PG Thesis
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Item Economic analysis of production, marketing and price behaviour of cocoa in Kerala(Department of Agricultural Economics, College of Agriculture,Vellanikkara, 2022) Anila, V S; Anil KuruvilaItem Multiphase analysis of cocoa production in Kerala(Department of Agricultural Statistics, College of Horticulture, Vellanikkara, 2020) Shivakumar, M; Ajitha, T KCocoa (Theobroma cacao L.) is a very important crop as it provides food, income, employment and resources for poverty reduction. It ensures livelihood for millions of small holder farmers and offers raw material for the multibillion global chocolate industries. Despite the fact that Kerala has enormous potential in terms of suitable agricultural land, cocoa has failed to become a significant crop. As its domestic production is not sufficient to meet the increased demand, the industry has to resort to substantial imports. So, a comprehensive study titled “Multiphase analysis of cocoa production in Kerala” has been made on different aspects of cocoa cultivation, management practices, production and the constraints faced by actual growers. The trend analysis and forecasting of yearly area, production and productivity of cocoa in Kerala using advanced time series models employed on the data for the period from 1980-2017 revealed a distinct quadratic trend for the area under cocoa, having an increasing trend now and more or less linear stochastic trends for production and productivity. The Holt’s exponential smoothing model was identified as the best to predict yearly area under cocoa with an adjusted R2 equal to 0.94. The yearly production of cocoa could be well modelled by ARIMA (0,1,1) with an adjusted R2 = 0.72. By incorporating area under cocoa as an independent variable, ARIMAX (0,1,0) model could improve the R2 to 0.84 to predict the yearly production of cocoa. The productivity of cocoa seemed to be constant for several years (0.45tonnes/ha) which was well predicted through the simple exponential smoothing model with an adjusted R2 = 0.84. Evaluation of the performance of 100 selected cocoa hybrids in the Cocoa Research Centre, College of Horticulture, KAU, Vellanikkara showed that the peak average monthly yield was in the month of November (18.14pods) followed by the yield in October (18.04) and December (14.56). A pattern of biennial tendency persisted for the yearly yields of the hybrids. The results of General linear model repeated measures ANOVA highlighted the existence of a significant Time x Factor interaction with a partial eta squared equal to 0.14 where factor denotes different subgroups of cocoa hybrids with homogeneous yield. After the first harvest, the peak average yield was noticed during the fifth year irrespective of different low and high yielding groups. The income from cocoa farming depends on healthy pods harvested. So, an attempt was also made to account for the frequency of number of infected pods from each tree and it could be well demonstrated by geometric distribution which is a special case of Negative binomial distribution. Owing to the fact that the infected pods might be the outcome of external factors like weather variables, the influence of those factors with cocoa yield was also investigated. A stepwise regression of yield on previous five month’s accumulated weather variables resulted in a parsimonious prediction equation with total number of rainy days as the single regressor which could explain 66% of the variation in yield. The adjusted R2 could be enhanced to 69% by incorporating maximum temperature as the second most important regressor. The vide variation realised in the average monthly yield of cocoa hybrids could be well captured through SARIMA (1,0,0) (1,1,0)12 model with an adjusted R2 = 0.92. An empirical analysis to identify the factors perceived by farmers to influence their cocoa production and ultimately their income was performed taking a total sample of 100 farmers from Veliyamattom Panchayat of Idukky district and Iritty Panchayat of Kannur district. From a path analysis through structural equation modelling several linear regression equations could be generated simultaneously leading to prediction equations for cocoa yield and income. The final model iterated resulted in goodness of fit measures viz; comparative fit index = 0.96 and Tucker Lewis index = 0.94. Price of cocoa turned out to be the most prominent factor which contributed to the income of a cocoa farmer highlighting the importance of fixing the marketing price of cocoa. Second factor was yield per tree which was the outcome of good quality seedlings, efficient cultivation practices, plant protection and disease management measures, protection from rodent attacks etc. Importance of access to credit which would help to overcome the problems of lack of capital was emphasised. Financial problems such as inability to get assistance from financial institutions, lack of proper marketing facilities including drying and fermentation facilities of cocoa beans also were noticed. Probit analysis identified the factors viz; age of the farmers, land holding size, experience in cocoa cultivation, membership in organisations like Krishibhavan, farmer’s club, Cooperative society, Banks, SHGs etc. and frequency of contact with extension personnel to be significant for decision making to implement plant protection measures which were inevitable for successful crop management and ultimately leading to the net income of farmers. The yield gap analysis revealed that as against the potential yield (dry bean weight) of 4kg/tree/year, the national average yield from cocoa farmers was only 2.5 kg/tree/year resulting in a yield gap of 37.5% which need adequate attention.Item Preliminary evaluation of double cross hybrids for yield and vascular streak dieback (VSD) disease resistance in cocoa (Theobroma cacao L.)(Deapartment of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Alfiya, A R; Minimol, J SCocoa is highly influenced by the climate change and growing environment, necessitating a long term and dynamic breeding programme. Even though the breeding programmes primarily focus on the development of high yielding varieties, outbreak of new pests and pathogens shift the priority to the development of resistant varieties. Vascular Streak Dieback disease (VSD) caused by Ceratobasidium theobromae (Samuels et al., 2012), pose a great threat to cocoa crop, causing complete defoliation and eventual death (Abraham et al., 2002). Even the high volume spray of chemicals was ineffective in disease control (Prior, 2007), and the only way to tackle it is to breed resistant varieties. Resistance breeding may result in yield reduction (Xu et al., 2017) however, breeding for double cross hybrids can overcome this situation (Gallais and Guy, 1971). Average yield superiority of the double cross hybrids over the F1 hybrids has been shown by many scientists (Sriani et al., 2003; Ghanwat et al., 2016). Twenty double cross hybrids, bred for vascular streak dieback disease and planted during 2017, were used for the present study. Morphological characterization of the hybrids was carried out based on the quantitative and qualitative characters. Thirteen pod characters, twelve floral characters, six bean characters and flush colour of the leaves were studied. Except colour of the petal and number of the ridges and furrows, all other characters have expressed high variability among the double cross hybrids. The double cross hybrids have exhibited significant difference for fat and polyphenol content. All the twenty double cross hybrids were screened and scored for the VSD resistance in the field condition, using the score chart (Abraham et al., 2000). Based on the disease intensity, they were classified into eleven resistant and nine partially resistant.Item Candidate gene analysis on self incompatibility in cocoa (Theobroma cacao L.)(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2020) Sharath Prabhakaran; Minimol, J SCocoa is a perennial tree with typical plant habit and specific fruit characteristics. It is highly influenced by climate changes and growing environment, which makes long term and dynamic breeding programme necessary (Malhotra and Hubali, 2016). Physiological and genetic investigations have unveiled that the yield potential of cocoa is not yet fully exploited (Bertus, 2004). Demand for chocolate is increasing at a rate of 15-20 per cent every year. To meet this demand, more area has to be brought under cocoa cultivation using improved genetic stock. Development of superior hybrids have significantly contributed to improve the cocoa productivity in many countries (Kennedy et al., 1987; Dias et al., 2003). Cocoa hybrids showed wide adaptability, low environmental interaction and improved yield, when compared to traditional cultivars (Dias et al., 2003). Self-incompatibility is a pollination control mechanism which prevents self-fertilization. Hence, this can be exploited in hybrid production by avoiding emasculation, which is a cumbersome process (Minimol and Amma, 2013). Moreover, emasculation will damage the flowers leading to reduced success rate. Conventionally, the self-incompatibility is measured by selfing 100 flowers per tree. If no fruit set is observed, then the plant is classified as self-incompatible (Mallika et al., 2006). This is a tedious process which will reduce the pace of breeding programme. In various other crops, many candidate genes have been reported for self-incompatibility (McCormick, 1998). However, the actual sequence variations in candidate genes are yet to be studied in cocoa. Identification of appropriate genes involved in self-incompatibility will help to identify its mechanism at an early stage and quicken the breeding programme. In this study, 10 candidate genes viz. Serine Receptor Kinase (SRK), S Locus Glycoprotein (SLG), Barely Any Meristem 1 (BAM1), Barely Any Meristem 2 (BAM2), COMPASS-like H3K4 histone methylase component (WDR5a), Voltage-dependent L-type calcium channel subunit (alpha-1F), Gamete Expressed Protein (GEX1), Zinc finger AN1 domain-containing stress-associated protein 12 (PMZ), ARM repeat-containing protein (ARC1) and Hapless 2 (McCormic, 1998; Lanaud et al., 2017) were characterized. These genes were reported to have involved in self-incompatibility in other crops. Genomic nucleotide sequences from reported host plant species were retrieved from the NCBI GenBank database. Using this information, homologous gene sequences of the candidate genes in cocoa were retrieved. Primer sets targeting major exonic regions for each of the candidate genes were designed. Genomic DNA was isolated from self-compatible genotype (GVI-167 x GIV-18.5) and self-incompatible genotype (IMC20) and the candidate genes were PCR amplified. Amplified products were sequenced and the variations in the sequences between the self-incompatible and self-compatible genotypes were analyzed, in comparison with a self-compatible reference genome (Argout et al., 2010). Between the self-incompatible and self-compatible genotypes, a total of 31 different SNPs were discovered among the genes studied. All of them were found to be heterozygous at the locus either in self-compatible or self-incompatible genotype. The maximum number of SNPs, a total of 12, were found in GEX1 gene. Four SNPs each were found in genes SRK, BAM2, WDR5a and Alpha1F whereas three SNPs were found in PMZ. No variation was seen in BAM1 and ARC1. SNP locus homozygous in self-compatible and heterozygous in self-incompatible, with the corresponding locus of self-compatible reference genome can be used as potential candidate for developing markers to distinguish them. Such SNPs are identified and recommended for further validation.Item DNA fingerprinting of selected cocoa (Theobroma cacao L.) varities of Kerala agricultural university(Department of Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2020) Megha Totaganti; Minimol, J SCocoa (Theobroma cacao L.), is an important tropical tree-crop belonging to the family Malvaceae. It has originated in South America (Wood and Lass, 1985) and was introduced to India, in 1798 at Courtallam in Tirunelveli district of the old Madras state (Ratnam, 1961). Now, cocoa is extensively cultivated in South Indian states and its cultivation is slowly extending to North Eastern states. Central sub-committee on crop standards has made the DNA fingerprinting data mandatory for the national release and notification of varieties. DNA markers, act as active tool to categorize and distinguish accessions and cultivars which have similar morphological characteristics. DNA fingerprinting is effectively used for cultivar identification, assessing seed purity of hybrids and to compare genetic similarities between the cultivars. DNA fingerprints act as a powerful tool to protect Plant Breeder’s Rights (PBR). In the present study, seven cocoa varieties, CCRP 3 (selection), CCRP 10, CCRP 11, CCRP 12, CCRP 13, CCRP 14 and CCRP 15 (hybrids) were fingerprinted. Molecular characterization was performed with genomic DNA isolated using modified Delloporta method (Ileana, 2005). Thirty five ISSR (inter simple sequence repeats) primers and 30 SSR (simple sequence repeats) primer combinations were screened for marker polymorphism, of which 23 ISSR and 17 SSR primer combinations were selected for further study. ISSR and SSR amplification patterns differed among the varieties and thus the DNA fingerprints from each primer combination were developed. ISSR primer UBC810 was found to distinguish CCRP 3 from other genotypes. Whereas, UBC835 and UBC857 produced unique amplicons in variety CCRP 10. Primer UBC810, UBC826, UBC841 and UBC854 generated unique amplicons and formed specific DNA fingerprints of the hybrid CCRP 11. Primer ISSR3, UBC815, UBC827, UBC854 and Oligo 05 gave highest (6) unique bands in CCRP12, whereas UBC 854 produced specific band in CCRP 13. Hybrid CCRP 14 generated unique amplicons with primers UBC855 and Oligo 07 which formed specific fingerprint of the hybrid. Similarly, CCRP15 generated three unique fingerprints with the primer UBC844 and Oligo05. In SSR marker analysis, all the seven genotypes have at least one unique band. mTcCIR40 generated unique amplicons at 250bp length in CCRP 3 and SHRSTc53 at 230bp in CCRP 10. mTcCIR10, mTcCIR8, mTcCIR11 and mTcCIR121 generated distinct bands in CCRP 11. In CCRP 12 genotype, primer mTcCIR18 (345bp), mTcCIR40 (200bp) and mTcCIR42 (210bp) produced specific band. Unique bands were generated by primers mTcCIR10(340bp), mTcCIR11 (310bp), mTcCIR12(270bp), mTcCIR22(200bp), mTcCIR24 (150bp), mTcCIR33 (300bp) and SHRSTc53 for CCRP12. DNA fingerprint generated for CCRP 14 revealed that unique bands were developed at 250bp (mTcCIR37) and 200bp (SHRSTc64). Similarly, CCRP15 developed specific fingerprint at 355 bp (mTcCIR18). ISSR amplicons shared by maximum of three varieties and SSR shared in four varieties were considered for developing final DNA fingerprint profile. The present study had facilitated to characterize the selected cocoa varieties of KAU and the data generated will be useful for varietal notification and in case of any third party litigations.Item Effect of Azospirillum and VA Mycorrhiza on the growth of cocoa seedlings and incidence of seedling blight disease(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2001) Sunitha Anie Cheriyan; Rajendran Pillai, M VItem Inheritance of molecular markers linked to vascular streak dieback disease resistance in hybrid progenies of cocoa (theobroma cacao L.)(Department of Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2019) Midhuna, M R; Minimol, J STheobroma cacao L. (also known as the chocolate tree) is a major cash crop and the costliest beverage crop. Andhra Pradesh is the leading cocoa producing state in India but Tamil Nadu ranks first with an area of 26,969 ha. Vascular Streak Dieback (VSD) caused by the fungus Ceratobasidium theobromae is a serious disease in cocoa. Since it is a vascular pathogen, chemicals have little effect on disease control. The most tenable and economic technique to tackle this disease is by evolving resistant materials. Kerala Agricultural University had initiated VSD resistant breeding since 1995. Seedlings from hybridization, exhibiting high levels of resistance were selected and field established. Nineteen hybrids, exhibiting resistance to VSD (after screening for a period of thirteen years), were selected for the present study. The progeny obtained from these hybrids by crossing it among themselves were used as plant materials for the study. Two thousand two hundred and thirty seven flowers were pollinated and seven pods were obtained. About two hundred and sixty nine seedlings were grown from the seven hybridized pods in which nursery screening for disease resistance was done. Inoculum was dispensed by keeping already infected seedlings around the experimental materials. High humidity was ensured by providing over head sprinkler system. Visual screening recorded one hundred and eighty seedlings as disease resistant, fourteen seedlings as partially resistant and seventy five seedlings as disease susceptible. Three ISSR markers (UBC 811, UBC 815 and UBC 857) and one SSR marker (mTcCIR42) linked with VSD resistance gene, identified and validated from the previous studies were used for screening of the one hundred and twenty seedlings out of which one hundred and six were resistant and fourteen were partially resistant. The polymorphic band of 950 bp, which was found to be linked with the gene conferring VSD resistance was recorded in seventy seven resistant seedlings and three partially resistant seedlings, when screened with the primer UBC 811. When screened with the primer UBC 815 (750 bp) and UBC 857 (450 bp), the polymorphic marker band which was found to be linked with VSD resistant gene from the previous studies, was present in only twenty five resistant and one partially resistant seedling and twenty one resistant and one partially resistant seedling respectively. When screened with SSR marker, the 200 bp marker band, which was tagged with the VSD resistant gene was detected in fourty six resistant and six partially resistant seedlings. The ISSR marker UBC 811 and SSR marker mTcCIR42 were found to be having comparatively good percentage of inheritance among the segregating progeny screened with a mean inheritance percentage of 71.70 per cent and 48.78 per cent respectively. Flanking sequences of the ISSR markers UBC 811, UBC 857 and SSR marker mTcCIR42 were extracted from the whole genome database of cocoa. The ORFs from the flanking sequences of UBC 811 were identified to be uncharacterized proteins by using BLASTp tool. One ORF from the upstream sequence of the UBC 857 had shown identity with beta tubulin chain. Analyzing the distance between the marker and the flanking region, it was deduced that UBC 857 is a part of beta tubulin gene. Two ORFs were identified from both the upstream and downstream flanking sequences of the SSR marker. Using BLASTp tool, it was analyzed that both the ORFs showed more than 97 per cent identity to beta tubulin gene. Analysing the spacing between the marker and the flanking sequences, it was deduced that both the ORFs are part of the same gene and the SSR marker mTcCIR42 lies within the beta tubulin gene. Tubulin beta chain belongs to the microtubular component of cytoskeletal elements which provides resistance by not allowing the fungi to penetrate the outer epidermal wall of the plants, hence protecting the plants from infection. The ISSR marker UBC 857 and the SSR marker mTcCIR42 are linked to the beta tubulin gene, which provides VSD resistance by giving resistance against penetration of the plant cell by the fungus. Nineteen seedlings were identified to be having three or more markers expressed. They can be planted in the field and can be further evaluated for yield and yield contributing characters. Sequence of the beta tubulin gene can be used for primer designing, which can be used for confirmation by screening in resistant genotypes of cocoa.Item Vascular streak dieback of cocoa and its management(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1996) Ajay Kumar, K M; Koshy, AbrahamVascular streak dieback (VSD) is a destructive disease of cocoa. Corticium culture medium, Water agar, Potato dextrose agar gave promising results in isolation of the pathogen. Petiole and midrib gave maximum success in isolation. Potato dextrose agar and Corticium culture media supported the growth of the fungus. Fusarium sp. And Colletotrichum gloeosporioides were the major contaminants interfering in the isolation of VSD. The morphological characters of the pathogen were studied from the sporophores occurring on naturally infected cocoa plants. Based on these characters, the pathogen causing VSD was identified as Oncobasidium theobromae Talbot and Keane. The disease produced various typical symptoms on leaves and stems of infected plants like pale green colour of leaves and subsequent yellowing with green islets, defoliation, brown marks on the scars of fallen leaves, axillary bud growth of the infected stem, rusty discolouration of cambium, vascular streak, whitish sporophores on the leaf scar of fallen infected leaves and finally the death of the infected twig. Histopathological studies showed the presence of fungal mycelium in the xylem vessels. Transmission studies by grafting and budding revealed no establishment of buds or grafts. But there was vascular streaking. No seed transmission was observed. In general Kitazin and Bavistin as a seed treatment had an effect on the height of plant and leaf production. Evaluation of cocoa types planted at three seed gradens indicated that some of them possess resistance/tolerance against VSD. Variation in disease incidence and intensity of VSD was noted in germplasm VI. Calixin spraying had an effect in preventing the incidence of the disease in seedlings.Item Genetic analysis of yield attributes in cocoa(Department of Agricultural Botany, College of Horticulture,Vellanikkara, 1993) Homey Cheriyan; Vijayakumar N KGenetic analysis of yield attributes in cocoa (Theobroma cacao L.) was carried out in College of Horticulture, Kerala Agricultural University, Vellanikkara, Trichur during the period 1992-93. Observations recorded on 16 characters including yield and yield attributes in 244 trees consisting of 19 hybrids and 15 parents revealed that variability in most of the characters were almost same for both the parent and the hybrid populations. Variability was maximum for yield expressed in terms of wet bean weight per tree, and number of pods. It was moderate for pod weight, wet bean weight per pod, dry bean weight and ratio of dry bean weight to wet bean weight. Hybrids showed significant diference among themselves for almost all characters. Yield, number of pods, fruit wall thickness at furrow, seed width, seed thickness and the ratio of dry bean weight to wet bean weight did not show significant difference among the parents. Parents, which are budded progenies of a single tree showed high amount of within variability. The wihin variability is ascribed to non- genetic reasons. Hybrids were more uniform and better yielding than parents. High heritability was obtained for pod length, pod weight, wet bean weight per pod, dry bean weight and number of beans per pod. Hertability was moderate for number of pods, pod width and seed thickness. Genetic divergence studies showed that the 34 genotypes did not show a natural grouping indicating that the genotypes were genetically similar. Path coefficent analysis revealed that number of pods contributes the maximum to yield followed by wet bean weight suggesting that selection based on number of pod and wet bean weight per pod would be effective in increasing yield. This experiment conveys that there is ample scope for hybridisation in cocoa. High yielding genotypes may be used as parents for hybridisation and high yielding progenies identified. These may be utilized in establishing poly cross gardens, thereby increasing the frequency of favourable genes in the population. Seeds from such gardens can be used for raising commercial plantations.Item Soil nutrirent dynamics in cocoa(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1995) Smitha, B; Wahid, P AAn investigation on the dynamics of soil nutrients in the rootzone of cocoa (Theobroma cacao) was conducted during 1993 – 94 at the College of Horticulture, Vellanikkara. Soil and leaf samples were taken from cocoa trees under the Cadbury – KAU Co – operative Cocoa Research Project, Vellanikkara. Cocoa variety used for the study was forastero. The soil of the site was laterite (Oxisol). The treatments consisted of factorial combinations of N, P and K fertilizers each at two levels (with and without), two levels (with and without) of irrigation and shade and seven age groups namely 1, 3, 4, 5, 6, 9 and 12 years. Soil samples were also collected from an uncropped and unfertilized area nearby. The impact of long – term inorganic fertilization, irrigation and shade and age of the tree on soil chemical characteristics as well as foliar nutrition of cocoa influenced by long – term inorganic fertilization, irrigation and shade were assessed. Continuous application of urea for a period of nine years increased soil acidity and availability of P, S, Fe and Mn. It also increased total soil P and Fe. But it resulted in depletion of available K, Ca, Mg, Zn and Zn and Mn reserves of the soil. Long – term application of superphosphate resulted in the build – up of available and total P in soil. It also improved the status of soil available Ca, S and soil reserves of Ca and S. But it depleted soil available and total K, available and total Zn, available Mg and Cu and total Mn. Muriate of potash application increased the available and total K content of the soil. On the other hand it caused depletion of available P, Ca, S, Mn, Cu and soil Ca and Mg reserves. Interactions among urea, superphosphate and muriate of potash were also significant with regard to the fertility of the cocoa rootzone is concerned. Increasing soil acidity due to urea application, enrichment of S and Ca due to superphosphate application, and decrease in available P and S due to muriate of potash application were highly influenced by depth. Regular irrigation over a period of five years resulted in reducing the availability of P, Ca, Mn and Cu. It also reduced the total P and Mn in soil. But available K, Zn, S and total S tended to increase with irrigation. In the irrigated plots, total and available P were significantly lower in the surface layers compared to that in unirrigated plots. Provision of shade for a period of 13 years resulted in the build – up of soil organic carbon, available P, Fe and soil reserves of P, Ca, S, Fe, Zn and Mn. On the other hand it decreased the concentrations of available and total K, available S, and Zn and total Mg. Irrigation x shade interaction significantly influenced the available P content of soil. Urea application increased the foliar concentrations of N, Fe, Mn and Cu, but it decreased the leaf K content significantly. Long – term superphosphate application reduced Zn content of cocoa leaf. Application of muriate of potash increased leaf K content, but depressed foliar mg content significantly. Leaf N and K contents of cocoa were highly influenced by N x K interactions. N x P interaction significantly affected foliar Zn concentration of cocoa. Foliar Zn recorded higher values in plants receiving no nitrogen and phosphorus. Irrigation resulted in increased foliar concentrations of almost all nutrients except that of Ca and Mg. Foliar Ca content was higher in unirrigated plants. Effects of irrigation on leaf Mg was not significant. Cocoa trees under shade recorded higher concentrations of N, P, Mg, Fe and Mn and Cu in their foliage while K content was higher in open grown plants. Irrigation x shade interaction significantly influenced foliar N content. Shaded and irrigated conditions resulted in highest foliar N content. Nutrient dynamics in rootzone of cocoa over a period of 12 years of crop growth and fertilization could be described by linear or quadratic model. The linear model was found to be a better fit for available and total K, available and total Mg, available Cu and total Zn. In the case of available and total P, available and total Ca, available Zn, total S and total Cu the changes in concentrations with time could be described by a quadratic model. Available Mn content of the soil showed steady increase with age up to nine years followed by a sharp decrease.