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Open Access
Management of banana pseudostem weevil odoiporus longicollis oliv.using entomopathogenic fungi
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Sahi Beegum, M K; KAU; Anitha, N
Investigation on “Management of banana pseudostem weevil, Odoiporus longicollis Oliv. using entomopathogenic fungi” was carried out in the Department of Agricultural Entomology, College of Agriculture, Vellayani. The study was conducted to screen four entomopathogenic fungi, to evaluate their biocontrol potential and to standardize the effective dose and method of application for the management of the banana pseudostem weevil. Four entomopathogenic fungi viz., Metarhizium anisopliae, Beauveria bassiana, Paecilomyces lilacinus and Nomuraea rileyi were tested against O. longicollis. Among them M. anisopliae and B. bassiana were found to infect O. longicollis grubs. Susceptibility of different stages of grubs to fungal infection was tested by using first, second, third, fourth and fifth instar grubs of O. longicollis and the results revealed that first and second instar grubs were more susceptible to fungal infection. Determination of effective dose of fungi against second instar grubs of O. longicollis was carried out by spraying the grubs with different concentrations of M. anisopliae and B. bassiana. The LC50 values of M. anisopliae and B. bassiana were 3.9 x 106 spores ml-1 and 1.6 x 105 spores ml-1 respectively. Evaluation of six naturally available solid media viz., rice bran, wheat bran, guinea grass, gingelly oil cake, coir pith, and neem cake were carried out for mass multiplication of M. anisopliae and B. bassiana. The results revealed that both rice bran and wheat bran were suitable for the mass multiplication of these fungi. The spore production was 9.26 x 106 spores ml-1 and 8.71 x 106 spores ml-1 respectively for M. anisopliae on first week after inoculation. For B. bassiana, the spore count was 503.42 x 106 spores ml-1 and 320.32 x 106 spores ml-1 respectively on first week after inoculation. Among the liquid media tried, coconut water and rice bran extract produced maximum mycelial growth and sporulation of fungi. For M. anisopliae the spore count was 7.77 x 107 spores ml-1 and 0.49 x 107 spores ml-1 respectively. B. bassiana recorded 440.03 x 106 spores ml-1 and 232.26 x 106 spores ml-1 respectively. M. anisopliae and B. bassiana grown in rice bran and wheat bran recorded maximum virulence on two weeks after storage and decreased thereafter. However, coconut water and rice bran extract showed maximum virulence on first week after storage and then found decreasing. Studies conducted to evaluate the compatibility of fungi with NeemAzal 0.4 per cent, chlorpyriphos 0.03 per cent, copper oxychloride 0.4 per cent and mancozeb 0.3 per cent revealed that all the pesticides tested inhibited the growth of M. anisopliae and B. bassiana. But the per cent inhibition was least in the case of NeemAzal 0.4 per cent. Field experiments were conducted with M. anisopliae and B. bassiana with chlorpyriphos (0.03 per cent) and NeemAzal (0.4 per cent) as checks. The plants were artificially infested with known number of grubs. Two experiments were conducted, one with prophylactic treatments and the other with curative treatments. Three application methods viz., leaf axil filling of spore suspension of M. anisopliae and B. bassiana, leaf axil filling of fungi in rice bran and stem injection of spore suspension were tested. Among these treatments leaf axil filling of B. bassiana spore suspension at 1.8 x 107 ml-1 as prophylactic treatment was most effective which gave 52.42 per cent mortality of grubs.
Open Access
Major spiders in vegetable ecosystem and their predatory potential
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Manu Mani, P; KAU; Hebsi Bai
Spider faunistic survey conducted in okra, brinjal, cowpea, bittergourd and amaranthus fields in Kalliyoor panchayat of Thiruvananthapuram district during the summer of 2004, revealed the prevalence of high density and diversity of spiders in the vegetable ecosystem. Hunting spiders were dominant in all the vegetable plots. Thirty species of spiders distributed in nine families were recorded with the number of species in each vegetable field ranging from 10 to17. Among the thirty species, 16 species were commonly seen in the different vegetable fields while 14 species were seen exclusively associated with a particular vegetable. Araneidae with ten species was the most represented family in the vegetable fields followed by Oxyopidae and Salticidae. The other families observed were Miturgidae, Thomisidae, Tetragnathidae, Corinnidae, Lycosidae and Clubionidae. Most of the spiders appeared during the vegetative and flowering stages of the crop. Few spiders were recorded in the early stage of the crops. Four spiders viz., O. javanus, C. danieli, N. mukerjei and T. mandibulata were dominant in all the vegetable plots among which O. javanus and C. danieli predominated. Studies on the seasonal influence showed no significant difference in the abundance of the spiders during summer and rainy seasons. Rather, the growth stages of the crops significantly influenced the build up of the spider population with higher population being observed during the reproductive phase. In general, the spiders preferred soft bodied insects like the hemipterans, lepidopterans, dipterans and coleopterans (eggs and grubs) for predation. While the spiders did not show any significant preference for the different hemipteran prey in a mixed diet, significant difference was shown for the different lepidopteran pests. O. javanus had the maximum preference for the lepidopteran pests Chemical insecticides were more toxic to the spiders than botanicals when tested at their recommended doses. Among the chemical insecticides, dimethoate 0.05 per cent, carbaryl 0.2 per cent and malathion 0.1 per cent were highly toxic. Even at different doses the insecticides were toxic to the spiders. Quinalphos 0.05 per cent and imidacloprid were less toxic. Between the two methods of application, topical application of insecticides was more detrimental to the spiders than release on treated plants. Among the spiders, T. mandibulata was more susceptible to the insecticides followed by C. danieli. O. javanus and N. mukerjei were less sensitive. While the fungal pathogens, M. anisopliae, P. lilacinus and Bt were safe to the spiders. F. pallidoroseum, Fusarium sp. and B. bassiana were pathogenic. Based on the results of the study, conservation of the spiders characteristic of the vegetable ecosystem would be a practical and ecologically and economically viable approach for pest suppression in vegetables. When there is a spurt in pest ravage, the protection afforded by the predator could be supplemented with judicious use of “spider friendly” insecticides.
Open Access
Wood property profile of rosewood (dalbergia latifolia roxb.) ceylon rosewood (albizia odoratissima (Linn.F) Benth.) and raintree(Samanea saman (jacq.) Merr.)
(Department of Tree Physiology and Breeding,College of forestry, Vellanikkara, 2005) Vinay Kumar, Sahu; KAU; Gopakumar, S
In the state of Kerala, heartwoods of lesser known timber species viz., Albizia odoratissima (Ceylon rosewood) and Samanea saman (rain tree) are allegedly being used as “substitutes” and “adulterants” for making furniture of Dalbergia. latifolia (Indian rosewood) mainly due to their similar wood colour. As this spurious practice has serious implication in timber trade, a study was undertaken to profile the selected wood properties of all these three species to highlight their similarities and differences. The study involved analyzing selected physical, mechanical, anatomical and biochemical properties of A. odoratissima and S. saman and comparing it with the wood properties of D. latifolia as available from relevant literatures. Variations of higher magnitude were noted between the three species for some wood properties, and with respect to few other properties, the differences were lesser. Significant variations were also observed between tissue types viz., sapwood and heartwood for some wood properties. Heartwood tissue types of S. saman and D. latifolia displayed high calorific value, where as, for A. odoratissima both tissue types (sapwood and heartwood) exhibited medium calorific value. The physical properties of the heartwood of A. odoratissima were observed to be higher than that of D. latifolia. S. saman possessed lower values for the physical properties as compared to D. latifolia. Basic specific gravity, radial and volumetric shrinkages (green to oven dry) were considerably different for all the three species. Generally, for both Ceylon rosewood and rain tree tangential shrinkage was higher than radial shrinkage for both the tissue types. Mechanical properties of A. odoratissima were superior to D. latifolia and S. saman, except modulus of elasticity in compression parallel to grain. On the other hand mechanical properties of S. saman were closer to D. latifolia. Measure of fibre stress at limit of proportionality and modulus of elasticity in static bending and modulus of elasticity in compression parallel to grain are considerably different for the three species. In A. odoratissima and S. saman, the mechanical properties of sapwoods varied non significantly with the strength properties of heartwoods. S. saman exhibited superior strength properties for heartwood over its sapwood. Vessel diameter, distribution of parenchyma and ray height can be used to differentiate the three species. In all the species, along the radial axis from pith towards periphery, the vessel diameter, ray height, ray width increased along the region of heart wood. Likewise, ray frequency, and vessel frequency decreased along radial axis in heartwood region. Average vessel diameter, ray height and ray width of sapwoods were greater than that of the heartwoods. Lignin, cellulose and holocellulose percent of A. odoratissima and S. saman were significantly greater than D. latifolia. Higher lignin, cellulose and holocellulose content are responsible for the higher strength properties of A. odoratissima. Methanol-acetone extracts of heartwood of D. latifolia exhibits specific peak wavelengths under spectrometric analysis, which are not found in the other two species. Phenolic compounds were observed to influence some of the physical properties.
Open Access
Major spiders in vegetable ecosystem and their predatory potential
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Manu Mani, P; KAU; Hebsi, Bai
Spider faunistic survey conducted in okra, brinjal, cowpea, bittergourd and amaranthus fields in Kalliyoor panchayat of Thiruvananthapuram district during the summer of 2004, revealed the prevalence of high density and diversity of spiders in the vegetable ecosystem. Hunting spiders were dominant in all the vegetable plots. Thirty species of spiders distributed in nine families were recorded with the number of species in each vegetable field ranging from 10 to17. Among the thirty species, 16 species were commonly seen in the different vegetable fields while 14 species were seen exclusively associated with a particular vegetable. Araneidae with ten species was the most represented family in the vegetable fields followed by Oxyopidae and Salticidae. The other families observed were Miturgidae, Thomisidae, Tetragnathidae, Corinnidae, Lycosidae and Clubionidae. Most of the spiders appeared during the vegetative and flowering stages of the crop. Few spiders were recorded in the early stage of the crops. Four spiders viz., O. javanus, C. danieli, N. mukerjei and T. mandibulata were dominant in all the vegetable plots among which O. javanus and C. danieli predominated. Studies on the seasonal influence showed no significant difference in the abundance of the spiders during summer and rainy seasons. Rather, the growth stages of the crops significantly influenced the build up of the spider population with higher population being observed during the reproductive phase. In general, the spiders preferred soft bodied insects like the hemipterans, lepidopterans, dipterans and coleopterans (eggs and grubs) for predation. While the spiders did not show any significant preference for the different hemipteran prey in a mixed diet, significant difference was shown for the different lepidopteran pests. O. javanus had the maximum preference for the lepidopteran pests Chemical insecticides were more toxic to the spiders than botanicals when tested at their recommended doses. Among the chemical insecticides, dimethoate 0.05 per cent, carbaryl 0.2 per cent and malathion 0.1 per cent were highly toxic. Even at different doses the insecticides were toxic to the spiders. Quinalphos 0.05 per cent and imidacloprid were less toxic. Between the two methods of application, topical application of insecticides was more detrimental to the spiders than release on treated plants. Among the spiders, T. mandibulata was more susceptible to the insecticides followed by C. danieli. O. javanus and N. mukerjei were less sensitive. While the fungal pathogens, M. anisopliae, P. lilacinus and Bt were safe to the spiders. F. pallidoroseum, Fusarium sp. and B. bassiana were pathogenic. Based on the results of the study, conservation of the spiders characteristic of the vegetable ecosystem would be a practical and ecologically and economically viable approach for pest suppression in vegetables. When there is a spurt in pest ravage, the protection afforded by the predator could be supplemented with judicious use of “spider friendly” insecticides.
Open Access
Effect of phosphatic fertilizer compounds on aquatic primary production in saline water
(Department of Fishery Hydrography, College of Fisheries, Panangad, 2005) Rajkumar, K R; KAU; Mrithunjayan, P S
Fish production in farms largely depends on the primary productivity In the water bodies. Among many factors, plant nutrient levels and their availability in absorbable forms for the plankton is the most important one contributing to primary production. The plant nutrient element, phosphorus often found to limit the production, mainly due to the behavior of phosphorus compounds to remain in unavailable form in aquatic environment. Hence it becomes imperative to supplement phosphorus in suitable chemical form to achieve better production. While the dosage is also important, the salinity of water bodies has an interactive effect. Thus species of compounds in phosphatic fertilizer is vital. In the present study, two types of phosphatic fertilizers and combination of these fertilizers with additives were tested for their effect on aquatic primary production. Synthetic fertilizer namely single superphosphate and natural phosphatic fertilizer namely rock phosphate were selected for study. Commercial grade trisodium phosphate was used as additive in combination with single superphosphate and rockphosphate in 1: 1 ratio with respect to phosphate- P. All the above four fertilizer materials were tested in brackishwater having two salinity levels, a low salinity level of approximately 10 ppt and a high salinity level of approximately 20 ppt. Each fertilizer was added in three different doses, ie, O.lppm, 0.2 ppm and 0.4 ppm of phosphate-P. A set of control with two salinity level of water and without adding fertilizer were also run. All the experiments were done in duplicate, in accordance with statistically designed 2x4x4 Factorial Completely Randomized Design. The experiments were conducted in wide mouth polythene drums having 25 litre capacity using 20 liters of water. The experiment was set up in a protected, undisturbed, elevated place and kept exposed to sun light for 30 days. Volume loss due to evaporation was compensated by adding appropriate amount of water having corresponding salinity. 140 Water samples were drawn on l " day (before the addition of fertilizer), i\ 14th and so" days and analysed for available phosphate, total phosphate, silicate, nitrite, nitrate, iron, water pH, dissolved oxygen, carbon dioxide, total alkalinity, total hardness and calcium. Productivity was assessed on 1 st day and so" day by estimating chlorophyll. The results were statistically analysed with ANOV A technique. In the experiment, maxrmum productivity in terms of chlorophyll (14.6mg/m3) was found under the treatment with single super phosphate along with additive trisodium phosphate when applied at a dose of 0.4 ppm of phosphate-P in the high saline media. For the same type of treatment in low salinity level, a little reduced value of productivity was observed (chloropyll =13.9 mg/rrr'), The next effective treatment was rock phosphate with trisodium phosphate at a concentration of 0.4 ppm of phosphate-P, here a chlorophyll concentration of 13.6mg/m3 and 12.6 mg/rrr' were obtained in high and low salinities respectively. The minimum productivity levels were observed in treatments with rock phosphate alone in all concentrations, compared to other treatments. It could be concluded from the experiments the following i) single super phosphate with a combination of trisodium phosphate was most effective compared to rock phosphate with trisodium phosphate, which could be due to the greater solubility of single super ph~sphate ii) single super phosphate was found to be more effective than rock phosphate, which could be due to the grater solubility as already explained. iii) the concentration level of 0.4 ppm of phosphate-P was found to be the most effective in enhancing the primary production compared to the lower doses tried ie, 0.1 and 0.2 ppm. iv) along with an increase in the available phosphate from the added fertilizers there was an increase in the primary production also v) salinity was found to have some effect on production, higher the salinity grater the production. This can be due to the availability of other minerals and intrinsic factors required for the synthesis of chlorophyll and biomass.
Open Access
Studies on the maturation and reproduction of pristolepis marginata jerdon under captive conditions
(Department of Fishery Biology, College of Fisheries, Panangad, 2005) Nisha, Raj; KAU; Anna Mercy, T V
Pristolepis marginata Jerdon commonly called “Malabar catopra” or “Malabar sunfish” or “Chutichi” in the vernacular is an attractive ornamental fish belonging to the family Nandidae. This species, which is endemic to the Kerala part of Western Ghats inhabits clear and rapid streams. The species has been enlisted as vulnerable by – the Conservation Assessment and Mangement Plan Workshop (CAMP, 1998) for fresh water fishes of India held at NBFGR, Lucknow. Conservation of the endangered/vulnerable fishes cannot become successful without protection to the resources, which support the diversity and abundance. Hence Pristolepis marginata was one of the prioritized species for the development of captive breeding technology under NBFGR – NATP programme entitled “Germplasm inventory evaluation and gene banking of fresh water fishes of India”. Anna Mercy et al., (2003) developed the captive breeding technology for Pristolepis marginata. In the present study, an attempt was made to understand the maturation and reproduction of P. marginata in captivity. Captively reared fishes from the NATP project of College of Fisheries were utilized for the present study. A total of 209 fishes (12 to 149 mm) were used for the study of reproductive biology. A six-stage key was used for the classification of the maturity stages. The size at first maturity for females and females were found to be 54 mm and 72 mm SL respectively. Gross picture of distribution of ova stocks in the anterior, middle and posterior regions of the ovary remained almost the same except for the slight variation in the percentage composition of the mode. Based on the ova diameter frequency studies, P. marginata was found to be a multiple spawner, which release eggs in two or three batches. Absolute fecundity of the fishes ranged from 1102 (first time spawner) to 4965 (repeat spawner) in fishes of size range 66 to 80 mm SL. Number and size of eggs was found to be directly proportional to the size and age of the fish. Fecundity showed a positive linear relationship with the length and weight of the fish as well as to length and weight of the ovary. The reproductive organs of P. marginata were built on the usual percoid plan with paired ovaries and testis. The ovaries of P. marginata showed asynchronous development, in which oocytes at all the stages of development were present in the same ovary at the same time. During the spermatogenesis, there is a gradual decrease in size of different stages from spermatogonia to spermatozoans. Length – weight relationship values showed that the juveniles are exhibiting allometric growth pattern with ‘ b’ value equal to 2.83. Males also showed allometric growth pattern with ‘b’ value equal to 2.68. Females have shown isometric growth pattern with ‘b’ value equal to 2.94. Average relative condition factor values were higher in juvenile (1.43) due to the higher growth rate encountered during this stage of the life cycle. Males showed higher average relative condition value than females.
Open Access
Integrated pest management in rice production: resource use efficiency and relative economics
(Department of Agricultural Economics, College of Horticulture, Vellanikkara, 2005) Saijyothi, D; KAU; Indira Devi, P
The present study entitled Integrated Pest Management in rice production: resource use efficiency and relative economics, was conducted in Kuttanad region of Kerala, India with the specific objectives of evaluating the economics of IPM technology over the traditional practice and to assess the resource use efficiency. The study pertaining to the summer crop in the area (November 2004 to February 2005) was undertaken during March to July 2005 A sample of 70 farmers each from IPM and Non-IPM category were selected by conducting a preliminary survey to categorise the farmers under each group. The production details of paddy were gathered from both the groups using a pretested structured questionnaire by personal interview method. The management under IPM programme starts from the very beginning of the crop calendar, starting with the varietal selection, its source, seed rate and method of planting. Though both types of farms were sowing only recommended varieties, seed rate was much above the recommended level in the case of non IPM group and they primarily relied on farm saved seeds. It was the reverse in the case of IPM farms. The level of application of fertilizers and soil ameliorants was lower in the case of IPM farms. Among the various inputs in crop production, labour was the most important single item of expenditure in paddy production. The total labour use in IPM farms was found to be 75 man-days per hectare i.e., 5.63 per cent higher than that of Non-IPM farms (71 man days per hectare). This is primarily due to the additional labour required in IPM farms for weeding (due to lesser amount of weedicide use), land preparation (additional ploughing), harvesting (higher yield) and IPM measures. Thus the total expenditure on seeds and sowing, fertilizer application and plant protection charges were 67.15 per cent higher in the Non-IPM group. Contrary to this, the expenditure on land preparation, weeding and harvesting operations together, were 11.93 per cent higher in IPM group. Total cost of cultivation was estimated as 5.07 per cent higher in Non-IPM group (Rs31536/ha) compared to IPM group (Rs 29841/ha) Apart from the cost saving, relatively higher yield (45.23 quintals per hectare) was also there in IPM farms compared to the other group.(44.46 quintals per hectare). The partial budgeting analysis have revealed that the cost saving coupled with higher yield realization in IPM farms has resulted in an additional net private gain in income to the tune of Rs 2824 per hectare Benefit cost ratio at Cost A1 was estimated as 1.85 (Non-IPM) and it was 2.06 for IPM farms inferring rice cultivation under IPM, as more beneficial than chemical based cultivation. At cost C3 level, the non IPM groups were more prone to risk as the BC Ratio was very close to unity Cobb-Douglas production function was fitted to assess the efficiency of resource use in paddy cultivation for both IPM and Non-IPM farms. It could be concluded that IPM farms were economically more efficient in resource utilization than the Non-IPM counter parts. Though most of the farmers were aware of the potential hazards of excessive chemical use in agriculture, and got exposed to adequate training, the spread of the technology is constrained by factors like, the perception of a yield loss, difficulties in water management and labour problems. But those who have adopted the technology was found to be aware of the short-term nature of yield reduction and cost saving aspects of the technology. The policy suggestions are made based on the findings and future line of work is also suggested.
Open Access
Seasonal occurance and ecofriendly management of pests of amaranthus
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Asha, J S; KAU; Nandakumar, C
Seasonal occurrence of pests, their natural enemies and leaf blight disease of amaranthus were studied in the Instructional Farm, College of Agriculture, Vellayani from April 2004 to April 2005. Leaf webbers Psara basalis F. and Hymenia recurvalis (F.) were the major pests of amaranthus and leaf blight disease caused by Rhizoctonia solani Kuhn. was the major disease. The leaf webber P. basalis was present in the field throughout the year. However the highest population and infestation was observed during the summer months. Maximum population of larvae was observed during the month of April 2004. The population and extent of damage by the pest exhibited significant positive correlation with maximum and minimum temperature. The leaf webber H. recurvalis was also present in the field throughout the year. The population and extent of damage by the pest was maximum during June, July and November 2004 and minimum during the summer months (April and May 2004). The population of the pest showed significant positive correlation with minimum temperature. The green grasshopper Atractomorpha crenulata F. was observed in the field throughout the year. Highest population was observed during the first fortnight of October 2004. The percentage of plants and leaves damaged by the grasshopper was maximum during the second fortnight of November 2004. The population and extent of damage of the grasshopper showed significant negative correlation with minimum temperature. The percentage of plants damaged by the tobacco caterpillar Spodoptera litura (F.) was maximum during the second fortnight of June 2004 and the leaves damaged was the highest during the first fortnight of June 2004. The leaf damage showed significant positive correlation with rainfall. A solitary braconid endoparasitoid Apanteles opacus (Ashmead) was found infesting the second instar larvae of H.recurvalis. The population of pupae of the parasitoid was maximum during the first fortnight of July 2004. Spider predators viz., Oxyopes spp., Cheiracanthium sp., Phidippus sp. and Tetragnatha sp. were found in the field throughout the year. Maximum population of spiders was observed during the second fortnight of September 2004. The population showed significant positive correlation with maximum temperature. The leaf blight disease caused by R. solani was observed throughout the year. The percentage disease index (PDI) was maximum during the second fortnight of December 2004. Studies on antifeedant effect of botanicals on major pests of amaranthus revealed that azadirachtin 0.0025 per cent was the best phagodeterrent followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. Six botanical pesticides were evaluated with malathion as check in a field experiment. The treatments included neem seed kernel extract five per cent (NSKE), neem cake (NC) soil application @ 250 kg.ha-1 at planting + neem cake extract (NCE) 10 per cent spray, azadirachtin 0.0025 per cent, cow’s urine 10 per cent + NSKE five per cent, Pongamia oil soap emulsion two per cent and annona seed extract two per cent. Three sprays of the treatments were applied on the crop during the experiment. The results revealed that all the treatments were significantly superior to control in reducing the population of pests and their damage. Azadirachtin 0.0025 per cent was the most effective treatment against leaf webbers and grasshopper. This was followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. The extent of damage caused by these pests in azadirachtin treated plots was statistically similar to that of malathion treated plots. . The extent of damage by the tobacco caterpillar was the lowest in NC soil application @ 250 kg ha-1 + NCE 10 per cent spray treatment. Higher population of spiders was found in botanical treated plots and control plots compared to malathion treated plots. The botanical treatments were not effective in containing the leaf blight disease. Maximum yield of marketable produce was recorded from malathion treated plots. However the B : C ratio was the highest (3.20) in botanical treatment, azadirachtin 0.0025 per cent (NeemAzal 1% TS @ 2.5 ml/litre) followed by cow’s urine 10 percent + NSKE five per cent (2.12) and NSKE five per cent (2.08). Three sprays of any of these botanicals at fortnightly intervals starting from two weeks after transplanting could manage the pests of amaranthus.
Open Access
Identification of drought tolerant cocoa types
(Department of Agronomy, College of Horticulture, Vellanikkara, 2005) Binimol, B; KAU; George Thomas, C
Experiments were conducted at the college of Horticulture, Vellanikkara to investigate the drought tolerant characteristics of the most promising cocoa varieties and accessions. The investigation involved a two-stage screening of cocoa seedlings and budlings and monitoring of their field grown plants. As the first step, a preliminary screening was done on six month old seedlings and budlings of ten cocoa cultivars released from Kerala Agricultural University and twenty promising accessions. A secondary screening of cocoa cultivars/accessions selected from the preliminary screening was then conducted. Simultaneously, field monitoring of cocoa trees of the varieties selected from the primary screening was also done. From the preliminary screening, seven apparently tolerant varieties were selected for secondary screening in both seedlings and budlings based on higher RWC and DWF, lower percentage of dried leaves and longer duration of life under during moisture stress. Three apparently sensitive verities were also selected based on opposite values of the above characters. Varieties identified in the preliminary screening were subjected to a secondary screening under three moisture regimes of no irrigation , watering once in five days (life saving irrigation), and regular watering. Observations on physiological parameters such as relative leaf water content, dry weight fraction, leaf drying percentage, number of days taken for complete drying, stomatal conductance, transpiration rate, leaf water potential, chlorophyll ‘a’, ‘b’ and total chlorophyll, chlorophyll stability index, leaf area per seedling, membrane stability, relative injury; growth characters like plant height, collar girth, number of leaves and total biomass; biochemical characters such as proline content and nitrate reductase activity were recorded. After conducting a cluster analysis, the varieties with high RWC, DWF, total chlorophyll content, leaf water potential and proline content; low stomatal conductance, transpiration rate and leaf area during water stress were rated as drought tolerant and with opposite characters as drought sensitive. Based on these, in seedlings; the varieties M 13.12, GII 19.5 and GVI 55 were ranked as moisture stress tolerant and GVI 61, GV 50 and GI 4.8 as sensitive under no irrigation. In budlings, the varieties GI 4.8 and GII 19.5 were selected as drought tolerant and GIII 4.1, GVI 51 and GII 12.3 as drought sensitive under no irrigation Important characters were also monitored in 16-year old clonal trees of the seedlings/budlings of the varieties selected from primary screening. Transpiration rate, stomatal conductance, leaf water potential, stomatal frequency, leaf thickness, bark thickness and soil moisture content were recorded during summer. The varieties GVI 61, M 13.12 and GI 4.8 showed drought tolerant features. The accession M13.12 (CCRP2) showed drought tolerant features in secondary screening of seedlings and field performance. The accession GVI 51, which showed sensitivity to moisture stress in seedlings (but tolerant in budlings) under secondary screening, was showing similar behavior of sensitivity in field grown plants. The study shows the possibility of exploiting drought tolerant features of cocoa varieties/accessions. However, final conclusions are difficult to be drawn as only 10 accessions were subjected to secondary screening and field monitoring, and data for only one year were collected. In the light of the promising results obtained, screening trails involving more number of varieties/accessions have to be conducted and monitored for more number of years to get consistent values.

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