Search

The objective of the present study was to find the genetic diversity of eight improved varieties and eighty-four traditional accessions of rice using nine polymorphic simple sequence repeat (SSR) markers. The SSR markers detected 32 alleles ranging from 2 to 5, with an average of 3.55 alleles per locus, indicating a high genetic diversity. The number of effective alleles (ne) ranged from 1.85 (RM208) to 3.84 (RM493), with an average of 2.64 alleles per locus, which reconfirms an existing broad genetic diversity. Nei's genetic diversity index was very high (0.5955), indicating a high mean expected heterozygosity (HE). RM493 recorded the maximum polymorphism information content (PIC) value (0.8814). The mean PIC value was 0.5955 for the used SSR markers. Out of nine SSR markers, seven scored more than 0.5 PIC values, proving their potential to be used as genetic markers. Shannon's information index (I) ranged from 0.65 (RM208) to 1.36 (RM493), with a mean value of 1.00. All genetic diversity indicators, na, ne, HE, PIC and I reflect the high genetic differentiation in representative sample of rice genotypes. According to the unweighted pair group method with arithmetic mean dendrogram and Nei's genetic distance, the ninety-two rice genotypes were classified into seven groups at an ~85 level of similarity with additional sub-clusters within each group. Rice genotypes with significant genetic divergence can be chosen for upcoming breeding programmes by assessing their positions within the dendrogram. In the dendrogram, genotypes sharing the same name were not clustered together, indicating their distinct genetic backgrounds despite them sharing the same name. The traditional rice accessions clustered together in the dendrogram can be further analysed using more polymorphic SSR markers. [ABSTRACT FROM AUTHOR]

Accessions of traditional rice play a crucial role in preserving the genetic diversity of commercial rice. They contain specific and useful traits that can help to improve the overall yield, which cannot be achieved by relying solely on improved rice varieties. This is because traditional rice accessions display a wide range of morphological characteristics that contribute to their unique yield determinants. Fifty traditional and forty-five improved rice genotypes were evaluated for thirteen agronomic traits (days to 50% flowering, plant height, number of tillers per plant, number of effective tillers per plant, number of leaves per plant, panicle length, flag leaf length, flag leaf width, number of grains per panicle, filled grain percentage, 100-grain weight at maturity, grain length, and grain width) to understand the yield determination of traditional and improved rice genotypes. Path analysis was carried out using IBM SPSS AMOS statistical software to understand the difference in the direct and indirect effect of the studied parameters. The direct effect of effective tillers per plant (ß = 0.519), filled grain percentage (ß = 0.496), and hundred-seed weight (ß = 0.403) on grain yield was high in improved rice varieties. In traditional rice accessions, the direct effect of effective tillers per plant (ß = 0.746) and filled grain percentage (ß = 0.395) on grain yield was high, but there was no direct effect of hundred seed weight. Filled grains per panicle recorded a moderate effect in both traditional (ß = 0.246) and improved (ß = 0.266) rice genotypes. None of the studied parameters directly and negatively affected the yield of improved rice varieties. Still, several traits (flag leaf length, days to 50% flowering, panicle length, seed length, and seed width) negatively affected the yield of traditional rice accessions. The contributions of yield determinants in traditional rice accessions deviated substantially from those observed in improved rice varieties, highlighting the critical role of plant architecture in determining the final yield. Fertile tiller number, filled grain percentage and grains per panicle are possible traits that can be used in direct selection criteria for improved and traditional rice genotypes for high yield. [ABSTRACT FROM AUTHOR]

A total of eighty different rice genotypes consisting of fifty-three traditional rice accessions and twenty-seven improved rice varieties were evaluated for salinity tolerance. To identify the tolerant genotypes and the relationship between tolerance level with plant height and dry matter accumulation, the seedlings were subjected to electrical conductivity (EC) ~12 dSm-1 for ten and sixteen days separately at the seedling stage. The salinity tolerance of the seedlings was evaluated by standard evaluation scores (SES). Plant height, and total, shoot, and root-dry matter were evaluated in stressed and controlled plants. Rathuheenati4992 was highly tolerant at salinity stresses, and Heenati4618, Kaluwee3728, Mawee (5531, 3618), and Pokkali3573 were highly tolerant at the 10-day and tolerant at the 16-day salinity stress. Pokkali3881 was moderately tolerant at both stress conditions. Improved rice varieties At354 and Bg250 were highly tolerant at 10-day salinity stress and tolerant at 16-day salinity stress. Cultivation of highly susceptible improved rice varieties, Bg360, At306, At362, Ld368 At405, At402, Ld371, Bw272-6b, Ld365, and Bg352 must be avoided in salinized soils. There was no correlation between plant height and salinity tolerance (r = -0.381, α = 0.000), salinity tolerance and total dry matter (r = 0.325 α = 0.002), salinity tolerance and root dry matter (r = 0.294, α = 0.008), or salinity tolerance and shoot dry matter (r = 0.061, α = 0.594). Plant height or dry matter accumulation can be considered unreliable parameters for salinity tolerance screening since they differ with the genotype. The highly tolerant and tolerant genotypes must be further studied at different growth stages. [ABSTRACT FROM AUTHOR]

Submergence-tolerant genotypes in rice are essential for flood-prone lands, and recent studies have focused on dissecting tolerance mechanisms considering morphological and physiological changes in the plants upon submergence. Thirty improved rice varieties and sixty-two traditional rice accessions were screened for submergence tolerance under complete 9-day and 14-day submergence stress at the two-week-old seedling stage. The submergence tolerance level of each rice genotype was evaluated according to IRRI guidelines based on survival rates. Accordingly, rice genotypes were categorized into four groups: tolerant, moderately tolerant, moderately susceptible, and highly susceptible. Two Mawee accessions (3704, 3618) were submergence tolerant at 14-day submergence stress. The traditional rice accessions Ratawee3466, Mawee (8552, 4145), and Heenati4935 and improved rice varieties Bw400 were moderately submergence tolerant at 14-day submergence stress. Survival rates of the rice genotypes, their initial plant height, and shoot elongation at 9-day and 14-day submergence stress showed that seedling elongation (escape strategy) or reduction of elongation compared to control plants (quiescence strategy) under submergence stress cannot be used as phenotypic markers for selecting rice genotypes for submergence tolerance in rice. Further, the escape strategy or the quiescence strategy was not unique to the genotype, and the survival strategy of some rice genotypes changed with prolonged submergence stress. The escape strategy tended to be an SOS (Save Our Souls) strategy under prolonged submergence stress from 9 days to 14 days. No correlations between initial plant height and survival rate or survival rate and the height gain or reduction at 9-day and 14-day submergence stress showed that the submergence tolerance mechanism in rice was genotype-specific. The submergence-tolerant and moderately tolerant rice genotypes could be further investigated in future studies. [ABSTRACT FROM AUTHOR]

Cinnamomum zeylanicum Blume, also known as true cinnamon, has gained more attention recently because of its proven medicinal properties. Having uniform quality raw materials is the key to the sustainability of pharmaceutical and other industries. Nevertheless, the majority of the cinnamon plantations in Sri Lanka and elsewhere have originated from highly cross-pollinated seeds. However, no reported studies exist on the variability of individuals caused by the natural cross-pollination of cinnamon. Therefore, our work focused on morphological, genetic, and biochemical characterization of a population of individuals that resulted from a single cross-pollination event of a known C. zeylanicum mother plant. The mother plant, the possible pollen donor and the selected progeny were assessed with several age- and environment-independent morphological traits and several Inter Simple Sequence Repeat (ISSR) regions. Progeny had significantly different leaf and apex shapes and ISSR regions were about 80% polymorphic compared to the parents. The morphological and genetic diversity of progeny was also represented in the cinnamaldehyde, cinnamyl alcohol and cinnamyl acetate content at the seedling stage. [ABSTRACT FROM AUTHOR]