Navegando por Autor "Santos, Manoel Xavier dos"

Agora exibindo 1 - 3 de 3

Association between Griffing's diallel and the adaptability and stability of Eberhart and Russel
(Genetics and Molecular Biology, 1999-09) Cruz, Cosme Damião; Pacheco, Cleso Antônio Patto; Santos, Manoel Xavier dos
The objective of the present work was to provide a methodology to study the inheritance of adaptability and stability through the breakdown of Eberhart and Russell regression coefficients and regression deviations in effects due to the mean and additive genetic effects (g i’s and g j’s ) as well as dominance effects (s ij’s ) of Griffing ́s methodology, when the diallel is conducted in several environments. It was concluded that the adaptability and stability parameters are determined in the same manner as are genetic effects. So an F1 cross inherits half the general combining ability (GCA) mean effect from each parent, while the effects due to specific combining ability (SCA) are subjected to the same considerations relative to s ij’s , i.e., they are dependent on specific com- binations.
Inbreeding depression of 28 maize elite open pollinated varieties
(Genetics and Molecular Biology, 2002) Cruz, Cosme Damião; Pacheco, Cleso Antônio Patto; Santos, Manoel Xavier dos; Parentoni, Sidney Netto; Guimarães, Paulo Evaristo de Oliveira; Gama, Elto Eugênio Gomes e; Silva, Álvaro Eleutério da; Carvalho, Hélio Wilson Lemos de; Vieira Júnior, Pedro Abel
The study of inbreeding depression is important for breeding strategies such as use of inbred progenies or extraction of inbreed lines. A diallel of 28 maize open-pollinated varieties was evaluated in 10 environments in the early 1990s. At the same time, S1 populations for each of the 28 varieties were evaluated in the same 10 experiments (environments). Yield reductions of the populations from S0 to S1 (mean of the 10 environments), varied from 34.6% (CMS-01) to 59.2% (CMS-30), with an average of 49.1%. Inbreeding depression was greater in populations with a wider genetic base, which had never been exposed to inbreeding (CMS-30, BR-107, PH4, Cunha, Saracura, Nitrodent, and Nitroflint). Inbred lines with greater yield means should be obtained from the BR-105, BR-111, CMS-01, CMS-03, BR-106, CMS-14c, and CMS-28 populations. The use of parameter estimates generated by analysis of inbreeding depression, allow to make inferences about frequencies of deleterious alleles in the population. The frequencies of favorable alleles in the parents can be obtained by diallel analysis. The association of these two types of information, can provide a better interpretation of the genetic parameters and also can improve the process of selection of parents for either an intra- or an inter-populational breeding program.
Incorporating different proportions of exotic maize germplasm into two adapted populations
(Genetics and Molecular Biology, 2000-06) Peternelli, Luiz Alexandre; Santos, Manoel Xavier dos; Pollak, Linda Maria; Pacheco, Cleso Antônio Patto; Guimarães, Paulo Evaristo Oliveira; Parentoni, Sidney Netto; Nass, Luciano Lourenço
Maize breeders frequently wish to use exotic germplasm in their breeding programs without losing specific characteristics of their adapted material. The objective of this study was to determine the optimal proportions of exotic germplasm to incorporate into adapted populations (F2 = 50% exotic, BC1 = 25% exotic, BC2 = 12.5% exotic and BC3 = 6.25% exotic) to form the initial foundation population and to determine the heterosis between adapted x exotics. We used six exotic populations of different origins and two adapted populations representing a Brazilian heterotic pattern. In 1993-94 and 1994-95, the parents, F1, F2, BC1, BC2, BC3 and four checks were evaluated in six environments in central Brazil using an 8 x 9 simple rectangular lattice design. Higher mean values for yield were obtained as the proportion of exotic germplasm decreased. Some backcrosses produced more than the adapted populations BR 105 (7.59 ton/ha) and BR 106 (8.43 ton/ha). The best results were obtained when incorporating 6.25 or 12.5% of exotic genes. This trend was true for root lodging, stalk lodging and ear diseases but not for plant and ear height. The midparent heterosis for yield varied from -16.1 to 40.3%. Midparent heterosis with positive and negative values were also found for the other traits. The results indicate the potential of exotic germplasm for developing good hybrids. After choosing the best exotic source, some recurrent selection might be appropriate in order to adapt and improve the exotic populations.