Screening of Rice Genotypes for Resistant to Rice Leaf Folder, Cnaphalocrocis medinalis Guenee and Identification of Associated Morphological Traits
Abstract
Screening of 23 rice promising genotypes based on per cent damaged leaves revealed that eleven genotypes were found moderately resistant viz., Kala Namak (12.32%), GNR-3 (13.41%), GNR-5 (13.45%), GRH-2 (13.92%), GNR-7 (14.43%), GR-15 (16.02%), Mahsuri (16.52%), GNRH-1 (16.62%), GR-17 (16.89%), GNR-2 (19.02%) and NVSR-396 (19.34%) (Scale-3). Whereas, two genotypes were found susceptible i.e. GNR-4 (37.32%) and GR-11 (39.11%) (Scale-7) and one genotype TN-1 (54.86%) was found the highly susceptible (Scale-9). The plant height exhibited the highly significant negative correlation with per cent damaged leaves (r = -0.6157) and number of larvae (r = -0.5621), while others parameters were found non-significant positive and negative correlation. The highest grain and straw yield were recorded in GRH-2 (5946 & 6667 kg/ha) and lowest were recorded in TN-1 (3874 and 4559 kg/ha), respectively. Grain and straw yield exhibited the highly significant negative correlation with per cent damaged leaves (r = -0.5882 and r = -0.5828, respectively) and number of larvae (r = -0.5776 and r = -0.5711, respectively) indicated that there was decrease in yield with increase in infestation and vice-versa.
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Introduction
Rice (Oryza sativa Linnaeus) belongs to the family of grasses (Poaceae) with most important cereal crops worldwide. It is grown over 120 million hectares to produce 600 million tonnes of grain with an average productivity of 5000 kg/ha (Jakarpong and Wiboon, 2017). India ranks first by covering the largest area (45 per cent) under rice and ranks second by contributing total food grain production of the world. In India rice is grown in 43.86 million hectares with 112 million tonnes production and the average productivity is about 2600 kg/ha (Anon., 2020). Rice production is confined to South and Middle Gujarat with wide range of agro-climatic variation within and between individual zones. Rice production is limited by both biotic and abiotic stresses of which insect pests alone caused about 25 per cent losses (Dhaliwal et al., 2007), hence there is need to reduce the yield losses due to major pests and diseases. Rice crop is attacked by more than 100 species of insects, out of them 20 species can cause economic damage during different stages of the crop (Jakarpong and Wiboon, 2017). Rice leaf folder is one of the most serious and most important pest of rice crop in Indian subcontinent (Shanmungam et al., 2006). Out of eight species of leaf folders, the widest spread and important one is Cnaphalocrocis medinalis (Guenee) (Pyralidae: Lepidoptera) (Bhatti, 1995). It was earlier considered a minor pest but now a days it assumed major pest status. Due to rice leaf folder, the loss may reach up to 63 to 80 per cent as reported by Rajendran et al. (1986). Host plant resistance is an important component of integrated pest management (IPM) for sustainable rice production. Screening of rice genotypes for resistance to leaf folder and identification of associated morphological traits can facilitate the development of resistant varieties, thereby reducing dependence on chemical insecticides. The present study was therefore undertaken to screen promising rice genotypes for resistance to rice leaf folder and to identify morphological traits associated with resistance.
Conclusion
The rice genotypes viz., Kala Namak, GNR-5, GNR-3, GRH-2, GNR-7, GR-15, GNRH-1, Mahsuri, GR-17, GNR-2 and NVSR-396 have been proved moderately resistant or least susceptible. Therefore, these genotypes could be utilized in further breeding programme. Their utilization could contribute to the development of leaf-folder-resistant rice varieties and support integrated pest management (IPM). Morphological traits associated with lower leaf folder infestation included longer plant height, more tillers, longer and thicker leaves, broader leaves, green leaf colour and late flowering. The highly significant negative correlation between plant height and infestation parameters suggests that plant height is an important morphological trait for resistance. Phyllotaxy showed no apparent effect on leaf folder infestation. Grain and straw yield exhibited highly significant negative correlations with per cent damaged leaves and larval population, confirming the impact of leaf folder infestation on yield. Thus, these resistant genotypes and associated morphological traits can be effectively utilized in breeding programmes for developing rice varieties with enhanced resistance to leaf folder.
Limitations of the Study: The study was conducted at a single location (Navsari, Gujarat) over two seasons. The genotype × environment interaction was not examined, and the mechanisms underlying the observed resistance were not investigated. Biochemical analysis (silica content, total phenols, etc.) was not performed. Future research should include multi-location trials, biochemical analysis, and investigation of the mechanisms of resistance (antixenosis, antibiosis, tolerance) in the identified moderately resistant genotypes.
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