Genetic variability and inter species relationship between wild and cultivated yams (Dioscorea spp.) from Koraput, India based on molecular and morphological markers.

Wild yams (Dioscorea spp.) are important tuber crops used both as vegetable and medicine by the tribal people of Koraput, India. There is deficiency of documented information on genetic structure and diversity of wild yams and its genetic assessment is necessary for crop improvement program. The present study assessed the level of genetic diversity of eight wild and one cultivated yam species of Koraput by using different morphological and molecular markers. Significant variation in different yield and morphological traits was observed among the studied yam species. The major morphological traits such as branch number, stem thickness, tuber depth, tuber length, number of tubers per plant and yield showed high genetic heritability accompanied with high genetic advance and major determinants of phenotypic diversity. Molecular profiling was carried out by taking five simple sequence repeat markers. A total of 10 polymorphic bands with an average of two were detected at the loci of the five markers across the nine yam species. Genetic similarity analysis revealed that some wild yam species such as D. oppositifolia, D. hamiltonii and D. pubera showed higher genetic similarity with cultivated (D. alata) species. The knowledge of the extent of genetic variations of wild yam species is important for planning of the genetic conservation and the utilization of this resource especially for genetic improvement.

Data on genetic potentiality of folk rice (Oryza sativa L.) genotypes from Koraput, India in reference to drought tolerance traits.

Precise physiological and molecular marker-based assessment provides information about the extent of genetic diversity, which helps for effective breeding programmes. We have conducted detailed physiological and molecular marker-based assessment of selected eight indigenous rice landraces from Koraput, India along with tolerant (N22) and susceptible (IR64) check varieties under control and simulated drought stress using polyethylene glycol (PEG) 6000. After exposure to different levels of drought stress, relative germination performance (RGP), seedling vigour index (SVI) and relative growth index (RGI) were significantly declined in all the rice landraces compared to the control plants and significant varietal differences were observed. Genetic relationship among the studied rice landraces was assessed with 24 previously reported drought tolerance linked Simple Sequence Repeat (SSR) markers. A total of 53 alleles were detected at the loci of the 24 markers across the 10 rice accessions. The Nei's gene diversity (He) and the polymorphism information content (PIC) ranged from 0 to 0.665 and 0 to 0.687, respectively. Six SSR loci, RM276, RM411, RM3, RM263, RM216 and RM28199, provided the highest PIC values and are potential for exploring the genetic diversity of studied rice lines for drought tolerance. Four rice genotypes (Butkichudi, Haldichudi, Machakanta and Kalajeera) showed the highest genetic distance with tolerant check variety (N22) and can be considered as valuable genetic resources for drought breeding program.

Ionic selectivity and coordinated transport of Na+ and K+ in flag leaves render differential salt tolerance in rice at the reproductive stage.

MAIN CONCLUSION: The present study shows that salt tolerance in the reproductive stage of rice is primarily governed by the selective Na+ and K+ transport from the root to upper plant parts. Ionic discrimination at the flag leaf, governed by differential expression of Na+- and K+-specific transporters/ion pumps, is associated with reduced spikelet sterility and reproductive stage salt tolerance. Reproductive stage salt tolerance is crucial in rice to guarantee yield under saline condition. In the present study, differential ionic selectivity and the coordinated transport (from root to flag leaf) of Na+ and K+ were investigated to assess their impact on reproductive stage salt tolerance. Four rice genotypes having differential salt sensitivity were subjected to reproductive stage salinity stress in pots. The selective Na+ and K+ transport from the root to upper plant parts was observed in tolerant genotypes. We noticed that prolonged salt exposure did not alter flag leaf greenness even up to 6 weeks; however, it had a detrimental effect on panicle development especially in the salt-susceptible genotype Sabita. But more precise chlorophyll fluorescence imaging analysis revealed salinity-induced damages in Sabita. The salt-tolerant genotype Pokkali (AC41585), a potential Na+ excluder, managed to sequester higher Na+ load in the roots with little upward transport as evident from greater expression of HKT1 and HKT2 transporters. In contrast, the moderately salt-tolerant Lunidhan was less selective in Na+ transport, but possessed a higher capacity to Na+ sequestration in leaves. Higher K+ uptake and tissue-specific redistribution mediated by HAK and AKT transporters showed robust control in selective K+ movement from the root to flag leaf and developing panicles. On the contrary, expressions of Na+-specific transporters in developing panicles were either down-regulated or unaffected in tolerant and moderately tolerant genotypes. Yet, in the panicles of the susceptible genotype Sabita, some of the Na+-specific transporter genes (SOS1, HKT1;5, HKT2;4) were upregulated. Apart from the ionic regulation strategy, cellular energy balance mediated by different plasma-membrane and tonoplastic H+-pumps were also associated with the reproductive stage salt tolerance in rice.

Leaf photosynthesis and antioxidant response in selected traditional rice landraces of Jeypore tract of Odisha, India to submergence.

Submergence tolerance in rice is important for improving yield under rain-fed lowland rice ecosystem. In this study, five traditional rice landraces having submergence tolerance phenotype were selected. These five rice landraces were chosen based on the submergence-tolerance screening of 88 rice landraces from various lowland areas of Jeypore tract of Odisha in our previous study. These five rice landraces were further used for detailed physiological assessment under control, submergence and subsequent re-aeration to judge their performance under different duration of submergence. Seedling survival was significantly decreased with the increase of plant height and significant varietal difference was observed after 14 days of complete submergence. Results showed that submergence progressively declined the leaf photosynthetic rate, stomatal conductance, instantaneous water use efficiency, carboxylation efficiency, photosystem II (PSII) activity and chlorophyll, with greater effect observed in susceptible check variety (IR 42). Notably, higher activities of antioxidative enzymes and ascorbate level were observed in traditional rice landraces and were found comparable with the tolerant check variety (FR 13A). Taken together, three landraces such as Samudrabali, Basnamundi and Gadaba showed better photosynthetic activity than that of tolerant check variety (FR 13A) and showed superior antioxidant response to submergence and subsequent re-aeration. These landraces can be considered as potential donors for the future submergence tolerance breeding program.