Prabhu Narayan Meena

Aim: To assess the dieback disease severity in Kinnow mandarin (Citrus reticulata Blanco) and to understand the role of weather variables on dieback. Methodology: Disease severity was recorded in the fixed orchards of the five randomly selected plants. The scoring was done on the infected twigs and branches per plant. AUDPC was determined based on the data recorded on different days. Correlation was performed to find out the effect of different weather factors on the severity of dieback. Results: The initial dieback disease symptoms were observed in the 11th SMW, which reached at peak (20.73%) in the 27th SMW. The studies revealed a strong positive correlation between minimum temperature and dieback severity and a moderate positive correlation with the maximum temperature (“r”=0.846, p<0.01 & 0.571, p<0.05), while the wind speed showed a moderate positive correlation (“r”=0.599, p<0.01) with dieback severity. Further, multiple regression predicts dieback severity based on weather conditions, with minimum temperature (X2) showing a particularly strong influence and explaining 72 percent of disease severity variability. Interpretation: The information from this study can be utilized to provide protective advisory services to farmers and to develop integrated disease management strategies for the timely management of dieback disease. Key words: AUDPC, Citrus reticulata, Dieback disease, Kinnow mandarin, Weather factors

Stem rot of groundnut (Arachis hypogaea L.) caused by Scelrotium rolfsii is the main threat to groundnut production, causing significant economic losses. The present study aims to provide an overview of the potentiality of Trichoderma viride (Tv), Trichoderma harzianum (Th), Pseudomonas fluorescens (Pf), and Bacillus subtilis (Bs), applied either individually or in mixed combination, against Sclerotium rolfsii (isolate SrBKN). The treatment with T. harzianum and P. fluorescens resulted in the highest mycelial growth inhibition (79.61, 83.51, and 86.77%), followed by T. viride and P. fluorescens (75.74, 79.63, and 83.14%). Under in vitro conditions, the combination of bio-agents at 5% culture filtrate proved to be superior against the test pathogen. Seed treatment and soil application of T. harzianum and Pf at 10 (5 + 5) g kg⁻¹ + 10 (5 + 5) kg ha⁻¹, followed by seed treatment and soil application of T. viride and Pf at 10 (5 + 5) g kg⁻¹ + 10 (5 + 5) kg ha⁻¹, resulted in the lowest disease incidence (7.40 and 8.0%), highest disease control (69.37 and 66.88%), maximum dry weight (151 and 147 g plant⁻¹), highest increase in dry weight (75.58 and 70.93), highest pod yield (2665 and 2498 kg ha⁻¹), and highest increase in pod yield (96.38 and 84.08%) under in vivo conditions. We present an effective bio-control-based management module from the lab to the field for the successful control of groundnut stem rot caused by S. rolfsii. Based on the results, it is concluded that the dual formulation of T. harzianum and P. fluorescens, followed by T. viride and P. fluorescens, were the most effective BCAs in suppressing the S. rolfsii. Therefore, an integrated disease management module with these BCAs needs to be developed and validated with a farmers’ participatory mode under field conditions.

Kinnow mandarin (Citrus reticulate Blanco) is one of the valuable fruit crops that mostly grown in North Indian states of India due to its high-quality juice content and resistant to decline. Pests psylla, whitefly, sooty mold and dieback damage new flush and fruits of mandarin are the most important biotic constraints affecting yield to the tune of 70 per cent. To manage these menace, farmers often resort to cocktail of pesticides without achieving the desired result. Hence, area wide implementation of Integrated Pest Management (IPM) in kinnow mandarin was implemented during 2021, 2022 and 2023 covering 5 villagesat Hisar, Haryana. The lowest average mean population of psylla and whitefly was recorded in IPM plots (4.82±4.69 no.of nymph and adult/10cm shoot and 2.80±1.56 no.of nymph and adult/leaf) compared to FP (6.67±3.15 no.of nymph and adult/10cm shoot and 3.89±1.51 no.of nymph and adult/leaf) and control (7.71±5.98 no.of nymph and adult/10cm shoot and 4.90±2.05 no.of nymph and adult/leaf) plots respectively. Similarly, minimum average mean disease severity of sooty mold and dieback was noticed in IPM plots (7.41±2.18 and 10.01±2.34%) compared to FP (9.31±2.97 and 12.11±2.65%) and untreated control (11.28±4.67 and 13.91±2.79%) plots. Likewise, low rate of Area Under Diseases Progress Curve (AUDPC) of sooty mold and dieback was observed in IPM followed by FP and in control plots. The Pearson correlation matrix reveals intricate relationships among the pests. The highest average fruit yield (t/ha) and B:C ratio was also recorded in IPM (22.46 & 4.34) compared to FP (18.88 & 3.16) and control (7.42 & 1.73). Besides, the IPM strategy has increased economic yield, the net profit by preventing pest resurgence, pesticide resistance, maintaining natural enemy diversity.

Groundnut (Arachis hypogaea L.) is an oilseed crop largely grown throughout the world. Ten isolates of S. rolfsii collected from groundnut grown areas were investigated for their morphological and genetic variability study. Based on morphological variability study, all isolates were divided in six groups based on sclerotia distribution pattern. Isolates produced number of sclerotia in range of 115–375 in light dark brown to dark brown colour while weight of hundred sclerotia and sizes of sclerotia was in range of 85.54–145.13 mg and 0.32–0.68 mm. Genetic diversity was studied through ITS amplification that produced rDNA amplicon size of 650–700 bp which confirmed that all isolates belong to Sclerotium rolfsii. RAPD primers confirmed genetic variation among the isolates. Highest numbers of amplicons (13) were observed in the OPA-9 primer. 102 polymorphic and 3 monomorphic bands were produced by RAPD primers. Isolates SrA-SrH (0.575), SrBKN-SrA (0.384) and SrBKN-SrBKL (0.330) exhibited highest similarity coefficient. Based on dendrogram generated by UPGMA, SrBKN, SrA, SrH, SrJPF, SrJPP and SrT isolates were considered in Group I. SrBKL showed highest (51%) diversity in Group II while Churu (SrC) isolate showed 49% diversity in Group III. Dendrogram and cluster analysis cleared that Group I was more genetically diverse among the isolates. Morphological and molecular diagnosis of the pathogen has a pivotal role in the implementation of chemical (fungicide) and biological (bio-agents) methods.

Groundnut (Arachis hypogaea L.) is an oilseed crop largely grown throughout the world. Ten isolates of S. rolfsii collected from groundnut grown areas were investigated for their morphological and genetic variability study. Morphological variability among the isolates was confirmed based on sclerotia distribution pattern, colours of sclerotia, number of sclerotia produced by isolate, weight of hundred sclerotia and different diameter sizes of sclerotia. Genetic diversity among the isolates was confirmed by using ITS primers that produced rDNA amplicon size ranging from 650-700bp which confirmed that all isolates belong to Sclerotium. RAPD primers confirmed genetic variation among the isolates. Highest numbers of amplicons (13) were observed in the OPA-9 primer. 105 polymorphic and monomorphic bands were produced by RAPD primers. Isolates SrA-SrH (0.575), SrBKN-SrA (0.384) and SrBKN-SrBKL (0.330) exhibited highest similarity coefficient. Based on dendrogram generated by UPGMA, SrBKN, SrA, SrH, SrJPF, SrJPP and SrT isolates were considered in Groups I. SrBKL shows highest (51%) diversity in Group II while Churu (SrC) isolate showed 49% diversity in Group III. Dendrogram and cluster analysis cleared that Group I was more genetically diverse among the isolates. Morphological and molecular diagnosis of the pathogen has a pivotal role in the implementation of chemical (fungicide) and biological (bio-agents) methods. Morphological study and diagnosis of pathogen by ITS and RAPD primers further exploited for genetically diverse strains of S.rolfsii.