Progress in ideotype breeding to increase rice yield potential

The ideotype approach has been used in breeding programs at the International Rice Research Institute (IRRI) and in China to improve rice yield potential. First-generation new plant type (NPT) lines developed from tropical japonica at IRRI did not yield well because of limited biomass production and poor grain filling. Progress has been made in second-generation NPT lines developed by crossing elite indica with improved tropical japonica. Several second-generation NPT lines outyielded the first-generation NPT lines and indica check varieties. China's "super"rice breeding project has developed many F1 hybrid varieties using a combination of the ideotype approach and intersubspecific heterosis. These hybrid varieties produced grain yield of 12 t ha-1 in on-farm demonstration fields, 8-15% higher than the hybrid check varieties. The success of China's "super" hybrid rice was partially the result of assembling the good components of IRRI's NPT design in addition to the use of intersubspecific heterosis. For example, both designs focused on large panicle size, reduced tillering capacity, and improved lodging resistance. More importantly, improvement in plant type design was achieved in China's "super" hybrid rice by emphasizing the top three leaves and panicle position within a canopy in order to meet the demand of heavy panicles for a large source supply. The success of "super"hybrid rice breeding in China and progress in NPT breeding at IRRI suggest that the ideotype approach is effective for breaking the yield ceiling of an irrigated rice crop

QTL Mapping of Yield, Yield Components, and Morphological Traits in Rice (Oryza sativa L.) Using SSR Marker

The experiment was aimed at identifying QTL (quantitative trait loci) controlling ten traits of yield, yield component and plant morphology of rice based on BC1F1 of IR75862-206-2-8-3-B-B-B//IR64 mapping population consisted of 115 plants.  It was arranged in Completely Randomized Design with three replicates.  Ninety three SSR markers spread across the twelve rice chromosomes were used to map the QTL.  These markers were mostly segregated according to Mendel Law except for fourteen markers.  There were eleven QTL detected in eight traits, i.e., heading date, flag leaf length, plant height, panicle length, panicle weight, seed set, weight of 100 grains, and grain weight per plant, meaning that one or two QTL were detected in each trait.  These QTL were located at chromosome 2, 3, 4, 6, 11, and 12.  Some QTL were located at the same chromosome even at the same location indicating the close association of the traits.  It also indicated that there were common QTL which were found across genetic background and specific QTL which were found at specific genetic background.  Further study was prospective for the molecular marker application in rice improvement.   Key words: QTL, agronomic traits, SSR, ric

Rice Molecular Breeding Laboratories in the Genomics Era: Current Status and Future Considerations

Using DNA markers in plant breeding with marker-assisted selection (MAS) could greatly improve the precision and efficiency of selection, leading to the accelerated development of new crop varieties. The numerous examples of MAS in rice have prompted many breeding institutes to establish molecular breeding labs. The last decade has produced an enormous amount of genomics research in rice, including the identification of thousands of QTLs for agronomically important traits, the generation of large amounts of gene expression data, and cloning and characterization of new genes, including the detection of single nucleotide polymorphisms. The pinnacle of genomics research has been the completion and annotation of genome sequences for indica and japonica rice. This information—coupled with the development of new genotyping methodologies and platforms, and the development of bioinformatics databases and software tools—provides even more exciting opportunities for rice molecular breeding in the 21st century. However, the great challenge for molecular breeders is to apply genomics data in actual breeding programs. Here, we review the current status of MAS in rice, current genomics projects and promising new genotyping methodologies, and evaluate the probable impact of genomics research. We also identify critical research areas to “bridge the application gap” between QTL identification and applied breeding that need to be addressed to realize the full potential of MAS, and propose ideas and guidelines for establishing rice molecular breeding labs in the postgenome sequence era to integrate molecular breeding within the context of overall rice breeding and research programs

Biofortification in underutilized staple crops for nutrition in Asia and Africa

Malnutrition is one of the biggest public health challenges of the century with about 2 billion people affected by it globally. Biofortification is the process of breeding micronutrients traits into staple food crops, which is bioavailable to make a positive measurable impact to the population that eats such staples on a daily basis. It is a cost-effective, sustainable strategy and complementary in nature to the existing market interventions. Iron pearl millet, iron beans, vitamin A cassava and orange sweet potato can contribute to increase household nutrition in the Asia and Africa. Over the years evidences gathered by partners in crop breeding, nutrition studies and delivery experiences will help to build the foundation for scaling out further to reach millions who need the most

Progress update: Crop development of biofortified staple food crops under Harvestplus

Over the past 15 years, biofortification, the process of breeding nutrients into food crops, has gained ample recognition as a cost-effective, complementary, feasible means of delivering micronutrients to populations that may have limited access to diverse diets, supplements, or commercially fortified foods. In 2008, a panel of noted economists that included five Nobel Laureates ranked biofortification fifth among the most cost-effective solutions to address global challenges such as reducing hidden hunger. The 2016 World Food Prize was awarded to biofortification. Biofortification involves breeding staple food crops to increase their micronutrient content, targeting foods widely consumed by low-income families in Africa, Asia, and Latin America. The focus is on providing sufficient levels of vitamin A, iron, and/or zinc through these crops, based on existing consumption patterns. HarvestPlus is part of the CGIAR Research Program on Agriculture for Nutrition and Health (A4NH). HarvestPlus works in partnership with more than 200 scientific and implementation organizations around the world to improve nutrition and public health by developing and promoting biofortified food crops that are rich in vitamins and minerals, and providing global leadership on biofortification evidence and technology. Crops bred for higher levels of micronutrients using conventional breeding methods have been released in 26 countries in Africa, Asia and Latin America, and are now being grown and eaten by millions of farmers and consumers. This paper reviews crop development progress and varietal release of primary (major) and secondary (regionally important) staple crops, with a focus on progress in Africa

Genetic erosion over time of rice landrace agrobiodiversity

Changes in global biodiversity at the genetic level have proved difficult to determine for most organisms because of lack of standardized, repeated or historical data; this hampers the attempts to meet the convention on biological diversity (CBD) 2010 targets of reducing loss of genetic diversity, particularly of crop species. For rice, where germplasm and genetic data have been collected throughout South and Southeast Asia over many decades, contrary to popular opinion, we have been unable to detect a significant reduction of available genetic diversity in our study material. This absence of a decline may be viewed positively; over the 33-year timescale of our study, genetic diversity amongst landraces grown in traditional agricultural systems was still sufficiently abundant to be collected for ex situ conservation. However, if significant genetic erosion does take place in the future as a result of accelerating global warming and/or major changes in land use or agricultural practices, will it be catastrophic or gradual, and how will it be detected? We have shown a strong link between numbers of landraces collected (and therefore extant) and genetic diversity; hence, we have a clear indicator to detect loss of genetic diversity in the future. Our findings lend considerable support for ex situ conservation of germplasm; the more than substantial genetic resources already in genebanks are now safe. On the other hand, it is the germplasm growing in farmers' fields, continually adapting genetically to changing environmental conditions and evolving novel genetic forms, whose future has been much less certain but can now be effectively monitored using our criteria

The Development and Characterization of Near-Isogenic and Pyramided Lines Carrying Resistance Genes to Brown Planthopper with the Genetic Background of Japonica Rice (Oryza sativa L.)

The brown planthopper (BPH: Nilaparvata lugens Stål.) is a major pest of rice, Oryza sativa, in Asia. Host plant resistance has tremendous potential to reduce the damage caused to rice by the planthopper. However, the effectiveness of resistance genes varies spatially and temporally according to BPH virulence. Understanding patterns in BPH virulence against resistance genes is necessary to efficiently and sustainably deploy resistant rice varieties. To survey BPH virulence patterns, seven near-isogenic lines (NILs), each with a single BPH resistance gene (BPH2-NIL, BPH3-NIL, BPH17-NIL, BPH20-NIL, BPH21-NIL, BPH32-NIL and BPH17-ptb-NIL) and fifteen pyramided lines (PYLs) carrying multiple resistance genes were developed with the genetic background of the japonica rice variety, Taichung 65 (T65), and assessed for resistance levels against two BPH populations (Hadano-66 and Koshi-2013 collected in Japan in 1966 and 2013, respectively). Many of the NILs and PYLs were resistant against the Hadano-66 population but were less effective against the Koshi-2013 population. Among PYLs, BPH20+BPH32-PYL and BPH2+BPH3+BPH17-PYL granted relatively high BPH resistance against Koshi-2013. The NILs and PYLs developed in this research will be useful to monitor BPH virulence prior to deploying resistant rice varieties and improve rice’s resistance to BPH in the context of regionally increasing levels of virulence