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2017 - 20192
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Author: Athulya, S Nair × Author: KAU × End date: 2019 × Start date: 2017 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Marker assisted backcrops breeding in rice for drought tolerance
    (Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2019) Athulya, S Nair; KAU; Abida, P S
    Rice {0ryza sativa L.) is one of the most important food crop grown across the globe. The crop is cultivated in diverse environments ranging from uplands to deep water ecosystems. Drought is one of the major constraints for rice production in rainfed lowlands. In the present scenario of climate change, the frequency of drought is more likely to increase in the future, making drought resistance in rice varieties indispensable. During the era of post-green revolution, many locally adapted traditional rice varieties (TRVs) were replaced by high yielding varieties (HYVs) that thrive best in the irrigated ecosystem. Most of these HYVs sutTer heavy yield loss even under mild water deficit conditions. Hence, improving drought tolerance of high yielding varieties is imperative. Considering this, the study 'Marker assisted backcross breeding in rice for drought tolerance,' was executed with an objective to improve drought tolerance in high yielding rice variety Ptb 39 (Jyothi; J) using Ptb 30 (Chuvannamodan; Ch) as donor parent, through marker assisted backcross breeding. Jyothi is a popular high yielding rice variety of Kerala derived from the cross between Ptb 10 and IR 8. Chuvannamodan is an improved landrace, recommended for ''Modan^ i.e., upland cultivation owing to its drought tolerance ability. Morphological characterisation of both the varieties was done at Regional Agricultural Research Station, Pattambi, during 2018. Chuvannamodan registered a higher vegetative growth than variety Jyothi. The plant height and the number of productive tillers were 141 cm and 33 respectively in Chuvannamodan, while, in comparison, it was 91 cm and 17 in Jyothi. It was also observed that Chuvannamodan flowered earlier (Days to 50% flowering: 76 days) than variety Jyothi (Days to 50% flowering: 93 days). However, Jyothi out-performed Chuvannamodan with respect to the yield traits like number of filled grains per panicle (Ch: 71 and J: 104), iOOO-grain weight (Ch: 27.00 g and J: 28.30 g), and grain density (Ch: 1.09 g/cm^ and J: 1.11 g/cm^). The sterility in Chuvannamodan and Jyothi was 11.40 per cent and 18.40 per cent respectively. The water mining traits like root length, root volume, root dry weight and root to shoot ratio were higher in variety Chuvannamodan. The root length, root volume, root dry weight and root to shoot ratio of Chuvannamodan was respectively 109cm, 96cm"\ 31.60g and 0.31, while, it was 68cm. 32cm^,14.40g and 0.24 respectively in variety Jyothi. The genetic polymorphism study between Jyothi and Chuvannamodan was I studied using 120 SSR markers. Forty-seven markers were found to be n, polymorphic between the two genotypes. Among these polymorphic markers, 24 are reported to be linked to drought tolerance traits. Forty five F1 seeds were obtained by hybridizing variety Jyothi (as female parent) and Chuvannamodan (as male parent). Staggered sowing of the two varieties was done at weekly intervals for this purpose. Only six Fj seeds germinated. The test for confirmation of hybridity was conducted in these plants along with the parents. The polymorphic markers RM3825 and RM263, which are reported to be linked to drought traits were used for hybridity testing. Two plants, P5 (Plant No.5) and P6 (Plant No.6), were confirmed to be true hybrids as they were found to be heterozygous for the parental alleles. The hybrids (P5 and P6), were then backcrossed to the recurrent parent Jyothi to produce BCiFi seeds (15 Nos.). Simultaneously, selfing of the Fis to generate F2S (300 Nos.) was also done. In order to advance further the marker assisted backcross breeding programme aimed at imparting drought tolerance to Jyothi, the BC1F1s produced need to be genotyped further to identify progenies with resistant alleles for drought tolerance. The F? population can be forwarded to develop RJLs (Recombinant inbred lines) that would enable mapping of qualitative traits and quantitative trait loci related to drought tolerance. The F2S can also serve as the base population for the development of advanced breeding lines through pedigree selection.
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    ThesisItemOpen Access
    Characterisation of boron deficient coconut palms (Cocos nucifera L.)
    (Department of Plantation Crops and Spices, College of Agriculture, Vellayani, 2017) Athulya, S Nair; KAU; Sreekala, G S
    The experiment entitled ‘‘Characterisation of boron deficient coconut palms ( Cocos nucifera L.)” was undertaken at farmer’s field in Kalliyoor panchayat of Thiruvananthapuram district during the period from April 2015 to March 2016. The objective of the study was to identify boron deficient coconut palms and predisposing factors responsible for deficiency based on the visual diagnosis and to study the morphological characters of boron deficient and healthy coconut palms. The survey was conducted among hundred coconut palms in Kalliyoor panchayat of Thiruvananthapuram district to identify coconut palms deficient in boron based on visual symptoms listed by CPCRI. Based on the symptoms a ten scale score was developed and boron deficient palms were categorized as mild, moderate and severe intensity and compared with soil and plant boron status . The field, soil , plant characteristics and management aspects of coconut palms deficient in boron were identified based on questionnaire prepared. The morphological and yield parameters were observed at 45 days interval for one year in five palms each from mild, moderate and severe intensity and was compared with healthy palms. The results of the survey showed that the boron deficiency in palms were restricted to age group between 20-45 years grown on red loam soil with pH 6.0-7.5. The deficiency symptoms were common in coconut fields where intercropping was practiced (63 %) and in other fields with poor agronomic management (37 %). Mite and coreid bug attack were prominent ( 89 % and 53 % respectively). Diseases among deficient palms were restricted to 26 percentage and leaf rot was the major one. Common visual symptoms of palms with mild intensity were reduced leaf size, length. hooked leaves, fused leaves, and leaflets with relatively higher internodal Necrotic inflorescence, reduced nut set, poor nut size, nuts with hen and chicken symptoms and crowded crown were prominent in moderate to severely intensity groups. The morphological and yield parameters of selected palms of four groups indicated significant difference between palms of healthy and severe intensity for number of leaves, leaflet internodal length, number of female flowers per bunch of unfertilized inflorescence, opened and unopened spadices, bunches per palm, malformed nuts, volume of nut water, weight of embryo and shell throughout the observation period . The cortical cells of root were loosely packed for boron deficient palms of moderate and severe intensity. Nuts from healthy palms when compared with that from the mild, moderate and severe intensity differed significantly with respect to weight of unhusked nut, weight of husked nut, nuts set per bunch, nuts per palm per year, polar and equatorial diameter of unhusked nut, thickness of husk , weight of opened nut, thickness of meat, weight of kernel ,weight of copra and oil content and the difference was proportional to enhancement in intensity of deficiency. The available boron status in soil and plant were significantly superior in healthy palms. Identification of predisposing factors revealed poor agronomic management, intensive cultivation and low organic matter resulted in B deficieny in Coconut growing areas. The results indicated that B had marked influence in enhancing the yield characteristics of coconut particularly of thickness of meat, weight of kernel, weight of copra, oil content etc. There is a significant reduction in the yield of deficient coconut compared to that of healthy palms. The study thus substantiate the importance of boron in the nutrition of coconut palms.