Genetic diversity of arboreal cotton populations of the Brazilian semiarid: a remnant primary gene pool for cotton cultivars.

Mocó cotton belong to the same species as the cultivated species, Gossypium hirsutum, and cultivated forms were mainly landraces but also developed as cultivars, bearing good fiber quality and drought tolerant when cropped as a perennial species. The northeast Brazil crop system based on this cotton type is finished, with a few small area planted in the three main States, where it was previously cultivated (Ceará, Paraíba, and Rio Grande do Norte), but in others, maintenance is accomplished by single dooryard plants. Plants were found in all visited Northeast Brazil municipalities, sometimes in the North of the country, and were collected for ex situ preservation and evaluation. Most of seeds had no fuzz (62.2%) and 94.6% of the genotypes presented spot in flowers. Seventy-one alleles were revealed in 12 loci. The genetic structure of the population evaluated by microsatellite markers shows two main groups, one comprising the Seridó region where landraces were originated and other comprising the state of Ceará, where a specific breeding program was developed. Genotypes collected in North Brazil States as well as those collected in Bahia, Alagoas, and Sergipe grouped with those collected in Ceará. The Mantel correlogram indicates a significant (P < 0.05) correlation between genetic and geographical distances up to 77 km. The ex situ maintenance and agronomical evaluation are the main concerns for mocó, as the use of the agricultural interesting traits, possibly introgressed to other genotypes, is predicted. The in situ preservation is still of interest since there is more diversity there than in the collected plants and some should be continued due to use as medicinal plant.

Genetic diversity of high performance cultivars of upland and irrigated Brazilian rice.

The objective of this study was to analyze the diversity and discrimination of high-performance Brazilian rice cultivars using microsatellite markers. Twenty-nine rice cultivars belonging to EMBRAPA Arroz e Feijão germplasm bank in Brazil were genotyped by 24 SSR markers to establish their structure and genetic discrimination. It was demonstrated that the analyzed germplasm of rice presents an expressive and significant genetic diversity with low heterogeneity among the cultivars. All 29 cultivars were differentiated genetically, and were organized into two groups related to their upland and irrigated cultivation systems. These groups showed a high genetic differentiation, with greater diversity within the group that includes the cultivars for irrigated system. The genotyping data of these cultivars, with the morphological e phenotypical data, are valuable information to be used by rice breeding programs to develop new improved cultivars.

Diversity and genetic structure among subpopulations of Gossypium mustelinum (Malvaceae).

Gossypium mustelinum is the only cotton species native to Brazil; it is endemic to the semi-arid region of the northeast. The populations are found near perennial and semi-perennial sources of water, such as ponds or pools in intermittent streams. Problems with in situ conservation derive from human interference in its habitat, mainly because of excessive cattle grazing and deforestation. Establishing efficient strategies for in situ conservation requires knowledge of the genetic structure of the populations. We evaluated the structure and genetic variability of populations of G. mustelinum in the Tocó and Capivara Rivers (State of Bahia). Two hundred and eighteen mature G. mustelinum plants were genotyped with SSR markers. The molecular data were used to estimate the allelic frequencies, the heterozygosity, the F statistics, and the genetic distance among the populations and among individuals. We found high genetic diversity among the populations. The FST indexes for each population were also high and strongly correlated with physical distance. The high estimated level of endogamy and the low observed heterozygosity are indicative that the populations reproduce mainly by self-fertilization and crosses between related individuals. Consequently, strategies for in situ preservation should include at least three occurrence sites of G. mustelinum from each population. For ex situ conservation, the collections should include as many sites as possible.