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

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.

Characterisation of advanced breeding lines for bacterial leaf blight resistance by morpho-molecular screening in rice (Oryza sativa L.)

Sixty advanced breeding lines of rice were evaluated for resistance to bacterial leaf blight (BLB) both phenotypically and genotypically at Regional Agricultural Research Station (RARS), Maruteru, Andhra Pradesh, India during kharif, 2023. Phenotypic screening was performed following the International Rice Research Institute (IRRI), standard evaluation system (SES) scale. Among the sixty entries, seven genotypes, 251-3-3-2, MS-1, NLR-163, NLR-164, NLR-945, CM-469 and BM-587, exhibited a highly resistant (HR) reaction with a score of 1, comparable to the resistant check RP Bio-226. Twenty-two lines expressed BLB severity of 13–25 % (score 5) and were categorised as moderately resistant (MR). Molecular profiling using gene-specific simple sequence repeats (SSR) markers revealed significant variation in resistance genedistribution. The presence of xa5, xa13, Xa21, Xa4 and Xa10 was detected in 9, 4, 23, 44 and 20 lines respectively. Two-gene combinations were identified in 20 genotypes, whereas 11 genotypes possessed three-gene combinations, highlighting the effectiveness of gene stacking for broad-spectrum BLB resistance. Notably, lines 251-3-3-2, MS-1, NLR-164, NLR-945 and BM-587 exhibited congruence between phenotypic resistance (score 1) and the presence of multiple resistance genes, indicating their potential as elite donors for BLB resistance introgression. Yield performance coupled with gene pyramiding further strengthened the value of several genotypes. The genotypes VP-R-157 (Xa4+xa13) recorded 22.3 g/plant, BM-588 (xa5+Xa21) yielded 21.2 g/plant, while CM-467 (Xa4+xa5+Xa10+Xa21) produced 25.1 g/plant. The genotypes CM-470, CM-446 and CM-449 yielded 26.3 g, 21.0 g and 21.5 g/plant respectively, each carrying the Xa4+xa5 gene combination. These genotypes hold substantial promise for direct varietal release or utilisation in hybridisation programs aimed at developing high-yielding, BLB-resistant rice cultivars.

Identification of Resistance Sources against Yellow Stem Borer (Scirpophaga incertulas Walker) in Rice under Field Conditions

Rice (Oryza sativa L.) is a crucial food crop, but its productivity is greatly affected by insect pests, particularly the yellow stem borer, Scirpophaga incertulas (Walker). This study evaluated rice cultivars for resistance to this pest under natural field conditions during the Rabi 2025-26 season at the Regional Agricultural Research Station (RARS), Warangal, Professor Jayashankar Telangana Agricultural University (PJTAU). Thirty rice cultivars, together with seven resistant and susceptible checks, were evaluated in a randomised block design (RBD) with two replications. Yellow stem borer (YSB) damage was recorded at the vegetative stage at 30 and 50 days after transplanting (DAT) and at the reproductive stage. Based on dead-heart incidence, five cultivars were classified as highly resistant, seven as resistant, ten as moderately resistant, seven as moderately susceptible, and one as susceptible. Based on white-ear incidence, five cultivars were highly resistant, seven were resistant, nine were moderately resistant, seven were moderately susceptible, and two were susceptible. WGL-1957 recorded the lowest dead-heart incidence and the highest grain yield, whereas IET 29877 recorded the lowest white-ear incidence and the second-highest grain yield. These resistant cultivars may serve as donors in breeding programmes for yellow-stem-borer resistance and may support integrated pest management strategies.

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

Sorghum is an important food and fodder crop in Eritrea, where production is constrained by several biotic and abiotic factors, including plant diseases. This study evaluated 23 sorghum accessions and three improved varieties for resistance to naturally occurring diseases under field conditions at Hamelmalo Agricultural College, Keren, using three replications. Genotypes were planted by the single-line method, and disease incidence and severity were assessed at the adult plant stage. Disease severity was rated on a 0–9 scale. Anthracnose, leaf blight, sooty stripe, target leaf spot, zonate leaf spot, and bacterial streak were recorded during the growing season. Disease occurrence and severity differed among the evaluated genotypes. Anthracnose was the most prevalent disease, occurring in 76.92% of entries, followed by leaf blight at 61.54%. Sooty stripe occurred in 23.08% of entries, zonate leaf spot in 11.54%, and target spot and bacterial streak each in 7.69%. Although target spot was less prevalent, relatively high severity was recorded in affected accessions. Anthracnose showed the highest overall severity, particularly in EG795, whereas zonate leaf spot and bacterial streak generally showed low incidence and severity. The variation observed among accessions and improved varieties indicates differential responses to natural disease pressure and identifies materials that warrant further evaluation as potential sources of disease resistance for sorghum improvement under Eritrean conditions.

Evaluation of Rice yellow mottle virus Resistance and its Impact on Agronomic Performance in Aromatic Rice Lines

Rice yellow mottle virus (RYMV) is one of the most destructive viral diseases limiting rice production in Africa. Identifying genotypes that combine resistance with superior agronomic performance is essential for developing improved cultivars. This study evaluated 61 aromatic rice lines and three reference genotypes differing in RYMV resistance under greenhouse conditions using healthy and mechanically inoculated plants. Agronomic and disease-related traits were analysed by two-way analysis of variance (ANOVA), principal component analysis (PCA), hierarchical clustering on principal components (HCPC), and the Multi-trait Genotype–Ideotype Distance Index (MGIDI). RYMV infection significantly affected all measured traits (P < 0.001), reducing grain yield (65.3%), above-ground biomass (23.6%), plant height (13.6%), panicle length (11.2%), panicle number (13.3%), and thousand-grain weight (16.2%), while increasing spikelet sterility by 208.0%. Significant genotype × health interactions revealed contrasting responses among genotypes. PCA explained 59.0% of the total phenotypic variation and showed that yield-related traits were negatively associated with spikelet sterility and disease severity. HCPC grouped the genotypes into four distinct clusters according to their agronomic performance and disease response. MGIDI identified ten superior genotypes (Remar2, Remar4, Remar11, Remar13, Remar28, RemarGT, K20-26, K20-Germ13, Basmati370, and the highly resistant control TOG5681) that combined high yield potential with reduced disease impact. These genotypes constitute valuable genetic resources for breeding high-yielding, RYMV-resistant aromatic rice cultivars.

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