ABSTRACT. Obtaining tomato cultivars resistant to pests through interspecific crosses between commercial cultivars and wild accessions is an important tool in integrated pest management. The aim of this study was to select tomato genotypes with high zingiberene (ZGB) levels that are resistant to the South American tomato moth (Tuta absoluta Meyrick) and to estimate genetic parameters of ZGB inheritance from the interspecific cross Solanum lycopersicum cultivar 'Redenção' x Solanum habrochaites var. hirsutum (PI-127826 accession). F 2 plants with different ZGB contents were selected and submitted to a tomato moth resistance test. ZGB content exhibits high broad sense heritability, with incomplete dominance of lower ZGB content. Furthermore, the level of ZGB in leaflets was estimated to be controlled by two genes. These results show that high ZGB levels are effective at conferring resistance to the South American tomato moth.

Tomato genotypes selected for their high foliar zingiberene (ZGB) contents in a segregating F2 population were assessed to determine their effect on behavior and biology of Tetranychus urticae Koch, the putative resistance mechanisms involved and the role of trichomes on that resistance. Genotypes with contrasting ZGB content (RVTZ-09 = low ZGB, RVTZ-79 = high ZGB, RVTZ-142 = high ZGB, and RVTZ-331 = high ZGB) were selected from an interspecific cross between wild S. habrochaites var. hirsutum accession PI-127826 (high ZGB content and resistant to mites) and S. lycopersicum cv. Redenção (low ZGB content and susceptible to mites). To determine the effect of these genotypes on mite behavior and biology, free- and no-choice tests, as well as biological studies were performed. Types and densities of trichomes on the foliar surface and their correlation with ZGB contents was determined. Genotypes rich in ZGB (RVTZ-79, RVTZ-142, and RVTZ-331) presented a high number of types IV and VI glandular trichomes, and both type IV and VI densities were positively correlated with ZGB content. In the free-choice test, T. urticae showed a high preference toward S. lycopersicum cv. Redenção and the genotype RVTZ-09 (low ZGB content), whereas, genotypes with high ZBG content were less preferred. Moreover, on high ZGB genotypes, increase in the egg incubation period and in total mortality of nymphs, and decrease of fecundity rate were observed, indicating deleterious effects in mite biology. Results indicated that high ZGB/high glandular trichome densities genotypes present both non-preference and antibiosis mechanisms of resistance to the mite.

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Background The root system plays a major role in plant growth and development and root system architecture is reported to be the main trait related to plant adaptation to drought. However, phenotyping root systems in situ is not suited to high-throughput methods, leading to the development of non-destructive methods for evaluations in more or less controlled root environments. This study used a root phenotyping platform with a panel of 20 japonica rice accessions in order to: (i) assess their genetic diversity for a set of structural and morphological root traits and classify the different types; (ii) analyze the plastic response of their root system to a water deficit at reproductive phase and (iii) explore the ability of the platform for high-throughput phenotyping of root structure and morphology. Results High variability for the studied root traits was found in the reduced set of accessions. Using eight selected traits under irrigated conditions, five root clusters were found that differed in root thickness, branching index and the pattern of fine and thick root distribution along the profile. When water deficit occurred at reproductive phase, some accessions significantly reduced root growth compared to the irrigated treatment, while others stimulated it. It was found that root cluster, as defined under irrigated conditions, could not predict the plastic response of roots under drought. Conclusions This study revealed the possibility of reconstructing the structure of root systems from scanned images. It was thus possible to significantly class root systems according to simple structural traits, opening up the way for using such a platform for medium to high-throughput phenotyping. The study also highlighted the uncoupling between root structures under non-limiting water conditions and their response to drought.

Tomato cultivars resistant to arthropod pests are an important tool to reduce the use of pesticides. Resistance sources can be found in wild Solanum species such as S. habrochaites, which shows high levels of zingiberene (ZGB). This study aimed to evaluate the resistance of a tomato F2 progeny to spider mite and whitefly by evaluating the ZGB content, in laboratory, in plants from the F2 population of the interspecific crossing Solanum lycopersicum cultivar Redenção x Solanum habrochaites var. hirsutum (PI-127826), F1 plants, susceptible plants (cultivar Redenção) and plants of the wild species (PI-127826). From the F2 population, six plants with high content and three with low content of ZGB were selected. For evaluating the impact of ZGB on the spider mite behavior, the distance walked by spider mites from a central point was measured on the selected plants and their parents. For whitefly, the number of eggs and nymphs were quantified. Spider mites travelled shorter distances in plants with high ZGB content. Also, the number of whitefly eggs and nymphs was lower in these plants. Higher ZBG contents affected negatively both the spider mite and the whitefly behavior.

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The aim of this study was to compare transgenic and conventional soybean cultivars in regard to yield performance and agronomic traits. Six soybean cultivars were tested: three conventional cultivars and their three isogenic transgenic derivatives, in two locations, Lavras and Patos de Minas in Minas Gerais, Brazil, in the 2012/13 crop season. Data on yield (kg•ha −1), plant height (cm), and tolerance to lodging were collected. The cultivars had different responses. The cultivar BRS/MG46 Conquista had lower yields than its isogenic derivative BRS Valiosa RR, but this was not seen with the conventional cultivar M-SOY 6101, which produced more than its isogenic derivative M-SOY 7211 RR. Between the isogenic cultivars BRS/MG68 Vencedora and BRS Favorita RR, there were no significant differences. Nevertheless, the contrast between the mean values of the transgenic and conventional cultivars shows that the conventional cultivars had mean values greater than the transgenic cultivars.

ABSTRACT. Currently, one of the acclaimed alternatives for increasing maize yield is accomplished through utilization of heterosis in hybrid cultivars. However, upon performing crosses between related pairs, there are losses due to inbreeding depression. Thus, the aim of this study was to estimate inbreeding depression and the contribution of loci in heterozygosity in different types of maize hybrids. Eight treatments were evaluated, considering the F 1 and S 0 generations of four commercial hybrids. A randomized block experimental design was used, with three replications, and plots consisting of two three-meter long rows at a spacing of 0.50 m. The traits evaluated were plant height, first ear height and husked ear weight. For ear weight trait, there was a significant difference, where the treatments could be classified into three distinct groups. In this case, the single-cross hybrids AG7088 2 F.B.S. Botelho et al. Genetics and Molecular Research 15 (3): gmr.15035497 and 30F90Y exhibited greater depression through inbreeding due to the greater contribution of loci in heterozygosity and consequent predominance of deviations due to dominance.