Background: Uma is a high-yielding, popular red-kernelled rice variety of Kerala; however, the occurrence of BB disease often causes severe yield reductions in this cultivar. Host plant resistance based on multiple genes is the most effective measure to impart durable resistance. Hence, efforts were undertaken to introgress the resistance genes, xa 5, xa13 and Xa21, from a BB-resistant variety, ISM, into Uma, using the MABB approach. Methods: Foreground selection was carried out using markers RG 556 and xa5 SR for xa5, RG136 and xa13 promoter for xa13 and pTA248 for Xa21 genes, respectively. The identified R-gene-pyramided plant was subjected to background selection using rice microsatellite markers for recurrent parent genome recovery. The phenotypic evaluation for BB resistance was carried out using the leaf-clipping method following the IRRI standard evaluation system, SES. Result: Molecular analysis of the recurrent parent Uma revealed the endogenous presence of R gene xa 5. The evaluation of BC2F1 lines identified a single plant pyramided with three resistance genes, with xa13 and Xa21 in the heterozygous condition, exhibiting a recurrent parent genome recovery of 70.45% and kernel characteristics similar to those of the Uma. Concurrently, BC1F2 lines generated from the cross were phenotypically screened for BB resistance, also identifying resistance to moderate resistance lines to the BB pathogen. Further advancement of these backcross generations was proposed to isolate gene pyramids homozygous for the resistance genes, with near-complete recurrent parent genome recovery.
Bhartiya Krishi, Anusandhan Patrika, L. Megha et al.· Bhartiya Krishi Anusandhan P...· 0 citations
Background: Brown planthopper (Nilaparvata lugens) is a major insect pest of rice that causes severe yield losses through direct feeding and hopperburn. The emergence of virulent populations and increasing concerns over insecticide resistance necessitate the identification of rice germplasm with effective host plant resistance for sustainable pest management.
Aims: To identify rice germplasm accessions resistant to N. lugens by evaluating antibiosis and tolerance mechanisms and to classify the accessions based on their resistance responses.
Study Design: Comparative laboratory screening of rice germplasm accessions using antibiosis and tolerance parameters, followed by multivariate analysis.
Place and Duration of Study: Department of Agricultural Entomology, Kerala Agricultural University, Thrissur, Kerala, India, during 2023–2025.
Methodology: Twelve rice germplasm accessions, together with the resistant check PTB 33 and susceptible check TN 1, were evaluated under controlled conditions. Antibiosis and tolerance were assessed using standard biological and plant response parameters. Data were analysed using analysis of variance, Spearman correlation, principal component analysis, and hierarchical clustering.
Results: Significant differences were observed among the germplasm accessions for all antibiosis and tolerance parameters (P < .001). TGC 108 and UN 46 22K exhibited lower honeydew excretion (27.2 and 28.4 mm²), reduced nymphal emergence (99.4 and 114.6 nymphs/accession), prolonged developmental periods (21.2 and 19.4 days), delayed wilting (25.0 and 22.7 days), and lower functional plant loss index values (22.7 and 25.2), indicating strong antibiosis and tolerance. Principal component analysis explained 97.02% of the total variation, and hierarchical clustering grouped the germplasm into three distinct resistance categories.
Conclusion: TGC 108 and UN 46 22K exhibited strong antibiosis and tolerance responses and emerged as promising donor sources for the development of brown planthopper-resistant rice varieties.
I. M. Swathy, M. Smitha, M. Chellappan et al.· Journal of Advances in Biolo...· 0 citations