Sharma, PushpSonika2021-08-232021-08-232020Sonika (2020). Effect of shading on the performance of Indian mustard (Brassica juncea L. Czern and Coss) genotypes (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810174254The present investigation was carried out to assess the effect of shading on the performance of Brassica juncea genotypes. Shading was done with nets for one month commencing from mid December 2018 – mid January 2019 which cuts 25-30% of natural sunlight. Flower and fruit initiation took more number of days while flowering and fruiting duration were reduced with shading. Differential behaviour with shading was reported for reproductive phase and days to maturity. PHR-126 took maximum days for flowering and siliqua initiation, PBR-396 for flowering completion and duration, PBR-561 for siliquing completion and duration. Reproductive phase was shortened by 2.3 days whereas days to maturity were comparable under control and shaded treatments. Chl a (23.8%), carotenoids (19.1%) and SPAD (8.5%) were significantly reduced after 10 days of shading and 31.5%, 27.9% and 6.7% after 30 days of imposed low light stress. However, chlorophyll b exhibited an increase of 16.7% and 37.5%. The photochemical efficiency of PSII was reduced by 2.8% under shade. Leaf traits like, leaf area, SLA, SLW, LWR and RWC declined under shade while RSD and WSD increased at both the studied stages. Leaf and stem anatomy was affected by low light stress as the thickness of tissues was reduced in comparison to control in all the studied genotypes. Kranti, PBR-450, PBR-396 and PBR-464 were registered for higher anatomical characteristics with minimum decline under low light stress as compared to control. Stomatal responsiveness to low light revealed smaller size of stomata with lower stomatal frequency and index on both the abaxial and adaxial leaf surface as compared to control. Antioxidative enzymes and MDA content increased whereas sugars and protein content decreased with shading assayed at two stages. Low light stress had a profound effect on growth parameters, yield components and seed yield in studied genotypes with a minimum reduction of 1.1% for plant height and 1.8% for primary branches in Varuna, 0.5% for length of main raceme in PBR-396 whereas 2.1% for secondary branches in PBR-561. PBR-396 suffered lesser reduction in seed yield followed by Kranti accompanied by lesser decline in the morphophysiological traits and increased antioxidative enzymes. Seed yield had positive association with phenological traits except flowering duration under low light stress. Stomatal length and size were significantly associated with seed yield under both stressed and non-stressed condition. Kranti, PBR-396 and PBR-464 were promising cultivars under low light stress with seed yield reduction of ≤ 20%, SSI (≤1.0), STI (≥0.5) and YSI (≥0.70).EnglishThesis