Genetic analysis of RILs for Al stress tolerance in Lentil (Lens culinaris Medik.) under acidic soils of Meghalaya.
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Date
2022-12
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College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University - Imphal
Abstract
Lentil (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.
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Keywords
RILs, Al stress, Lentil, Genetic analysis