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ThesisItem Open Access Development of chilli (capsicum annuum l.) hybrids with leaf curl virus resistance, high yield and quality(Department of Vegetable Science, College of Agriculture , Vellayani, 2019) Vijeth, S; KAU; Sreelathakumary, IThe investigation entitled “Development of chilli (Capsicum annuum L.) hybrids with leaf curl virus resistance, high yield and quality” was carried out at the Department of Vegetable Science, College of Agriculture, Vellayani, during the period of 2015-2018. The study was aimed at identification of sources for chilli leaf curl virus (ChiLCV) resistance, development of chilli hybrids with ChiLCV resistance, high yield and quality and studying the gene action of ChiLCV resistance. The investigation was conducted in four experiments. In experiment I (a), 70 chilli genotypes were evaluated for yield and quality traits. The best genotypes based on per se performance were CHIVAR-9 for plant height (73.33 cm), CHIVAR-4 for primary branches plant-1 (4.77), Jwalasakhi for days to first harvest (42.00 days), CHIVAR-7 for fruits plant-1(137.33), Vellayani Athulya for days to first flower (26.94 days), fruit length (8.50 cm), fruit girth (4.78 cm) and fruit weight (7.57 g), CA-32 for yield plant-1 and yield plot-1 (587.33 g and 16.10 kg/6.48m2 respectively), Punjab Sindhuri for vitamin C (120.33 mg 100 g-1) and Byadagi Kaddi for carotenoids (331.33 mg 100 g-1). Seven genotypes viz., CHIVAR-3 (L1), CHIVAR-7 (L2), CHIVAR-6 (L3), CA-32 (L4), Vellayani Athulya (L5), Keerthi (L6) and CHIVAR-10 (L7) were selected based on selection index ranking for utilization as lines in line (L) × tester (T) analysis. Among the 70 genotypes screened against ChiLCV under field condition [experiment I (b)], 23 were moderately susceptible, 12 each were susceptible and moderately resistant, ten were symptomless, six were resistant, five were highly resistant and two were highly susceptible. The selected ten symptomless and five highly resistant genotypes were subjected to artificial screening by using whitefly mediated and graft inoculations in experiment II (a). Six genotypes were symptomless under whitefly mediated inoculation, among which, four genotypes viz., Sel-3, Sel-4, Sel-6 and CHIVAR-1 showed highly resistant reaction under graft inoculation. The resistant genotypes identified under artificial inoculation by Polymerase Chain Reaction (PCR) using universal primers (AV494/AC1048) for the confirmation of ChiLCV. All the graft inoculated genotypes showed presence of virus. However, in the whitefly mediated inoculation, four genotypes viz., Sel-3 (T1), Sel-4 (T2), Sel-6 (T3) and CHIVAR-1 (T4) did not show any amplification for presence of virus. Hence, they were used as testers (male parent) in line (L) × tester (T) analysis. The overall disease score was higher with graft inoculation than whitefly mediated inoculation. The BLAST analysis of the amplified sequence showed 93 per cent similarity to Tomato leaf curl Karnataka virus (ToLCKV). Seven genotypes (lines) with high yield and quality attributes were crossed with four highly resistant genotypes (testers) in line (L) × tester (T) mating design in experiment III (a) to produce 28 F1 hybrids. These hybrids were evaluated along with parents and two checks (CH-27 and Arka Harita) for yield and quality attributes and ChiLCV resistance during summer in 2017 [experiment III (b)]. Based on per se performance most promising hybrids were L3 × T2, L6 × T1, L1 × T1, L7 × T1 and L3 × T1 for yield traits and L4 × T1, L4 × T2, L4 × T3 and L7 × T1 for quality traits. The superior crosses based on heterobeltosis, standard heterosis and SCA effects were L3 × T2, L1 × T1, L7 × T1, L6 × T1, L3 × T1, L2 × T4, L4 × T1, L5 × T3 and L5 × T4 for yield attributes; L4 × T1, L4 × T2, L3 × T1, L7 × T1, L3 × T2, L6 × T3 and L1 × T1 for quality traits; L6 × T1, L7 × T4, L3 × T2, L7 × T1 and L7 × T3 for ChiLCV resistance. Lines vs. testers showed significant differences for all the characters except for plant height. The GCA effects for testers were significant for all the traits except for days to first harvest. The ratio of σ2GCA/σ2SCA was less than unity for all the characters, which indicated the predominance of non-additive gene effects in the inheritance of these traits. The contribution of lines were more compared to testers for all the characters except for primary branches plant-1. The superior lines based on GCA effects were L1, L3, L7 and L6 for yield attributes; L2, L3, L4 and L7 for quality traits and L1, L2 and L4 for ChiLCV resistance. Among testers, T1 and T2 were best general combiners for yield and quality traits, and T1 and T3 for ChiLCV resistance. The hybrids viz., L3 × T2, L7 × T1, L1 × T1, L6 × T3, L1 × T4, L4 × T2, L5 × T3, L5 × T4, L7 × T3 were most promising with desirable SCA effects, heterosis and per se performance for yield and quality attributes and they were moderately resistant to ChiLCV except L5 × T3 and L5 × T4. The hybrid L1 × T1 and L7 × T1 had both parents with high GCA effects for yield plant-1. All the four testers were symptomless and among seven lines, two were moderately resistant and five were moderately susceptible. Among 28 F1 hybrids, 12 showed moderate resistant reaction, 11 were moderately susceptible and five susceptible. The check hybrids CH-27 and Arka Harita were moderately resistant and susceptible respectively. Three superior crosses identified from line (L) × tester (T) analysis viz., cross 1 (L1 × T1), cross 2 (L3 × T2) and cross 3 (L7 × T1) were utilized for generation mean analysis. The six generations (P1, P2, F1, F2, BC1 and BC2) of three crosses were developed and evaluated during 2018 summer. Both simple and joint scaling tests were significant for all the characters in all the crosses indicating the inadequacy of additive-dominance model and involvement of digenic or higher order non-allelic gene interactions. Duplicate type of epistasis was observed for plant height, days to first flower, days to first harvest, fruit length, fruit girth, vitamin C, carotenoids and ChiLCV resistance (cross 1); plant height, primary branches plant-1, days to first harvest, fruit girth, fruit weight, fruits plant-1, vitamin C, carotenoids and ChiLCV resistance (cross 2); primary branches plant-1, days to first flower, days to first harvest, fruit girth, fruit weight, fruits plant-1, yield plant-1, vitamin C, carotenoids and ChiLCV resistance (cross 3). These crosses can be improved by biparental mating between recombinants in early segregating generation and delaying the selection in the advanced generations. Complementary type of epistasis was noticed for fruits plant-1, yield plant-1 and yield plot-1 (cross 1); fruit length, yield plant-1 and yield plot-1 (cross 2); plant height and yield plot-1 (cross 3). Additive, additive × additive or complementary gene interactions are fixable, thus, these crosses can be exploited effectively through pedigree method of selection. For ChiLCV resistance dominance (h) gene action, additive × additive (i), additive × dominance (j) and dominance × dominance (l) type of gene interactions are significant. Among them, the former three are in negative desirable direction. The four ChiLCV resistant genotypes identified in this study could be used as potential parents for ChiLCV resistance breeding programme. The 93 per cent similarity of the amplified sequence to ToLCKV suggests that, it could be a strain of ToLCKV responsible for ChiLCV disease. The parents L1, L3, T1 and T3 were superior on the basis of GCA effects for most of the economic traits studied. The hybrids L3 × T2, L7 × T1, L1 × T1, L6 × T3, L1 × T4, L4 × T2 and L7 × T3 were most promising for yield and quality traits, and were moderately resistant to ChiLCV. The dominance (h) gene action and dominance × dominance (l) epistasis were predominant for yield and quality traits indicating the importance of heterosis breeding in varietal improvement of chilli. The ChiLCV resistance could be improved through recombinant breeding or recurrent selection.ThesisItem Open Access Aggrading lateric soils (ultisol) using biochar(Department of Soil Science, College of Horticulture, Vellanikkara, 2019) Rajakumar, R; KAU; Jayasree Sankar, SThe present investigation was undertaken at College of Horticulture, Vellanikkara and Agricultural Research Station, Mannuthy during 2016-2018. The study consisted of production and characterization of bioehar from coconut based materials, an incubation experiment, and two field experiments. The incubation experiment was conducted for 15 months to study the dynamics of C and N in soil over time and the soil samples were analyzed for C and N fractions at three months' interval. Two field experiments were carried out sequentially, wherein Chinese potato was raised to study the direct effect of bioehar and vegetable cowpea was the test crop to study the residual effect of bioehar applied to the first crop. Three levels of bioehar (5, 7.5, 10 t ha"'), FYM 10 t ha"', soil test based POP + bioehar 10 t ha"' and soil test based POP were the treatments, for both incubation and field experiments. Soil test based POP consisted of NPK and FYM 10 t ha"'. Control plots without the addition of biochar/fertilizers were also maintained. Recovery of bioehar from coconut husk and shell (1:1) on pyrolysis was 22 per cent. The produced bioehar had an alkaline pH (10.01), high EC (3.42 dS m"'), C (64.14 %), CEC (15.78 cmol (+) kg"'), and C: N ratio (113:1). Total N, P, K, Ca, Mg and S contents were 0.567, 0.982, 4.175, 1.19, 0.456 and 0.244 per cent, respectively. Regarding physical properties, bioehar had low bulk density (0.128 Mg m"^), very high porosity (84.63 %) and WHC (307.3 %). Basicity and acidity of bioehar were 2.02 and 0.08 mmol g"', respectively. The surface morphology and chemistry studied using SEM, TEM, FT-IR and Raman spectroscopy revealed the porous, aromatic and recalcitrant nature of bioehar and the presence of functional groups mainly carboxyl, hydroxyl and carbonyl. Results of incubation experiment revealed that the content of organic carbon - (OC), water soluble carbon (WSC) and microbial biomass carbon (MBC) increased up to 6 months of incubation and decreased thereafter. In the case of permanganate oxidizable carbon (POXC) and hot water soluble carbon (HWSC), a decreasing trend was noticed. While the highest value of WSC and HWSC were recorded in FYM 101 ha"', all other C fractions were higher in the treatments viz. soil test based POP + bioehar 10 t ha"' and bioehar 10 t ha"'. With an increase in levels of bioehar, the labile C fractions viz. POXC and MBC increased. The labile C fractions in soil were in the order POXC > HWSC > MBC = WSC. As regards the N fractions, NH4-N declined steadily at 3 months, then increased up to 9 months of incubation after which it decreased till the incubation ended. The NO3-N and amino acid N increased up to 12 months of incubation and slightly declined thereafter. Increase in total hydrolysable N was noticed up to 6 months of incubation and thereafter, a progressive decrease was noticed. While the total N content decreased over the incubation period, the KMn04-N increased. With an increase in levels of biochar, the NO3-N and KMn04-N increased. The treatments soil test based POP + biochar and soil test based POP were equally superior to other treatments with respect to N fractions. Results of field experiments revealed the superiority of biochar 10 t ha"' in increasing soil pH and NH4OAC-K and reducing the exchangeable acidity. The treatments soil test based POP + biochar and soil test based POP were superior with respect to most of the soil properties. Application of biochar at 10 t ha"', either alone or in combination with POP improved the soil properties viz. OC, dehydrogenase activity, CEC, MWHC and hot water soluble B. With an increase in levels of biochar, the soil properties viz. pH, CEC, WHC, dehydrogenase activity, NH4OACK, Ca, HCl-Zn and humic acid increased. With respect to the growth parameters and yield of Chinese potato, application of soil test based POP + biochar and soil test based POP were comparable. The same treatment soil test based POP + biochar that faired in terms of direct effect proved good in residual effect as well, as reflected from the plant growth and yield of cowpea. Path analysis had shown that the soil properties viz. OC, MBC, Bray-P, NH4OAC-K, Ca and EC directly influenced the tuber yield, reinstating the role of biochar in yield improvement. The nutrient content in plant parts and its uptake varied among treatments and corroborated the trend. Considering the quality attributes of Chinese potato, the treatments biochar 10 t ha"' and soil test based POP + biochar recorded higher CHO content. Protein content was highest in the treatments soil test based POP and soil test based POP + biochar. The advantage of biochar on increasing protein content and decreasing crude fibre content was visible in the succeeding crop of cowpea also, thus establishing its high residual effect. The study revealed the potential of biochar as an amendment in the highly weathered, nutrient-poor acidic laterite soils of the tropics. Its application brought about increase in soil pH, addition of basic cations, improvement in CEC and WHC, and gradual release of nutrients to the growing plants. The overall improvement in physical, chemical and biological soil conditions through biochar could promote plant growth, yield as well as quality. The positive effect of biochar could be observed in combination with soil test based fertilizer application also.ThesisItem Open Access Characterization of Mycosphaerella spp. causing sigatoka leaf spot disease complex of banana in Kerala and its management(Department of Plant Pathology College of Horticulture, Vellanikkara, 2019) Milsha George; KAU; Anita Cherian, KSigatoka leaf spot disease complex caused by Mycosphaerella spp. is a serious constraint to banana cultivation in Kerala. The present study was undertaken to characterize the associated pathogen and to develop an integrated management package against this disease. The project initiated with purposive sampling surveys conducted in various districts representing different agroclimatic zones of Kerala viz. Malappuram (Northern zone), Palakkad (Northern zone), Thrissur (Central zone), Ernakulam (Central zone), Wayanad (High range zone) and Trivandrum (Southern zone). The percent disease severity (PDS) ranged from 3.33 to 43.90%. The correlation analysis of PDS with weather parameters showed a positive correlation with rainfall however, it was found to be negatively correlated with temperature. The study on symptomatology revealed that there were six types of symptoms noticed on banana var. Nendran (AAB), two types each on Palayankodan (AAB) and Njalipoovan (AB), while only one type of symptom was recorded on Robusta (AAA) and Kadali (AA). Isolation of the pathogen could be achieved on potato dextrose agar medium after 10- 12 days of incubation at very specific conditions. The fungal colony was slightly raised with irregular margin and greyish velvety appearance. Studies on morphological structures revealed that the conidia were hyaline to olivaceous brown in colour which measured about 24.29 - 71.89 µm length x 0.91 - 2.40 µm width with 3-8 septations. The sexual structures were flask shaped perithecia containing long asci bearing eight ascospores. Based on cultural and morphological characters, the pathogen was identified as Mycosphaerella eumusae. The identity of the pathogen was further confirmed by PCR based molecular characterization. In silico analysis of the sequences of the isolates showed 99 -100% homology to Mycosphaerella eumusae. Hence, it is concluded that the pathogen associated with Sigatoka leaf spot disease of banana in Kerala is identified as Mycosphaerella eumusae Crous & Mourichon (anamorph Pseudocercospora eumusae Crous & Mourichon). The screening of accessions maintained in the Germplasm of Banana Research Station, Kannara was done to assess their disease reaction and were grouped into six categories. Five resistant varieties viz., Pisang Lilin, BRS 1, BRS 2, FHIA 01 and FHIA 23 and susceptible varieties viz., Nendran, Grand Naine, Robusta, Moris and Kadali were further selected to investigate the anatomical, biochemical and molecular basis of host plant resistance. Anatomical studies revealed that the resistant varieties were characterized by thicker cuticle, epidermis and mesophyll tissues compared to the susceptible varieties. The number of stomata and the stomatal pore width were more in susceptible varieties compared to the resistant varieties. The biochemical basis of resistance was assessed by quantifying phenols, reducing sugars, non reducing sugars and the activity of defense related enzymes viz., peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in both resistant and susceptible varieties. The results revealed that the phenols, reducing sugars and the defense related enzymes were higher in resistant varieties compared to susceptible ones. The amplification of genomic DNA of resistant and susceptible varieties using Sequence characterized amplified region (SCAR) markers yielded an amplicon of size 644bp in resistant cultivars while the bands were absent in susceptible cultivar. The BLASTn analysis of the sequence of the amplicons showed 90 per cent sequence homology to genomic sequences of Kanthali SCAR marker OPA1363 which is tightly linked to Sigatoka leaf spot disease resistance. Field experiments were conducted to evaluate the efficacy of chemical fungicides and organic / inorganic preparations for disease management. Among the various chemical fungicides, foliar spraying with trifloxystrobin (25%) + tebuconazole (50%), 0.4g/l) was found to be the best followed by copper hydroxide, hexaconazole (5%) + captan (70%), 2g/l) and Bordeaux mixture (1%), without leaving any toxic residues in the harvested fruits. The results of the experiment on disease management using organic / inorganic preparations revealed the effectiveness of PGPR mix II (consortium of Pseudomonas fluorescens and Bacillus subtilis), 2% followed by Pseudomonas fluorescens (2%) given as foliar spray. It is concluded that the present study has enlightened our knowledge on the etiology and management of Sigatoka leaf spot disease of banana cultivation in Kerala.