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Open Access
Identification of genetic stock for drought tolerance and candidate gene analysis in cocoa(Theobroma cacao L.)
(Department of plantation,spices,medicinal and aromatic crops, college of agriculture ,Vellanikkara, 2023-09-21) Suchithra, M.; KAU; Suma, B
Water deficit stress is considered as one of the most limiting factor for production in cocoa. Preliminary efforts have been made in Kerala Agricultural University to identify drought tolerant cocoa genotypes. The present study was an attempt made to identify the cocoa genotypes and hybrids that can tolerate drought condition. The study was conducted at Department of Plantation crops and spices, College of Agriculture (CoA) and Cocoa Research Centre and College of Agriculture, Vellanikkara, Thrissur. Thirty exotic genotypes and six pre-released hybrids were taken as materials for the study. They were budded on 6 month old rootstock of seedling raised from polyclonal gardens. GIV 18.5 (progeny of pods from Nileshwar) identified susceptible genotype was used as check in the experiment. Five month old budded plants of thirty exotic cocoa genotypes and six hybrids along with check variety were subjected to drought screening by following gravimetric method. Control plants were maintained at fully irrigated condition under 100 per cent field capacity. Field capacity was maintained at 40 per cent for stress condition. Based on the percentage of retained leaves genotypes and hybrids were categorised as highly tolerant (more than 70% leaves retained), tolerant (40-70% leaves retained), susceptible (10-40% leaves retained) and highly susceptible (less than 10% leaves retained). Various physiological and biochemical parameters related to drought were analyzed. The physiological parameters, relative water content, chlorophyll stability index, membrane stability, photosynthetic rate and chlorophyll content were recorded high in tolerant and highly tolerant genotypes and hybrids whereas these parameters were comparatively low in susceptible and check variety. The control plants at 100 per cent field capacity recorded high value for all these parameters. However in terms of transpiration rate a reverse trend was observed among genotypes and hybrids. Low transpiration rate was recorded in highly tolerant and tolerant hybrids whereas ii susceptible genotypes and hybrids had high transpiration rate under stress condition. The control plants under fully irrigated condition of 100 per cent field capacity also had high transpirational rate. This indicated the ability of tolerant genotypes and hybrids to conserve water during stress. The leaf temperature did not shown any significant variation among the genotypes and hybrids studied under both the field capacity level. In case of biochemical parameters, proline content, glycine betaine content and superoxide dismutase activity were found to be high in tolerant and highly tolerant genotypes and hybrids and was low in susceptible and check variety. The control plants kept under 100 per cent filed capacity level shown less values for all these parameters. However, all the plants showed reduced nitrate reductase activity under drought stress. The control plants recorded high nitrate reductase activity at 100 per cent field capacity level. Correlation studies showed that all physiological and biochemical parameters except transpiration rate and leaf temperature have positive correlation with percentage of leaves retained. Effect of these parameters on percentage of leaves retained was estimated using path analysis. Parameters having direct effect on leaf retention were proline, nitrate reductase activity, SOD, glycine betaine, cell membrane stability and relative water content. These characters were analyzed for their genetic parameters and it was found that all these characters are having high heritability and genetic gain. D 2 statistics analysis revealed that the 30 genotypes and 6 hybrids along with check were grouped into 6 clusters indicating the presence of diversity for different traits. Four different isolation methods were compared in this experiment to identify the best method that could produce high-quality total RNA free from contaminants and genomic DNA. RNA obtained through the SDS- tertiary butanol method (Gesteira et al., 2003) has high quantity and quality, followed by the modified SDSphenol method (Deepa et al., 2014) in both fresh and frozen leaves. iii The transcriptome of highly drought tolerant exotic genotype (T85/799) and highly drought sensitive check variety CCRP 5 was analysed using mRNA sequencing under control (100% FC) and drought stress condition (40% FC). Drought has up-regulated 1540 and 1148 DEGs and downregulated 1502 and 1250 DEGs respectively in tolerant and sensitive libraries. The PCA scatter plot shows that replicates of the well watered samples (control) of highly drought tolerant genotype and drought susceptible check variety CCRP 5 form distinct groups highlighting differences between the two genotypes. Volcano plot depicted the significance of differentially expressed genes in control and drought stress treated samples of highly tolerant and susceptible genotype. In both the tolerant and susceptible genotypes, the majority of the genes within the biological process category were linked to GO terms that fall under the subcategories of "metabolic process," "cellular process," and "single organism process." “Enzyme catalytic activity”, “water channel activity”, “binding” and “transporter activity” were the most abundant terms in molecular function category in both the genotypes under stress. There were 17 pathways significantly enriched (FDR-adjusted p-value < 0.05) in tolerant genotype for upregulated genes and the most enriched pathways including metabolic pathways (178 genes) followed by biosynthesis of secondary metabolites (121 genes), phenyl propanoid biosynthesis (29 genes), carbon metabolism (29 genes), glyoxylate and decarboxylate metabolism (16 genes), MAPK signalling pathway plant (14 genes) and starch and sucrose metabolism etc. Most of the Transcription Factors (TFs) identified families were enriched in, B3, bHLH, WRKY, ARF, ARR B, FAR, LBD, MADS and ERF. These TFs could be grouped into 10 families. The major upregulated genes families in tolerant genotype includes protein kinase, protein phosphatase type 2c, zing finger proteins, laccase gene, cytokinin dehydrogenase, cytochrome p450, galactinol synthase, NAC Domain protein, peroxidase, protein ubiquitin E3 ligase, mannitol dehydrogenase, fatty acid desaturase, UDP glycosyl transferase, Aquaporin PIP, Glutathione dependent genes, iv cellulose synthase and heat shock proteins etc.The major upregulated genes families in susceptible genotype includes LEA protein, PSII protein, peroxisomal membrane proteins, ABC transporter, ABA hydrolyse, phenyl alanine n-monoxygenase, tyrosine carboxylase, plastocyanin, trehalose phosphate phosphatase and expansin etc. RNA-Seq analysis showed that highly drought tolerant exotic genotype (T85/799) activated more number of drought responsive genes than drought sensitive check variety CCRP 5. Several drought-responsive genes were upregulated in the tolerant genotype such as those encoding TFs, cytochrome 450, and membrane transporters, and those associated with carbohydrate metabolism and flavonoid biosynthesis. These genes might confer drought tolerance in this cocoa genotype at the molecular level. Identified drought- responsive genes and metabolic pathways were targets for future studies in order to understand the molecular mechanism of drought tolerance in cocoa. Physiological and biochemical parameters also indicated the better performance of the tolerant genotype over the susceptible genotype under drought stress conditions. These results were a first step to understanding the molecular mechanisms of drought tolerance in cocoa and lay a foundation for its genetic improvement.
Metadata only
Value addition of jack fruit through microbial processing
(Department of Community Science, College of Agriculture , Vellayani, 2021) Bensi, P S; KAU; Suma, Divakar
Open Access
Evaluation of cashew (Anacardium occidentale L.) hybrids for yield and quality
(Department of Plantation Crops and Spices, College of Agriculture,Vellanikkara, 2021-12-30) Jintu, Varghese; KAU; Jalaja S, Menon
The demand of cashew (Anacardium occidentale L.) for export and local consumption is increasing in the country and there is a gap of 7 lakh tonnes in the production to meet the requirement. Due to pressure on land, the possible way to increase production is to increase productivity by adopting improved varieties. Hybrid vigour was well exploited in cashew. Cashew Research Station, Madakkathara has developed many hybrids through hybridization programmes which are maintained in the farm. In the present study 19 hybrids of stabilized yield along with 11 cross parents and check variety Poornima were evaluated for yield and quality traits during the year 2020-2021. Qualitative and quantitative parameters including those of growth, inflorescence, apple, nut, yield and biochemical attributes revealed a spectacular array of variations among the tested genotypes. Among hybrid population, upright and compact canopy with intensive branching habit, yellowish red flush colour and pyramid shaped loose inflorescence were predominating. Early flowering from October was recorded in 13 cashew hybrids and four parents. Cluster bearing habit was observed in hybrids H03-113/1 (4.65 fruits), H03-55/10 (4.55 fruits) and H03- 53/9 (4.10 fruits). The apple weight varied from16.83 g (H03 55/10) to 137.49g (Priyanka). Nut weight of more than 10g was observed in hybrids H03-21/10, H03- 97/2, H03-36/8, H03-110/1, H03-52/6, H03-52/7, H03-52/5, HO3-95/4 and H03- 18/17 and these can be represented as bold nut hybrids. The average kernel weight varied from 1.62g (H03-55/10) to 4.19g (H03-95/4). Nut yield above 18 kg/tree was recorded in hybrids, H03-92/3 (20.2 kg), H03-52/5(21.5kg), H03-36/8(22.10 kg), H03-110/1(23.40 kg), H03-97/2 (24.50 kg), H03-21/10 (25.20 kg) and in parent, Amrutha (21.3kg) and check variety, Poornima (20.0 kg). In biochemical analysis, TSS ranged from 13.150Brix (H03-18/17) to 17.40Brix (H03-53/9). Vitamin C content ranged from 107.5 to 220.15mg/100ml. Lowest tannin content was shown by hybrid H03-55/11(0.085%), H03-92/3(0.09%) and H03-55/10(0.09%). The hybrids H03-57/4, H03-110/1, H03-113/1, H03-52/5 and xx H03-21/10 and parents, Dhana, Madakkathara-1, Vridhachalam-3, and K-22-1 were less susceptible to TMB. Nut yield per tree was found to possess significant positive correlation with nut weight, kernel weight, apple weight, number of bisexual flowers and shelling percentage. In the principal component analysis 85.92% of total variability was explained by the first three components with an eigen value greater than one. The characters like yield per plant, apple weight, shelling percentage, kernel weight, nut weight and bisexual flowers contributed more towards diversity. Eight hybrids viz., H03-21/10, H03-97/2, H03-36/8, H03-110/1, H03-52/6, H03-52/7, H03-52/5 and H03-95/4 were placed in the first quadrant along with check variety Poornima. Magnitude of heterosis was calculated for 19 hybrids over mid parent (relative heterosis), better parent (heterobeltiosis) and standard variety (standard heterosis). The above eight hybrids along with H03-18/17 exhibited better heterosis. The hybrids, H03-36/8, H03-97/2, H03-110/1, H03-21/10 and H03-52/5 which exhibited heterosis and nut weight above 10g, tree yield above 18kg, kernel weight above 2.5g and shelling per cent above 28 were selected as promising types. Hence these hybrids may be recommended for commercial cultivation. Further studies should be undertaken with different traits for exhaustive evaluation for commercialization. The hybrids H03-52/6, H03 -52/7, H03-95/4 and H03-18/17 having good yield and quality traits can be utilized for crop improvement programmes.
Open Access
Characterization and quality analysis of black pepper (Piper nigrum L.) genotypes of Kerala
(Department of Plantation Crops and Spices, College of Agriculture, Vellayani, 2021) Reshma, P; KAU; Sreekala, G S
The present study entitled “Characterization and quality analysis of black pepper (Piper nigrum L.) genotypes of Kerala” was taken up with the objectives of survey, characterization and quality analysis of black pepper genotypes of Kerala based on morphological and biochemical parameters. The survey conducted in black pepper plantations and homesteads in fourteen locations of six Agro-Ecological Units (AEUs) identified twenty one genotypes. Five genotypes designated as G1 (Wayanadan), G2 (Chumala), G3 (Vellayaranmunda), G4 (Nadan), G5 (Nadeshan) from AEU 21 (Wayanad Eastern Plateau), six genotypes designated as G6 (Karimunda), G7 (Neelamundi), G8 (Cheppukulamundi), G9 (Vattamundi), G10 (Thulamundi), G11 (Manjamunda) from AEU 12 (Southern and Central Foothills), three genotypes designated as G12 (Chengannurkodi), G13 (Vellanamban), G14 (Jeerakamunda) from AEU 14 (Southern High Hills), three genotypes designated as G15 (Kuthiravally), G16 (Kottanadan), G17 (Arimulak) from AEU 3 (Onattukara Sandy Plains), two genotypes designated as G18 (Padappan), G19 (Karivilanchy) from AEU 8 (Southern Laterites) and two genotypes designated as G20 (Narayakodi) and G21 (Panniyur 1) from AEU 4 (Kuttanad) were selected for the study. Twenty one genotypes were morphologically characterized for both qualitative and quantitative characters. Thirty four qualitative characters were observed and among those only twenty two characters showed variability. Characters such as runner shoot production, pubescence on stem, type of veining, leaf texture, spike colour, spike orientation, spike shape, spike fragrance, spike proliferation, colour change while fruit ripening, fruit taste and seed texture were uniform in all the selected genotypes. The UPGMA dendrogram divided all the genotypes into 15 clusters at 73 per cent similarity. Sensory evaluation of the selected black pepper genotypes showed a significant variation for colour, odour, taste and flavour. G16 (Kottanadan) was significantly superior in taste while G15 (Kuthiravally) was superior in odour and flavour. Thirty four quantitative characters were recorded for plant, leaf, inflorescence, fruit and seed characters. Summarizing these quantitative characters using descriptive statistics revealed wide range of variability in number of well developed fruits per spike, number of spikes per 30 cm2 , number of spikes per vine, bulk density and specific leaf area. Principal component analysis was undertaken to examine the variation and to estimate the relative contribution of various trait for total variability. The principal component analysis for twenty three yield related characters revealed seven principal components at 85.53 per cent variability. The eleven quantitative characters such as juvenile leaf length, leaf length, leaf width, number of spikes/30 cm2 , number of spikes per lateral branch, number of spikes per vine, number of nodes per lateral branch, number of well developed berries per spike, berry diameter, support height and vine column diameter contributed more to the yield. The score plot identified fifteen clusters in which genotypes with superior yield namely, G1 (Wayanadan), G4 (Nadeshan), G5 (Nadan), G15 (Kuthiravally) and G21 (Panniyur 1) formed unique clusters. Minimal data set generated for black pepper included four characters namely, number of nodes per lateral, number of well developed berries/spike, number of spikes/30 cm2 and berry diameter. The principal component analysis for five physiological parameters revealed one principal component at 73.34 per cent variability. Genotypes with high leaf thickness, high relative water content, high epicuticular wax, low specific leaf area and low stomatal density were associated with drought tolerance in black pepper. Sixteen clusters were identified based on score plot. Biplot analysis identified genotypes G16 (Kottanadan), G13 (Vellanamban), G6 (Karimunda), G7 (Neelamundi), G18 (Padappan) and G20 (Narayakodi) as most desirable genotypes for drought tolerance. The principal component analysis for six quality attributes revealed two principal components at 66.62 per cent variability. The genotypes were grouped into seventeen clusters based on score plot while the biplot identified genotypes G16 (Kottandan), G15 (Kuthiravally), G21 (Panniyur 1), G19 (Karivilancy), G17 (Arimulak), G13 (Vellanamban) and G6 (Karimunda) as the high quality ones. The genotypes studied for qualitative, quantitative, physiological and quality traits showed a moderate variability and can be used in the selection of suitable parents for breeding purpose and gene mapping studies.
Open Access
Growth, yield and essential oil production responses to microbial elicitation in Ocimum basilicum L.
(Department of Plantation Crops and Spices, College of Agriculture, Vellayani, 2021) Rajeswari, E; KAU; Deepa, S Nair
The seeds of O. basilicum used for the study were sourced from Anand Agricultural University, Gujarat. The study was carried out in two phases: Phase 1- Seed priming using fungal derivatives for enhanced germination. Phase 2- Evaluation of the effect of foliar application of fungal derivatives for growth, yield and essential oil production. In the first phase of study, the seeds were subjected to various priming treatments using fungal derivatives viz., Trichoderma viride cell wall extract (1 %) (TCWE), Trichoderma viride culture filtrate (1 %) (TCF), Piriformospora indica cell wall extract (1 %) (PCWE), Piriformospora indica culture filtrate (1 %) (PCF) and hydro priming, maintained upto 30 days after sowing. The seeds without any priming were taken as the absolute control. In the second phase of study, the 30 days old seedlings of O. basilicum were transplanted to grow bags. The foliar spray of corresponding fungal derivatives (cell wall extract and culture filtrate) at 1 % concentration were given to plants at fortnightly intervals from transplanting to 90 days after sowing. The treatment without any foliar application was taken as the absolute control. The seeds bioprimed with PCF @ 1 per cent recorded the highest germination per cent (96%), survival per cent (96%) and had taken minimum number of days (3 days) to initial sprouting. While TCF @ 1 per cent exhibited the highest germination index (34.50) and lowest mean germination time (6.29 days). With regard to seedling development, PCF @ 1 per cent recorded a significantly higher shoot length (21.50 cm), root length (19.50 cm), seedling length (41.00 cm) and seedling vigour index (39.37). The highest (1.07) allometric index was observed in the treatment PCWE @ 1 per cent. At 110 DAS, the plants subjected to foliar application with PCF @ 1 per cent exhibited higher plant height (80.20 cm), collar girth (6.03 cm), leaf area (4010.82 cm2 ), number of branches (28.00) and number of flowering shoots (104.00). The same treatment induced early flowering (55 days) in O. basilicum. The foliar spray treatment with PCF @ 1 per cent exhibited significantly higher total chlorophyll content (1.20 mg g-1 ) and polyphenol content (84.31 mg PE g-1 ) at 110 DAS. The plants subjected to foliar application with PCF @ 1 per cent recorded maximum leaf biomass (210.00 g and 19.04 g), stem biomass (135.33 g and 12.21 g), herbage yield (345.33 g and 31.25 g), root biomass (52.00 g and 4.63 g) and total plant biomass (397.33 g and 35.88 g) respectively, on both fresh weight and dry weight basis. The same treatment recorded the highest leaf biomass (125.33 g and 12.44 g), stem biomass (76.00 g and 7.31 g), and herbage yield (201.33 g and 19.75 g), on fresh weight and dry weight basis respectively, in the ratoon crop harvested 60 days after the first cut. PCF @ 1 per cent was also observed to give the highest essential oil content (2.11 per cent and 1.00 per cent) and oil yield (443.10 g and 19.04 g, respectively) in terms of both fresh and dry leaf weight. This is followed by PCWE @ 1 per cent and TCF @ 1 per cent in terms of oil content and yield. In the first phase of study, PCF @ 1 per cent gave better performance in terms of seed germination, seedling growth and seedling vigour index. The transplanted seedlings from the same treatment when subjected to foliar application with PCF @ 1 per cent at fortnightly intervals gave the highest plant growth, biochemical and yield parameters in the second phase of study. Hence, it can be inferred that biopriming followed by foliar application of the fungal derivative PCF @ 1 per cent would give superior performance in terms of plant growth, yield and essential oil production in O. basilicum.

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