Recently, a mini core panel of 98 genotypes representing the diversity of Indian rice germplasm was identified. This mini core is a very important resource that can be evaluated for specific traits of interest to identify superior genotypes that could be used as parents in breeding programmes. The present study was focused on a systematic evaluation of mini core rice collection along with a set of germplasm from the North Eastern Hill Region under cold stress with following specific objectives: To study and compare the effect of three dates of sowing (early, medium and late) on rice mini core collection with respect to yield contributing traits, to determine the trait that most affects yield under stress through path coefficient analysis, to study the effect of cold stress at booting stage on pollen and spikelet fertility under controlled low temperature conditions and to identify tolerant and susceptible genotypes.
Rice farming is the largest single use of land for producing food. Ninety percent of the rice is produced in Asia, and it totaled 696 million tons in 2010. Rice production is one of the most important economic activities on Earth. Only 7% of all rice production is exported from its country of origin.
Various abiotic stresses directly or indirectly affect the physiological status of rice and negatively alter its overall metabolism, often with impacts on grain yield. Cold stress is one of the abiotic stresses which are common problem of rice cultivation. Cold stress causes various injuries to rice seedlings in low-temperature and high-altitude areas and is therefore an important factor affecting rice production in such areas. Rice is a cold-sensitive plant that has its origin in tropical or subtropical areas, and cold damage can cause serious yield losses. Low temperature effects the rice cultivation mainly in two stages of development i.e., seedling and booting. In both of them, cold temperature has harmful effects on crop productivity, as in the first case the number of established plants is affected and in the booting stage pollen sterility can be induced by cold, decreasing the final number of grains.
Table of Contents
1. INTRODUCTION
2. REVIEW OF LITERATURE
2.1. Status and importance of rice
2.2. Effects of cold stress in rice
2.3. Physiological basis of cold tolerance at vegetative and booting stage
2.4. Molecular basis of cold tolerance
2.5. Importance of diverse germplasm core and mini core collections
2.6. Path analysis and principal component analysis for yield contributing traits
3. MATERIALS AND METHODS
3.1. Description of the study area
3.2. Field screening for cold tolerance
3.3. Statistical/Genetic analysis
3.4. Screening for cold tolerance at seedling stage
3.5. Chlorophyll estimation
4. RESULTS
4.1. Analysis of variance (ANOVA)
4.2. Analysis of variance for G X E
4.3. Path Analysis studies
4.4. Identification of genotypes tolerant to low temperature
4.5. Relative performance of genotypes under late sown condition as compared to timely sown condition
4.6. Principal Component analysis
4.7. Pollen viability test
4.8. Seedling stage screening for cold tolerance
4.9. Chlorophyll content
5. DISCUSSION
5.1. Identification of important traits
5.2. Identification of important genotypes under cold stress at reproductive stage
6. SUMMARY AND CONCLUSION
Research Objectives and Core Themes
This thesis aims to systematically evaluate the performance of a rice mini core collection alongside various landraces under cold stress conditions to identify genotypes and traits suitable for future breeding and molecular studies. The research specifically focuses on comparing yield-contributing traits across different sowing dates to determine their resilience at the reproductive stage.
- Screening of mini core rice genotypes for cold stress tolerance at the reproductive stage.
- Application of path coefficient analysis to understand the direct and indirect impacts of various traits on grain yield.
- Assessment of pollen viability and spikelet fertility as indicators of cold tolerance in rice.
- Identification of superior and stable genotypes for cultivation in mid- to high-altitude, cold-prone regions.
Excerpt from the Book
2. REVIEW OF LITERATURE
Rice (Oryza sativa) is the second most important staple crop in the world and has originated in a tropical region and 90 per cent of the rice is produced and consumed in S. E. Asia. It can be classified into two major cultivar types. Indica cultivars are grown mostly in the hot and humid tropical lowlands; japonica cultivars are grown in the temperate and sub-temperate regions and the high altitude areas of the tropics.
More than half of the world population depends upon rice as it is the staple food of many developed and developing countries around the globe. It is grown in 114 countries across the world on an area about 160.88 million hectares with annual production of 477.08 million tonnes, with an average productivity of 4.42 ton ha-1. During the recent past (2012-13 to 2013-14) the world production of rice has increased by 1 per cent (from 472 million ton to 477 million ton), trade by 8 per cent (from 38 million ton to 41 million ton) and consumption by 3 per cent (from 469 million ton to 481 million ton) (GoI, 2015). More than 90% of the world’s rice is produced and consumed in Asia where it is an integral part of culture and tradition and more than 250 million farm families are cultivating rice in Asia (Hossain and Pingali, 1998). Even though the production is growing annually, the increase in population has become more rapid. World population is increasing at an alarming rate and is expected to reach about billion by the end of year 2050. Global rice production needs to raise about 700 million tonnes to feed an additional 650 million rice eaters by 2025 using less water and less land, which is a great challenge in Asia (Dawe, 2003).
Summary of Chapters
INTRODUCTION: Provides context on the global importance of rice, the physiological impact of cold stress at critical developmental stages, and the specific challenges faced in the North Eastern regions of India.
REVIEW OF LITERATURE: Surveys existing research on rice cultivation, physiological and molecular responses to cold stress, and the role of mini core collections in plant breeding.
MATERIALS AND METHODS: Details the experimental design, site description, genotype selection process, data recording criteria, and the statistical methods used for evaluating cold tolerance.
RESULTS: Presents findings from the analysis of variance, path coefficient studies, and identification of genotypes tolerant to low temperatures through phenotypic and molecular markers.
DISCUSSION: Interprets the findings regarding important traits and stable genotypes, connecting the experimental results with established breeding objectives to enhance cold resilience.
SUMMARY AND CONCLUSION: Synthesizes the core findings and emphasizes the potential for identified superior landraces to serve as critical resources for future breeding programs.
Keywords
Rice cultivation, cold tolerance, reproductive stage, mini core collection, path coefficient analysis, spikelet fertility, pollen viability, abiotic stress, germplasm, North Eastern region, yield components, principal component analysis, breeding programs, genotype identification.
Frequently Asked Questions
What is the fundamental focus of this research?
The research focuses on evaluating the response of a diverse rice mini core collection to cold temperature stress, specifically during the critical reproductive stages of crop growth.
Which specific areas of India are of particular concern?
The study highlights the North Eastern region of India, where mid- and high-altitude areas frequent low temperatures that negatively impact long-duration or late-sown rice varieties.
What is the primary goal of the study?
The aim is to identify superior, cold-tolerant rice genotypes and key phenotypic traits that can be targeted in breeding programs to stabilize or enhance productivity under low-temperature conditions.
What scientific methodologies were employed to analyze the data?
The researchers used Analysis of Variance (ANOVA), path coefficient analysis to evaluate trait influence on yield, and Principal Component Analysis (PCA) for data reduction and characterization.
What does the main body of the work cover?
It covers field screening, assessment of biological and morphological traits under different sowing dates, pollen viability tests, and seedling stage physiological evaluations under controlled cold treatments.
Which keywords best characterize this work?
The work is defined by terms such as cold tolerance at the reproductive stage, rice mini core collections, genotype selection, path coefficient analysis, and sustainable productivity for hill regions.
Why is the reproductive stage considered so sensitive to cold?
The reproductive stage, particularly the booting phase, is highly sensitive because cold stress can disrupt mitosis and pollen maturation, leading to increased spikelet sterility and reduced nutrient supply to anthers.
What did the study conclude regarding the role of biological yield?
Biological yield was identified as a critical trait, exhibiting a strong, positive direct effect on grain yield under cold stress, making it a reliable target for phenotypic selection indices.
- Arbeit zitieren
- Bapsila Loitongbam (Autor:in), Denisha Rajkhowa (Autor:in), Priyanka Irungbam (Autor:in), 2023, Evaluation of Rice Mini Core Collection. Response to Low Temperature at Reproductive Stage, München, GRIN Verlag, https://www.grin.com/document/1340515
