Distinct Resistance Groups in Rice Germplasm from Kerala Based on Antibiosis and Tolerance Traits to Brown Planthopper, Nilaparvata lugens (Stal)

Bridging germplasm and mechanisms: screening for resistance and decoding defense strategies against rice gall midge (Orseolia oryzae Wood-Mason) in rice

Identification of novel source and inheritance of resistance to bacterial wilt (Ralstonia solanacearum) in tomato (Solanum lycopersicum L.) for sustainable disease management

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease severely restricting tomato (Solanum lycopersicum L.) productivity in tropical and subtropical regions. The purpose of this study was to identify novel sources of resistance and explicate the inheritance pattern of bacterial wilt resistance in tomato.  A total of 59 genotypes, including open-pollinated lines, hybrids and breeding accessions, were subjected to screening experiments during two consecutive seasons (2022–2023 and 2023–2024) under controlled net house conditions at Centurion University of Technology and Management and natural epiphytotic field conditions at Indian Institute of Horticultural Research - Central Horticultural Experiment Station , Bhubaneswar, India. Disease severity was evaluated using percent disease index (PDI) and area under disease progress curve (AUDPC). The open-pollinated cultivar ‘Utkal Kumari (BT-10)’ exhibited consistent high resistance, with significantly lower AUDPC values (<150 vs >1800 in susceptible checks) and high survival rates (90 %) across environments. Among others, tomato cultivars Arka Samrat, Arka Abhed and JK Desi, demonstrated significant resistance while genotypes such as Pusa Ruby and EW815 were consistently highly susceptible. A segregating F₂ population derived from a cross between resistant ‘BT-10’ and susceptible ‘Pusa Ruby’ exhibited continuous variation in disease response. Chi-square analysis revealed significant deviation from a 3:1 Mendelian segregation ratio (χ² = 72.30, P < 0.01), indicating a quantitative mode of inheritance. These findings highlight the potential of Utkal Kumari and allied resistant lines as donors for resistance breeding and emphasize the need to integrate robust phenotypic screening with molecular approaches for durable and strategic bacterial wilt management in tomato.

Evaluation of Maize Germplasm for Resistance against Invasive Insect Pest Fall Armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Background: Fall armyworm (Spodoptera frugiperda J. E. Smith) is an invasive insect pest of maize that can cause substantial foliar damage and adversely affect crop production. Host-plant resistance offers a sustainable and environmentally compatible approach for managing this pest; however, information on resistance in diverse maize germplasm remains limited. Therefore, identifying resistant genotypes is important for supporting the development of fall armyworm-resistant maize. Aims: The present study screened 25 maize genotypes for resistance to the invasive insect pest fall armyworm under artificial infestation conditions. Study Design: A randomised block design (RBD) with three replications was used. Place and Duration of Study: The study was conducted during Kharif 2025 at the Winter Nursery Centre, ICAR-Indian Institute of Maize Research, Rajendranagar, Hyderabad. Methodology: Fall armyworm larvae were reared on a chickpea-casein-based artificial diet, and first instar neonates were released onto plants at the V5 phenological stage. Leaf damage rating (LDR) was scored on a 1-9 scale at 7, 14, and 21 days after infestation (DAI); genotypes were categorised as resistant (1-3), moderately resistant (3-6), and susceptible (6-9). Results: The LDR at 14 days after infestation varied from 2.58 to 7.34 across genotypes. Three genotypes, CML 71 (2.81), DMRE-63 (2.58), and CML 67 (2.92), were classified as resistant; 19 genotypes were moderately resistant; and three genotypes, MIL 9-1662 (6.2), CM 202 (6.44), and Sarhad HSRB (7.34), were susceptible. Conclusion: The resistant genotypes identified in this study may serve as valuable sources of resistance for incorporation into maize breeding programmes aimed at developing FAW-resistant genotypes.

Screening of Tomato Germplasm for Resistance to Fusarium Wilt Caused by Fusarium oxysporum f. sp. lycopersici under in vivo Conditions

Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici, is a major constraint on tomato production worldwide. The present study was undertaken to evaluate thirty tomato germplasm accessions obtained from the ICAR-Indian Institute of Vegetable Research (IIVR), Varanasi, for their response to Fusarium wilt under field conditions during the 2023 and 2024 cropping seasons at SKUAST-Jammu, Chatha. The thirty germplasm accessions were evaluated under artificial disease pressure, and disease development was assessed through disease incidence, apparent infection rate (r), and area under the disease progress curve (AUDPC), with Pusa Ruby included as the susceptible cultivar. Significant variation was observed among the germplasm accessions in disease development and progression. Based on pooled disease incidence, one germplasm accession was categorised as tolerant (T), two as moderately susceptible (MS), ten as susceptible (S), and seventeen as highly susceptible (HS), whereas no germplasm accession showed resistant (R) or moderately resistant (MR) reactions. The germplasm accessions also exhibited considerable differences in infection rate and AUDPC values, reflecting variability in the speed and cumulative development of Fusarium wilt. Arka Saurabh exhibited comparatively lower disease development, while highly susceptible germplasm accessions showed rapid disease progression and greater disease accumulation. The identified tolerant and less susceptible germplasm accessions can be utilised as potential sources in tomato improvement programmes for developing Fusarium wilt-resistant cultivars.

Fungicidal Management of Sheath Rot (Sarocladium oryzae) Disease on Rice Production in Guyana and Assessment of Socio- Economic Benefits.

Sheath rot caused by Sarocladium oryzae (Sawada), is a major disease of rice that can significantly reduce grain yield and quality, resulting in economic losses for farmers. This study evaluated the efficacy of selected fungicides for the management of sheath rot disease under field conditions in Guyana and also assessed the potential socio-economic benefits. Three field trials were conducted during the Spring and Autumn cropping seasons of 2022 and the Spring cropping season of 2024 at the Plant Pathology Department Experimental Area, Guyana Rice Development Board (GRDB), Rice Research Station (RRS), Burma. The experiments were established using a Randomized Complete Block Design (RCBD) with four replications per treatment. The rice variety GRDB 14 was grown under recommended agronomic practices, and fungicides were applied at their respective rates. Results from the three trials demonstrated that most fungicidal treatments reduced sheath rot disease severity and improved growth and yield parameters compared with untreated control. The most effective treatments were Top Cop at 250 ml/ac, Onix at 350 ml/ac, Curacarb at 250 ml/ac, Saaf at 300 g/ac, and the positive check, Fugi One at 300 ml/ac, which reduced disease severity by 68.00–76.00% relative to the untreated control. Other treatments also reduced disease severity by 31.99–48.00%. Yield responses were mostly positive across the trials, with increases ranging from 2.23–34.23% in Spring 2022, 8.69–90.98% in Autumn 2022, and 3.31–70.43% in Spring 2024 over the untreated control. The reduction in disease severity and some levels of increase in grain yield indicate that effective fungicide use can enhance rice productivity and profitability. In general, increased yields can improve the overall farm income, strengthen household livelihoods, and contribute slowly towards reduction of poverty leading to greater economic returns. Furthermore, improved productivity supports sustainable rice production, enhances food security, and allows for benefits to stakeholders throughout Guyana’s rice value chain. Based on the consistent performance of Top Cop at 250 ml/ac, Onix at 350 ml/ac, Curacarb at 250 ml/ac, Saaf at 300 g/ac, and the positive check, Fugi One at 300 ml/ac are recommended for the management of sheath rot disease, particularly in areas where the disease is most prevalent.

Morphological and Molecular Screening for Bacterial Leaf Blight Resistance in Land Races of Rice (Oryza sativa L.)

Bacterial leaf blight (BLB) of rice, caused by Xanthomonas oryzae pv. oryzae, is a major constraint on rice production, and the use of resistant genotypes is an important approach to disease management. The present study screened 40 rice genotypes for BLB resistance using morphological evaluation and molecular markers linked to seven resistance genes: xa5, Xa7, xa8, Xa10, xa13, Xa21 and Xa33. Field screening was conducted at RARS, Maruteru, during kharif 2023 using artificial inoculation by the leaf-clipping method, and disease reactions were assessed according to the Standard Evaluation System. Morphological screening categorised entries as highly resistant, resistant, moderately resistant, susceptible or highly susceptible according to diseased leaf area. Molecular screening was performed using gene-linked markers to determine the presence of the target resistance genes. Nineteen genotypes were identified as carrying two or three BLB resistance genes. Phenotypic evaluation based on diseased leaf area showed variation in resistance among the 40 genotypes and supported the molecular screening results. Jaavepula-2, Basmati, Tulasi baso and Kundadam-2 carried three resistance genes, while Kalamuch and Loyamalli carried the Xa7 and Xa21 combination and exhibited phenotypic resistance. The combined morphological and molecular screening therefore identified rice genotypes with multiple BLB resistance genes that may serve as donor parents in marker-assisted breeding programmes aimed at improving BLB resistance in rice.