Abstract
Biomass production is important in increasing yield not only for food but also for bio-fuel production that depends on high dry matter. Due to climate change, occurrence of drought may be prevalent and this affects both grain and biomass yields in crops including rice. The objectives of this study were to determine the performance of selected high biomass breeding rice lines to different levels of drought and use several drought tolerance indices to identify best genotypes that could be grown in unfavorable water stressed areas. A rainfed and flooded trial was conducted to evaluate 20 selected breeding lines for biomass production and ten entries from the same set were grown in the greenhouse at three different field capacities (FC, 50%, 75%, 100%). Most of the genotypes performed well under non-stressed conditions (flooded and 100% FC) but some genotypes performed well in water stressed condition. The plants had lower plant height, tiller plant-1, and total biomass at maturity under rainfed conditions and their flowering was delayed compared to flooded conditions. In the greenhouse, water stress slowed the rate of increase in height, and produced lower shoot and root weight, percent dry matter (% DM) and total biomass. However, drought enhanced the rate of tiller production. Two genotypes were found to more tolerant to drought stress and could be used for cultivation under water stress condition to get optimum biomass yields. These genotypes can be identified using drought tolerance indices, particularly stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP) and harmonic mean (HARM), as these have a similar ability to separate drought sensitive and tolerant genotypes. Genetic and molecular analyses, and detailed characterization of these genotypes will help understand their inheritance pattern and the number of genes controlling the traits and determine specific leaves and root traits important in developing high biomass rice.
Highlights
Rice (Oryza sativa) is the staple food for a large part of the world’s human population, which is the most consumed cereal after wheat
The analysis of variance showed that the differences in the number of days to first tiller, rates at which tillers were produced, shoot and root fresh and dry weight as well as the total fresh and dry biomass in three levels of FC and in genotypes was significantly different
The genotypes grown at 100% FC had significantly faster tiller emergence and the rate of increase in plant height than those grown at 75% and 50% FC but plant grown at 50% FC had fastest rate of tiller production (Table 1)
Summary
Rice (Oryza sativa) is the staple food for a large part of the world’s human population, which is the most consumed cereal after wheat. Rice which is grown in humid tropics in rainfed (dry land) areas covers 19% of the total rice production areas and the 15 million hectares of rain dependent rice fields contribute about 4% of total world rice production [2] (GRiSP, 2013). These areas generally suffer from drought but may have acidity of soil and deficiency of phosphorus and zinc. Drought is one of the most important limiting factors in the production of the major crops in the world and affects 20% of the total rice-growing area in Asia [3] (Pandey and Bhandari, 2008). The current drought resistance levels and those needed for rice grain yield stability are significantly different as rice is very sensitive to water scarcity [8] (Xiao et al, 2007)
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