Browsing by Author "Achamma Oommen"

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Anther culture in cocoa
(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1992) Sunil, K P; Achamma Oommen
Investigations on anther culture of cocoa (Theobroma cacao L.) were carried out at the College of Horticulture, Kerala Agricultural University, Vellanikkara, during 1990-'92 with the objective of studying the amenability of cocoa anther under in vitro conditions for the production of haploids. The fertility and viability of pollen grains of cocoa were found to be 35 and 61 per cent respectively. Anthers at tetrad stage (bud length 1.75 mm) were subjected to a two-stage culture procedure involving incubation and subculture (after 4 weeks) on modified H3 basal medium supplemented with 1 mg 1-1 NAA and 0.1 mg 1-1 2-iP for 50 days (stage 1) and subsequent weekly transfer to ½ Ms basal media supplemented with 0 to 1 mg 1-1 2-iP and 0 to 3 mg 1-1 GA3 (stage II). Proembryoids were obtained in stage 1 medium via callus within 45 days of culture, only when anthers derived from Criollo, Trinitario and H2 were cultured. Serial subculturing of embryoids in stage II media led to formation of shootlets and rootlets. With four sub- cultures in stage II in a span of one month, the embryoids could be germinated into plantlets of size 2.5 cm with two leaflets and one rootlet. This is the first report of plantlet recovery from cocoa anthers via indirect embryogenesis. The plantlets were dried up after an elapse of 3 months. The most favourable combination for root development was Ms medium supplemented with 2 mg 1-1 2-iP, 0.1 mg 1-1 NAA and 126 mg 1-1 PG. The factors influencing anther callus induction were: stage of anther development, minimum temperature in the field of donor plants, type and strength of basal medium, type and concentration of auxins and cytokinins, carbohydrate source, sucrose level, presence of CW and PG, physical environment and gamma and UV rays. Anther callus multiplication was influenced by type of basal medium; type and concentration of growth regulators; carbohydrate source; sucrose level; presence of amino acids; organic supplements; ethylene releasing and inhibiting chemicals; adenine and its derivatives; unusual regulants.; gibberellins and growth inhibitors; light and gamma rays. The factors influencing indirect embryo- genesis were found to be stage of anther development and light. Hybrid genotype (H2 and H1) responded more favourably to callus induction, callus multiplication, callus rhizogenesis and were stable with respect to seasonal changes. However, they took more number of days for callus initiation. Criollo took minimum period for callusing. Chlorine water treated for 3-4 min was the best chemical identified for surface sterilization of flower buds of cocoa. A single auxin or cytokinin alone in the basal medium could not initiate anther callusing. Thermic shock pre-treatments were ineffective for callus induction. Light had no role in callus induction. UV rays had no role in altering anther callus growth. Time of subculturing in cell suspension culture was found to be 15 days. Calloids developed in cell suspensions were not amenable to organogenesis or embryogenesis. Isolated microspore culture was unsuccessful.
Chlorophyll content as an index for selection in Rauwolfia spp.
(Kerala Agricultural University, 1996) Narayanan, A K; Luckins C Babu; Namboodiri, K M N; Achamma Oommen; Augustine, A
Combining ability in pigeonpea (Cajanus cajan [L.] millsp)
(Kerala Agricultural University, 1996) Achamma Oommen; Namboodiri, K M N; Vijayakumar, N K
Even though both additive and nonadditive gene effects were found to be important in the expression of the characters studied, the additive gene effects were having more influence than nonadditive gene effects. Number of primary branches was determined by additive and nonadditive genes, whereas number of secondary branches was influenced by additive genes. All the other nine characters were determined by additive genes. Among the five parents studied, PLA 550 was the best general combiner and among the crosses UPAS 120 x 1C 15708 was having good sea for all the characters.
Concept of ideal plant type (ideotype) in horsegram (Dolichos Biflorus L.)
(Kerala Agricultural University, 1995) Swapna, M; Achamma Oommen; Namboodiri, K M N; Luckins C Babu
The concept of an ideal plant type in horsegram was studied based on crop growth rate (CGR), net assimilation rate (NAR), leaf area index (LAI) and harvest index (HI). A plant type with peak CGR, NAR and LAI at the middle growth period was found to be the best. Efficient partitioning of the total dry matter produced towards the reproductive parts was very important for a higher harvest index.
Genetic analysis in red gram (Cajanus cajan L.)
(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1990) Achamma Oommen; Narayanan Namboodiri, K M
The research project "Genetic analysis in red gram" was carried out in the College of Horticulture, Kerala Agricultural University, Vellanikkara, Trichur during the period 1985-90. A 5 x 5 diallel cross, excluding reciprocals conducted in red gram revealed the predominance of additive gene effect for all the characters except days to first flowering. The combining ability analysis showed PLA-550 as the best general combiner; and the F 1 of the cross UPAS-120 x I.C. 15708 to have good specific combining ability. Negative heterosis over both the parents was exhibited by UPAS-120 x I.C. 15708 and PLA-550 x PLA-600 for days to first flowering and days to maturity which showed that early maturing segregants could be obtained from these crosses. The same crosses showed relative heterosis for yield also. The analysis of generation means by using six parameter model revealed the importance of both additive and dominance gene effects in the expression of most of the characters. Additive x additive and dominance x dominance effects showed influence in the expression of the characters. Among the components of variances dominance variance was higher for most of the characters. Heritability in narrow sense was found to be low. Number of clusters per plant and number of pods per plant were highly correlated with yield in parents, F 1 's and F2's. As the yield and yield components in the present study were under all the three types of gene action viz., additive, dominance and epistasis, reciprocal recurrent selection procedure seems to be the best suited method of breeding for improvement of this crop.
Genetic analysis of certain clones,hybrids and inbreds in cocoa
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 1998) Rose Mary Francies; Achamma Oommen
Genetic studies in cocoa (Theobroma cacao L.) using various population viz., clones, biclonal crosses, biclonal pair crosses and inbreds were undertaken in College of Horticulture, Kerala Agricultural University, Thrissur, during 1994-97. The study assessed variability, association of yield attributes and relative importance of these attributes for yield variation using multiple regression and path analysis. Selection indices, inbreeding depression and limits to genetic diversity for heterosis were also worked out. Wide spectrum of variability existed in the populations studied. The highest variability was observed in yield of dry beans/tree and precocity of bearing (pods/tree - 5 years from planting), whereas, traits pod width and bean width showed low variability. Clones GI 10.2, S 27.16, GI 14.17 of Clonal base population, hybrids H'8 (GI 5.9 x GII 23.3), H2 (M 13.12 x GI 5.9) of Series IV biclonal crosses and hybrids H4 (M 16.9 x GII 19:5), H3 (M 16.9 x GII 20.4) of Series 11 biclonal crosses, exhibited superior yield - performance. Yield however, recorded only moderate heritability and therefore moderate expected genetic advance. Strong correlation was observed for yield with pod weight, dry weight/bean and efficiency index but not with precocity of bearing, chlorophyll contents and net photosynthesis rate. Multiple regression and path analysis revealed the importance of dry weight/bean, bean size and efficiency index in determining the yield in cocoa. High correlation exhibited by many traits was due to indirect effects. Selection index for yield, based on the above traits viz., dry weight/bean, bean length, bean thickness and efficiency index recorded a relative efficiency of 150.35 per cent over direct selection. Inbreeding depression was observed for growth traits. The rate of depression was more in the second inbred generation as compared to that in the first inbred generation. Number of hybrids exhibiting relative heterosis in desirable direction ranged from one (eg. pod width, bean length and thickness) to seventeen (number of beans/pod). Considerable genetic divergence among clonal genotypes was evident. Results indicated that the chances for occurrence of a high frequency of heterotic crosses and high values of heterosis are more, when the parental divergence is moderate.
Genetic analysis of some quantitative characters in pigeonpea
(Kerala Agricultural University, 1994) Achamma Oommen; Namboodiri, K M N; Unnithan, V K G
Out of the eleven quantitative characters studied in pigeonpea, days to flowering alone was influenced by non-additive genes and all the remaining characters by additive genes. The proportion of dominant and recessive genes was equal for plant height and number of clusters per plant, whereas more than one recessive gene was present for eveiy dominant gene in the expression of days to maturity. The remaining eight characters showed the presence of one to two dominant genes for every recessive gene.
Genetic analysis of yield and yield components in pigeonpea (Cajanus Cajan (L.) Mill sp.
(Kerala Agricultural University, 1999) Achamma Oommen; Namboodiri, K M N; Unnithan, V K G
Generation mean analysis carried out in pigeonpea to estimate gene effects revealed that, yield and yield components AK under all the three types of gene action. v\/.-, additive, dominance and epistasis. Hence reciprocal recurrent selection seems to be the best suited method of breeding for improvement of this crop.
Genetic resource evaluation of groundnut (Arachis hypogaea L.) for resistance to tikka leaf spot
(Division of Agricultural Botany, College of Horticulture, Vellanikkara, 1989) Sajikumar, T A; Achamma Oommen
The research project " Genetic resource evaluation of groundnut Arachis hypogaea L.) for resistance to tikka leaf spot was carried out at the College of Horticulture, Kerala Agricultural University, Vellanikkara, during 1988-89. Two hundred and fifty six groundnut genotypes available in the Department of Agricultural Botany were made use of for the study. A susceptible variety- TMV 2- was used as control. A field screening study was conducted with the 257 genotypes during July- November 1988, in arandomised block design with two replications. Disease rating was done with the aid of a diagramatic chart and the groundnut accessions were grouped into different categories such as immune, highly resistant, resistant, moderately resistant , moderately susceptible, susceptible and highly susceptible , based on the percentage of infection on leaves . Out of the 257 genotypes used for screening studies, four genotypes were moderately susceptible , 197 susceptible and 56 highly susceptible to tikka leaf spot. None of the varieties was immune highly resistant or moderately resistant.
Germplasm evaluation in horse gram (Dolichor biflorus. L.)
(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1993) Swapna, M; Achamma Oommen
A study was undertaken in the Department of Agricultural Botany, College of Horticulture, Vellanikkara during October 1992 to February, 1993 to assess the variability existing in a population of 50 genotypes of horse gram. Evaluations based on the physiological parameters were also carried out. The results revealed the presence of sufficient genetic variability in the different genotypes studied, which were of different geographical origin. High heritability and genetic advance exhibited by the characters, length of pods and number of pods per plant point towards the possibility of these traits to be improved by direct selection. Environmental effect was found to be comparatively higher for yield and number of seeds per pod. Correlation studies indicated maximum correlation of yield with number of seeds per pod and number of pods per plant. Association studies among the different traits showed positive significant correlations between the character pairs, plant height and length of pods, number of primary branches and number of pods per plant, days to 50 per cent flowering and days to maturity; length of pods and number of seeds per pod and 100 seed weight and days to maturity. Divergence analysis gave eleven clusters of which, cluster II and VI showed maximum distance of the cluster members from cluster centroids. The members of these two clusters could be considered superior as parents, for hybridization programme. The maximum mean value for yield was exhibited by members of cluster II. The maximum contribution towards genetic divergence was made by the character 100 seed weight. Growth analysis based as physiological parameters like dry matter production, NAR, CGR, LAI and HI suggested that an ideal plant type will be one in which maximum dry matter production, net assimilation rate and leaf area index was observed during the middle growth stage. An efficient partitioning of dry matter towards the reproductive parts was also an essential criterian.
Somatic embryogenesis in cocoa (Theobroma cacao L.)
(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1993) Jolly Antony; Achamma Oommen
Investigation on somatic embryogenesis in cocoa (Theobroma cacao L.) were carried out at the college of Horticulture, Kerala Agricultural University, Vellanikkara during the period 1989-91, with the objective of studying the developmental potential of somatic embryos and its differentiation into plantlet by means of in vitro techniques. Stem and leaf segments, cotyledons and enbryonic axes of embryos collected from four typical genotypes of cocoa namely criollo, Amelonado, Amazon-forastero and Trinitario were used as explant. Cotyledons and embryonic axes of immature embryos (100 days pot anthesis) when incubated on MS basal semisolid medium supplemented with NAA 2 mg/1, thiamine 1 mg/1, casein hydrolysate 0.2 per cent (W/V) and coconut water 15 per cent (v/v) under dark for seven weeks resulted in high frequency and intensity of embryogenesis. Stem segements remined recalcitrant without embryoid regeneration, while leaf segments had a little potential. Auxins conditioned the culture for embryogenic competence while cytokinins had an inhibitory effect. The effect of NAA 2ppm was not replaceable by other auxins such as IAA, 2, 4-D. 2,4-D was a poor quantitative and qualitative stimulant of embryogenesis. Studies on auxincytokinin interaction revealed the counteracting effect of cytokinin on auxin. Fully mature embryoids germinated in hormone-free liquid medium consisting of half the salt concentration of MS and 5 per cent sucrose when incubated at 3000 lux (16 hours) for two weeks. De-cotyledonisation of embryoids and its rinsing with sterile distilled water and dessication, each for three minutes, enhanced the differentiation into plantlet. Shoot growth was stimulated by exogenous supply of NAA, GA3 and coconut water. In vitro rooting was promoted by reducing the salt concentration of MS medium to half strength and supplementing with IBA and activated charcoal. Germination and regeneration of embryoid into plantlet was dependent on its size. Sizes ranging from 0-4 mm were sub-optimal for germination and differentiation. Larger embroids (4-6 mm) had greater potential for differentiation. Quantitative and qualitative differnces were expressed by cocoa genotypes. Amelonado was found to be superior to Criollo and Amazon types for the induction of embryogenesis from cotyledons. Trinitario was the least efficient. Embryogenic potential of Amazon embryonic axes was superior to Criollo and Amelonado types. Trinitario embryonic axes remained recalcitrant. Plantlets were derived from embryoids within a time span of 13 weeks in Amelonado, Criollo and Amazon types.
Studies on the f2 generation of inter-varietal crosses in rice
(Kerala Agricultural University, 1983) Achamma Oommen; Abraham, A T
In the study of the Fa generation of the cross of two improved dryland strains and a locai medicinal variety of rice with two high yielding varieties revealed that all the characters under observation were inherited polygenically. F2 segregants surpassing the higher parental limit in their mean yield were obtained. No significant correlation was observed between yield and plant height, number of tillers, panicle length and 1000 grain weight.