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Manzanilla D.O.,International Rice Research Institute | Paris T.R.,International Rice Research Institute | Tatlonghari G.T.,International Rice Research Institute | Tobias A.M.,International Rice Research Institute | And 6 more authors.
Experimental Agriculture | Year: 2014

The risks of flooding in rice production include losses that can affect some 13 million ha of rice lands in Southeast Asia. This study integrated social and gender perspectives into the varietal evaluation process to contribute to planned faster uptake of submergence-tolerant rice (Sub1) varieties. In this study, the participatory varietal selection (PVS) process was used in eliciting male and female farmers' opinions with respect to selecting popular varieties with the SUB1 gene introgressed, for added tolerance of flash floods of up to two weeks. Fifteen Sub1 varieties and the farmers' local check were tested under the PVS researcher-managed (PVS-RM) trials, which involved farmers' preference analysis (PA). The farmers tested the pre-selected lines with the SUB1 gene in their own fields to further evaluate their performance under varying conditions. During flooding, farmers experienced lower production depending on water depth, timing with respect to rice growth stage, duration, frequency of occurrence and quality. On-farm PA results showed wide variability in the performance of the Sub1 varieties compared with local popular varieties. This implies the need for further testing of pre-released lines in terms of adaptability and the continuous development of rice genotypes for varying flood-prone rice ecosystems. Women are as knowledgeable as men because of the significant roles they play in rice production and food preparation. Moreover, farmers and breeders have almost the same criteria in choosing the best performing rice lines. Sensory tests revealed the eating and cooking qualities important to farmers. The findings of this study can provide feedback to breeding programmes to ensure a greater likelihood of adoption and ultimately increasing rice productivity in submergence-prone rice areas. Copyright © Cambridge University Press 2013.

Lang N.T.,Cuu Long Delta Rice Research Institute CLRRI | Phuoc N.T.,Cuu Long Delta Rice Research Institute CLRRI | Thu Ha P.T.,Cuu Long Delta Rice Research Institute CLRRI | Toan T.B.,PCR Biotechnology Company | And 4 more authors.
Sabrao Journal of Breeding and Genetics | Year: 2015

Development of rice varieties tolerant to submergence, high-yielding and good quality is essential due to increased flooding in the lowland areas in the Mekong delta, Vietnam. The purpose of this experiment was to develop rice varieties tolerant to submergence on the basis of a combination of two breeding methods by molecular markers, single cross and backcross. Evaluating tolerance of F8 and BC2F4 generation on the basis in the field of flooded and unflooded conditions to select promising lines to meet for farmers applying into production. The Sub1 gene was introgressed into the new breeding lines. Some high yielding and good submergence tolerant lines were developed (e.g. BC2F4-4-3) however, also many lines failed were not acceptable due to their long duration between 120-130 days or their high rate of unfilled grain. This is a opportunity to improve good rice varieties for condition of breeding submergence rice varieties in Vietnam. © Society for the Advancement of Breeding Research in Asia and Oceania (SABRAO) 2015.

Chauhan B.S.,University of Queensland | Namuco O.S.,International Rice Research Institute | Ocampo L.A.L.,International Rice Research Institute | Son T.T.N.,Cuu Long Delta Rice Research Institute CLRRI | And 4 more authors.
Crop Protection | Year: 2015

Direct seeding has been practiced in the districts of Phuoc Thoi, Thoi Lai, and Co Do in the Mekong Delta region of Vietnam, where majority of the farmers practice wet direct-seeded rice (WDSR), Oryza sativa L., for crop establishment. WDSR reduces the cost of inputs such as labour, time, and water prior to crop establishment in the field. Like other rice systems, WDSR is beset by many constraints, foremost of which is weed infestation. Surveys were conducted for two consecutive dry seasons (2012 and 2013) among farmers and/or households (FH) in these three districts to document the cultural practices used and the accompanying production constraints in WDSR. The results showed seeding rates of up to 100-300 kg ha-1, using farmers' own seed stock. Farmers broadcast pre-germinated seeds manually because of limited (or no) access to drum seeders. The most important production constraint identified was severe weed infestation, particularly by grass species, such as Echinochloa crus-galli (L.) P. Beauv., Leptochloa chinensis (L.) Nees, O. sativa L. (as volunteers from previous seasons), and O. sativa f. spontanea or weedy rice. Most farmers were aware of the presence of weedy rice in their fields and the damage it does to the crop. They enumerated numerous strategies to improve current practices to manage weeds. Despite the constraints, yield across the sites for two years ranged from 6.27 to 8.27 t ha-1, which may be considered higher than those obtained from other rice ecosystems across Asia. This also highlights that there is further scope to increase the rice yield in weedy rice infested fields. © 2015 Elsevier Ltd.

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