanding tahan Angke pada dua musim tanam. Galur isogenik tersebut, yaitu IRBB 55, IRBB 60, dan IRBB 61. Ketiga galur isogenik tersebut dapat dijadikan tetua tahan dalam perakitan varietas unggul baru tahan HDB.Kata kunci: Seleksi ketahanan, aksesi plasma nutfah padi, hawar daun bakteri. ABSTRACTRice cultivation in Indonesia has been faced with many obstacles, including the attack of bacterial leaf blight (BLB) that caused by bacteria Xanthomonas oryzae pv. oryzae (Xoo).Resistant variety was considered as the cheap technique to control BLB disease and could be used by rice farmers. Germplasm accessions as a source to build resistant varieties must be known their resistance to BLB disease. This study aimed at selecting the resistance germplasm accessions to BLB pathotype III, IV, and VIII. Observations BLB disease severity was done by measuring the longest length of symptoms at the age of two, three, and four weeks after inoculation (WAI). The result showed that three germplasm accessions from near isogenic lines were not significantly different with the check varieties (Angke) in their resistance to Xoo pathotype III, IV, and VIII in two cropping seasons. The isogenic lines were IRBB 55, IRBB 60, and IRBB 61 can be used in the assembly of resistant new varieties to BLB.
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