Field Evaluation of Sorghum Accessions and Improved Varieties for Resistance to Major Diseases under Natural Infection Conditions

Field Validation of Fungicides for the Management of Rice Brown Spot Disease (Bipolaris oryzae)

Brown spot, caused by Bipolaris oryzae, is an important constraint to rice production under favourable disease conditions. This study evaluated the field efficacy of eight fungicides against brown spot and assessed disease severity among rice genotypes cultivated in farmers’ fields. A randomised complete block design with three replications was established at Rampur, Chitwan, using the susceptible cultivar Sankharika. Eight fungicide treatments and an untreated control were compared following three foliar applications at seven-day intervals. Disease severity and the area under the disease progress curve (AUDPC) were determined, and grain yield was correlated with AUDPC. A roving survey was also conducted at 21 locations in Chitwan and Nawalparasi districts. All fungicide treatments reduced final disease severity relative to the untreated control. Metalaxyl 8% + mancozeb 64% WP recorded the lowest mean AUDPC (436.85), followed by carbendazim (470.50) and hexaconazole (482.20). Hexaconazole recorded the lowest final disease severity (28.90%), whereas the untreated control recorded 45.20%. The association between grain yield and AUDPC was weak and not statistically significant (r = −0.031). The survey identified six genotypes, with maximum severity of 78% in Samba Mansuli and Sabitri and minimum severity of 26% in Kalo Basmati. These findings indicate differential fungicide performance and genotype responses under the evaluated field conditions and support further multilocation and multiseason validation.

Leaf and Dwarf Disease Incidence and Severity in Sweet Corn Hybrids, Along with Their Implications for Ear Yield

The production of sweet corn encounters considerable challenges stemming from biotic stressors, especially foliar diseases and viral infections, which diminish productivity even with expanded cultivation areas. This study was performed to evaluate the influence of prevalent leaf and dwarf mosaic virus diseases on the ear yield of 17 sweet corn hybrids. The study was conducted at the coastal area of Bengkulu University's experimental station (15 m asl). The experiment was set up on a randomized complete block design with three replications to allocate 15 experimental hybrids and 2 commercial varieties on the plots, each with a population density of 48 plants. Data were collected for leaf disease incidence, severity, and progress, dwarf disease symptoms, ear length and diameter, ear weight (unhusked and husked), kernel row number, kernel number per row, and ear yield. Leaf spots, eyespot with halos, corn leaf blight, and corn rust were the prominent leaf diseases found on the plant population as measured at three months after planting (MAP), with the level of incidence ranging from 23.29% to 32.17%, and the level of severity ranging from 15.17% to 21.67%. No significant differences were observed among the hybrids for the level of disease incidence and severity, and all hybrids exhibited moderate resistance to the leaf diseases under consideration. However, the evaluation of disease progress using the area under the disease progress curve (AUDPC) formula indicated that Caps3 × Caps17B was the most susceptible hybrid, while Caps2 × Caps22 was the most resistant hybrid. Dwarf disease, as indicated by variegata symptoms, was not found in all hybrids, notably in Caps3 × Caps17A, Caps15 × Caps22, Caps17A × Caps22, and Caps17B × Caps23. The remaining hybrids showed the symptoms, with incidence varying between 1.0% and 3.0% of the plant populations. The observations made on the characteristics of crop productivity showed that significant variations among the hybrids existed for ear yield and its contributing traits.

Epidemiological Evaluation and Molecular Identification of the Leaf Rust Resistance Gene Lr13 in Selected Egyptian Wheat Cultivars Under Climatic Influences

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.

Evaluation of Local Rice Genotypes from Southwest Aceh for Resistance to Bacterial Leaf Blight (Xoo Strain VIII)

Local rice germplasm is a valuable genetic resource for developing bacterial leaf blight (BLB)-resistant and high-yielding rice cultivars. However, information on the resistance of Southwest Aceh local rice to Xanthomonas oryzae pv. oryzae (Xoo), particularly during the generative stage, remains limited. Previous studies have mainly focused on commercial cultivars or vegetative-stage screening, leaving the resistance potential of local germplasm at the reproductive stage largely unexplored. This study aimed to evaluate the resistance of local rice to BLB at the generative stage of plant growth. The research was conducted at Experimental Field, Teuku Umar University. West Aceh (4°08′33″ N; 96°11′54″ E). Fifteen local rice genotypes, together with resistant and susceptible control varieties, were evaluated following artificial inoculation with Xoo strain VIII. Disease resistance was assessed based on incubation period and lesion length, while agronomic performance was evaluated using key yield-related traits. Seven local genotypes Itam Tangke Lango, Jantong, Jempa Puteh, Manyam U, Pade Manggeng-1, Pade Manggeng-2, and Rangan Lango were classified as resistant based on lesion length. Among the evaluated genotypes, Sikleng exhibited superior agronomic performance, producing the highest number of productive tillers (27.50) and grains per panicle (317.73). The novelty of this study lies in evaluating Southwest Aceh local rice germplasm for bacterial leaf blight resistance at the generative stage using Xoo strain VIII while integrating disease resistance with yield-related agronomic traits. The identified resistant genotypes provide valuable donor parents for breeding BLB-resistant, high-yielding rice cultivars and contribute to sustainable rice production and regional food security.

Response of tropical maize inbred lines to maize streak virus and major agronomic traits

Maize streak virus (MSV) is a major constraint on maize production in the dry and hot tropics, where susceptible cultivars suffer complete yield loss. The objective of this study was to assess the response of tropical-environment-adapted maize inbred lines for MSV resistance and major agronomic traits to identify parental lines for resistance breeding. Seventy-four inbred lines, including six controls, were evaluated under artificial MSV inoculation over two seasons using an 8 × 10 alpha lattice design. A significant variability (P ≤ 0.05) was detected among genotypes for MSV resistance and yield components. Area under the disease progress curve (AUDPC) ranged from 0.00 to 240.6, disease incidence from 0 to 100%, and grain yield from 0.54 to 4.99 t ha⁻¹. Genotype-by-season interactions were significant for disease incidence and yield-related traits, with most traits showing moderate to high heritability. MSV disease parameters were negatively correlated with grain yield and agronomic traits. Elite parental lines MM05, MM17, MM19, and MM25 were identified as valuable donor parents combining MSV resistance with superior grain yield and favourable agronomic performance. Lines MM10, MM11 and MM72 were identified for hybrid breeding due to their combination of high grain yield and MSV tolerance. Finally, MM36 and MM35 were recognised for their outstanding grain yield performance, attributable to their MSV tolerance. The identified inbred lines provide complementary sources of MSV resistance and represent valuable donor parents for introgression and developing high-yielding MSV-resistant maize hybrids.