ABSTRACT Large amounts of nitrogen (N) fertilizers applied to maize cropping systems support high yields but cause adverse environmental impacts. The development of cultivars with higher N use efficiency is essential to maintain sustainable production. Thus, the present study aimed to select popcorn inbred lines efficient and responsive to N fertilization expressing high popping expansion. Fifty-one popcorn inbred lines from different origins were evaluated in the field under low and high N availability, arranged in a randomized complete block design with three replications. The two main traits of economic interest in the crop were evaluated: grain yield (GY) and popping expansion (PE). A joint analysis of variance was performed and a scatter plot was generated to classify the inbred lines regarding the response to the N use, focusing on GY. For PE, a Scott-Knott grouping of means was conducted. Within the panel of evaluated popcorn inbred lines, it was possible to identify sources of favorable alleles for nitrogen use efficiency and popcorn expansion, highlighting the inbred lines L205, L206, L217, and L395. These genotypes emerge as potential parents to be included in mating blocks for the development of hybrids and/or breeding populations with high nitrogen use efficiency and popping expansion.

ABSTRACT Ear rot caused by fungi of genus Fusarium (FER) is one of the potentially harmful diseases to grain quality in maize. Given the capacity to produce mycotoxins, FER presents a risk to food safety. This study sought to identify parents and indicate hybrids of popcorn with a higher level of resistance to the incidence and severity of FER. Hybrids were produced from the crossing of 15 lines in S7 generation and 5 testers. The hybrids, together with the parents and five more genotypes used as control, were evaluated in a field trial. It was used a randomized block design arranged in 10 x 10 lattice. Data were submitted to analysis of variance by the F test (p < 0.05) and then by the mean grouping test of Scott Knott (p < 0.05). The results showed the possible to explore new sources of resistance to FER among germplasm evaluated. Both additive and non-additive gene effects are important in FER resistance. To obtain gains in FER resistance, the development of popcorn hybrids should consider the use of parental lines with low means of severity and good general combining ability.

ABSTRACT The present study resulted from the lack of information on the genotypic expression ruling the resistance to rust and on the main traits of economic importance to the herein addressed crop. The combining ability of 16 popcorn lines and hybrids was assessed in partial diallel cross in two representative locations in Rio de Janeiro State, Brazil, where forty simple hybrids were obtained. The experiments followed a completely randomized block design with four repetitions and were conducted under natural infestation conditions in order to test the southern rust severity in the entire plant (SSW) and in the leaf of the first ear (SFPE), as well as the morpho-agronomic traits of greater interest: grain yield (GY) and popping expansion (PE). Additive gene effects prevailed in PE and the non-additive ones stood out in GY; however, both gene effects were important to the southern rust resistance characteristics (SSW and SFPE). Hybrids L65 × P10 and P7 × L70 presented appropriate specific combining ability (SCA) values in all traits; therefore, they were promising for the selection of superior genotypes. Lines L80, L76 and L77 expressed negative general combining ability (GCA) values in SSW and SFPE; line P10 recorded high and positiveGCA values in GY and PE.

O insucesso na obtenção do estande ideal é uma das causas da diminuição do rendimento das culturas. Nesse sentido, torna-se importante investigar os efeitos gênicos relacionados à qualidade de sementes. No presente trabalho objetivou-se avaliar a capacidade geral (CGC) e específica (CEC) de combinação e o efeito recíproco (ER) da qualidade de sementes de milho-pipoca e a correlação entre os testes de germinação e de vigor com a emergência no campo, visando à obtenção de híbridos com maior germinação e vigor. Avaliaram-se dez linhagens em cruzamento dialélico completo, com recíprocos. A qualidade das sementes foi avaliada por meio dos testes de germinação (TG), computando-se plântulas normais fortes (PNft) e fracas (PNfr), anormais (PA) e sementes não germinadas (SNG) e pelos testes de vigor de frio modificado (TFM), foram avaliadas plántulas normais (PNF) e anormais (PAF) e sementes não germinadas (SNGF) e pela matéria seca das plántulas (MS). De acordo com a análise de variância a CGC, a CEC e o ER foram significativos para todas as variáveis. Os componentes quadráticos relacionados aos efeitos de CEC foram maiores que os relacionados com a CGC para as características PNfr, PA, SNG, PAF e SNGF, indicando a maior significância dos efeitos não-aditivos. As estimativas mais favoráveis para CGC, foram expressas pelas linhagens P3 e L70. As melhores combinações híbridas: P1xL70, P3xP6 e P8xL70. O ER demonstrou que nos híbridos P1xL70 e P3xP6 as linhagens L70 e P3 devem ser utilizadas como genitora feminina nesses cruzamentos, respectivamente. A maior estimativa de correlação com a emergência em campo ocorreu para TFM, com magnitude de 0.667.

The failure to obtain the ideal stand is one of the causes of decreased crop yields, in this sense it is important to investigate the genetic effects related to seed quality. The aim of this study was to measure the general combining ability (GCA), the specific combining ability (SCA) and the reciprocal effects (RE) for popcorn seed quality in addition to evaluate the association between germination and vigor tests with field emergencein order to identify hybrids with better germination and vigour. Ten inbred lines were evaluated using a complete diallel cross with reciprocals. Seed quality was measured by germination tests (GT) and by modified cold vigour tests (MCV). In the GT, the numbers of strong normal seedlings (SNS), weak normal (WNS), abnormal (AS) and ungerminated seeds (UGS) were counted. In the MCV, the numbers of normal seedlings (NPC), abnormal (ASC) and ungerminated seeds (UGSC) were counted, and the plants' dry matter (DM) was measured. Analysis of variance for GCA, SCA and RE were significant for all variables. The quadratic components for SCA were higher than those for GCA for the SNS, AS, UGS, ASC and UGSC traits, which indicates higher significance for the non-additive effects. The most favourable GCA estimates, were found in lines P3 and L70. The best hybrids were P1xL70, P3xP6 and P8xL70. The RE results showed that L70 and P3 should be used as the female parent in the P1xL70 and P3xP6 hybrid crosses, respectively. The MCV was the test that was most strongly correlated with field emergence, with a magnitude of 0.667.