KAVITHA, KMADHAVI, M2020-10-222020-10-222019D10,406https://krishikosh.egranth.ac.in/handle/1/5810153609Sorghum, Sorghum bicolor L. Moench is the most important cereal crop grown in India during both Kharif and Rabi seasons for multiple uses as food, feed, fodder and fuel crop. Rice weevil, Sitophilus oryzae L. is the most important insect pest infesting sorghum causing an annual loss of 25 – 40 per cent after six months of storage. Present study was conducted for evaluation of sorghum cultivars against rice weevil to identify resistant genotypes which could be used in longer storage conditions and also utilized for insect resistance breeding programmes. Forty seven sorghum genotypes representing hybrids (8), varieties (28), parental lines (3) and checks (8) were evaluated to identify least susceptible genotypes based on adult emergence, oviposition, mean development period, index of susceptibility, weight loss (per cent), germination (per cent) and biochemical attributes (protein, fat and starch). Based on mean adult emergence, the genotypes namely, N 13 (29.17), N 14 (38.67), 104 B (41.40), NJ 2647 (41.80) and CSV 13 (41.83) were found least susceptible. Considering the adult weevil population and oviposition, the genotypes, viz., N 13, N 14, 104 B, NJ 2647, CSV 13, CSH 15 R, C 43 and CSH 13 were found recording low susceptibility to S. oryzae. Among these genotypes, high protein (14.53 – 12.45 %), fat (3.88 – 3.52 %) and starch (71.85- 70.84 %) were observed in CSH 15R, CSH 13, CSH 25, CSV 13, CSV 18, N 13, N 14, NJ 2647, NTJ 4 and rabi female parental line 104 B recording low oviposition resulting in less weevil population showing the antibiosis mechanism. Rabi female parental line (104 B) has recorded minimum rice weevil population (41.40) with high protein (12.74 %), fat (3.67 %) and starch (71.85 %) contents the storage for a period of 90 days. Maximum mean development period of 48.91 days was observed in 104 B. Least index of susceptibility was recorded in N 13 (6.72) when compared to the genotype, CSH 24MF (19.74). Less weight loss due to weevil infestation was recorded in 104 B (1.07 %) and NJ 2647 (1.07 %). After 60 days of infestation maximum seed germination was observed in the genotype, CSH 13 (78.67 %). Maximum grain hardness was observed in sorghum genotype, NJ 2647 (6.44 kgf/mm2 ) with low weevil population showing antixenosis mechanism. Maximum test weight of 4.05 g was recorded in CSV 18 when compared to other genotypes. Length breadth ratio ranged from 1.06 (CSH 35) to 1.33 (N 13). The grain hardness was significantly negatively correlated with adult emergence (r = -0.468) where seed size played an important role in determining the pest infestation and adult emergence. The protein, fat and starch content in different sorghum genotypes was significantly negatively correlated with adult emergence and oviposition. From the present investigation, the sorghum genotypes, viz., N 13, N 14, 104 B, NJ 2647, CSH 13, CSH 15R, CSV 13, C 43 and NJ 2446 were found promising which could be utilized in rice weevil resistance breeding programme for further evaluation and also safely stored for longer durations.EnglishThesis