Nirmaljit KaurYadav, Himal2022-07-302022-07-302021Yadav, Himal (2021). Efficacy of Plant Growth Regulators on Fruit Developmental Disorder of Ber cv. Thai Apple (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810185920Studies were carried out to evaluate the “Efficacy of Plant Growth Regulators on Fruit Developmental Disorder of Ber cv. Thai Apple” at the Fruit Research Farm of Department of Fruit Science and laboratories of Department of Botany, Punjab Agricultural University, Ludhiana during the years 2019-20. Two foliar applications of NAA (10ppm and 20ppm), GA3 (10ppm and 20ppm) and CPPU (5 ppm and 10 ppm), first during 3rd week of October and second one month after the first application were given to the ber cultivars Thai apple and Umran, keeping unsprayed trees as control. The developmental studies were made at periodic interval, i.e. 15 DAFS till 180 DAFS stage for Umran and 30 DAFS till 105 DAFS for Thai Apple. At all the stages of development, the fruit weight, length, breadth and pulp weight was maximum with the application of 20 ppm NAA which was statistically higher than the control fruits in ber cv. Thai Apple. While in Umran, maximum fruit weight, length, breadth and pulp weight was attained with 20 ppm GA3. The stone weight and size increased from the initial stage till 70 DAFS and then decreased till maturity due to the developmental disorder in untreated trees of Thai Apple. The maximum stone weight, stone length and breadth was recorded with NAA (20 ppm) which was statistically higher than the control in ber cv. Thai Apple. While in Umran, maximum stone length, breadth and weight was observed with 20 ppm GA3. The ber cv. Umran fruit does not have the development disorder in the form of pit splitting, hence it was used as a check variety to compare the differences with ber cv Thai Apple which has pit split disorder. There was 96.66% pit splitting in fruits of untreated trees of Thai Apple, with maximum reduction in splitting with NAA (20 ppm) followed by GA3 (20 ppm). There were large irregular shaped hollow cavities in the mesocarp of fruits of untreated trees of Thai Apple, while no such hollow cavities were seen in the foliar treated fruits of Thai Apple. Therefore two foliar applications of 20 ppm NAA, first during the 3rd week of October i.e., at peak flowering stage followed by second spray after one month resulted in reduction of pit splitting to 30 per cent against untreated control in ber cv. Thai Apple which is attributed to the cell enlargement caused by the synthetic auxin NAAEnglishThesis