University of Agricultural Sciences, Raichur

ABSTRACT Powdery mildew is a serious disease of sunflower in tropical and subtropical regions. A total of 221 genotypes—comprising Cytoplasmic Male Sterility lines, restorers, inbreds and stable interspecific recombinant inbred lines (IRILs)—were screened for field resistance to the disease. The IRILs, developed from a cross between the susceptible prebred line PS‐2023 and a resistant accession (PRA‐1823) of diploid annual species Helianthus praecox , displayed distinct and contrasting reactions to powdery mildew during the initial field screenings. Phenotypically superior susceptible and resistant IRILs, which also possessed multiple desirable agronomic traits, were further evaluated with artificial inoculation in greenhouse and multilocation field trials, along with established resistant and susceptible checks. Results indicated that the line PMS‐27 (PM‐1), previously classified as susceptible, consistently exhibited susceptibility across all locations. The percent disease index (PDI) of PMS‐27 ranged from 14.3% to 85.6% within 15 days post‐inoculation (dpi) with a conidial suspension, and disease progression continued, reaching a score of 9 by 45 dpi. In contrast, two resistant IRILs (PMR‐16 and PMR‐27) initially recorded low average PDIs of 4.8% and 5.3%, respectively, with no disease development further; these lines were scored as 0/1 at 45 dpi across all test locations. Previous studies from the authors' laboratory confirmed the presence of a dominant resistance gene in H. praecox and established the role of MLO (Mildew Locus O) genes in conferring susceptibility. The resistant and susceptible IRILs identified in this study therefore offer significant potential for advancing research on host–pathogen interactions and for developing durable powdery mildew resistance in sunflower.

In the present study, 214 rice germplasm accessions were evaluated along with four check varieties using an augmented randomized complete block design to study the genetic variability, correlation, path analysis and genetic diversity studies for yield and yield attributing traits. Analysis of variance revealed significant differences among the germplasm for different traits. The high genotypic coefficients of variation, and phenotypic coefficients of variation were observed for biological yield (46.86%, 46.92%), harvest index (36.44%, 36.47%), High broad-sense heritability across all studied traits, high estimates of genetic advance in percent of the mean were observed for many traits except days to maturity and days to 50% flowering. biological yield, harvest index, number of spikelets per panicle, exhibit significant positive correlation with grain yield. Principal component analysis revealed that the first five principal components with eigenvalues >1 explained 64.34% of the total variation. Cluster analysis grouped the genotypes into five distinct clusters, with the maximum inter-cluster distance observed between Cluster I and Cluster V (6.00), indicating the highest genetic divergence between these clusters. Overall, the substantial genetic variability and divergence observed among the rice germplasm accessions provide ample of scope for the selection and hybridization of genetically diverse parents to develop high-yielding rice varieties.

The brown planthopper Nilaparvata lugens (Stal) is a major pest of rice, causes high economic losses by reducing yield. In India, most populations of N. lugens could not be managed probably due to high genetic variation in populations. Hence, the study was conducted to investigate the genetic diversity of N. lugens in south Indian populations. A total of eight populations were collected from Karnataka, Telangana, Andhra Pradesh, Tamil Nadu and Kerala. DNA extraction, PCR amplification and sequencing done using the COI gene primer. The study identified eight haplotypes having high haplotype diversity and nucleotide diversity along with two polymorphic sites and two mutations. Neutrality tests (Tajima’s D, Fu’s Fs) indicated no significant deviation from neutrality. The high genetic diversity highlights the adaptive potential of N. lugens to environmental shifts, host resistance and management practices. Such adaptability makes N. lugens a serious threat to rice cultivation, as it can overcome existing control measures. The findings emphasize the importance of continuous molecular monitoring to track evolutionary dynamics in developing effective and sustainable pest management strategies.

A field experiment was conducted at ICAR-KVK, Kalaburagi-I during Kharif season 2025 with an objective to study the “Evaluation of Bio-efficacy of the Triple Super Phosphate for cropping systems in Kalaburagi location over conventional Phosphorous sources in Pigeonpea”. The soil was clayey in texture and experiment was laid out in randomized block design with three replications and comprised of 12 treatments. Growth parameters at harvest and yield parameters viz plant height, number of primary branches and secondary branches and yield parameters viz grain yield, stalk yield and husk yield were recorded. Among the treatments, application of recommended nitrogen and phosphorus through triple super phosphate (TSP) along with FYM (10 t ha-1) recorded significantly higher plant height (160.52 cm), primary branches (14.08 plant-1) and secondary branches (21.49 plant-1) also with higher grain yield (1160 kg ha-1), stalk yield (2768 kg ha-1) and husk yield (268 kg ha-1). However, the results for the treatment with recommended N (urea) and P (TSP) recorded plant height (158.24 cm), primary branches (12.71 plant-1) and secondary branches (19.88 plant-1) also with grain yield (1000 kg ha-1), stalk yield (2307 kg ha-1) and husk yield (196 kg ha-1) were statistically found on par with the previous treatment mentioned. The results indicated that integrated nutrient management involving TSP and organic sources enhances growth and yield through improved nutrient availability and uptake.

Xanthomonas oryzae pv. oryzae, the pathogen causing bacterial blight of rice, is an age old disease that has caused serious threat to the crop. Hence, this experiment was conducted using different commercially available antibiotics, antibacterial chemicals, bioagents and organic extracts to test their efficacy against the pathogen and devise management strategies against the disease. In vitro efficacy studies revealed that, among the antibiotics, 2-bromo 2-nitro propane 1,3-diol (Bacterinashak) (8.33 mm), an immunomodulator and among the antibacterial chemicals, copper oxychloride 50% WP (Blitox-50) (9.08 mm) showed a good inhibition of the bacterium and were statistically better than other treatments. Pseudomonas fluorescens (23.67 mm) among the bioagents and sea weed extract (Humicil) (6.50 mm) among the tested organic extracts were found to be significantly superior in inhibiting the pathogen. In summary, all the treatments exhibited a strong inhibition over the control and these could be used as potential strategies to manage the disease under field conditions.