MSc

The present study entitled “ Assessment of water stress tolerance in selectively fertilized coconut (cocos nucifera L.) hybrids” was carried out in the department of objective was to access the physiological and molecular basis of water stress tolerance in selectively fertilized coconut hybrids and to screen coconut genotypes for water stress tolerance through water potential for pollen germination.
The study was conducted as two experiments. In the first experiment, Nine year old field grown coconut palms of the following varieties, Kerasfree (WCT * MYD) selectively fertilized, Keraganga (WCT * GB) (WCT * MYD) selectively fertilized, Keraganga (WCT * GB) selectively fertilized, Kerasfree (WCT * MYD), Keraganga (WCT * GB) and west coast k Tall (WCT) planted at regional agricultural research station, Pilicode, Kasergod were used as the experimental material for this study. The experiment was laid out in Randomized Block Design (RBD) with four replications during February 2018-April-2018. Water stress was imposed by withdrawing irrigation for three months and physiological and biochemical observations were record at monthly interval
The selective fertilization technique is Characterized by artificially imposing the desired selsctive pressure during pollen germination, so that the pollen grains which are tolerant to selection pressure only during pollen germination, so that the pollen grains which are tolerant to selection pressure only will germinate and fertilize the ovule.
On physiological analysis the selectively fertilized Kerasree and Keraganga showed higher stomatal conductance, transpiration rate, photosynthetic rate, relative water content and cell membrane stability index than normal Kerasree and Keraganga hybrids. Epicuticular wax deposition was highest in Kerasree S F (2.57 mg/10cm2). Among all genotypes lowest carbonisotop discrimination value was observed in Kerasree S.F (19.90%) followed by WCT (20.08%) which is an indication of high water use efficeiency. Leaf temperature was also lowest in Kerasree S.F(27.77C).
The biochemical parameters like total soluble proteins, proline content and anti oxidentenzymes viz SOD and peroxidase activities were maximum in selectively fertilized Kerasree. The selectively fertilized coconut hybrids recorded the lowest membrane damage (lipid peroxidation value) under water stress condition compared to normal hybrids. Kerasree S F retained maximum chlorophyll contnt (1.26 mgg) followedby Keraganga S F (0.95mgg)
In SDS – PAGE analysis a specific protein of around 66-70 kDa was expressed in WCT. Molecular analysis was done using drought related four SSR primers viz CnCirE2, CnCirE10, CnCirE12, and CnCirH4 were evaluated and polymorphism was observed for three markers.
The second experiment was conducted to screen 30 coconut genotypes for water stress tolerance through critical water potential for pollen germination. Significant genetic variation in critical water potential for pollen germination was observed. Critical water potential varied from -0.2MPa to 0.5MPa.
The study revealed that selectively fertilized hybrids were more drought tolerant compared to normal coconut hybrids. By selective fertilization technique it may be possible to add water stress tolerance trait to high yielding coconut hybrids.