PhD Thesis
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Item Response of cucumber (Cucumis melo L.) to drip irrigation under varying levels of nitrogen and potash(Department of Agronomy, College of Agriculture, Vellayani, 1997) Lakshmi, S; Sasidhar, V KItem Ecofriendly production of slicing cucumber (cucumis sativus L) through organic sources(Department of Agronomy, College of Agriculture, Vellayani, 2006) Asha K Raj; Lakshmi, SItem Development of parthenocarpic gynoecious hybrids in cucumber (Cucumis sativus L.) for protected cultivation(Department of Olericulture, College of Horticulture, Vellanikkara, 2017) Ajay Bhardwaj; Pradeepkumar, TItem Genetic diversity and combining ability in cucumber (Cucumis sativus L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2017) Suma, A; Elsy, C RAssessment of genetic diversity is the key tool in any crop improvement and germplasm management programme. Evaluation of genetic variation will help to provide valuable information about new sources of genes. The studies on combining ability and heterosis can support utilization of promising lines in further crop improvement programmes. Cucumber (Cucumis sativus L. 2n= 2x= 14) is an indigenous vegetable crop of India. Even though rich diversity for cucumber is available in India, studies on genetic diversity of this crop are scanty. Therefore, the present project was proposed to explore genetic diversity in cucumber using morphological and molecular markers and to study combining ability and heterosis in selected genotypes. Morphological characterization of 50 accessions of cucumber revealed presence of significant difference among accessions for majority of vegetative, floral and fruit characters. Mean days to first male and female flower opening was 36 and 43 days respectively. Majority of the accessions possessed elliptical elongated fruits with light green skin colour and white flesh colour. Sixteen accessions exhibited significantly higher fruit length than AAUC-2, the standard check, the maximum being exhibited by IC613472 (20.85 cm). Accessions with oblong ellipsoid fruits possessed higher fruit diameter. Mean fruit weight showed high variability among accessions with a range of 33 g to 343 g. Fourteen accessions exhibited significantly high yield than AAUC-2. Number of fruits per plant, yield per plant, loss of weight during storage and sex ratio showed high values for all the genetic parameters studied. IC613481 was the promising genotype identified in morphological characterization, followed by IC613480. Cluster analysis grouped accessions into seven distinct clusters based on the level of similarity in quantitative characters. Random grouping of accessions into various clusters indicated absence of parallelism between genetic diversity and geographical diversity. Cluster II and III were the largest clusters, with 14 accessions each and Cluster V and VI, the smallest ones with single accession each. Results of Principal component analysis revealed that first three principal components, with Eigen values more than unity accounted for 85.80 per cent of cumulative variance, contributed by fruit weight, fruit length, fruit diameter and days to first harvest. The diversity analysis of the accessions was done using DIVA-GIS by generating grid maps. The results of the study indicated that highly diverse accessions with respect to the selected characters were sourced from Mizoram, Tripura and West Bengal. Molecular characterization revealed high level of genetic distinctness between genotypes. SSR11742 and AF202378 were found to be highly polymorphic markers, with high polymorphism information content and number of polymorphic bands. In-depth evaluation of selected 22 genotypes revealed significant difference for all fruit characters except days to last harvest and harvest duration and further revealed the superiority of IC613480. Evaluation of 15 hybrid combinations developed through half diallel mating design and their parents indicated presence of significant difference among parents and hybrids for various characters studied. Among the parental genotypes, IC613480, exhibited significantly high GCA effects for fruit length, number of fruits per plant and yield per plant whereas IC595508A, for fruit weight and loss of weight during storage, and IC613485 for fruit diameter, thus proving to be promising parents for accumulating genes for these characters. The hybrids, IC613480 x IC595508A and IC613480 x IC613471 showed significant SCA effects for yield per plant and sex ratio. IC613480 x IC613471, IC613480 x IC595508A and IC613471 x IC595508A were exhibiting significantly high relative heterosis, heterobeltiosis and standard heterosis for number of fruits per plant and yield per plant. IC613480 and IC613485 were the most promising genotypes identified from the study whereas IC613480 x IC613471 was the most promising hybrid based on SCA effects, heterosis, per se performance on yield contributing characters and organoleptic qualities. This hybrid showed high fruit length (17.01 cm), yield per plant (2163.45 g), number of fruits per plant (11.43) and sex ratio (0.11). IC613480 x IC613476 and IC613485 x IC595508A were the other promising hybrids.Item Nutrient interactions in soil test crop response studies on cucumber ( Cucumis sativus L) in the laterite soils of Kerala.(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 2011) Sajnanath, K; Hassan, M AA comprehensive approach has to be adopted for efficient fertilizer use, incorporating soil test, field research and economic evaluation of the results for providing a scientific basis for the process of enhancing and sustaining food production as well as soil productivity with minimum environmental degradation, it needs more. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop. In Kerala, many studies have been conducted to get a fertilizer prescription equation for targeted yield in various crops like rice, banana etc. A programme was formulated to investigate the nutrient interaction in soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of Kerala. In this, the field works were conducted as per the pattern of soil test crop response correlation studies. A gradient crop experiment was conducted in the experimental field of AICRP on STCR using maize. The purpose is to create a fertility gradient in the field by applying different doses of fertilizers. The area was divided into three strips and the doses of nutrients were applied as per STCR pattern of fertilization for maize. The crop was harvested and the plant samples were taken for analysis. The pre and post experimental soil samples were analysed. It was found that fertility gradients were developed in the field. Using the data on dry matter production in various strips, the nutrient uptake was also determined. A test crop experiment was designed in the same field where the gradient crop was raised. There were 24 treatments with three control plots. The treatments included four levels of nutrients and three levels of farm yard manure. The crop, cucumber (Var.: AAUC-2), popularly known as salad cucumber, was raised and managed as per package of practices of KAU. The soil samples were collected before, at flowering and harvest stages during the experiment. The plant samples were collected at flowering and harvesting stages. The total dry matter production and yield were taken treatment wise at the harvest. The soil samples were analysed for various chemical parameters. The data on yield, uptake of nutrients, nutrient status, nutrient requirement, quantity of farm yard manure applied were used for formulating the fertilizer prescription equations for cucumber. Using these equations, the quantity of fertilizers to be used to get a target of yield can be calculated if the available nutrient status is known. The equations thus developed were verified in farmers' field at four locations; Pallikandam, Maraikkal, Ayiloor and Vithanassery. The fields were laid out with five treatments and four replications. The treatments were (i) farmers' practice (ii) KAU package, (iii) soil testing laboratory method, (iv) STCR method with a target of 30 t ha-I and (v) STCR method with a target of 35 t ha-I. The soil samples were analysed before raising the crop and the quantities of fertilizers to be applied were computed for various treatments. The plant and soil samples at flowering and harvest stages were analysed for pH, EC, CEC, Organic Carbon, available N, P, K, Ca, Mg, and micronutrients such as Fe, Mn, Cu and Zn. The total dry matter production and yield were taken treatment wise at the harvest. The data were used for- statistical analysis for assessmg direct and indirect effect of nutrients on yield and nutrient interactions. A positive correlation was observed between organic carbon' and soil parameters at flowering stage. At the harvesting stage, there was a positive correlation was found between yield and major nutrients. The interaction between available P in the soil and Nand K in the plant was observed. The availability ofP in plant was negatively correlated with Fe in the soil. The targeted yield equations for cucumber could produce the yields of 30 and 35 t ha-I from the verification experiments conducted at the different locations. The B:C ratio also was higher in the STCR methods over the farmers' practices, blanket recommendations and STL recommendations. The information generated in the project will help in making the soil testing programme scientifically sound in terms of achieving predicted yields, maintaining soil fertility and helping the extension agencies in ensuring balanced fertilizer use according to the soil fertility status and crop requirement.Item Efficacy of Neoseiulus longispinosus (Evans) (Mesostigmata: Phytoseiidae) for the management of Tetranychus urticae Koch (Prostigmata: Tetranychidae) on cucumber under protected cultivation(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 2017) Neena Lenin; Haseena BhaskarA study was undertaken at the Acarology laboratory, Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2013-2016, to investigate the biology, incidence, crop phenology relationship and natural enemies of the two spotted spider mite, Tetranychus urticae Koch infesting cucumber in polyhouse as well as to study the biology, efficacy and prey stage preference of the predator, Neoseiulus ongispinosus (Evans) on T. urticae and standardize the optimum predator: prey ratio of N. longispinosus for biological control of T. urticae in polyhouse. Purposive surveys, conducted in fifteen polyhouses in four districts of Kerala viz., Thrissur, Palakkad, Wayanad and Thiruvananthapuram, revealed the occurrence of four species of tetranychid mites, namely, Tetranychus truncatus Ehara, T. urticae Koch, T. okinawanus Ehara, Eutetranychus orientalis (Klein) and one species of tarsonemid mite, Polyphagotarsonemus latus (Banks) on cucumber. The occurrence of T. truncatus and T. okinawanus is a new report on cucumber in polyhouse. Hence, DNA barcoding was carried out to confirm the species identity of T. truncatus (TOCRF001-15) and T. okinawanus (TOIR001-15). Studies on the relationship of crop stage and mite incidence on cucumber revealed that the population of spider mites was significantly higher during the late fruiting stage of the crop, followed by early vegetative stage. Relatively lower population was recorded at flowering stage and early fruiting stage.Four species of insect predators and six species of mite predators were recorded in association with spider mites on cucumber. The insect predators were Stethorus pauperculus (Weise), Oligota sp., Scolothrips sp. and an unidentified species of Cecidomyiidae. The predatory mite fauna included Agistemus garrulus Chaudhari, Amblyseius paraaerialis (Muma), Cunaxa sp., Cheyletus sp., Neoseiulus longispinosus (Evans) and Tydeus gossabaensis Gupta.Neoseiulus longispinosus was found to be the predominant species of predatory mite on spider mites infesting cucumber. Tetranychus urticae recorded a developmental period of 6.75 days in male and 7.15 days in female. Adult male lived for 8.95 days while mated and unmated female lived for 11.59 days and 13.04 days, respectively. Mated and unmated females recorded a fecundity of 47.91 and 36.08 eggs, respectively. The sex ratio was female biased (1:4.6) in T. urticae. Total developmental period of N. longispinosus was 3.91 and 4.27 days for male and female, respectively. Adult male lived for 19.66 days and the female, for 22.75 days. On an average, a single female laid 31.33 eggs and the progeny consisted of both males and females in the ratio 1:3.31. Parthenogenesis was not observed in N. longispinosus. The adult of N. longispinosus recorded significantly higher predation compared to the nymph. Both nymph and adult, showed preference towards egg compared to active stages of the prey. The time needed to eliminate the available prey population was found to increase with increase in prey density. Studies conducted to identify the optimum predator: prey ratio required for field release of N. longispinosus against T. urticae on cucumber in the laboratory showed that, at ratios of 1:5 and 1:10, the prey population was completely eliminated by tenth day. The prey population recorded in the ratios, 1:20, 1:25 and 1:33 were on par with this. In the polyhouse, the predator: prey ratios of 1:20 and 1:25 were found to significantly reduce the population of T. urticae on cucumber. The present study has revealed the potential of the predatory mite, N. longispinosus as a biocontrol agent of the spider mites. The short life cycle, longer life span of adults, female biased sex ratio and preference for egg stages and above all, the density dependant nature of the prey predator relationship, brought out in the present study could provide a platform for viable biocontrol strategy based on N. longispinosus for management of spider mites under protected cultivation in Kerala.