Dissemination and outscaling of submergence-tolerant rice (Sub1 lines) in Southeast Asia

Mega varieties introgressed with the SUB1 gene (IR64, Swarna, Sambha-Mahsuri, BRII, TDK, and CR 1009) and other lines possessing SUB1 were deployed in Southeast Asia to evaluate their performance and facilitate their adoption. Evaluations was achieved through on-station multilocation yield trials under normal and flooded conditions, followed by participatory varietal selection (PVS) and preferential analysis (PA) conducted in selected farmers' fields. The results confirmed the effectiveness of SUB1 in natural farmers' fields, identified most adopted genotypes to particular niches, provided information on floods and risks, and validated the importance of PVS and PA as essential tools to ensure adoption. Farmers recognized the importance of SUB1 and the yield advantage it offered when incorporated into popular varieties; this is reflected on the increasing demand for seed supply of the favored genotypes. Some varieties were selected in countries different from their origin- PSBRc 68 yielded 4.8 t/ha and was the top choice in Laos. Swarna-Sub1 performed consistently well in four countries and was the top choice in Vietnam, Sambha Mahsuri-Sub1 and IR64-Sub1 performed well in Indonesia but was only second to their best local check, Ciherang in the Philippines IR49830-7-1-2-3 and BRII-Sub1 yielded 5.1 and 4.7 t/ha, respectively, and were the top farmers' choices. Formal registration and accreditation was achieved for IR64-Sub1 (NSIC 194 or Submarino 1) in the Philippines and for IR70213-9-CPA-UBN-2-1-3-1 (INPARA-3), IR64-Sub1(INPARA-4) and Swarna-Sub1 (INPARA-5) in Indonesia. Such successful undertaking can be made possible only through the conserted efforts of farmers, local officials, collaborators, scientists, and other associations. Apparently, these Sub1 varieties provide considerable security for farmers in flood-prone areas, and the PVs and feedback approaches enable swift recognition of desirable varieties suitable for local farmers' needs. Its approach also helped speed the release and commercialization of the new varieties to ensure a sufficient seed supply for farmers.