José Baldin Pinheiro

Estrutura genética e fluxo gênico em populações naturais de cagaita

Este trabalho teve por objetivo o estudo da variabilidade genetica em 10 populacoes de cagaiteiras (Eugenia dysenterica), da regiao Sudeste do Estado de Goias. Foram identificados 54 locos marcadores RAPD, para a caracterizacao da variabilidade genetica, avaliada por meio da analise da variância molecular (AMOVA). Foi verificado que 27,03% da variabilidade genetica esta entre populacoes, e 72,97% dentro de populacoes, indices obtidos a partir do valor de fST igual a 0,2703. Foi estimado o coeficiente de correlacao de Pearson (r) entre a matriz de distâncias geneticas (1 - indice de similaridade de Jaccard) e de distâncias geograficas, tendo sido encontrada forte correlacao positiva. Os resultados sugerem que essas populacoes estao se diferenciando por um processo estocastico havendo fluxo restrito dependente da distribuicao geografica.

Adult attractiveness and oviposition preference of Bemisia tabaci biotype B in soybean genotypes with different trichome density

Bemisia tabaci consists of a complex of morphologically indistinct biotypes, varying with respect to their host ranges and ability to transmit plant viruses. Biotype “B” has increased in importance at every growing season in soybean crops in Brazil. The objective was to evaluate B. tabaci biotype B infestations in 24 soybean genotypes, including cultivars of expression for planting and the main sources of insect resistance. The study was performed in a greenhouse with evaluations for adult attractiveness and oviposition preference (free-choice test); these parameters were correlated with trichome density. Three evaluations were carried out, and counts were obtained for number of adults, eggs, and trichomes on the abaxial surface of the leaves. The experimental design consisted of randomized blocks (192 plots). In all three evaluations, “Coodetec 215” was the most attractive to adults; the least attractive cultivars were “IAC 18” (first); PI 274453, “IAC 18,” and D 75-10169 (second); and “IAC 24” (third). As to oviposition preference, “Coodetec 215” showed the highest mean in all evaluations; the lowest means corresponded to “IAC 18” (1st); PI 274453 (2nd); and PI 274453 and L1-1-01 (3rd). No significant correlation was observed between trichome density and oviposition preference and adult attractiveness. Considering all parameters and focusing on commercial germplasm, “IAC 24,” as well as “BRS Barreiras,” “IAC 18,” “IAC 17,” and “IAC 19” can be indicated for planting in regions and/or seasons where B. tabaci biotype B is a problem for soybean production or even in properties where other crops affected by this whitefly are grown simultaneously with soybean or after this legume is grown.

Genetic gain in the breeding program of common beans at IAC from 1989 to 2007

The goal of the present work was to evaluate the genetic gain obtained in grain yield for the common bean genotypes from 1989 until 2007, at the Instituto Agronomico de Campinas, in the state of Sao Paulo. Genetic gain has been separated into two research periods; the first, from 1989 to 1996, and the second, from 1997 to 2007. In the first period, a genetic gain of 1.07 % per year was obtained, whereas for the second period, the gain was zero. However, the mean yield of the evaluated lines was approximately 1000 kg ha-1 superior to the figures obtained in the first period. The main cause for the absence of genetic gain in the second period is that the focus of the breeding program was changed to grain quality. The individualized analysis of the genotypes with carioca grains in the second period indicated the lack of genetic gain during the investigated period.

Patterns of nuclear and chloroplast genetic diversity and structure of manioc along major Brazilian Amazonian rivers

Background and AimsnAmazonia is a major world centre of plant domestication, but little is known about how the crops were dispersed across the region. Manioc (Manihot esculenta) was domesticated in the south-western Amazon basin, and is the most important staple food crop that originated in Amazonia. Current contrasting distributions may reflect distinct histories of dispersal of bitter and sweet manioc landraces. To produce new insights into the evolutionary history of the crop, we investigated the contemporary genetic diversity and structure of bitter and sweet manioc along major Amazonian rivers.nnnMethodsnThe patterns of genetic structure and diversity of wild and cultivated sweet and bitter manioc with four chloroplast and 14 nuclear microsatellite markers were evaluated. Results were interpreted in terms of the crops dispersal.nnnKey resultsnNo phylogeographic patterns among rivers were detected, and genetic structure among rivers was confounded by the bitter-sweet divergence. However, differences in the distribution of nuclear diversity and somewhat distinctive patterns of genetic structure across rivers were observed within bitter and sweet manioc.nnnConclusionsnVarious pre-Columbian and post-European conquest events in the history of Amazonian occupation may explain the absence of clearer patterns of genetic structure. However, the wide distribution of the most common chloroplast haplotype agrees with an early dispersal of manioc across Brazilian Amazonia. Furthermore, differences in genetic structure and in the spatial distribution of genetic diversity suggest that bitter and sweet manioc had distinct dispersal histories. Knowledge about how prehistoric and contemporary Amazonian peoples manage their crops is valuable for the maintenance and conservation of the impressive diversity of their native crops.

Mating System and Effective Population Size of the Overexploited Neotropical Tree (Myroxylon peruiferum L.f.) and Their Impact on Seedling Production

The reproductive system of a tree species has substantial impact on genetic diversity and structure within and among natural populations. Such information, should be considered when planning tree planting for forest restoration. Here, we describe the mating system and genetic diversity of an overexploited Neotropical tree, Myroxylon peruiferum L.f. (Fabaceae) sampled from a forest remnant (10 seed trees and 200 seeds) and assess whether the effective population size of nursery-grown seedlings (148 seedlings) is sufficient to prevent inbreeding depression in reintroduced populations. Genetic analyses were performed based on 8 microsatellite loci. M. peruiferum presented a mixed mating system with evidence of biparental inbreeding (t^m-t^s = 0.118). We found low levels of genetic diversity for M. peruiferum species (allelic richness: 1.40 to 4.82; expected heterozygosity: 0.29 to 0.52). Based on Ne(v) within progeny, we suggest a sample size of 47 seed trees to achieve an effective population size of 100. The effective population sizes for the nursery-grown seedlings were much smaller Ne = 27.54-34.86) than that recommended for short term Ne ≥ 100) population conservation. Therefore, to obtain a reasonable genetic representation of native tree species and prevent problems associated with inbreeding depression, seedling production for restoration purposes may require a much larger sampling effort than is currently used, a problem that is further complicated by species with a mixed mating system. This study emphasizes the need to integrate species reproductive biology into seedling production programs and connect conservation genetics with ecological restoration.

Heritability of agronomic traits correlated with reduced stink bug damage in an F2:3 soybean population derived from IAC-100

ABSTRACT In Brazil, some of the most important insect pests causing damage to soybean (Glycine max) are stink bugs. Soybean production would increase if varieties with enhanced resistance were developed. The aim of this work was to examine different traits associated with plant development, and yield-related traits, in an F2:3 soybean population in a stink bug-infested field and to evaluate genetic parameters and correlations among those traits. The parents and progeny from 229 F2 plants developed by crossing a resistant cultivar (IAC-100) with a susceptible cultivar (CD-215) were evaluated in three replications in a single environment. Seven agronomic traits and eight indicators of insect resistance were measured. Genotypes showed significant differences for all traits except lodging. The grain-filling period exhibited a positive genotypic correlation of 0.66 with hundred-seed weight, whereas a negative genotypic correlation of −0.53 was found between pod damage index (%) and weight of healthy seeds. In general, a shorter pod-filling period, lower weight of hundred-seeds, lower indices of pod damage, and higher seed-yield per plant were phenotypic traits of genotypes resistant to these insects.

Characterization of Genetic Variability and Population Structure of the Tick Amblyomma aureolatum (Acari: Ixodidae)

Abstract The hard tick Amblyomma aureolatum (Pallas) is a vector of the bacterium Rickettsia rickettsii, the etiologic agent of Brazilian spotted fever (BSF) in parts of Brazil. Despite its wide distribution in southeastern South America and its public health importance, there is no information about genetic variation of this species that might help to understand the epidemiology of BSF. Using data from eight microsatellite markers and ticks from six localities, we used a population genetics approach to test the hypothesis that tick populations from areas with the presence of R. rickettsii are genetically different from ticks from areas without R. rickettsii. Contrary to expectations, we found low genetic structure between studied regions. Thus, the presence of R. rickettsii in the specific area is more likely correlated with ecological and the environmental conditions or due to unknown gene coding regions of A. aureolatum genome that would be related to R. rickettsii infection resistance.