Ph.D

The present study entitled “Organic nutrition for yield and quality in chilli (Capsicum annuum L.)” was conducted at the Department of Plant Physiology, College of Agriculture, Vellayani during the period 2021 to 2024 with an objective to elicit information on the physiological, molecular, yield and quality attributes as influenced by the application of soil amendments and foliar nutrition in organically grown chilli. The study consisted of three experiments and the chilli variety used for all the three experiments was Vellayani Athulya. The firstexperiment(potculture)focusedonassessingtheeffectofsoilapplicationof organic amendments on physiological, flowering and yield parameters in chilli. The experiment I employed a simple CRD with eight treatments consisting of various organic amendments with three replications. The treatments consisted of T1-soil application of FYM asperKAUOrganicPOPandT2-soilapplicationofFYMasperKAUPOPwhichweretaken asControl1andControl2respectivelyandtheremainingtreatmentswereasperKAUOrganic POPwhereinFYMwassubstitutedwithvermicompostandgoatmanureandtheircombination with biochar. All soil organic amendment treatments showed an increased growth compared to control treatments which were not supplemented with extra nutrients as that of other treatments.Amongthetreatments,T8[FYMsubstitutedwithgoatmanureasperKAUOrganic POP (2017) + Rice husk biochar]recorded the highest values for physiological and growth parameters such as total chlorophyll content, water use efficiency, carotene content, relative watercontent,plantheight(85.70cm),numberofbranches(5.33),shootweight(42.23g),root weight (9.20g), root : shoot ratio (0.22). In addition the best flowering characters such as earliestdaystofirstflowering(22days)andhighestnumberofflowersplant-1(44.67)aswell as best yield attributes such as earliest days to first harvest (41 days), highest percentage of fruit setting(64.18%), number of fruits plant -1 (28.67 ), fruit length (15.30cm),fruit girth(9.30cm),fruitweight(17.70gfruit-1),yield(507.41gplant-1)andB:Cratio(1.92)were obtained for the treatment T8, when compared to the control treatments.
The experiment II (pot culture) was focused to assess the effect of foliar fertilization on physiological, flowering, yield and quality parameters in chilli. The experiment employed asimpleCRDwith7treatmentsconsistingofdifferentorganicfoliarsprayswith3replications. Beforeplanting,allthepotsweresubjectedtothebesttreatment(T8)fromexperimentI(BT1) ie;SoilapplicationofFYMsubstitutedwithgoatmanureinKAUOPOP+Ricehuskbiochar. Then various organic foliar fertilizer treatments such as T1-Panchagavya (3%), T2- Fish jaggery acid(3%), T3-Vermiwash (20%),T4- Humic acid (0.05%) and T5- Azolla liquid extract(75mlL-1)weregiventotheexperimentalplantsasperthetreatmentsandcompared withT6-Control1[KAUOPOP(2017)+waterspray]andT7-Control2[KAUP Thefoliarspraytreatments(T1toT7)were given three timesat30daysinterval starting from 15DAT.All the organic foliar spray treatments showed enhanced growth of chilliwhencomparedtocontroltreatments.Amongtheseventreatments,T1hasrecordedthe best values for physiological and growth parameters such as total chlorophyll content, water use efficiency, carotene content, relative water content, plant height (89.67 cm), number of branches(5.31),shootweight(41.00g),rootweight(9.31g)androot :shootratio(0.23).Also better flowering characters such as highest number of flowers plant-1(48.33)and earliest days firstflowering(21days)aswellasbestyieldattributessuchasearliestdaystofirstharvest (40.33days),highest percentage of fruitsetting(62.76%),number of fruits plant-1(30.33),fruit length(15.50cm),fruitgirth(9.53cm),fruitweight(11.41gfruit-1),yield(571.23gplant-1) andB:Cratio(2.07)wereobtainedinthetreatmentT1.Thequalityparameterssuchashighest total sugars (4.57 mg g -1 fresh fruit weight), total phenolic content (24.46 mg g -1 fresh fruit weight) , shelf life (14.33 days), N, P, K content (3.65%, 0.42% and 3.94% %), membrane integrity (88 %) and lowest PLW (12.00%) were also observed significantly higher for the treatment T1. The same treatment has resulted in 49% & 77% increase in capsaicin content and24%&45%increase in vitamin C content compared to both the control treatments (KAU Organic POP and KAU POP respectively).
The third experiment was carried out in the field to assess the effect of foliar fertilization on quality parameters and nutrient uptake in chilli. The best treatment from experiment II (BT 2) ie; combination of best organic amendment and best foliar spray was taken as T1 and it was compared with both the controls (T2-Organic POP with waters prayand T3- KAU POP with water spray). The experiment employed a simple RBD design with 3 treatmentsand7replications.Thequalityparametersandnutrientuptake(N,P,K)bythecrop were analysed at the harvest stage and the soil analysis was done before transplanting as well as after harvest.The results from the third experiment revealed that the foliar fertilization had significant influence on quality parameters and nutrient uptake in chilli. Compared to both the controls (T2 and T3), the treatment T1 showed significant influence on quality parameters in chilli fruits and nutrient uptake in chilli plants.T1 also has shown improved quality parameters such as capsaicin content(0.84%), shelf life (15 days), membrane integrity (88.41%),Vitamin C content (121.38 mg 100 g-1 fresh fruit weight) and lowest Physiological LossofWeight(PLW)(13.23%)inchillifruitandhighestN(132.23kgha-1),P(31.32kgha-1), K (122.34kg ha-1) uptake) in chilli plants compared to the controls (T2 and T3).
Whensoilanalysiswascarriedoutaftertheharvest,improvementinsoilpH,soilEC, organic carbon, available nitrogen, phosphorous and potassium were noticed. In T1, the increaseinthesoilorganiccarboncontentwasfoundapproximately27%and35%higherthan both the controls, T2 (Control 1) and T3 (Control 2) respectively, whereas the available N content in soil (627.2 kg ha-1) was about 19% higher when compared individually with both the treatments T2 (Control 1) and T3 (Control 2). Also in T1, the available P (336 kg ha-1) content in the soil was higher by 20% and 29% than the treatments T2 Control 1) and T3 (Control 2) respectively and available K (371.05 kg ha-1) was 33% and 91% higher than the treatments T2 (Control 1) and T3 (Control 2) respectively.
Inthethirdexperiment,molecularanalysisandexpressionprofilesofthegenespAMT, Pun 1, CaAMT,FdGOGAT and GS2 werecarried out byusing qRT-PCR(Quantitative Real- Time PCR) technique. The treatment T1, was found to result in the upregulation of gene expression of Pun 1 (in fruits) as well as CaAMT and Fd GOGAT (in the roots). But the gene expression of pAMT (in fruits) and GS2 (in roots) were down regulated in the treatment T1 when compared with both the controls (T2 and T3).
The present study on the moderately pungent variety ‘Vellayani Athulya’ revealed notably low expression of pAMT, despite its intermediate pungency level. This observation suggests that in such varieties, even modest Pun1 activity may be sufficient to channel the limited pool of vanillylamine toward capsaicin synthesis and Pun1playsa more decisive role than pAMT in determining final capsaicin levels. The integrated use of goat manure, biochar, and panchagavya in T1 created optimal conditions for Pun1 gene upregulation and capsaicinoid biosynthesis, leading to increased capsaicin content and enhanced pungency and the treatment combination enhanced nitrogen uptake and assimilation through Up regulation of key genes involved in ammonium transport(CaAMT) and assimilation(GS and GOGAT),ultimately contributing to improved capsaicinoid biosynthesis in chilli variety Vellayani Athulya.
The present study has revealed that the physiological, molecular, yield and quality attributesweregreatlyinfluencedbytheapplicationofsoilamendments,FYM substituted with Goatmanure(1tha-1)inKAUOPOP+Biochar(0.5%w/w)andfoliarnutritionofPanchagavya (3%)in organically grown chilli. The outcome of the programme emphasizes the importance ofapplicationoforganicsoilamendmentsandfoliarnutritionincropmanagement.Thisstudy also highlights the significance of exploration of genes and their regulatory mechanisms in quality improvement in organically grown chilli.