Selection of inbred maize (Zea mays L.) progenies by topcrosses conducted in contrasting environments.

The aim of this study was to identify inbred progenies of S0:1 maize (Zea mays L.) plants that were efficient at a low level of technology and responsive at a high level of technology through the use of topcrosses. Two contrasting environments were created using two levels of base fertilization and topdressing, so that the levels of nitrogen, phosphorus, and potassium were applied four times higher in one environment than in the other. We used S0:1 progenies derived from commercial hybrids in topcrosses with two testers (an elite line from the flint heterotic group and an elite line from the dent heterotic group). The progenies and three controls were evaluated in an augmented block design in Nossa Senhora das Dores, SE, Brazil in the 2010 crop season. The average grain yield in the high-technological level was 21.44% greater than that in the low-technological level. There were no changes in progeny behavior in the two technological levels for grain yield. The testers did not differ in the average grain yield of the progenies at the two technological levels. Therefore, it is possible to select progenies derived from commercial hybrids that have an efficient response to fertilization.

Nucleolar activity during larval development of Myrmeleon uniformis Navas, 1920 (Neuroptera, Myrmeleontidae).

It has been reported in the literature that the Malpighian tubules of Neuroptera in the third instar undergo drastic histological changes, when they stop functioning in osmoregulation and start to secrete silk fibers for a cocoon. Therefore, to increase our knowledge about these cellular alterations that occur in the larvae of Neuroptera, we analyzed the cells that constitute the Malpighian tubules of each larval instar of the species Myrmeleon uniformis, with emphasis on nucleolar activity. Malpighian tubules, after being removed, were fixed on a slide using liquid nitrogen and stained by silver impregnation. In addition, total protein of the tubules was quantified. By analyzing the cells in the first instar larval stage, we observed only two silver-stained nucleolar regions. In cells of second instar larvae, there was an increase in the number of stained regions, and in the third instar, the number of nucleolar regions was very large. Agarose gel electrophoresis indicated that third instar larvae had high synthetic activity, where the total amount of proteins was larger in third instar stage than in the other larval stages. Furthermore, the most abundant proteins displayed molecular weights of about 32-43 kDa and were probably precursors of silk fibers. Thus, the results obtained showed that nucleolar alterations occur in the cells of the Malpighian tubules of larval instars of M. uniformis and this is directly related to the production of silk fibers used by the pupa to ensure the completion of metamorphosis.

Diallel among twenty eight varieties of maize

Twenty eight varieties of maize of different maturities and types of endosperm were assessed together with 378 F(1), and seven commercial hybrids (controls) in three locations: Sete Lagoas, MG, Goiânia, GO, and Londrina, PR. The varieties represent germplasms adapted to different areas of Brazil,used in the breeding program at the National Maize and Sorghum Research Center at Sete Lagoas, MG. The joint analysis of variance for ear weight showed significance (P < O.O1) for environments, entries, varieties, heterosis, mean heterosis, variety heterosis, specific heterosis, environments x entries and environments x varieties. The average yield of the varieties varied from 2,322 to 7,704 kg/ha, while for the intervatietal hybrids the variation was from 4,112 to 8,363 kg/ha. The mean heterosis was 489 kg/ha and the varietal heterosis varied from -589 to 1,339 kg/ha. The highest specific heterosis was obtained for the BR 105 x BA III - Tusón crossing. Some intervarietal hybrids were higher yielding than the best control. This is promising for breeding purposes, since new synthetic varieties can be formed or used to begin programs to produce hybrids. No association was found between heterosis and endosperm type.