Popping Expansion Research Articles

Potencial de melhoramento e divergência genética de cultivares de milho-pipoca

O objetivo deste trabalho foi avaliar o potencial de melhoramento e a divergência genética de nove cultivares tropicais de milho-pipoca. A divergência genética foi estimada por meio da técnica de análise multivariada e as cultivares foram agrupadas com base na distância generalizada de Mahalanobis (DGM), utilizando o método de otimização de Tocher e a dispersão gráfica. Com produtividade de grãos acima de 3 t/ha, destacaram-se as cultivares CMS 43, IAC 112, Viçosa, CMS 42 e Branco, e com índices de capacidade de expansão acima de 24 (v/v), as cultivares IAC 112, RS 20 e Zélia. As estimativas da DGM indicaram (RS 20 e Beija-flor) e (Rosa-claro e RS 20) os pares de cultivares mais distantes geneticamente, e (IAC 112 e Viçosa) e (Branco e CMS 42), os pares mais similares. Foram identificados três ou quatro grupos divergentes dependendo do método de agrupamento. Para o melhoramento de milho-pipoca, as cultivares com maiores potenciais são RS 20, Zélia, IAC 112 e Beija-flor. As cultivares apresentam divergência genética.

Eficiência da seleção de progênies S1 e S2 de milho-pipoca, visando à produção de linhagens

Cem progênies S1 e duzentas e vinte e cinco progênies S2, obtidas da população de milho-pipoca Beija-Flor, foram testadas com relação à produção e capacidade de expansão. Os ensaios foram conduzidos em campo experimental da Universidade Federal de Viçosa, em Coimbra, MG, no ano agrícola 1998/99. Parâmetros genéticos foram estimados e os ganhos preditos com seleção foram calculados de acordo com vários critérios de seleção. Variabilidade genotípica significativa foi observada para os caracteres produção e capacidade de expansão (CE). Embora tenha sido observada correlação genotípica negativa entre os caracteres, os índices de seleção foram eficientes em identificar famílias que possibilitaram ganhos preditos simultâneos em produção e CE. As famílias S2 e S3 oriundas, respectivamente, das famílias S1 e S2 testadas, foram avaliadas no ano agrícola 1999/2000. Com base nos resultados dessa avaliação, os ganhos realizados foram calculados, para cada critério de seleção, e a eficiência da seleção foi avaliada. Houve boa concordância entre os ganhos preditos e realizados, quanto às progênies S1. Os quatro critérios que produziram as maiores estimativas de ganhos são os mesmos que deram os quatro maiores ganhos realizados, embora não na mesma ordem. Da mesma forma, os dois que deram as menores estimativas de ganhos são também os que deram os dois menores ganhos realizados, quando considerada a variável CE. Em relação às progênies S2, houve concordância em relação ao sentido das mudanças previstas em cinco critérios, quando considerada a variável produção, e em seis, quando CE foi considerada.

Análise dialélica e heterose de populações de milho-pipoca

Realizaram-se cruzamentos dialélicos entre nove populações de milho-pipoca (Zea mays L.) - UNB-2, RS-20, UEM-J1, UEM-M2, CMS-42, CMS-43, Viçosa, Beija-flor e a geração avançada do híbrido triplo Zélia - para a obtenção dos 36 híbridos F1's a fim de alcançar informação dos valores da capacidade combinatória e heterose. Essas populações e os F1's foram avaliados em ensaios, em dois anos agrícolas (98/99 e 99/00), em Iguatemi (PR), com três repetições por ano. Os resultados permitiram recomendar compostos formados entre as populações de alta capacidade geral de combinação (CGC) para rendimento de grãos, UNB-2 e CMS-42 e as populações de alta CGC para capacidade de expansão, Zélia, RS-20 e UEM-M2. As populações Beija-flor e RS-20 foram recomendadas para iniciar programa de seleção recorrente recíproca, pois se complementam em relação ao rendimento de grãos e à capacidade de expansão (CE). Para CE, houve heteroses positiva e negativa, verificando-se dominância não unidirecional.

Genetic gain for grain yield and popping expansion in full-sib recurrent selection in popcorn

A first cycle of full-sib recurrent selection was conducted in a popcorn base population, with the objective of improving popping expansion and grain yield as recommended in a previous study by Pereira and Amaral Junior (2001). Seventy five full-sib families were obtained and evaluated in a randomized complete block design, with two replications within set, in two distinct environments: Experimental Station at PESAGRO-RIO in Campos dos Goytacazes and in Itaocara, Rio de Janeiro, Brazil. The analysis of variance revealed significant differences for families within set for all evaluated traits, indicating the presence of sufficient genetic variability to be exploited in future recurrent selection cycles. To select the superior families for recombination, the main trait was the popping expansion and at the same time, low grain yield families were avoided. So, the predicted genetic gains were respectively 10.39% and 4.69% for popping expansion and for grain yield. The relatively high genetic gain estimated for both traits is a good indication of the viability of this breeding procedure. Also, the generated population in future cycles must be evaluated in comparison to other genetic materials, to be released as a new improved popcorn variety for the North and Northwest regions of the Rio de Janeiro State, Brazil.

Mapping QTL for popping expansion volume in popcorn with simple sequence repeat markers.

Popping expansion volume is the most important quality trait in popcorn ( Zea mays L.), but its genetics is not well understood. The objectives of this study were to map quantitative trait loci (QTLs) responsible for popping expansion volume in a popcorn x dent corn cross, and to compare the predicted efficiencies of phenotypic selection, marker-based selection, and marker-assisted selection for popping expansion volume. Of 259 simple sequence repeat (SSR) primer pairs screened, 83 pairs were polymorphic between the H123 (dent corn) and AG19 (popcorn) parental inbreds. Popping test data were obtained for 160 S(1) families developed from the [AG19(H123 x AG19)] BC(1) population. The heritability ( h(2)) for popping expansion volume on an S(1) family mean basis was 0.73. The presence of the gametophyte factor Ga1(s) in popcorn complicates the analysis of popcorn x dent corn crosses. But, from a practical perspective, the linkage between a favorable QTL allele and Ga1(s) in popcorn will lead to selection for the favorable QTL allele. Four QTLs, on chromosomes 1S, 3S, 5S and 5L, jointly explained 45% of the phenotypic variation. Marker-based selection for popping expansion volume would require less time and work than phenotypic selection. But due to the high h(2) of popping expansion volume, marker-based selection was predicted to be only 92% as efficient as phenotypic selection. Marker-assisted selection, which comprises index selection on phenotypic and marker scores, was predicted to be 106% as efficient as phenotypic selection. Overall, our results suggest that phenotypic selection will remain the preferred method for selection in popcorn x dent corn crosses.

Estimation of genetic parameters and prediction of gains for DFT1-Ribeirão popcorn population

In order to evaluate the potential for improvement of DFT1- Ribeirao popcorn populations by estimating the genetic parameters and prediction of gains with selection among half-sib families, 121 half-sib families extracted from that population were evaluated . The lattice was used with two replications. Elevated grain yield and acceptable popping expansion (PE) were observed. Additive genetic variance was significant for most of the evaluated characters, including productivity and PE. The narrow sense heritabilities were 67.84% ( grain yield ) and 60.97% (PE). The DFT–Ribeirao population produced 4918.0 kg/ha and 20 mL/g PE, which can be reduced to 4724.0 kg/ha and PE 23 mL/g in the next cycle. Ten families were selected based on PE and proportion of lodge plants (PLP). A 35% decrease in PLP, 9.58% gain in PE and 2.67% decrease in grain yield are expected in the base population. It may be concluded that DFT1–Ribeirao population shows additive genetic variability of the principal characters and adequate mean grain yield; popping expansion limitations and lodge plant and ear disease percentages. In the next cycle, the population will show a reduced lodge percentage, and increased PE, maintaining the same grain yield, thus having a potential to be used in popcorn breeding programs.

Estimation of Genetic Components in Popcorn Based on the Nested Design

The quantification of genetic components in a base population is essential for the definition of the best breeding strategy to maximize the genetic gains. To evaluate several agronomic traits such as grain yield (GY) and popping expansion (PE) in half-sib and full-sib families derived from an open pollinated popcorn population, this study used a nested design, in two contrasting environments in the Northern Fluminense region of Rio de Janeiro, Brazil. Results showed: a) high significance of male and female within male sources of variation for most traits studied; b) absence of genotype by environmental interaction for PE; c) overdominance for GY and additivity for PE; d) low narrow sense of heritability for GY as opposed to PE; e) intermediate family heritability mean for GY and high for PE; and f) high genetic gain estimates for both GY and PE provided by the full-sib recurrent selection. These results indicate the perspective of success for intrapopulation breeding methods in popcorn for popping expansion allowing the prediction of satisfactory genetic gain for the Northern Fluminense.

Effect of some pretreatments on popping expansion of rice

Pre-drying of paddy (var. Intan) to 9% moisture before finally adjusting it to the optimum moisture of 14% greatly improved its popping expansion. This benefit seemed to originate from improved lemma-patea interlocking and greater grain hardness brought about during pre-drying. Soaking paddy in 2% NaCl solution increased its popping expansion appreciably, but pre-drying it did not further improve popping. Superficial application of salt solution suppressed popping. Soaking paddy in water drastically lowered its popping expansion, apparently due to loosened husk interlocking and a softened endosperm; pre-drying of water-soaked paddy could not restore subsequent expansion. Hence pre-drying is recommended in the production system of popped rice. Soaking in salt solution seems less practical and wetting of paddy is to be avoided. Cracks in rice did not seem to affect popping.

Basis for varietal difference in popping expansion of rice

Twenty-five varieties of paddy differing widely in their popping expansion were analysed for their chemical and physical characteristics. Non-starchy polysaccharides (tested in 10 varieties), amylose and protein; grain length, thickness and weight; huskto- kernel gap; and thickness of pericarp and aleurone layer (in 10 varieties) were unrelated to popping expansion. Tightness of husk (lemma-palea) interlocking and grain hardness were strongly positively correlated with popping and 'white belly' (grains containing opaque, chalky regions) was negatively correlated. Multiple correlation analysis showed that these three Cactors could explain 80% of the variation in popping expansion among the variations; these factors along with the content and thickness of husk, equilibrium moisture of paddy, and cracked grains together explained over 95 % of the variation. Grain breadth was positively correlated to white belly and thus indirectly affected popping inversely.

European Corn Borer (Lepidoptera: Pyralidae): Yield Losses and Damage in Popcorn in Relation to Hybrid and Stage of Plant Development

During a 2-year period, two popcorn hybrids (Iopop 12 and Indiana AES experimental hybrid 8365) were infested with European corn borer (ECB), Ostrinia nubilalis (Hübner), egg masses at five plant-growth stages (mid-whorl, late whorl, tassel emergence, anthesis, and 14 days after anthesis). Six levels of infestations were used (none, natural, 0.5, 1, 2, and 4 egg masses per plant). Considerable yield loss occurred in Iopop 12 from as few as 0.5 egg masses per plant at all plant-growth stages. Yield losses in hybrid 8365 were significant but less than in Iopop 12. Yield potential of Iopop 12 was greater than that of hybrid 8365, but potential yield losses and damage from ECB infestation were also greater. ECB infestation had no effect on popping expansion of either hybrid.

Parent‐Offspring Popping Expansion Correlations in Progeny of Dent Corn ✕ Popcorn and Flint Corn ✕ Popcorn Crosses1

Experiments were conducted to determine the potential for use of dent ✕ popcorn (Zea mays L.) and flint ✕ popcorn crosses as breeding material for popcorn improvement. Two popcorn inbreds were crossed to both a dent and a flint inbred and several F1 plants from each cross were selfed. F2 plants from each of the four crosses were grown in 1979, self‐pollinated, and crossed to a single‐cross popcorn tester. The ears from the F2 plants were evaluated for popping expansion. The F3 and test‐cross families were grown in 1980 and evaluated for popping expansion. The popping expansion differences among the F3 families from all four crosses were highly significant. Linear correlations between the F2 and the F3, and the F2 and the test‐cross popping expansions were determined, and all correlation coefficients were highly significant. In the correlations of the F2 with the F3 the two flint ✕ popcorn crosses had coefficients of +0.84** (significant at the 0.01 level of probability) and +0.81**, which were the highest obtained, and the two dent ✕ popcorn crosses had coefficients at +0.63* and +0.76*. These high correlations, and the significant differences among F3 families, show that selection for popping expansion in F2 ears would be effective in population improvement. F3 families from the dent and flint corn crosses to one popcorn inbred had similar popping expansion means and ranges, indicating that popping expansion could be as easily recovered from crosses to dent corn as from crosses to flint corn.