The aim of this study was to identify inbred progenies of S 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 S 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.

ABSTRACT. Increasing phosphorus use efficiency in agriculture is essential for sustainable food production. Thus, the aims of this study were: i) to identify phosphorus use efficiency (PUE) in popcorn lines during the early plant stages, ii) to study the relationship between traits correlated with PUE, and iii) to analyze genetic diversity among lines. To accomplish this, 35 popcorn lines from Universidade Estadual de Maringá breeding program were studied. The experiment was conducted in a growth chamber using a nutrient solution containing two concentrations of phosphorus (P): 2.5 µM or low P (LP) and 250 µM or high P (HP). After 13 days in the nutrient solution, root morphology traits, shoot and root dry weight, and P content of the maize seedlings were measured. A deviance analysis showed there was a high level of genetic variability. An unweighted pair group method with arithmetic mean (UPGMA) clustering analysis identified three groups for the LP treatment (efficient, intermediate, and inefficient) and three groups for the HP treatment (responsive, moderately responsive, and unresponsive). The results of a principal component analysis and selection index were consistent with the UPGMA analysis, and lines 1, 2, 13, 17, 26, and 31 were classified as PUE.

Popcorn is an important agricultural crop that is consumed as a snack food worldwide. In Brazil, the lack of cultivars with high potential grain yield and popping expansion volume is a vital problem. Therefore, the present study aimed to evaluate the genetic divergence among elite popcorn lines using amplifi ed fragment length polymorphism (AFLP) markers to estimate the general and specifi c combining ability (GCA and SCA, respectively), and correlate the genetic distance with the SCA and hybrid means. For the genetic divergence study, 45 popcorn inbred lines of different hybrids and varieties were evaluated. Subsequently, 10 inbred lines were selected for diallel analysis; grain yield (GY) and popping expansion (PE) were evaluated in three environments. A wide variability of popcorn inbred lines was observed based on the AFLP markers. After evaluating the hybrids, a signifi cant effect was observed for GY and PE, with some experimental hybrids with higher potential GY and PE than the commercial cultivars. From the diallel analysis, a signifi cant effect was observed for GCA for GY and PE; therefore, the lines differed in the frequency of favorable alleles, with promising inbred lines for forming hybrids or synthetic varieties. However, for SCA, no signifi cant effect was observed for these traits. Genetic distance did not correlate with GY and Ŝ ij , demonstrating an absence of consistency in the prediction of heterotic groups for popcorn using AFLP markers.

The development of new popcorn cultivars that include wide adaptation, high stability and superior performance characteristics is one of the main alternatives to mitigate the effects of the genotype × environment interaction. In this sense, our main goal was to evaluate the adaptability and stability of new popcorn hybrids using Bayesian additive main effects and multiplicative interaction (BAMMI) method for grain yield (GY) and popping expansion capacity (PE) traits. We evaluated GY and PE from 45 new popcorn hybrids and three commercial cultivars (IAC-125, Pop Top and Top Ten) as checks in six different environments. Genotype × environment interaction, correlation and stability analyses were performed using Bayesian approaches. The full models tested presented the lowest deviance information criterion (DIC) values when compared to null models, indicating the presence of the genotype × environment interaction for both evaluated agronomic traits. Negative correlations were observed between GY and PE (r = -0.24, 95% highest posterior density [HPD] = -0.31; -0.17) and confirm the difficulty to perform selection simultaneously for both characteristics. UEM-3 and UEM-7 hybrids showed wide stability and high a posteriori averages for GY and PE. Both cultivars can be registered and recommended for cultivation in popcorn producing regions.