Genetic Variability, Heritability, and Trait Associations in Rice Genotypes under Low Nitrogen Conditions
M. V. S. K. Rohit
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India and Department of Genetics and Plant Breeding, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India.
Bokka Kiranmayee
Department of Genetics and Plant Breeding, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India.
P. Akshay Goud
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
K. Eshwar
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
Parminder Singh Saini
Department of Genetics and Plant Breeding, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India.
P. Mathan Kumar
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
T. Harisha
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
M. S. Anantha *
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
C. Gireesh
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
Deepak Sharma
Department of Genetics and Plant Breeding, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India.
P. Senguttuvel
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
R. M. Sundaram
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
C. N. Neeraja
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
S. V. Sai Prasad
Department of Genetics and Plant Breeding, ICAR- Indian Institute of Rice Research, Hyderabad, Telangana, India.
*Author to whom correspondence should be addressed.
Abstract
Nitrogen is a primary macronutrient required for rice growth and development. The present study evaluated sixty rice genotypes across two seasons under low-nitrogen conditions. Mixed-model ANOVA indicated significant genetic variability for all evaluated agronomic traits. To rigorously account for environmental variation, best linear unbiased prediction (BLUP) estimates were derived using a mixed linear model framework. This approach applies shrinkage towards the population mean, thereby reducing the inflation of extreme values and isolating stable genotypic effects. High heritability in conjunction with high genetic advance was recorded for 100-seed weight, total and filled grains panicle-1, biological yield, and grain yield, indicating the predominance of additive gene effects. Grain yield demonstrated stable genetic control, establishing it as a reliable selection criterion. BLUP-based ranking identified RPR-6 (4.16), MS15 (3.03), MS22 (2.24), Rasi (2.06), and RPR-4 (1.72) as superior, stable genotypes across seasons. Specifically, RPR-6 and MS15 exhibited coordinated improvements in sink strength and biological yield, while MS22 and Rasi demonstrated highly efficient biomass partitioning. Correlation analysis revealed strong positive associations between grain yield and biological yield, while a significant negative correlation existed between biological yield and harvest index. Cluster analysis grouped genotypes into distinct clusters, identifying Cluster 2 as a source of high-yielding lines. Ultimately, this exploitable variability will provide a valuable foundation for breeding rice cultivars adapted to a low-nitrogen environment.
Keywords: Rice (Oryza sativa L.), Low-nitrogen conditions, genetic variability, broad-sense heritability, genetic advance, Best linear unbiased prediction, grain yield, trait correlations, Hierarchical clustering, genotype selection