The purpose of this work was to evaluate the yield performance of Bt maize hybrids under field conditions with damage of the Spodoptera frugiperda in a completely randomized blocks design, under a factorial scheme, with four replications. Six treatments (five Bt maize hybrids and one non-Bt hybrid) were evaluated, with and without control of the S. frugiperda. In the evaluations of number of larvae and average damage scores on maize plants there was a lower incidence and lower damage of larvae on the genotypes containing Leptra® and Viptera 3® technologies and for the productive parameters there was no significant difference between the studied genotypes, even with and without chemical control of the pest. It was concluded that there are genotypes of corn resistant to S. frugiperda, however, there was no significant difference in the yield performance of the different hybrids when comparing the difference between lack of control and chemical control in the infestation conditions found in this study. This suggests that the levels of economic damage of S. frugiperda on corn crop are higher than the levels of infestation occurred in the study.

Baru (Dipteryx alata Vog.) is a species with great economic and environmental potential; it has popular acceptance, besides being a very productive species. Alternative propagation methods are important for species maintenance and exploration. Thus, micropropagation emerged as an alternative technique, providing genetic stability and the production of a large number of seedlings. The aim of the present investigation was to develop a callus induction protocol for in vitro baru explants. The tested explants were nodal, internodal and foliar segments. The explants were disinfected for 30 seconds in 70% alcohol (v/v) and 2 minutes in sodium hypochlorite (1.25% active chlorine). This was followed by triple washing. The inoculation was carried out in test tubes containing 15 mL MS medium (30 g L-1 sucrose, 6 g L-1 agar and 100 mg L-1 ascorbic acid) supplemented with 2.0 mg L-1 naphthalene acetic acid (NAA). The solution also contained 0.0, 2.5 or 5.0 mg L-1 of 6-benzylaminopurine (BAP) with the pH adjusted to 5.8. In the incubation phase, the explants were cultured for seven days in the dark and then subjected to a photoperiod of 16 hours (43 µmol m-2 s-1) at 25 ± 2 °C. The treatments were studied with 2.5, 5.0, 7.5 or 10.0 mg L-1 BAP additions to the MS. Callus formation, contamination and oxidation evaluations were undertaken. The results obtained when using 2.0 mg L-1 NAA concluded that such a treatment should be used to induce callogenesis from nodal explants, while for the tested baru leaf explants, the best results for callus formation were given by the combination of 2.0 mg L-1 NAA with 2.5 mg L-1 of BAP to.

Sugarcane, as a glycophyte, shows sensitivity to saline soils at various stages of its growth. The aim of this study was to evaluate the in vitro priming response in two sugarcane varieties (RB966928 and RB867515). Micropropagated plants, from meristems, received priming treatments by adding the salts (NaCl and KCl) in different concentrations (0.0; 12.5; 25.0 and 50.0 mM), in the MS medium. Subsequently, the plants were cultivated in rooting medium without addition of salts, acclimatized and submitted to gradient ex vitro saline stress with 20  40 and 60 mM, of each salt, for 30 days. The analyzed variables were dry matter of shoot and root, number of tillers and estimation of chlorophyll content. The experiment was carried out in a 2 × 2 × 4 factorial arrangement, in a completely randomized experimental design. Twenty replicates were used throughout the experiment. Data were submitted to analysis of variance and regression and the means were compared by Tukey's test, at a 5% probability level. The priming treatments presented a significant effect, with triple interaction, in the chlorophyll index. In the treatment with NaCl, the variety RB966928 showed an increase in the chlorophyll index with the increase of treatment levels, up to an optimal limit of 31.47 mM. On the other hand, the variety RB867515 showed decreasing in chlorophyll index. In contrast, in KCl treatment, the variety RB867515 presented the increase at the chlorophyll index with the maximum point of 25 mM. For the variables, shoot dry matter (SDM) and root dry matter (RDM) there was a significant difference (p < 0.05 and p < 0.01, respectively) only between the varieties. The variety RB966928 presented higher SDM and RDM in relation to the variety RB867515. Studies are recommended with increasing the duration of the priming treatments and more detailed study of the culture throughout its productive cycle.

BACKGROUND: Corn intercropped with ruzigrass is common in Brazil, and it can improve the physicochemical features of soils, increase water retention, and suppress the emergence of resistant weeds and soil nematodes. As both corn and ruzigrass are hosts to Spodoptera frugiperda (the main corn pest in South America), the cultivation of both these plants in the same place at one time motivates investigation into the pest population dynamics. We hypothesize that the intercropping system influences S. frugiperda pressure and leaf injury in corn. Considering that if corn hybrids with high dose toxin expression are used, ruzigrass may be a potential host to susceptible S. frugiperda larvae, consequently an alternative refuge and be included as a tool for the resistant management of Bt corn. To test these hypotheses about the use of ruzigrass as an alternative host of S. frugiperda in an intercropping system with corn, we conducted field trials in three seasons to verify S. frugiperda population dynamics and leaf injury to crop systems. In addition to phenotypic evaluation, we also characterized molecularly S. frugiperda strains collected in corn and ruzigrass to identify strain differences.RESULTS: The insects collected in both corn and ruzigrass were identified as corn strains. Ruzigrass was used as a S. frugiperda host during all crop cycles. The intercropped system did not increase the S. frugiperda population or leaf injury on Bt corn. CONCLUSION:The results suggest that the intercropped system is not prejudicial to Bt corn cultivation since high dose concept applies to all larvae instars. The results also suggest that ruzigrass may be used as a promising alternative refuge in Bt corn agroecosystems, if compliance with management strategies is followed.

No abstract