B. Maçãs

Bio: B. Maçãs is an academic researcher. The author has contributed to research in topics: Germplasm & Japonica. The author has an hindex of 1, co-authored 1 publications receiving 80 citations.

Genetic relatedness of Portuguese rice accessions from diverse origins as assessed by microsatellite markers

Abstract: Simple sequence repeat (SSR) markers detect a significantly high degree of polymorphism in rice (Oryza sativa L.) and are particularly suitable for evaluating genetic diversity among closely related cultivars. A total of 176 rice accessions originating from 19 countries in the Portuguese working germplasm collection and two standard rice varieties (IR36-indica and Nipponbare-japonica) were analyzed for DNA profile using 24 SSR loci covering two loci per chromosome. A total of 184 alleles were detected. The number of alleles per locus ranged from 3 to 16, with an average of 7.7, and the PIC value ranged from 0.179 to 0.894 with an average of 0.667. All the loci were polymorphic among the accessions and clearly distinguished the indica and japonica subspecies. At 20% similarity, cluster analysis of the 178 accessions revealed three major groups, japonica, basmati, and indica (Groups I, II, and III, respectively). The japonica group contained 87% of the accessions and showed a wide range of similarity values (0.21-0.92), revealing a high degree of diversity among the accessions. Many of the accessions included in this study are morphologically similar and lack pedigree information. Hence, identification of genetic distances among the accessions should improve their use in breeding programs. As a result of this study, genetically diverse parents can be identified, increasing the usefulness of germplasm collections by broadening the genetic base of rice varieties.

SSR marker-based molecular characterization and genetic diversity analysis of aromatic landreces of rice (Oryza sativa L.)

Abstract: Molecular characterization of the genotypes gives precise information about the extent of genetic diversity which helps in the development of an appropriate breeding program. In the present study, a total of 24 SSR markers were used across 12 elite aromatic rice genotypes for their characterization and discrimination. Among these 24 markers 9 microsatellite markers were showed polymorphism. The number of alleles per locus ranged from 2 alleles (RM510, RM244, and RM277) to 6 alleles (RM 163), with an average of 3.33 alleles across 9 loci obtained in the study. The polymorphic information content values ranged from 0.14 (RM510) to 0.71 (RM163) in all 9 loci with an average of 0.48. RM163 was found the best marker for the identification of 12 genotypes as revealed by PIC values. The frequency of most common allele at each locus ranged from 41% (RM163, RM590, and RM413) to 91% (RM510). The pairwise genetic dissimilarity co-efficient indicated that the highest genetic distance was obtained between Basmati PNR 346 and Deepa; Basmati PNR 346 and Patnai-23; Dolargura and Sugandha; Bhogganijia and Sugandha; and finally between Dolargura and Chinikani (88.89%). Opchaya, Basmati PNR 346 and Sugandha had close similarity among them but showed wide dissimilarity with other genotypes. Being grouped into distant clusters Dolargura and Opchaya could be utilized as potential parents for the improvement of fine grain aromatic rice varieties. Genotypes Deepa and Patnai-23 (having zero dissimilarity) might have possessed somewhat similar genetic background and more markers are needed to discriminate them. The microsatellite marker based molecular fingerprinting could serve as a sound basis in the identification of genetically distant accessions as well as in the duplicate sorting of the morphologically close accessions.

Genetic analysis of basmati and non-basmati Pakistani rice (Oryza sativa L.) cultivars using microsatellite markers.

Abstract: Information of genetic variability and relatedness among rice genotypes is essential for future breeding programmes and derivation of superior cultivars. The objective of the present study was to evaluate the genetic relationship among traditional and improved cultivars of Pakistani rice and to determine differences in the patterns of variation between two indica rice groups: basmati and nonbasmati. Forty-one cultivars were evaluated by means of 30 microsatellite markers distributed over the whole rice genome. A total of 104 alleles were detected by 30 markers, all of them (100%) were polymorphic. The number of alleles generated by each marker ranged from 2 to 6 with an average of 3.5 alleles marker. Polymorphism information content (PIC) varied from 0.259 to 0.782 with an average of 0.571. A significant positive correlation (r = 0.71**) was found between the number of alleles at SSR locus and the PIC values. Pair-wise Nei and Li’s similarity coefficients ranged from 0.10 to 0.99. A dendrogram based on cluster analysis by microsatellite polymorphism grouped 41 rice cultivars into 2 major groups effectively differentiating the late maturing, tall and slender-grain basmati and other aromatic rice cultivars from the early, short statured, short bold and long bold grain non-aromatic cultivars. Higher level of genetic diversity between basmati and non-basmati support the concept that former had a long history of independent evolution and diverged from nonbasmati rice a long time ago through human selection and patronage. Present investigation further indicated that genetically basmati rice is different from that of coarse indica and japonica type. The results suggested that microsatellite markers could efficiently be utilized for diversity analysis, and differentiation of basmati and non-basmati rice cultivars. In addition, marker-based identification of traditional basmati rice may help in maintaining the integrity of this high quality product to the benefit of both farmers and consumers.

Genetic Diversity and Population Structure in a European Collection of Rice

Abstract: In southern Europe, rice (Oryza sativa L.) is grown as an irrigated crop in river deltas where it plays an important role in the agroecological equilibrium through soil desalinization. In these regions, rice is at the northern limit of its natural area of adaptation. Special cultivars are needed for these challenging conditions. Using modelbased and distance-based approaches, we analyzed the genetic structure of the European Rice Germplasm Collection (ERGC), which is composed of 425 accessions, using 25 simple sequence repeat (SSR) markers. We compared it with a reference set of 50 accessions that are representative of the diversity of O. sativa. Most of the ERGC accessions (89%) clustered with japonica types. The ERGC japonica accessions were classifi ed into three groups: one group close to rice types of tropical origin that are found in the United States and Argentina and two groups of temperate origin showing less differentiation. The three japonica groups could be characterized according to their grain type and maturity class, which are the most strongly selected traits in European breeding programs. We extracted a core collection of 250 japonica accessions and characterized it using 70 single nucleotide polymorphisms (SNPs). The SSR and SNP dissimilarity matrices coincided reasonably well and for the best-supported structure, the percentages of admixture were highly correlated. The core collection can be used as an association panel to search for alleles of interest for temperate areas or as a training population for genomic selection. (Resume d'auteur)