Kiran RanaSAWRAJ JIT SINGH2024-08-242024-08-242024-06-19https://krishikosh.egranth.ac.in/handle/1/5810213681The present investigation entitled “Studies on underlying mechanisms of hygienic behaviour in honey bee, Apis mellifera L.” was conducted during the year 2022-23 in the Department of Entomology, Dr. YSP University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh and Molecular Laboratory of Division of Plant Protection, Central Potato Research Institute, Shimla, Himachal Pradesh. The hygienic behaviour of 30 A. mellifera colonies was assessed by using two brood killing methods viz. pin-killed brood (PKB) and freeze killed brood (FKB) for three alternate brood cycles in the University Apiary. The results showed that all screened colonies initiated hygienic response within 24h of stimulus in both PKB and FKB methods. Significant variations in hygienic behaviour through PKB assay (57.56-99.33%) and FKB assay (55.33-93.56%) were recorded. The per cent hygienic behaviour in all three time slots (24h, 48 h, 72 h) was recorded significantly maximum during the first brood cycle compared to second and third brood cycles. It was observed that the stimulus for hygienic response of A. mellifera worker in pin killed brood method was faster in comparison to freeze killed brood method. Present studies revealed that hygienic behaviour significantly positively correlated with colony parameters viz. bee strength, brood area, honey stores and pollen area, whereas, a significant negative correlation was found with mite infestation. On the basis of selection index, the superior maternal stock (M-12, M-9, M-18, M-24 and M-25) towards hygienic behaviour were multiplied and evaluated further for hygienic response in subsequent generation (F1). It was observed that the level of hygienic behaviour based on the maternal selection of queen honey bee remained relatively unchanged during the first generation of study. This study is the first of its kind in India to characterize the transcriptomic basis of the differential performance of hygienic behaviour of the honey bee (A. mellifera). Out of 174 differentially expressed genes (DEGs), transcriptomic profiling revealed 130 upregulated, while 44 DEGs were downregulated in honeybees. Hygienic behaviour was found to rely on a limited set of genes. The immune-related genes (LOC100578745, LOC406142 and LOC406144) encoded for antimicrobial peptides (Hymenoptaecin and Abaecin) were more likely to be involved in the hygienic behaviour. These genes represent the overall health of the bees and further require functional validation. Further, no pathogenic bacterial isolates were found in hygienic colonies, whereas, in non-hygienic colonies, 64% of the bacterial isolates were pathogenic and 36% were healthy. Two lactic acid bacterial isolates that have probiotic potential and one actinomycete were identified in hygienic colonies only. The three isolates of pathogenic fungi that are responsible for chalkbrood and stonebrood disease in honey bees were identified in non-hygienic colonies. Pathogenic fungi responsible for stonebrood disease in honeybees were isolated for the first time in India.EnglishThesis