Kalita, PrakashKalita, Jiliksweta2024-01-192024-01-192021https://krishikosh.egranth.ac.in/handle/1/5810206410Banana (Musa spp.) is one of the most important commercial fruit crops especially in the tropics and has high consumer demand worldwide. It contains good amount of health benefitting anti-oxidants, minerals and vitamins. Banana is a tropical fruit crop which belongs to the family ‘Musaceae’. It is a mesophytic plant and it’s cultivation is mostly confined between 30N and 30S of the equator with a mean temperature of 27C to 35C. Banana ranks first in production and third in area among fruit crops in India. India is the largest producer of banana in the world with a productivity of 35.8 metric tonnes/ha. Assam has a productivity of 13.9 t/ha (Hazarika et al., 2020). The lower productivity of banana in Assam may be attributed to certain abiotic stresses like moisture deficit, low temperature etc. The banana plant is susceptible to cold and frost if the temperature drops below 15C during the winter months of November and December (Simmon, 1959) and the situation in Assam also resemble this. When fruiting occurs in winter there will be slow development of bunches and the fruit may never fill well enough to become marketable because of the insufficient leaf surface and slow leaf activities (Lomas, 1970). The major effects of cold stress include growth reduction, leaf wilting, chlorosis, inhibition of photosynthetic performance, changes in membrane integrity and loss of cell compartmentation (Bo et al., 2017), impairment of enzymatic activity (Cheng and Song, 2006) and over-accumulation of reactive oxygen species (ROS) which ultimately may cause plant death (Suzuki et al., 2012). Keeping these facts in view, a study was conducted at the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat during the year 2020-2021. Twenty germplasm of banana viz., Sutijahaji(G1),Agnisagar(G2) Grand Naine (G3), Bogimanohar (G4),Amrit Sagar (G5),Digjowa (G6),Chenichampa(G7),Banria (G8),Barjahaji (G9), GobinTulsi (G10), Doodhsagar (G11), Balhakual (G12), Assamese Malbhog (G13), Simolu Manohar (G14), Jatikal (G15), Athiya (G16), Kachkal (G17), Bhimkal (G18), Honda (G19) and Savari (G20)were taken as test material to evaluate their response towards naturally occurring low temperature in Assam. Banana suckers of uniform size arising from the main crop during the month of February were used to grow the ratoon crop. Data on various morpho-physiological parameters were recorded in the months of August, December, January and February when the crop attained the age of 6th, 10th, 11th and 12th month. Low temperature progressively reduced the values of relative leaf water content, chlorophyll content (a,b, total), number of functional leaves, leaf area, stomatal conductance, transpiration rate, photosynthetic rate, quantum efficiency of PSII, days taken for leaf senescense etc. as compared to the August sampling while the lipid peroxidase activity ,intercellularCO2 concentration and days taken for leaf emergence was increased under low temperature. The germplasm Barjahaji (G9) showed higher values with respect to all parameters except lipid peroxidation, intercellularCO2 concentration and days taken for leaf emergence. As compared to August sampling, during winter months the reduction in values of various parameters was comparatively low in the germplasm Barjahaji (G9), Bhimkal (G18), Ahtiya(G16), Simolumanohar (G14) and Bogimanohar (G4). These germplasm were found to be superior in our study in terms of RLWC, Chlorophyll ‘a’, Chlorophyll ‘b’, total chlorophyll, number of functional leaves, leaf area, stomatal conductance, transpiration rate, photosynthetic rate, quantum efficiency of PSII, days taken for leaf senescense, number of hands per bunch, number of fingers per hand, weight of finger, and bunch weight. On the other handthese germplasm showed lower values of lipid peroxidation, intercellular CO2 concentration and days taken for leaf emergence during the winter months (December, January and February). During February, germplasm Barjahaji(G9),Bhimkal(G18),Athiya(G16)showed better recovery in RLWC by 2.62%, 5.11% and 2.63%, respectively, in photosynthetic rate by 7.71%, 7.56% and 2.84% , respectively and in quantum efficiency of PSII by 23.00%, 20.83% and 20.65%, respectively. The germplasm Bogimanohar (G4) also showed recovery in quantum efficiency of PSII by 19.60%. In the present study, the germplasm Barjahaji (G9) (17.68kg Bunch-1) was found to be thehighest yielder followed by Bhimkal (G18) (17.23kg Bunch-1) and Bogimanohar (G4) (17.18kg Bunch-1) whereas, the germplasm Chenichampa (G7) (11.27kgBunch-1) was found to be the lowest performer in this regard.Barjahaji ,Bhimkal and Bogimanohar registered 56.87%, 52.88% and 52.44% higher yield , respectively, over Chenichampa. From the correlation study, it was found that the banana yield was positively and significantly correlated with the parameters viz., number of fingers per hand (r= 0.4405), number of hands per bunch (r= 0.3536) weight of finger (r= 0.7348), number of functional leaves (r= 0.3685), and leaf area (r= 0.3299). From physiological point of view the germplasm Barjahaji(G9), Bhimkal (G18), Ahtiya(G16),Simolumanohar (G14) and Bogimanohar (G4) were found to be tolerant against low temperature as these germplasm have exhibited better values of physiological traits that are known to contribute positively towards growth and development and in majority of the cases towards yield.EnglishThesis