Patrícia Guimarães Santos Melo

Genetic progress after cycles of upland rice recurrent selection

Periodic assessment of the genetic progress made in recurrent selection programs is essential for assessing the evolution of the programs and identifying the main factors that have contributed to this progress. This study aimed to estimate genetic progress in grain yield, plant height and days-to-flowering achieved in the CNA6 population of upland rice (Oryza sativa L.), after four cycles of recurrent selection; and evaluate the genetic potential of this population to generate superior inbred lines after each selection cycle. The experimental data were obtained from progeny yield trials of each recurrent selection cycle. These trials were carried out in two or three locations per cycle, and consisted of S0:2 progenies and at least three checks. Federer’s augmented block design, with one replication on location (the environment), was adopted. Results revealed genetic progress for grain yield and plant height, with total genetic gains of 375.87 kg ha−1 and -3.90 cm, respectively, during the four selection cycles. The annual relative gain observed for grain yield was 1.54 %. The genetic potential of the population was analysed by the expected proportion of superior inbred lines. The standard adopted as the limit for obtaining superior inbred lines was the average of the checks for each trait. The genetic potential for grain yield and plant height increased during the study period. For days-to-flowering, no genetic gain occurred; however, the genetic potential of the population to generate superior inbred lines for this trait was maintained after the selection cycles.

Comparison of inoculation methods for selecting common bean genotypes with physiological resistance to white mold

A bstractAlthough different methods of inoculation have been proposed to assess the reaction of common bean to white mold (WM) caused by Sclerotinia sclerotiorum, a thorough comparison among them is lacking. In this study, six approaches were tested to identify the most reproducible and efficient method for discriminating six common bean genotypes of carioca market class based on their resistance to white mold. These included: modified straw test (ST), cotton pad (CP), infected flower on intact plant (IFIP) or on detached leaf (IFDL), and mycelium disc on intact plant (MDIP) or on detached leaf (MDDL). All experiments were conducted in a greenhouse or laboratory in a completely randomized design with four replicates. Several statistics including coefficient of variation (CV), standard deviation, intraclass correlation coefficient (ICC), p value for Bartlett’s test for homoscedasticity and sensitivity ratio (SR) were used as criteria for discrimination. The Spearman’s correlation coefficient was used to test the association between the methods. Results showed ST as the most suitable for selecting WM-resistant genotypes, followed by the IFIP method.

Variabilidade genética durante quatro ciclos de seleção recorrente em arroz

The objective of this work was to estimate genetic and phenotypic parameters among progenies of the CNA6 population of upland rice (Oryza sativa) for grain yield and plant height in four cycles of recurrent selection, in order to evaluate the genetic variability and the genotype × location interaction. The experimental data were obtained from yield trials of S0:2 progenies, which were carried out in the experimental design of Federer’s augmented blocks, without replications for progenies within each location. The effect of S0:2 progenies was significant in all cycles for grain yield and in the first three cycles for plant height, indicating the maintenance of the population’s genetic potential to generate transgressive progenies. The participation of the component of the progeny × location interaction in phenotypic variance was of high magnitude. The genetic variability of the CNA6 population of upland rice is maintained for grain yield and plant height during the four cycles of recurrent selection.