Genetic Studies for Yield and Physiological Traits in Three Line Aerobic Rice Hybrids  

Sathya Ramalingam , S. Jebaraj
Department of Plant Breeding and Genetics, Agricultural College and Research Institute, Madurai, 625104, India
Author    Correspondence author
Plant Gene and Trait, 2013, Vol. 4, No. 9   doi: 10.5376/pgt.2013.04.0009
Received: 30 May, 2013    Accepted: 01 Jul., 2013    Published: 25 Jul., 2013
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Sathya and Jebaraj., 2013, Genetic Studies for Yield and Physiological Traits in Three Line Aerobic Rice Hybrids, Plant Gene and Trait, Vol.4, No.9 48-52 (doi: 10.5376/pgt.2013.04.0009)


Sufficient genetic variability was recorded among the 90 hybrids and 21 parents of rice genotypes under aerobic condition. Genotypic and phenotypic correlations were ascertained for grain yield and its components. The results revealed that the traits productive tillers per plant, panicle length, spikelet fertility, harvest index, proline content, SPAD chlorophyll meter reading, chlorophyll stability index, relative water content and dry root weight as they expressed significant and positive correlation with single plant yield and also positive inter correlations among themselves. Therefore, selection for any one of the above characters would bring in simultaneous improvement of other characters and ultimately improving the grain yield.

Aerobic rice; Genotypic correlation; Phenotypic correlation; Drought

Rice is the staple food for over 70% of Asians, the majority of whom are living below the poverty line. More than 90% of the world’s rice is produced and consumed in Asia (Barker et al., 1999) and rice production must be increased by an estimated 56% over the next 30 years to keep up with population growth and income-induced demand for food in most Asian countries where about 75% of total rice production comes from irrigated lowlands (Maclean et al., 2002). Almost 25% of the world’s rice is grown under rainfed lowlands and frequently affected by uneven rainfall distribution. Another 13% of the rice area under cultivation is always subjected to water stress during the growing season (Bouman et al., 2007). Food security in Asia and the increasing scarcity of fresh water resources for agriculture in many areas are stimulating the development of aerobic rice production system (Tuong et al., 2005).

Aerobic rice is high-yielding rice grown under nonflooded conditions in nonpuddled and unsaturated (aerobic) soil. It is responsive to high inputs, can be rainfed or irrigated and tolerates occasional flooding (Maclean et al., 2002). The water use of aerobic rice was about 60% less than that of flooded rice and total water productivity was 1.6 to 1.9 times higher (Vijayakumar et al., 2006).
The success of plant breeding programme depends to a greater extent on the knowledge of the genetic architecture of the population and selection of appropriate breeding method for the improvement of traits of interest. It is essential to estimate the various types of gene action for the selection of appropriate breeding procedure to improve the quantitative and qualitative characters (Banumathy et al., 2003).
Keeping in view the genetic studies in aerobic rice were undertaken to estimate the phenotypic and genotypic correlations of yield under aerobic conditions.
Results and Discussion
Analysis of variance showed significant differences among the parents and hybrids for all the 19 traits studied. The line×tester interaction was significant for all the characters studied (Table 1; Table 2). The results of correlation analysis given in the Table 3 revealed that single plant yield exhibited positive and significant association with panicle length, harvest index and proline content. This was in conformity with the findings of Jayasudha and Deepak Sharma (2010) for harvest index and Michael Gomez and Rangasamy (2002) and Yogameenakshi et al (2004) for proline content.

Table 1 Analysis of Variance of RBD for different biometrical traits

Table 2 Analysis of variance of RBD for different physiological traits

Table 3 Phenotypic correlation coefficients between single plant yield and component characters

Even though grain yield under stress is the primary trait of selection in breeding programme for drought prone environments, low heritability of yield necessitates an alternative approach such as selection of secondary and putative traits. The inter correlation between yield contributing characters may affect the selection for component traits either in favourable or unfavourable direction. Days to 50 per cent flowering showed positive and highly significant association with filled grains per panicle as reported by Yogameenakshi et al (2004). Similarly positive and significant relationship was observed between productive tillers per plant and 100 grain weight. Similar results were reported by Anbumalarmathi and Nadarajan (2008). Panicle length had positive and significant association with harvest index, proline content, dry root weight, root: shoot ratio and single plant yield. This is in conformity with the findings of Vinothini and Ananda Kumar (2008). The trait, spikelet fertility showed positive and significant association for root dry weight and root: shoot ratio. This is in accordance with the reports of Malarvizhi et al (2010).
Knowledge on inter relationship between drought tolerant traits may facilitate breeders to decide upon the intensity and direction of selection pressure to be given on related traits for the simultaneous improvement of these traits. The association of harvest index with proline content and single plant yield was positive and highly significant. Similarly proline content had highly significant and positive association with single plant yield and SPAD chlorophyll meter reading with root length, Chlorophyll stability index had positive and significant association with relative water content and dry shoot weight. The association between relative water content and dry shoot weight was also positive and significant while highly significant and positive association was observed between dry root weight and root: shoot ratio. Similar results were reported by Malarvizhi et al (2010). The genetic association concluded that selection for productive tillers per plant, panicle length, spikelet fertility, harvest index, proline content, SPAD chlorophyll meter reading, chlorophyll stability index, relative water content and dry root weight would likely boost the grain yield in rice.
Materials and Methods
The study was conducted in the Research farm of the Department of Plant Breeding and Genetics, Agricultural College and Research Institute, Madurai, Tamil Nadu, India during 2009-2011. Six Lines and 15 Testers were subjected to crossing by ‘Line×Tester’ mating design (Kempthorne, 1957). Ninety hybrids along with six lines, 15 testers and one check were raised in a Randomized Block Design (RBD) with three replications under non-puddled and non flooded aerobic soil, during Rabi, 2010. The hybrids along with their parents were maintained under irrigated condition upto 55 days. From the 56th day onwards the treatment plot was maintained under aerobic condition. For every irrigation thereafter, soil sampling was carried out before and after irrigation to assess the soil moisture content. Irrigation was given only when hair line crack was noticed in the treatment plot and the control plot was maintained under normal flooded condition till maturity. Five plants were selected at random and tagged. Data were recorded at panicle initiation (75~80 days), flowering and maturity stages for physiological and quantitative traits. Observations of B lines were recorded for the corresponding A lines.
Observations were recorded for the drought tolerant, yield and its component traits viz., Days to 50% flowering (DF), Plant height (PH), Number of Productive tillers per plant (PT), Number of panicles per plant (PP), Panicle length (PL), Filled grains per panicle (FG), Spikelet fertility (SF), Hundred grain weight (HGW), Proline content (PC), SPAD chlorophyll meter reading (SCMR), Chlorophyll stability index (CSI), Relative water content (RWC), Biomass yield (BMY), Dry shoot weight (DSW), Dry root weight (DRW), Root / shoot ratio (RS), Root length (RL), Harvest index (HI), Single plant yield (YLD) under water stress and fully irrigated (control) conditions as per the Standard Evaluation System (1996). The analysis of variance of RBD and their significance for all the characters were worked out as suggested by Panse and Sukhatme (1964). The genotypic correlation coefficients between yield and yield components as well as among the yield components were worked out. From the analysis of variance and covariance tables, the corresponding genotypic variances and covariances were calculated by using the mean square values and mean sum of products as suggested by Johnson et al (1955b). The significance of genotypic correlation coefficient was tested by referring to the standard table given by Snedecor and Cochran (1961).
We are very much grateful to The Pioneer Hibred International, Inc., for providing me Pioneer Hibred International Scholarship of $15000 to carry out this doctoral programme successfully.
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