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ThesisItem Embargo Genetic diversity analysis for nutrient efficiency and identification of nutrient responsive genes in cassava (Manihot esculenta Crantz)(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2023-02-10) Swathy Sivan; KAU; Arya, KThe present study entitled “Genetic diversity analysis for nutrient efficiency and identification of nutrient responsive genes in cassava (Manihot esculenta Crantz)” was carried out in the Department of Plant breeding and Genetics, College of Agriculture, Vellayani and Division of Crop Improvement, ICAR-CTCRI, Sreekariyam, during 2019-2022. The study was undertaken to screen and characterize N and K-efficient genotypes in cassava and identify the traits contributing to nutrient efficiency and study their gene expression. Thirty genotypes of cassava comprising of landraces, released varieties and pre-release accessions from ICAR-CTCRI and KAU were taken for the study. Field evaluation was done to identify low input nutrient efficient lines where analysis of variance revealed significant difference among the genotypes for all the characters studied except the girth of tuber. High GCV, PCV, heritability and genetic advance were observed for traits like tuber yield, N and K efficiency, plant height, number of leaves, number of branches, stem N and K content. Tuber yield was positively correlated to N and K efficiency, plant height, leaf and stem weight, stem girth, mean weight of tubers, number of nodes, girth and length of tubers, while negatively correlated to tuber starch and dry matter content. Path analysis showed that tuber length gave highest positive direct effect on yield followed by number of tubers, number of leaves, tuber starch content, plant height and nitrogen efficiency. Diversity studies grouped the genotypes into eleven clusters and the characters that gave the maximum contribution to divergence were tuber dry matter content, N and K efficiency. Root studies on thirty genotypes revealed that root traits like number of nodal roots, basal roots, adventitious roots, storage roots and root length displayed significant positive correlations with N and K efficiency. Evaluation of five highly nutrient efficient genotypes at the three levels of fertilizers (0%, 25% and 50% of the recommended dose of fertilizers) showed overall significance for traits like plant height, the number of leaves retained, stem weight per plant, girth of the stem, tuber yield, length of tuber, stem K content, tuber K content, total N and K uptake, N and K efficiency. The highest yielder was KBH 18 followed by 8S501-2. Maximum N efficiency was observed for KBH18 followed by 15S409, while maximum K efficiency was recorded for 8S501-2 followed by 15S409. Results showed that from 0 to 25 % there is an escalation in tuber yield as well as N and K efficiency, while the values at 25 and 50% are on par. All the selected four genotypes showed significant superiority over the K efficient check variety – Sree Pavithra – in terms of tuber yield, N efficiency and K efficiency. The study identified nine nutrient responsive genes in cassava which includes NRT1, NRT3, NLP1, GPT2, AMT1, TAR2 for nitrogen and KUP3, KUP4, KUP8 for potassium. Expression studies done using these genes in contrasting genotypes for N and K efficiency raised under field conditions showed significant upregulations and downregulations in their expression for efficient and less efficient genotypes. Allele mining for allelic variations in contrasting genotypes (15S409 and Export kappa) for two genes (AMT2 and NTR3) didn’t show much significant variation. Although SNP differences were observed for NRT3 gene, further functional studies are required to confirm this result. The study identified three main nutrient efficient genotypes viz., KBH18, which was the highest yielder, highest in N efficiency and third highest in K efficiency, 8S501-2, which was second highest in yield, highest in K efficiency, third highest in N efficiency and also exhibited early bulking and 15S409, which was the third highest yielder, second highest in N efficiency & K efficiency. The superior genotypes identified in the present study can be subjected to field trials for confirming their superiority and release as a variety.ThesisItem Embargo Gene action and gene expression analysis in yardlong bean(Vigna unguiculata ssp. sesquipedalis(L.) Verdcourt) for drought tolerance(Kerala Agricultural University, 2022) Rahana, S N; KAU; Beena, ThomasThesisItem Open Access Morpho-molecular characterisation of D x D hybrids developed using 'annur', the dwarf ecotype of WCT coconut ( Cocos nucifera L.)(Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad, 2021) Anuprasad, T E; KAU; Sujatha, RCoconut is one of the most extensively grown crop in the world, playing a significant role in the economic, cultural, and social life of over 80 tropical countries. Coconut cultivars are classified into tall (variety typica) and dwarf (variety nana) types. Short statured palms are currently receiving more attention due to various socio-economic factors. However, the poor quality of nuts for various processing aspects and high susceptibility of dwarf palms to pest and diseases makes them unsuitable for large scale cultivation. The solution for this problem is development of suitable hybrids by combining the desirable features of tall and dwarf palms. West Coast Tall (WCT) is the most widely cultivated variety in Kerala and several ecotypes of WCT were reported. In a study initiated in 2005 at RARS Pilicode, an ecotype of WCT was detected in Annur, a place in Kannur district which showed dwarfing nature with nut qualities similar to WCT. The Annur ecotype was crossed in 2007-08 with the dwarf cultivars Malayan Yellow Dwarf (MYD) and Gangabondam (GB). The hybrid seed nuts along with interse seed nuts of Annur were planted at RARS Pilicode in 2009. The first flowering was recorded in 2014. The present study aims at evaluation of plant stature, yield, nut quality and other important morphological traits of Annur and the hybrids developed from it. The interse of Annur, Annur x GB and Annur x MYD were compared with corresponding characters of the respective parents as well as WCT, Keraganga (WCT x GB) and Kerasree (WCT x MYD). Significant reduction in height was observed for hybrids viz. Annur x MYD (2.251 m) and Annur x GB (2.065 m) which was on par with Annur (2.725 m) and considerably lower than the corresponding values of dwarf cultivars viz., MYD (5.2 m) and GB (8.885 m). Number of nuts per palm per year was on par in Annur (58.2) and Annur x MYD (55.4) while that was lower in hybrid Annur x GB (34.3). However, since the palms started flowering only in 2014, stabilization of yield is not attained. Nut weight and kernel thickness were significantly higher in Annur x MYD whereas these were on par in Annurand Annur x GB. Copra content in Annur and both hybrids were on par. In general, Annur x MYD showed superior performance for nut characters compared to Annur x GB. Annur palms were significantly similar to WCT for most of the characters except height, rate of leaf production, nuts per bunch, nut water content. When the yield of hybrids of Annur were compared with the standard check varieties viz., Keraganga (WCT x GB) and Kerasree (WCT x MYD), (101.5 and 104.25 nuts per palm per year) yield of Annur x GB and Annur x MYD were low. However, both hybrids showed nut characters similar to the respective released varieties ie, Annur x GB was similar to Keraganga and Annur x MYD showed similar nut characters with Kerasree except copra content (161.432 g and 193 g respectively). Better palms from each cross were analysed and palm numbers 1, 2, 15, 19, 20 and 28 were identified as better palms from interse of Annur. The better performing palms of hybrid, Annur x MYD were palm numbers 43, 44, 47 and 49. Three palms from Annur x GB (palm numbers 53, 55 and 56) were identified as better palms. Correlation analysis revealed significant positive genotypic correlation of nut yield per palm with all reproductive and yield characters and with most of vegetative and nut characters. Path coefficient analysis showed high positive direct effect on number of female flowers per inflorescence, number of bunches per palm per year, number of nuts per bunch, pole to pole circumference of nut, nut weight (with husk), shell and meat weight, quantity of liquid endosperm and copra content. High heritability coupled with high genetic advance was exhibited by the characters height of palm, leaf length, number of green leaves, number of inflorescences at the time of observation and number of female flowers per inflorescence. This indicates that these characters are governed by additive gene action and selection based on these characters will be effective. For both hybrids, height of the palm showed negative heterosis which indicates the dwarf nature of the hybrids. In hybrid Annur x MYD, most of nut charactersshowed heterosis over mid parent (relative heterosis) and better parent (heterobeltiosis). The standard heterosis was significant when compared with Keraganga but was not significant with Kerasree. Molecular characterization of the Annur (interse) and the hybrids from it was also attempted using Simple Sequence Repeat markers (SSR). Good quality genomic DNA is the prerequisite for any molecular work. DNA was isolated from all the parental palms as well as check cultivar Kerasree. The quality and quantity of genomic DNA obtained was verified using agarose gel electrophoresis and spectrophotometer. The quantity of DNA samples ranged from 350 to 1300 ng/μl with good quality. Screening of SSR markers for parents and check palms revealed polymorphism for the primers CAC02, CAC11, CNZ40, CnCirA9, CnCirB12, CnCirC3, CnCirC5, CnCirC7, CnCirE2, CnCirE12, CnCirF2, CnCirG11, CnCirH4 and CnCirH7. Out of 34 SSR markers, 27 were monomorphic between WCT and interse of Annur. Genetic Similarity analysis using the SSR markers revealed the high similarity between of interse palms of Annur and WCT. Dwarf palms viz. MYD and GB also showed high genetic similarity with each other. The present study revealed that the genotype Annur is a dwarf ecotype of WCT with similar nut quality and hence is a very promising genotype for breeding for dwarfness. The hybridization of ecotype Annur with MYD is found to be superior in yield characters compared to the hybridization with Gangabondam. However, both hybrids inherited the short stature from Annur and are promising. Since the yield characters needs to be stabilized, evaluation based on important vegetative and reproductive characters as well as molecular fingerprinting needs to be continued inorder to identify the full potential of these dwarf hybrids.