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Inter Specific Indica-japonica Drought Tolerant Rice Genotypes for Aerobic Condition | OMICS International
ISSN: 2375-4338
Rice Research: Open Access
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Inter Specific Indica-japonica Drought Tolerant Rice Genotypes for Aerobic Condition

J Aravind, Farhad Kahani and Shailaja Hittalmani*
Marker Assisted Selection Laboratory, Genetics and Plant Breeding, University of Agricultural Sciences, GKVK, Bangalore 560065, India
Corresponding Author : Shailaja Hittalmani
Professor and University Head
Genetics and Plant Breeding
University of Agricultural Sciences
GKVK, Bangalore 560065, India
Tel: 91-8023624967
E-mail: [email protected]
Received: October 02, 2015; Accepted: November 02, 2015; Published: November 06, 2015
Citation: Aravind J, Kahani F, Hittalmani S (2015) Inter Specific Indica-japonica Drought Tolerant Rice Genotypes for Aerobic Condition. J Rice Res 3:154. doi:10.4172/2375-4338.1000154
Copyright: © 2015 Aravind J, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Abstract

Rice is premier food crop of Asia and is cultivated in a variety of ecosystems. Twenty six medium duration Indica/Japonica, Recombinant Inbred Lines (RILs) of the cross IR50 × Moroberekan cross, their parents and popular rainfed aerobic rice varieties MAS 946-1, Rasi and Sahabhagi Dhan were evaluated under rain fed, drought and aerobic conditions with objective of identifying genotype for aerobic and stress situations. Observations were recorded for plant and yield traits. Field evaluation during wet season revealed significant differences among the means of genotypes except for panicle length, drought recovery score, relative grain yield and relative biomass yield under different stress levels during dry season of 2011. RILs IM036, IM095, IM090, IM014, IM167, IM039, IM192 and IM176 performed superior under aerobic condition in wet season while, IM192 and IM176 were superior under rain fed condition also. IM160, IM096, IM104, IM046 IM192, IM109, IM36, IM181, IM14, IM176, IM167 and IM95 were high yielding in aerobic condition in dry season 2011. IM 167 was superior for grain yield under both conditions except under moisture stress period of 60 to 70 Days after sowing (DAS). IM95 was superior for stress period of 100 to 115 DAS and aerobic condition, whereas IM176 for aerobic and stress period 60 to 70 DAS. IM181 was superior under all the conditions after 60 to 75 DAS. IM36 was superior under all the conditions except for stress period 100 to 110 DAS. Superior genotypes identified for both drought and aerobic situations will be recommended for water scarce situation in India.

Keywords
Drought; Aerobic; Rain fed; Indica-Japonica; Rice
Introduction
Rice (Oryza sativa L.) is one of the major staple food crops for about 65% of the world’s population. It is one of the most economically important food crops in the world. It is the most important grain with regard to human nutrition and caloric intake, providing more than one fifth of the calories consumed worldwide by the human beings. The green revolution led to a tremendous increase in tropical rice production. Much of these yield increases were seen in the irrigated and stress free ecosystems. However, according to various estimates, we will have to produce 40% more rice by 2030 to fulfil the food grain demands of the growing population, from less land, with less water, less labor and fewer chemicals. The most pragmatic approach to meet this demand is to breed rice tolerant to biotic and abiotic stresses which hamper production. Drought is the most serious constraint that limit rice yields, especially in rain fed ecosystems, as it is a highly water intensive crop (2500 Lkg-1 of rough rice). In India the drought during 2009 had caused a significant drop in rice production as compared to previous years. In the present era of climate change, water scarcity is escalating and irrigation is becoming a costly input. Consequently development of high yielding lines of rice, tolerant for drought stress prone ecosystems is an essential and practical strategy to increase rice production and ensure livelihood security for farmers. Breeding for drought tolerance is widely perceived as a difficult task as it is a complex trait controlled by poly genes having varying effects, and is dependent on drought timing and severity. Moreover the different drought tolerance traits differ in their ease of screening, nature of inheritance and heritability. Low heritability under stress for yield per se has forced the breeders to turn to secondary traits for selection. However, broad-sense heritability of grain yield under reproductivestage drought stress was observed to be high and comparable to that of grain yield estimated in non-stress conditions by several authors [11-15] indicating that selection for yield under drought stress is repeatable. Water is most limited and essential natural resource in agriculture. The dwindling water resources reveal a grim situation for low land puddled rice cultivation. Because of increasing water scarcity, there is a need to develop alternative systems that require less water there are examples of restriction of cultivation of rice and sugarcane to save water for other domestic purpose during scarcity. To keep up the rice production during irrigation water shortage, alternate methods of cultivation of rice is essential. One such strategy is cultivation of rice under aerobic situation. This method of cultivation involves direct seeding with surface irrigations when required and is characterized by aerated soil environment during the entire period of crop growth comparable to other cereals like maize and irrigated Ragi. Aerobic rice could be successfully cultivated with 600 to 700 mm of total water in summer and entirely on rainfall in wet season. New varieties specially bred for this situation are most suitable for such cultivation to achieved high yields. Varieties suitable for this type of cultivation also possess ability to withstand intermittent drought spells with minimum yield loss with maximum potential of 6 tons per hectare. Irrigation is given at an interval of 5 days up to 25 days; 5 to 7 days once up to 50 days and during grain filling stage irrigation is provided once in 3 days. Aerobic cultivation with suitable varieties saves about 50 to 60% of irrigation water. It is also reported that amount of methane emitted under aerobic situation is very low and contributes to lowering of greenhouse gas emission. Rains fed lowland rice ecosystems are highly variable and unpredictable in nature (Yoshida, 1977). Multiple abiotic stresses such as unfavorable soil conditions, regional weather patterns, topography, pests and weeds all contribute to the complexity of the ecosystem. Asia is the biggest rice producer and consumer, accounting for 90 per cent of the world’s production and consumption of rice. The worldwide harvested area of rain fed lowland rice is estimated to be 46 to 48 million hectares. Of this, 90% is in South and Southeast Asia. Rice farming in these rains fed areas is risk-prone. Yields remain low, about 1.5 to 2.5 t ha in most areas. The income of most farmers is low and they are challenged by erratic yields. In Asia, about 50% of all the rice land is rain fed and although rice yields in irrigated ecosystems have doubled and tripled over the past 30 years, only modest gains have occurred in rain fed rice systems. The water supply in rain fed areas principally comes from rainfall. Uncertainty in the timing of rainfall and variability in its intensity and its distribution cause either flood or drought stress in rain fed lowland rice production ecosystem. Recombinant inbred lines are stabilized breeding lines which are one of the widely used mapping populations derived from the F2 of a cross between parents differing for the trait of interest by repeated inbreeding and represents permanent mapping family, developed one such recombinant inbred (RI) population in rice derived from the cross between IR 50, an indica variety susceptible to drought stress and Moroberekan, a West African upland japonica variety that has substantial resistance to drought. Preliminary evaluation revealed wide variability for yield and drought response in the population. In the present study, an attempt was made to identify medium duration IR50/Moroberekan RILs for grain yield under aerobic, rainfed and stress conditions [1-24].
Materials and Methods
Experimental material
A set of twenty six selected medium duration IR50/Moroberekan recombinant inbred lines (RILs) developed by Girish et al. at marker assisted selection laboratory, along with the two parents and four checks (MAS 946-1, Rasi, Sahbhagi Dhan and OYR-128) were used for the study. The RILs were selected based on maturity duration. Earlier flowering is advantageous over late flowering in terms of higher spikelet fertility, higher harvest index and higher yield, as it helps to counter terminal drought stress [23-25] (Table 1).
Experimental site
The investigation was carried out in two experiments during wet season 2010 and dry season 2011 under aerobic, rain fed and drought conditions at ‘K’ block, GKVK, Bangalore, representing the eastern dry zone with a red sandy loam which is located at the latitude of 12° 58’ North; longitude 77° 35’ East and altitude of 930 m above mean sea level. The experiment was laid and in randomized complete block design (RCBD) during wet season 2010 and in split plot design (SPD) during dry season 2011.
Method of sampling and observations recorded
Two plants were selected at random in each genotype in each replication for recording observations. Data was collected for traits such as number of tillers per plant, panicle number, plant height (cm), panicle length (cm), panicle weight (g), grain yield (g), biomass yield (g), harvest index, total number of grains per panicle, percentage sterility, test weight (g) and days to 50% flowering under three conditions while data on visual drought scores such as days to leaf rolling, leaf rolling score, leaf drying score and drought recovery score, were recorded only in the stress treatments [26]. Traits such as relative grain yield, relative biomass yield and relative spikelet fertility were computed as ratio between the respective parameters under stressed and control (aerobic) plots. Mean values of the traits were used for statistical analysis.
Statistical analysis
The analysis of variance (ANOVA) for different characters was carried using the mean data for aerobic and rain fed condition separately for Experiment 1 and by split plot analysis for with stress treatments considered as main plot treatments for Experiment 2 according to the method given by [27]. The co-efficient of variability (CV) at phenotypic level for all the characters were analyzed by applying the formula suggested by [28]. Heritability in broad sense (h2) estimates was computed by the formula suggested by [29].The extent of genetic advance expected through selection for each of the character was calculated as per the formula suggested by [30] (Table 2).
Results and Discussion
Evaluation of rice genotypes under aerobic and rain fed situation in wet season 2010
The analysis of variance for twelve quantitative traits of the genotypes evaluated in Experiment 1 indicated significant difference among the means of different genotypes for all the traits except for test weight under aerobic condition and percentage sterility under rain fed condition, thus indicating the scope for selection. The differences in the mean performance of the genotypes under aerobic and rain fed conditions can be attributed mainly due to genotypic differences and interaction between genotypes and environment. All the RILs showed reduction in grain yield under rain fed condition as compared to irrigated. The reduction in grain mean values in yield and yield contributing traits is probably due to the long period of stress experienced during peak reproductive stage. A few RILs such as IM- 82 and IM160 showed very low grain yield reduction under stress condition. Such lines can be used to study the mechanism of drought tolerance involved. On comparison with the high yielding checks, a few RILs showed better performance for grain yield than MAS 946-1 under aerobic and rain fed conditions. Sahbhagi Dhan, Rasi and OYR- 128 checks and RILs like IM 14, IM36, IM90 IM95, IM176 and IM192 performed superior than the high yielding parent IR 50 under aerobic condition. The RILs IM176 and IM192 were found superior to IR50 with respect to grain yield under rain fed conditions. This may be due to the fact that IR50 was developed for irrigated situation (Tables 3 and 4) (Figures 1 and 2).
Different genetic variability parameters were estimated using appropriate formulas and procedures. The range in the mean values reflects the extent of phenotypic variability present in the plant material (RILS). High range was noticed for plant height, number of tillers per plant, panicle number, and percentage sterility, total number of grains per plant, biomass yield and grain yield. High phenotypic coefficient of variability (PCV) was observed for number of tillers per plant, panicle number, percentage sterility, grain yield per plant, panicle weight and total number of grains per panicle whereas high genotypic coefficient of variability (GCV) was observed for number of panicle per plant, total number of grains per panicle and percent sterility under both aerobic and rain fed conditions. Moderate phenotypic coefficient of variability was observed for harvest index, panicle length, bio mass yield and plant height and for characters such as plant height, days to 50% flowering, and panicle number, moderate genotypic coefficient of variability was estimated. The GCV indicates the extent of genetic variability present for different characters and does not indicate heritable component of variability. To know the heritable component of the variability, heritability estimates were computed. Heritability values are important since their magnitude indicates the accuracy with which a genotype can be recognized by phenotypic expression. Though heritability estimates indicate the efficiency of selection system, its scope is restricted as they are prone to environmental effects. However, heritability values with genetic advance provide better response in selection program. High heritability was noticed for plant height and days to 50% flowering, moderate heritability recorded for number of tillers, number of panicles, panicle length, biomass yield, and total number of grains per panicle under both rain fed and aerobic conditions. Grain yield and harvest index showed low heritability under aerobic conditions and high heritability under rain fed condition. The remaining traits showed low heritability under aerobic and rain fed conditions. Comparable heritability’s between the control and stress treatments have been reported by [15,16,31-33] have reported moderate to high heritability under stress for grain yield. Genetic advance as percent mean was high for plant height, days to flowering, total number of grains per panicle and percent sterility whereas that for number of tillers, panicle length, biomass yield, and harvest index were reported to be moderate. Grain yield showed moderate GA as percent of mean under aerobic situation and high GA as percent of mean under rain fed conditions. This indicates the feasibility of selection for yield under rain fed condition (Table 5).
Evaluation under aerobic and drought situations in dry season 2011
The different RILs showed varying response to different drought stress treatments in Experiment2. Split-plot design was used for analysis of variance of different traits. Most of the RILs yielded better under aerobic condition. However, RILs like IM16, IM36, IM39, IM64, IM82, IM90, IM95, IM110, IM172 and IM173 showed higher yields under stress situations. Many RILs also out yielded the high yielding parent IR 50. These are ideal candidates to study the mechanism of drought tolerance involved. The split-plot design is as special type of design used for two factorial experiments, where the sub plot treatment effects and interaction effects can be determined with increased precision [34].The results of analysis of variance show that the effect of stress treatment on the variability was significant for all the traits except panicle length, drought recovery score, relative grain yield and relative biomass yield. Significant differences due to interaction between stress and genotypes were detected only for panicle length, days to 50% flowering, days to leaf rolling and leaf drying score. The genetic parameters estimated in the present population are due to additive effect as it is composed of stabilized RILs. The traits number of tillers, number of panicles, plant height grain yield, harvest index, percent sterility leaf drying score, leaf rolling score and relative grain yield showed high PCV and GCV values (Tables 6-8).
High values of broad sense heritability obtained can be attributed to lower differences between PCV and GCV values. However, phenotypic coefficient of variability is not very reliable since it includes both genetic and environmental effects and if the latter portion is large, selection will be inefficient. Thus, heritability values were estimated since its magnitude indicates the accuracy with which a genotype can be recognized by phenotypic expression. In present study heritability in broad sense was calculated. High heritability coupled with high GA observed for plant height, similar findings were reported for plant height by [35,36]. Moderate heritability and high genetic advance as percent of mean was observed for number of panicles, grain yield, harvest index, leaf rolling score, relative grain yield and relative biomass yield, indicating the suitability for improvement through selection. Moderate heritability and moderate GA as percent mean was observed for panicle length and days to leaf rolling, this was in conformity with the findings of [37]. Drought related traits like leaf rolling score and relative spikelet fertility showed low heritability and genetic advance. Similar results were obtained by [38].
Identification of superior genotypes for grain yield under different situations
The genotypes were classified based on grain yield under various conditions and the RILs IM036, IM095,IM090, IM014, IM167, IM039, IM192 and IM176 were identified as superior under aerobic condition, IM192and IM176 were superior under rain fed condition during wet season 2010. In the evaluation under different drought treatments, IM160, IM096, IM104, IM046 IM192, IM109, IM36, IM181, IM14, IM176, IM167 and IM95 were be superior in aerobic condition IM90 was superior only under stress 3 (100-110DAS) and stress 4 (100- 115DAS) IM 36 was superior under all the conditions except for stress 3 (100-110DAS), and IM I4 was superior under reproductive stage stresses stress 3 and 4; and under aerobic condition during dry season 2011. IM 167 was superior under all the conditions except stress 1(60- 70DAS). IM 95 was superior for stress 4 and aerobic condition, whereas IM176 for aerobic and stress 1. IM181 was superior under all the conditions except stress 2 (60-75DAS). The high yielding RILs under different conditions are being tested in large scale for further selection suitable for target aerobic and drought conditions (Figure 3).
Acknowledgment
The financial assistance to Dr. Shailaja Hittalmani, from The Rockefeller Foundation USA, and ICAR- is gratefully acknowledged.
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