Patrícia Guimarães Santos

Progresso genético obtido pelo melhoramento do arroz de sequeiro em 21 anos de pesquisa em Minas Gerais

This work aimed to estimate the genetic gain obtained by the upland rice (Oryza sativa L.) breeding program developed in Minas Gerais State, Brazil, in cooperation with Empresa de Pesquisa Agropecuaria de Minas Gerais (Epamig), Embrapa-Centro Nacional de Pesquisa de Arroz e Feijao (CNPAF), Universidade Federal de Lavras (UFLA) and Universidade Federal de Vicosa (UFV), from 1974/75 to 1994/95. Results of the comparative trials of upland rice cultivars and lines conducted over the above quoted period were utilized. Because of irregular rainfall distribuition and the distinctive response of different cycles to climatic conditions, the option was to divide them into two groups, one encompassing the early genotypes and the other those of medium cycle. The achieved result showed that an average genetic gain of 1.26% and 3.37% for the early group and medium cycle, respectively, occurred. In addition, it was found that the early group statistically outyielded (P £0.01) as to grains the medium cycle group, denoting that in Minas Gerais the short cycle cultivars should be preferred.

Avaliação do progresso genético obtido em 22 anos no melhoramento do arroz irrigado em Minas Gerais

The goal of this work was to evaluate the performance of the genetical improvement program of irrigated rice in the State of Minas Gerais, Brazil. The grain yield data of the advanced comparative trials of both cultivars and lines of irrigated rice, conducted in several regions of the State of Minas Gerais over the period of 1974/75 to 1995/1996 were utilized. The average genetical gain obtained was of 33 kg/ha/year (0.98%), being highly significant (P< 0.01). The 22 year period was subdivided into two phases: at the first phase (1974/75 to 1979/80), a gain of 203 kg/ha/year (6.06%) was noticed, which was highly significant, and the second phase (1980/81 to 1995/96) presented a gain of 15 kg/ha/year (0.25%) being non significant. The high gain of the first phase is ascribed to the replacement of traditional high size and poor yielding potential for breeding materials such as Inca, BG 90-2 and MG 2. In the second phase of the program, increased attention was given to obtain materials more resistant to diseases and with better grain quality and non-significant gains for yield were obtained.

Associação entre a incidência de brusone e a presença de Pyricularia grisea nas sementes de arroz

This work was conducted in two cities of Minas Gerais State: Lavras, in the agricultural years of 1994 to 1997, and Lambari, from 1995 to 1997, where 16 to 25 rice (Oryza sativa L.) genotypes were tested, in two cropping systems: traditional upland and sprinkler-irrigated upland. The aim was to determine the relationship between incidence of panicle blast in the field and ocurrence of Pyricularia grisea on the harvested seeds. The occurrence of panicle blast in the field was evaluated by means of a score scale and the presence of the fungus on seed was determined by utilizing the filter paper method. There was positive and significant correlation between the genotypes in the two cropping systems. Correlation between panicle blast incidence and fungus presence on the seed was not consistent among the evaluated trials.

Estimates of genetic and phenotypic parameters in a segregant population of rice irrigated by continuous flooding

Estimates of genetic and phenotypic parameters were obtained by using data from families of a recurrent selection program in rice. An experiment using population CNA-IRAT 4ME/1/1 was conducted at two locations (Lambari and Cambuquira) in the State of Minas Gerais, Brazil. At Lambari, families S0:2 and S0:3 were assessed during crop seasons 1992/1993 and 1993/1994, respectively. In the Cambuquira trial, only S0:3 families were tested in 1993/1994. The experimental design was a 10 x 10 lattice with three replications. The following traits were assessed: grain yield (GY), mean number of days to flowering (FL), plant height (PH), and the incidence of neck blast (NB) caused by Pyricularia grisea and grain staining (GS) caused by Drechslera oryzae. This population proved to be promising for recurrent selection, as it had high average yield and genetic variability. Heritability estimates obtained using variance components were generally greater than estimates of realized heritability, and heritability obtained by parent-offspring regression