Ram SinghNain, Jitender2016-11-102016-11-102011http://krishikosh.egranth.ac.in/handle/1/84813Twenty five genotypes of okra, Abelmoschus esculentus (L.) Moench were evaluated during crop season 2009-10 and twenty two genotypes were evaluated during crop season 2010-11 for field resistance to two spotted mite Tetranychus urticae Koch. On the basis of observation on incidence of T. urticae, seven genotypes namely, two least susceptible (HB-02-14-1-1 and HB-02-17-1) and two moderately susceptible (HTB-1-17-5 and HRB-107-4-1), two highly susceptible (HBT-6-15-3-7 and BB1) and one popular variety Hisar Unnat were selected for elaborate studies under field and laboratory conditions. During crop season 2009-10 two least susceptible genotypes of okra HB-02-14-1-1 (24.19/cm2)and HB-02-17-1(27.21/cm2) differed significantly (P< 0.05) from highly susceptible genotypes HBT-6-15-3-7 (43.11/cm2) and BB1(42.35/cm2) in respect of mite population. Similar results were obtained during 2010-11. Population of T. urticae was found more on top strata of dorsal surface (30.95/cm2) and ventral surface (55.86/cm2) followed by middle strata on dorsal surface (25.17/cm2) and ventral surface (46.31/cm2) and bottom strata on dorsal surface (15.02/cm2) and ventral surface( 29.75/cm2) of okra plant in 2009-10. Similar trend of population distribution was recorded in season 2010-11. Highly susceptible genotype HBT-6-15-3-7 was more preferred for egg laying (52.61/leaf disc).Whereas least susceptible genotypes HB-02-14-1-1(18.66) and HB-02-17-1(23.24) genotypes supported less number of eggs. Survival of T. urticae was also less on least susceptible genotypes HB-02-14-1-1(13 %) and HB-02-17-1(15 %) in comparison to highly susceptible genotypes HBT-6-15-3-7(73%) and BB1 (57%). Biology of two spotted mite T. urticae was studied on these promising genotypes. Shortest incubation period ( 4.57days), larval period (3.97 days), nymphal period (4.22 days), larval plus nymphal period (8.18 days) and total life period ( 17.85 days) was observed on least susceptible genotypes(HB-02-14-1-1 and HB-02-17-1) and longest incubation period ( 3.16 days), larval period (5.16 days), nymphal period( 4.46 days), larval plus nymphal period (9.48 days) and total life period (21.19 days)was found on highly susceptible genotypes (HBT-6-15-3-7 and BB1), respectively. Shortest oviposition period was observed on HB-02-14-1-1(5.66 days) and longest on BB1 (8.61 days) and shortest longevity of female was found on okra genotype HB-02-14-1-1(8.28 days) and longest on HBT-6-15-3-7(11.71days). Female to male ratio was found maximum on moderately susceptible genotype of okra namely HRB-107-4-1(4.3:1) and minimum on least susceptible genotypes HB-02-14-1-1(2.4:1). This indicated antibiosis mechanism of resistance. Correlation of length of trichome with larval plus nymphal survival (r= 0.82) was positively significant (P<0.05). Sugar and phosphorus were positively correlated with larval period (r= 0.71 and r= 0.73) and nymphal period (r= 0.74 and r= 0.72) but negatively correlated with larval plus nymphal survival (r= -0.81 and r= -0.91). Potassium showed significantly positive correlation with nymphal period (r= 0.94) and negative correlation with larval plus nymphal survival (r= -0.91). Antinutritional compounds tannin and phenols showed positive correlation with larval period (r= 0.88 and r= 0.81) and nymphal period (r= 0.76and r= 0.78), but negatively significant (P<0.05) correlation with larval plus nymphal survival (r= -0.78 and r= -0.79), respectively. Only relative humidity (r= 0.77) had significantly (P<0.05) positive correlation with mean population of T. urticae in crop season during 2009-10. Other weather parameters did not show any correlation with T. urticae population during crop season 2009-10 and 2010-11.enGenotypes, Vegetables, Tetranychus urticae, Biological phenomena, Planting, sexual reproduction, Crops, Eggs, Seasons, DiseasesThesis