Mitigating risks in flash flood-prone areas with submergence tolerant rice

The Philippines is vulnerable to typhoons and floods. This is experienced in top rice producing provinces in Central Luzon, viz. Nueva Ecija, Pampanga, Tarlac, Pangasinan and Bulacan, with affected areas of 40% to 80%. Growing rice in flood-prone areas is a high risk venture. Flooding in low-lying areas in Nueva Ecija results in 50%-60% yield loss and 30% negative net income. Yield is less than 2.0t/ha or nothing for farms kept idle during wet season. The use of submergence tolerant rice is a sustainable and more permanent measure to mitigate and better manage rice production in flash flood-prone areas. In this research, 30 genotypes, including IRRI-developed Sub1 breeding lines, introgressed with SUB 1 gene, and PhilRice-developed non-Sub1 lines, were evaluated in the low-lying flood-prone farmers' field in Barangay [village] Papaya, San Antonio, Nueva Ecija. Considering the 2008 WS field performance under submergence stress at vegetative stage, nine most adapted Sub1 genotypes were identified, yielding at least 2.0t/ha and 4.0t/ha under severe and moderate stress, respectively. These genotypes include PSB Rc68, IR07F102 (IR64-Sub1), IROF 102 (Swarna-Sub1) (BC3F3), IR05F101 (Swarna-sub1) (BC2F3), IRO7F287 (Samba Mahsuri-sub1), IR07F289 (TDK-sub1), IRO7F290 (BR11-sub1), IR49830-7-1-2-3, IR57514-pm1-5-B-1-2. For none sub 1 entries, IVC-2, IVC-3, IVC-94, IVC-109, IVC-113, PR37416-18-1 and PR37435-30-1 were promising, yielding more than 1.0t/ha with stress. In 2009 WS, the on-farm trial was flooded in September and October, at reproductive stage, brought by typhoons Maring, Ondoy and Pepeng. Despite the submergence stress, compounded by damage from siltation and late drought, seven genotypes, PSB Rc68, IR57514-PMI-5-B-1-2, IR49830-7-1-2-3, IR05F102, PR37416-18-1, PR37435-30-1 and IVC-21, yielded 1.09-1.87 t/ha. Other entries, including local checks, yielded from 0.21-0.89 t/ha. Stability of the lines has to be evaluated further in multi-location adaptation and acceptability trial, before they can be provided to farmers as measures to mitigate flash flood related risks in rice production.