Genetic diversity and population structure ofBrachiaria brizantha(A.Rich.) Stapf accessions from Ethiopia

Abstract

Brachiaria (Trin.) Griseb., consisting of over 100 species, is distributed across the tropics, particularly tropical Africa (Renvoize et al. 1996). Seven Brachiaria species of African origins-B. arrecta, B. brizantha, B. decumbens, B. dictyoneura, B. humidocila, B. mutica and B. ruziziensis-are used for pasture production (Keller-Grein et al. 1996). Brachiaria produces a high amount of quality biomass and improves livestock productivity (Reid et al. 1973; Jotee 1988; Holmann et al. 2004). Moreover, Brachiaria is adapted to drought and low-fertility soils, sequesters carbon, enhances nitrogen use efficiency, and subsequently minimises eutrophication and greenhouse gas emission (Subbarao et al. 2009; Arango et al. 2014; Moreta et al. 2014). Brachiaria is the most extensively cultivated tropical forage in monoculture supporting millions of livestock across the globe with an acreage of over 99 million ha in Brazil alone (Jank et al. 2014). The International Center for Tropical Agriculture (CIAT) and Brazilian Agricultural Research Corporation (EMBRAPA) developed some improved Brachiaria cultivars (Argel and Keller-Grein 1996) for the tropical Americas. Evaluations of eight improved Brachiaria cultivars in Kenya revealed

Genetic Diversity and Population Structure of Brachiaria (syn. Urochloa) Ecotypes from Uganda

“…Our results were similar to studies of Pessoa-Filho et al [47] and Vigna et al [49] on Brachiaira ruziziensis and Brachiaria brizantha, respectively. The partitioning of molecular variations for the Ugandan ecotype population was similar to those reported in other studies [30,31,60].…”

“…The average polymorphism information content of SSR markers used in this study was 0.89 conferring them as highly informative and capable to differentiate well among the Ugandan Brachiaria ecotypes ( Table 1). The mean PIC values (0.89) deduced for markers in this study were comparable to studies of Silva et al for the top 30 most informative markers [21], Kuwi et al [30], and Pessoa-Filho et al [47] although it was higher than those reported in other studies [31,48,49]. Interestingly, the number of SSR alleles detected in this study (n = 584) was higher than those reported by Vigna et al [49], Jungmann et al [1], and Pessoa-Filho et al [47], but was lower than in the study of Trivino et al [50].…”

“…The SSR markers have multiple uses including cultivar identification, genetic diversity studies, and genome mapping [45]. For example, SSR markers have been used to assess genetic diversity in various plant species such as pearl millet, rice, sweet cassava, and Brachiaria grass [26,[29][30][31]45,46].…”

“…Allele calling and sizing were performed manually using GeneMapper Software v4.1 (Applied Biosystems, Foster City, CA, USA). The SSR fragments were analyzed following a dominant scoring scheme as the information on ploidy levels for Ugandan ecotypes was not available [29][30][31]. Well defined clear peaks were binned according to expected product size and data was exported to Microsoft Excel for analysis.…”

“…These markers are proven to be the most suitable for the genetic diversity studies in Brachiaria grass and other forages [1,18,[27][28][29][30][31]. This study has set up a national collection of Brachiaria ecotypes in Uganda, documented natural genetic diversity and population structure of ecotypes, and recognized the merits of these ecotypes in Brachiaria grass conservation and improvement programs.…”