In Argentina, maize (Zea mays L.) hybrids selected for silage production and local adaptation are not available for most temperate regions where silage maize can be produced. This study sought maize landraces that could be used as germplasm sources to enhance forage yield and quality in warm temperate areas and emphasized eight landraces not previously selected for grain yield. These were crossed in a diallel mating design and the 28 F1 population hybrids, the eight parental populations, and four commercial hybrids were evaluated in four environments in Argentina for combining abilities and to determine heterotic patterns among germplasm sources, using a biplot diallel analysis. Significant midparent heterosis (MPH) was observed for ear yield (EY), stover yield (SY), and whole plant yield (WY). General combining ability (GCA) effects were significant for EY, SY, and WY. Specific combining ability (SCA) effects were not significant for any trait. The graphical representation offered by biplot analysis allowed a rapid and effective overview of GCA and SCA effects of the populations, their performance in crosses, as well as grouping patterns of similar genotypes. Significant variation among checks was observed for EY and SY. On average, commercial hybrids had greater EY, but lower SY, than landraces and population hybrids. Some landrace crosses showed superior or similar WY than commercial checks, indicating the breeding potential of the evaluated germplasm.Abbreviations: ATC, average tester coordinate; ED, in vitro digestibility of ear dry matter; EY, ear dry matter yield; GCA, general combining ability; GGE, genotype main effect plus genotype 3 environment interaction; INTA, Instituto Nacional de Tecnología Agropecuaria; LAMP, Latin American Maize Project; MPH, midparent heterosis; NIRS, near infrared reflectance spectroscopy; PC, principal component; PC1, first principal component; PC2, second principal component; SCA, specific combining ability; SD, in vitro digestibility of stover dry matter; SY, stover dry matter yield; WD, in vitro digestibility of whole-plant dry matter; WY, whole-plant dry matter yield.

The cultivation of popcorn in Argentina has increased greatly in the last ten years: demand by the MERCOSUR countries is high, as is profitability. Nearly all Argentine production is exported since internal consumption is tiny -less than 5% of total production. «Popped corn» is produced by the explosion of the caryopsis due to the cooking temperature. Maize kernels, which are small and hard, are composed of three structural units: the pericarp, the endosperm, and the AbstractFourteen commercial popcorn maize hybrids were evaluated in a randomised block design in three locations for two years with the aim of introducing this crop into a region of the Buenos Aires province, Argentina, an area characterized by changing environmental conditions. The traits evaluated were grain yield, expansion volume, kernel width, kernel length, caryopsis roundness index, ear diameter, ear length, kernel density before expansion, expanded kernel density and prolificacy index. The interaction genotype x environment revealed environments favourable towards yield but which were simultaneously unfavourable towards expansion capacity, as well as genotypes stable for one of these variables but unstable for the other. However, some environments and genotypes were simultaneously favourable to both. Only a weak negative correlation was found between grain yield and expansion capacity, suggesting this relationship may not be very strong in these modern hybrids. Rounded grains showed higher expansion capacities, but this characteristic was negatively correlated to yield; roundness is therefore not recommended as a selection criterion. The prolificacy index correlated positively with yield but not with expansion volume, and is therefore a potential selection criterion.Key words: Zea mays L., genotype x environment interaction, expansion capacity. Resumen Interacción genético-ambiental en cultivos de maíz reventón para rendimiento y calidad del granoSe evaluaron 14 híbridos simples de maíz reventón, siguiendo un diseño de bloques al azar con tres repeticiones, en tres localidades de la provincia de Buenos Aires, Argentina, de condiciones variables en precipitación y tipo de suelo: Luján, Esteban Echeverría y Chascomús, durante dos años. Se analizaron las relaciones entre variables morfológicas, su influencia sobre rendimiento y capacidad de expansión: ancho y largo de grano, índice de redondez del cariopse, diámetro y largo de la espiga, densidad del grano sin expandir y del grano expandido e índice de prolificidad. El estudio de la interacción genético-ambiental mediante método AMMI mostró grupos de ambientes favorables para rendimiento y desfavorables para capacidad de expansión. En el caso de los genotipos se observó estabilidad para una variable e inestabilidad para la otra. No obstante, ciertos ambientes y genotipos resultaron con elevados valores para ambas variables. Se corroboró una débil correlación negativa (r = -0.16*) entre rendimiento y capacidad de expansión, sugiriendo que en los híbridos modernos tal tendencia no es tan marcada...

should also be practiced on whole-plant digestibility (Barriè re et al., 1997). Stover is as important as the ear Maize (Zea mays L.) is an excellent feed, whether fresh, chopped, because it contributes half of dry matter yield. Roth et or ensiled. Silage maize hybrids have been developed for temperatecold regions of Europe and North America, but limited research al. (1970) suggested that silage maize is primarily a high has been done to develop silage hybrids for temperate and warm-energy feed, and that its nutritive value can be enhanced temperate regions. This study was conducted to identify inbred lines by increasing its digestibility. They also proposed that that could be used to enhance the stover and ear fractions of existing selection for improvement of silage maize should be hybrids for warm-temperate areas. Forty-five single-cross hybrids based on whole-plant digestible dry matter yield. Gewere developed from 10 inbred lines and evaluated in six environnetic variation in digestibility and energy value was demments. Ten inbred lines were evaluated for potential to improve the onstrated in experimental and commercial hybrids (Vatbest hybrids by Dudley's and Metz's methodologies. Hybrids differed tikonda and Hunter, 1983), suggesting that maize forage significantly (P Ͻ 0.01) for ear (EY), stover (SY), and whole-plant quality could be improved via selection. Deinum and dry matter yield (WY), in vitro digestibility of whole-plant dry matter Bakker (1981), Vattikonda and Hunter (1983), and Ar-(iDW), and whole-plant digestible dry matter yield (WDY), differences among hybrids were not significant for in vitro digestibility of gillier et al. (1997) reported that characteristics related ear (iDE) and stover (iDS). Four outstanding hybrids were selected to forage digestibility were consistent over a wide range as target hybrids for improvement on the basis of YS i (Kang's Yieldof environments. Stability Statistic) of mean WDY and their stability across environ-Methods have been developed to select for grain yield ments. Inbred lines that were able to increase SY were not the same and stability of grain yield across environments (Kang ones that would increase EY. Inbred PR4 had outstanding potential Bachireddy et al., to improve the SY of any hybrid. Inbred B84 had greatest potential 1992). These methods have not been applied previously to enhance EY. Inbred lines showed differential capacity to generate to maize forage yield, although both high and stable improvement according to the fractions that were evaluated. Finally, levels of forage production are desired by growers. In inbred lines from the North American Corn Belt did not demonstrate addition to the difficulty in selecting stable, high-yieldpotential for enhancing SY when they were compared with local flint inbred lines.

Argentina is the first popcorn exporting country worldwide. In 1997-1998 harvest season, 40,000 ha were sown with a production of 125,000 tons; 120,000 tons of this production were exported to more than 40 countries. The objectives of this study were to isolate and to identify the fungi present in this cereal and to assess the occurrence of mycotoxins in freshly harvested popcorn in Buenos Aires province, Argentina, in 1999. All popcorn samples showed fungal contamination. A total of 4,211 isolates were recovered from popcorn kernel samples. The prevalent species isolated wasFusarium verticillioides followed byPenicillium funiculosum, F. graminearum andAlternaria alternata. No aflatoxins, zearalenone, deoxynivalenol or ochratoxin A were detected in the 42 popcorn simples. All samples but one were contaminated with fumonisins (FB) in a range in ug/kg of (not detected-529) for FB1; (not detected-216) for FB2 and (not detected-103) for FB3. Fumonisin contamination levels in Argentinean popcorn were lower than observed in flint corn. No significant differences in fungal and fumonisins contamination levels were observed in the different tested hybrids.

Maize (Zea mays L.) is an excellent feed, whether fresh, chopped, or ensiled. Silage maize hybrids have been developed for temperate‐cold regions of Europe and North America, but limited research has been done to develop silage hybrids for temperate and warm‐temperate regions. This study was conducted to identify inbred lines that could be used to enhance the stover and ear fractions of existing hybrids for warm‐temperate areas. Forty‐five single‐cross hybrids were developed from 10 inbred lines and evaluated in six environments. Ten inbred lines were evaluated for potential to improve the best hybrids by Dudley's and Metz's methodologies. Hybrids differed significantly (P < 0.01) for ear (EY), stover (SY), and whole‐plant dry matter yield (WY), in vitro digestibility of whole‐plant dry matter (iDW), and whole‐plant digestible dry matter yield (WDY), differences among hybrids were not significant for in vitro digestibility of ear (iDE) and stover (iDS). Four outstanding hybrids were selected as target hybrids for improvement on the basis of YSi (Kang's Yield‐Stability Statistic) of mean WDY and their stability across environments. Inbred lines that were able to increase SY were not the same ones that would increase EY. Inbred PR4 had outstanding potential to improve the SY of any hybrid. Inbred B84 had greatest potential to enhance EY. Inbred lines showed differential capacity to generate improvement according to the fractions that were evaluated. Finally, inbred lines from the North American Corn Belt did not demonstrate potential for enhancing SY when they were compared with local flint inbred lines.