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Central Agricultural University, College of Post Graduate Studies in Agricultural Sciences, Umiam
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ThesisItem Open Access Agro–morphological characterization and genetic diversity analysis of aromatic rice (Oryza sativa L.) genotypes using SSR Markers.(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University , Imphal, 2019-03) Pramod Kumar; Singh, K. NorenRice (Oryza sativa L.) has been referred as “Global Grain” and it is the most important cereal crop belonging to Poaceae family with chromosome no. 2n = 24. Being rich in flora and fauna, the North East Region of India is home to various locally adapted aromatic and quality land races of rice viz. Joha, Chakhao and Tai cultivars grown in the states of Assam, Manipur and Mizoram respectively and a number of other aromatic rice cultivars are also grown in the states of Sikkim and Tripura viz. Krishna Bhog, Brimphul, Kalanunia and local Basmati. The basic requirement of a crop improvement programme is the information on extent of variation, estimates of heritability and genetic advance in respect to yield and yield contributing traits. Therefore, characterization of germplasm is of great significance for current and future agronomic and genetic improvement of the crop. The present study entitled “Agro–morphological characterization and genetic diversity analysis of aromatic rice (Oryza sativa L.) genotypes using SSR markers” was conducted to evaluate a set of aromatic rice based on agro-morphological traits and SSR markers. A total of 42 different aromatic rice genotypes including 4 check varieties and 26 SSR markers were used in the experiment. All the selected genotypes were evaluated in an augmented experimental design. A total 51 traits both morphological and quantitative nature were recorded. Grain yield per plant is significantly correlated with numbers of effective tillers and number of seeds per panicle. The analysis of variance showed that all the quantitative traits under study except effective tillers per plant were highly significant value at 1% and 5% level of probability. The genetic distance between the 42 accessions of aromatic rice ranged from 0.03 to 0.87. Out of 26 primers used 16 polymorphic primers. Genotype RM495 (82.6%) recorded highest per cent of polymorphism whereas RM124 (2.4%) recorded lowest per cent of polymorphism. Out of 42 aromatic genotypes of rice IC-342368 and IC-401209 were maximum genetic distance on the basis of morphological analysis. Whereas, maximum genetic dissimilarity was found between IC-137401 and Ja-Shulia genotypes. The genetic dissimilarity between the 42 accessions of aromatic rice ranged from 0.06 to 0.42. Hence it will be used as further breeding programme as a new tools in favour of crop improvement.ThesisItem Open Access Grain quality characterization and molecular diversity analysis of aromatic rice (Oryza sativa L.) genotypes using SSR Markers(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University , Imphal, 2018-11) Rani, Wadbok; Singh, K. NorenRice is one of the world’s most important cereal crops. It belongs to grass family Poaceae (2n = 24). There are 25 species of genus Oryza, and only two species, namely Oryza sativa and Oryza glaberrima are cultivated. Aromatic rice constitutes a small but an important sub-group of rice. These are rated best in quality and fetch much higher price than high quality non-aromatic rice in international market. In spite of their importance, pace of improvement of this group of rice has been rather slow. In addition to other problems related with their cross compatibility with high yielding non-aromatic rice and high dependence of expression of quality traits on environmental factors, lack of information on various aspects of these rice too have contributed towards the slow pace of improvement of these rice. Quality rice are characterized by not only aroma but several other traits like grain length and width, elongation after cooking, amylose content, gelatinization temperature etc. Grain quality in rice is very difficult to define with precision as preferences for quality vary from country to country. The concept of quality varies according to the preparations for which grains are to be used. Although some of the quality characteristics desired by grower, miller and consumer may be the same, yet each may place different emphasis on various quality characteristics. The present investigation was carried out for grain quality characterization and genetic diversity analysis of 32 aromatic rice genotypes using SSR markers. A total of eight quality parameters related to grain were estimated and three nutritional estimation were also carried out using standard protocols. Maximum variations among the genotypes were observed for amylose content (AC), kernel length (KL), gel consistency (GC), carbohydrate content (CC) and protein content (PC). AC ranged from 2.97% to 20.60%, GC from 20.31 mm to 86.49 mm, CC from 29.83% to 82.18% and PC from 2.35% to 11.69%. In terms of nutritional quality analysis, Ja-Pnah (82.18%) followed by IC-465275 (81.55%) recorded the highest carbohydrate content. The other genotypes which were statistically at par with Ja-Pnah were IC-394788 (74.76%), IC-351517 (76.70%), IC-342368 (76.80%), Tai Sanghan (77.01%), Chakhao Amubi (77.38%), IC-464363 (77.53%), Faisenbuman Chakhao (78.01%), IC-342353 (78.93%), IC-464661 (79.66%) and IC- 464684 (79.95%). CT3-D-4 (11.69%) recorded the highest protein content %) which was statistically at par with Chakhao Poireiton (10.80%), CT3-D-6 (10.19%) and CT3-D-10 (10.51%) whereas IC-137342 (0.99%) recorded the highest fat content. Highest GCV was recorded for AC followed by PC suggesting selection based on the trait would be effective. The heritability recorded for the trait studied was high indicating that selection for quality traits is effective. The genetic diversity study was done using 24 SSR markers out of which 11 were polymorphic. The dendrogram generated by using Darwin 6.0.15 software identified three major clusters (I, II, and III). Cluster I is the largest cluster with 15 genotypes, Cluster II is the second largest cluster with 13 genotypes and Cluster III consisted of 4 genotypes. Among the polymorphic markers, number of alleles ranged from 2 (RM11, RM25 and RM 552), 3 (RM125), 4 (RM44, RM316, RM215 and RM271) and 6 (RM447). Highest PIC value was recorded for RM447 (0.750) and lowest for RM125 (0.236). Heterozygosity (He) value ranged from 0.127 (RM484) to 0.782 (RM447). Maximum diversity was observed between IC-137401 and IC-342368 (0.98), followed by IC-342368 and IC-326284 (0.97). The genetic diversity studies conducted will help in further crop improvement programmes in identification and germplasm preservation.ThesisItem Open Access Crossability studies and genetic diversity in Blackgram using molecular markers(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University , Imphal, 2018) Singh, Puyam Tondonba; Khanna, V. K.Blackgram productivity has remained low in subtropical and tropical Asia, it is important to estimate the genetic diversity in the existing cultivars in order to see if the lack of genetic variability might be the constraining factor. Crossability studies among cultivated blackgram (Vigna mungo) varieties and genetic diversity analysis using SSR markers. In the present study, a total of 35 blackgram accessions were used to evaluate the genetic diversity using 30 SSR markers. Out of these accessions, 5 random accessions were selected for the crossability studies. A total of 15 crosses were made and pollen fertility, pollen germinability and pollen tube growth rate was recorded after every 2 hours, 4 hours and 6 hours of pollination. These three parameters were used to generate a correlation matrix with pod set, to see if any abnormalities in these parameters is the cause of reduced pod set. The maximum pollen fertility between the five selected parents was observed in KU-16-33 (94.06 %) and minimum in GP-IPU-99-238 (90.35%). However, highest pod set was observed in PANT-U-6 (91.66 %). Upon selfing, maximum pollen germinability was found in PANT-U-31 (70.00%) and minimum was in PANT-U-6(62.66 %). Longest pollen tube growth was observed in PANT-U-6 (295.51 μm) and shortest in GP-IPU-99-238 (243.30μm). In case of crosses, maximum pollen germination was observed in GP-IPU-99-238 X PANT-U-6 (58.57%) and minimum in KU-16-33 X GPIPU-99-238 (51.33%). The highest pod set was observed in KU-16-33 X KU-16-26 (70.58%) and least was in KU-16-26 X GP-IPU-99-238 (54.55 %). Longest pollen tube was observed in crosses of KU-16-33 X KU-16-26 (244.11 μm) and minimum in GP-IPU-99-238 X PANT-U-31 (217.10 μm). A steady increase in pollen germination rate and pollen tube growth rate was recorded. The final reading in pollen tube growth revealed that pollen tube was almost 3-4 times than that of the initial stages. These data were subjected to Pearson’s correlation coefficient matrix which showed that there was non significant significant correlation between pollen fertility and pod set and high significant correlation was seen between pollen germinability, pollen tube growth rate with the podset. A total of 30 SSR primers were screened for genetic diversity analysis in 35 accesions of Blackgram out of which a total of 11 primers were found to be polymorphic. A total of 357 bands were generated and 119 of these bands were polymorphic with32.97% polymorphism and the rest 238 bands are monomorphic with 66.6% monomorphism. Based on the Polymorphism Information Content (PIC) value, two primers, CEDG 118 and CDEG 279 were found to be informative.The PIC value showed a range from 0.109 to 0.582. The observation recorded on all the molecular data were subjected to simple matching coefficient. The genetic similarity between the 35 accessions of blackgram was assessed by simple matching coefficient and it ranged from 0.14 to 0.78. The least genetic similarity was observed between the genotypes KU-16-30 and KU-16-33 with a coefficient of 0.82.These two accessions could be used for breeding purpose for crop improvement. The greatest similarity was observed between the accessions GP-PGRU-9514 and GP-134.16.50 748 having a coefficient of 0.14. These data were used to generate a Neighbor Joining tree. In the factorial analysis plot, the first axis in the plot explained 18.66 % variation, second, third, fourth and fifth components explained 12.36 %, 9.95 %, 7.66 % and 6.44 %, respectively among the 35 accessions of Blackgram. The five components explained a total of 55.17 % of total variation.ThesisItem Open Access Selection for hard endosperm, Tryptophan content and yield contributing traits in F3:4 QPM families(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) S. Mariyappan; Sen, DevyaniThe present investigation was undertaken for selection of QPM inbred lines with hard endosperm and high tryptophan content in a set of 60 F 3:4 QPM families shortlisted from four QPM crosses V341 X V 373, CML 165 X V 373, CML 161 X V 341and CML 161 X V 373. A total of 681 cobs harvested from sib matings within different families were screened for opacity and sixty lines with index scores of 2 and 3 (hard endosperm) and high seed index value was further selected for determining tryptophan content using Hopkins-Cole reaction. The % tryptophan was found to range from amaximum of 0.095% to a minimum of 0.020%. Twenty two lines with tryptophan % inthe range of 0.095% to 0.073% could be identified. Differences in tryptophan content between normal and QPM lines were significant. High genetic gain and realized heritability could be recorded for % tryptophan increase in most of these twenty two lines studied. These lines were further charcterized at the DNA level along with dive low QPM and two normal maize genotypes using twenty o2 specific reported SSR markers. Distinct polymorphism was observed between the normal and a majority QPM inbred lines with respect to all the three gene specific SSR markers phi 057, phi 112 and umc 1066 validating the identity of the lines. Cluster analysis using Unweighted Neighbour Joining based on allelic data grouped the lines into three major clusters.QPM lines with high % tryptophan grouped into Clusters I and II while QPM lines with low % tryptophan grouped into Cluster III. The genetic distance based on dissimilarity matrix ranged from a minimum of 0.10 to a maximum of 0. 47. The polymorphism information content (PIC) ranged from 0.19 to 0.65 with an average of 0.44. Yield/plant calculated for the different families as total kernel weight (g) was the most variable traits and ranged from 88 to 28 g for the twenty two high QPM families. Based on these studies, QPM lines with more than 0.090% tryptophan can be shortlisted for further use to initiate a hybrid breeding programme for QPM.ThesisItem Open Access Molecular characterization of advanced breeding lines of lowland rice and their evaluation for grain quality traits(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) I. Gopinath; Rai, MayankEvery third person on earth consumes rice every day in one form or another, hence it is called as the staple food. India shares the largest area under rice cultivation but stands as the second largest producer of rice, next to china. The demand for rice will increase with population growth, whereby the decline in milled rice production is challenging. This necessitates the need for diverse and highly productive breeding lines combined with good quality traits for future breeding programs or for multiplication and better returns for farmers. Hence the present investigation was undertaken to characterize twenty two advanced breeding lines of lowland rice derived from nine pedigrees to ascertain genetic relationship and diversity among the genotypes using a set of thirty SSR markers and twenty four random SNPs with ten gene specific SNPs followed by evaluation for fifteen grain quality traits. Population structure analysis using STRUCTURE software revealed the ancestry shared among the breeding lines. Sixteen breeding lines were catergorized as admixtures as they showed less than 85% of the estimated ancestry. These admixtures or breeding lines having differences in ancestry share could be preferred for further breeding programs or multiplication. Divergence analysis showed that maximum Euclidean distance was observed between CAUS116 and CAUS117 followed by CAUS116 and CAUS120, whereas, the minimum Euclidean distance was observed between CAUS110 and CAUS111. Ward’s hierarchical clustering approach grouped genotypes into two major clusters that were further subdivided into sub groups. Maximum variation among the genotypes was observed for amylose content, seed breadth and gelatinization temperature which classified the breeding lines into three classes while the traits such as grain length:breadth ratio, linear elongation and protein content categorized the breeding lines into two classes, respective to the values recorded under each trait. Highly significant variation was observed for all the traits evaluated. Amylose content ranged from 18% to 27% among the breeding lines while the protein content ranged from 11% to 5.5%. CAUS122 and CAUS107 were found to contain highest amount of iron and zinc. Highest GCV was recorded for amylose content suggesting selection based on the trait would be effective. Similarly, among physical traits highest GCV was recorded for grain length breadth ratio. The heritability recorded for the quality traits was high indicating that selection for quality traits is effective. Therefore, based on these results the diverse breeding lines having higher yield with better grain quality could be considered for future breeding methods as parents or can be released as varieties after multi-locational evaluation.ThesisItem Open Access Morphological characterization and in vitro regeneration in strawberry (Frageria sp.)(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) Dutta, Chumki; Sen, DevyaniMorphological evaluation as per defined DUS descriptors for seven cultivated varieties of strawberry (Fragaria x ananassa Duch.) viz., Camarosa, Chandler, Festival, Sweet Charlie, Nabila, Sabrina and Winter Dawn were done in the farmer’s field across four locations of Sohliya, Umsning, Umktieh and Pynursla in Meghalaya where strawberry is commercially grown following recommended package of practices. Of the thirty one qualitative traits studied, variation was observed for nineteen traits. Wide variation was also observed for the fourteen quantitative traits pertaining to fruit size, number of fruits/ inflorescence and total soluble solids (TSS) among others. A comparison between observed and expected cultivar specific DUS character values revealed differences in 25% of the cases for eight fruit traits studied indicating that varietal performance is possibly affected by different micro climatic conditions and presence of variability within the clones of the cultivars. Correlation studies revealed that TSS was significantly correlated to fruit size and achenes/fruit while number of fruits/inflorescence was highly significantly correlated to number of flowers/inflorescence. Number of achenes/fruit correlated highly significantly to diameter of calyx in relation to diameter of fruit and number of flowers/inflorescence was significantly correlated to petiole length and petal length: breadth. Petal length: width ratio was highly significantly correlated with flower diameter and significantly to petiole length. Pooled ANOVA for the common varieties Festival and Winter Dawn grown in all the four locations studied revealed that G x E component was highly significant for fruit specific traits indicating differential performance from location to location as a result of genotype x environment interaction. The effect of growth regulators on in vitro regeneration was also studied in Camarosa, Chandler, Festival and Winter Dawn. Best sterilization results were obtained for explants sterilized using Tween 20, 0.1% Bavistin, 0.1% Ascorbic acid + 0.1% Streptomycin and 0.1% Mercuric chloride for 30, 45, 40 and 8 minutes respectively. Sixteen different concentrations and combinations of growth regulators were used out of which regeneration from runners was successfully observed in six combinations of growth regulators. MS media supplemented with 5 mg/l BAP+ 1 mg/l IAA produced maximum percent survival of explants and maximum number of shoots while MS medium supplemented with 4 mg/lBAP + 1 mg/l IAA produced the highest shoot length. Rooting was observed in half strength MS media supplemented with 0.5 mg/l IBA. Rooted plantlets were transferred to soil where they showed 66.67% survival.ThesisItem Open Access Characterization and evaluation of advanced breeding lines of lowland rice with respect to agro-morphological traits(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) Rai, Ashish; Rai, MayankRice (Oryza sativa L.) is the primary food source for more than a third of the world’s population. There is an urgent need of developing HYVs to increase rice productivity in India as well as North Eastern Hill Region. The present investigation was carried out to evaluate twenty four breeding line of rice with respect to performance, variability, heritability, character association and genetic divergence of sixteen qualitative characters and sixteen quantitative characters. The experiment was laid out at CPGS Campus, Umiam, Meghalaya in a randomized block design with three replications during kharif season, 2017. Visual observations were recorded on five plant basis as per standard descriptors on sixteen qualitative characters viz., basal leaf sheath color, leaf auricle, leaf ligule, ligule shape, leaf collar, flag leaf: attitude of blade, leaf sheath anthocyanin colouration, leaf blade: anthocyanin, panicle secondary branch, leaf senescence, spikelet: color of tip of lemma, panicle: exsertion, panicle: awns and lemma: anthocyanin coloration of area below apex. Data were recorded on days to 50% flowering, plant height, tillers per plant, panicle per plant, panicle length, leaf length, leaf width, leaf area index, canopy temperature, biological yield, spikelet per plant, no. of grains per plant, spikelet fertility (SF), harvest index, 1000 grain weight and grain yield per plant. Analysis of variance indicated the existence of significant differences among genotypes for all the characters studied except leaf width and harvest index. The characters viz., days to 50% flowering, leaf length, leaf width exhibited high heritability and panicle per plant, canopy temperature, spikelet per plant, no. of grains per plant, spikelet fertility, harvest index, and yield per hectare exhibited medium heritability. Character association studies revealed significant and positive association of grain yield per plant with tillers per plant, panicle per plant, no. of grains per plant, spikelet fertility. Therefore, these characters could be used as criteria for selection of genotypes with high seed yield. Path coefficient analysis revealed highest direct effect on grain yield for number of grains per panicles and 1000 grains weight.1000 grains weight exhibited strong positive direct effect on seed yield, however, it contributed negatively seed yield through number of grains per panicle. Based on 16 quantitative character and 16 qualitative character Euclidean distance was calculated between each set of progeny and the two checks. The maximum distance was observed between CAUS122 and CAUS110 and minimum distance was observed between CAUS120 AND CAUS106. Clustering analysis led to the grouping of lines into 2 major groups. Both the checks were grouped in second cluster which was further dividing in 3 sub-clusters. Based on per se performance with respect to yield components, blast resistance and divergence, CAUS105, CAUS104, CAUS107, CAUS121 were identified as the best progenies that could be nominated for multilocation trials, or used as parents for further population improvement.ThesisItem Embargo Evaluation of rice (Oryza sativa L.) genotypes of North Eastern Hill Region (NEHR) for traits associated with anaerobic germination.(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural Univerity, Imphal, 2022-10) Afeefa C. H.; Laloo, BingialaDirect seeding is recently becoming increasingly popular among rice producers because of its ease of cultivation, economic benefits, early crop maturity, and greater yield. However, around one-third of all rice produced globally is grown in flood-prone locations, making flooding the third biggest source of stress that impedes rice production. Anaerobic germination (AG) which refers to a seed's innate ability to germinate under oxygen deficiency by acquiring the necessary energy through anaerobic respiration is a crucial characteristic for enhancing direst seeded rice. Reports of high yielding varieties tolerant to anaerobic germination are few, hence it is important to evaluate the rice genetic diversity to develop variety with these characteristics. It would also enable flooding the field during the earliest stages of germination as a successful weed control technique. In the present study, a set of 60 rice genotypes, which were collected from different parts of the North Eastern Hill Region was screened for various traits associated with anaerobic germination. A preliminary nursery evaluation of morphological traits showed significant variation among the set of genotypes for all the traits (speed of germination, germination percentage, visual scoring of seedling vigour, shoot length, thickness of stem, number of leaves, leaf area index). Anaerobic experiment was designed to screen the genotypes under the anaerobic condition with 8 cm of submergence as well as a controlled set-up. The observations were recorded till 21 days after sowing. All the morpho-physiological parameters (seedling vigour index, germination percentage, speed of germination, survival percentage, shoot length, root length, fresh weight, dry weight, number of leaves) showed high significant genotype x treatment (anaerobic and control conditions) interaction suggesting that there is a significant variance in the genotypes with respect to submergence. The correlation study did not reveal significant correlation between traits under nursery and anaerobic condition except for shoot length (r=0.43) and number of leaves (r=0.32). Amongst the traits studied under anaerobic treatment, seedling vigour index-II showed significant and positive correlation with 11 other anaerobic traits namely seedling vigour index-I (r= 0.94), speed of germination (r= 0.88), survival percentage (r=0.84), germination percentage (r= 0.79), relative germination percentage (r= 0.46), number of leaves (r= 0.43), fresh weight (r= 0.38), dry weight (r= 0.34), root length (r=0.33), plant portion above water (r = 0.32) and shoot length (r = 0.31). PCA registered a cumulative variation of 63.3 % from the first two PCs, with PC1 accounting for 42.9% and PC2 accounting for 20.4 % of the total variation. Based on PCA, contrasting genotypes were identified, where four were identified as tolerant (Lakang Baso, Sahbhangi Dhan, CAUS 107 and CAUS 123) and the rest as susceptible (BLM, Chakhao Poireiton, Phourel and Mailung). The alpha amylase and peroxidase enzyme activity in the selected genotypes showed significant and considerable variation among genotypes. The tolerant genotypes showed higher alpha amylase activity with an average of 228.51 μmol/min as compared to the susceptible ones (77.15 μmol/min). The correlation study revealed that there is a positive correlation between alpha amylase activity and all the 13 anaerobic traits, in which, survival percentage (r= 0.84), number of leaves (r= 0.93), speed of germination (r= 0.76), germination percentage (r= 0.77), relative germination percentage (r= 0.72) and anaerobic germination index (r= 0.73) showed a significant and positive correlation. However, there was no significant correlation between peroxidise activity and any of the nursery traits or anaerobic traits. The traits such as seedling vigour index, survival percentage, germination percentage, shoot length and alpha amylase activity were amongst the promising indicators for tolerance to germination under anaerobic conditions. The identified contrasting genotypes in the study could be a valuable resource for future breeding programs.ThesisItem Embargo Genetic analysis of RILs for Al stress tolerance in Lentil (Lens culinaris Medik.) under acidic soils of Meghalaya.(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University - Imphal, 2022-12) Mahanta, Mayurakshee; Singh, K. NorenLentil (Lens culinaris ssp. culinaris) popularly known as “Masoor” in India, is an important pulse crop used both as food and feed because of its protein-rich seeds and straw. There is immense potential to increase area under lentil cultivation in NEH Region including Meghalaya attributing to suitable climatic factors. However, the soils of NEH Region including Meghalaya are acidic in nature where Aluminium (Al) stress becomes one of the prime limitations for production of crops specially pulses like lentil, as Al solubilizes into phytotoxic forms at low pH, explicitly below 5.0, causing root growth inhibition, reduced plant vigour and finally reducing grain yields to large extents. The present study involved screening for Al stress associated chromosomal regions and markers. tolerance in a RIL population of lentil developed from a cross between BM- 4 (Al sensitive parent) and L- 4602 (Al tolerant parent) through phenotypic evaluation in the field, root growth studies, organic acid exudate analysis under hydroponics and molecular studies to identify The variance analysis combined over two locations revealed highly significant genotype x location interaction for the traits under study except DM, NPB and SPP, whereas variance due to genotypes was highly significant for all the 10 characters. Among all the characters, high Hbs2 coupled with high GA% were observed in NPB, PH and 100 SW which suggested preponderance of additive gene effects in the inheritance of these traits. A highly positive and highly significant correlation was observed between SYP with PPP (0.84**), BYP(0.79**), SPP (0.47**) and NPB (0.30**) and a positively significant correlation with 100 SW (0.1955*). Path analysis revealed that, PPP (0.840) had the greatest direct effects in influencing SYP, followed by BYP (0.795), SPP (0.474), NPB (0.309) and HI (0.307) suggesting the importance of improving SYP by selecting these traits. ANOVA for root and shoot traits screened under hydroponics culture treated with Al (148μM) revealed presence of highly significant genotypic differences for all the traits. High GCV coupled with high H2bs and GA% were observed for RRG, RL, RFW, SFW, RDW, TRL, TRSA and TRV. Also, RRG showed highly significant positive correlation with SYP. Analysis of organic acid exudation from roots of lentil in response to toxic level of Al (148μM) led to identification of citric acid, malic acid, oxalic acid and fumaric acid in the root exudates. Citric acid was exudated in highest amount in all the genotypes, while it was observed that most of the tolerant genotypes exudated more organic acids as compared to sensitive ones. Citric acid was found to be positively and significantly correlated with RRG and seed yield. SSR based genotyping of extreme RILs having contrasting response to Al toxicity identified the markers significantly associated with more than one trait viz. PBA_ LC_1247 with RRG and TRSA, PLC_104 with RRG, TRL, TRSA, TRV and SYP, LcSSR 17 with RRG and TRL, PLC_ 91 with TRL, TRSA, SYP, PBA_LC_327 with TRL, TRSA, TRV, PBA_LC_118 with TRL, TRSA, PBA_LC_1401 with TRL, TRSA and TRV and PLC_46 with Root Al content and SYP. Considering the presence of positive alleles for majority of the associated markers, explaining more than 10% of trait variations (R2) and based on all the phenotypic screening methods the RILs identified as high yielding and Al tolerant are LRIL-92, LRIL-96, LRIL 97, LRIL-109, LRIL- 143, LRIL-144 and LRIL-148. It was observed from our study that, for root re-growth, total root length and root Al content, the associated chromosomal regions were located on chromosome 1 and chromosome 4; while for total root volume and seed yield per plant the associated regions were located on chromosome 1 and chromosome 3; and for total root surface area the associated regions were located on chromosome 1, suggesting that chromosome 1, chromosome 3 and chromosome 4 of lentil harbours the regions or QTLs that are associated with tolerance to Al toxicity stress in lentil. With further evaluation these RILs may serve as important Al toxicity tolerant varieties suitable for acidic soil conditions of Meghalaya. Also, these lines can be used as parents for generating new crosses for further genetic studies. The markers identified as associated with Al tolerance may facilitate in marker assisted selection programmes for developing Al tolerant varieties.
