ABSTRACT. This research aimed to explore the reproductive characteristics of three species of Psidium (P. guajava L., P. cattleyanum Sabine, and P. guineense Sw.) and estimate a probable reproduction strategy based on the pollen:ovule (P:O) methodology. The number of pollen grains per floral bud (NGPB), number of pollen grains per anther (NGPA), number of anthers per flower bud (NAB), number of ovules per flower bud (NOB), and the P:O ratio of each species were estimated. All species had a P:O ratio over 2,000 and were classified as xenogamous. P.guajava presented the highest values for all characteristics evaluated, with the NGPB at 3,777,519, the NOB at 584.50 and a P:O ratio of 6,462.82. Similarly, P. cattleyanum had a P:O ratio of 5,649.89 (NGPB 762,736 and NOB 135). However, P. guineense was considered facultative xenogamous, with P:O of 2,085.75, the NGPB at 741,484 and the NOB at 355.50. Thus, it was concluded that the studied species have a preference for allogamy and require many pollen grains to fertilize each ovule, demonstrating that the transfer of pollen to the stigma is not very specialized.

RESUMO O capim-elefante sofre sucessivos cortes em avaliações periódicas, possibilitando identificar clones com alta estabilidade para a produção de matéria seca, podendo ser utilizados para a produção de energia. O presente estudo foi realizado para avaliar a estabilidade na produção de matéria seca, considerando métodos paramétricos e não paramétricos, em genótipos de capim-elefante para produção de biomassa submetido a cortes sucessivos nas condições climáticas do Norte Fluminense (RJ, Brasil). A variável medida nos 40 genótipos foi a produção de matéria seca (DMY) em 2009, 2010 e 2011 em um experimento de campo em blocos casualizados com duas repetições. Cada amostra foi cultivada em diferentes condições ambientais. Os métodos de estabilidade testados foram de Yates e Cochran, Plaisted e Peterson, Wricke, Annicchiarico, Lin e Binns e Kang e Phan. Os resultados indicaram que o corte (E) e os genótipos (G) influenciaram significativamente no desempenho para a produção de matéria seca. Os métodos de estabilidade não-paramétrica foram eficientes para a avaliação da estabilidade no rendimento da matéria seca. Os genótipos Mercker, Pinda-México, Mercker 86-México, Guaçu/IZ, Mercker Pinda, P-241-Piracicaba e Cubano Pinda tiveram uma estabilidade estável na produção de matéria seca. Por conseguinte, existem genótipos que podem ser explorados em futuros programas de melhoramento, a fim de melhorar a produtividade de capim elefante no ambiente.

ABSTRACT The elephant-grass undergoes successive cutting and periodical evaluations that it possible to identify clones with high stability for dry matter production, which can be used for energy production. The present study was carried out to evaluate stability dry matter yield for different parametric and non-parametric methods in elephant grass genotypes for biomass production undergoes successive cutting in the agroclimatic conditions of the Norte Fluminense (RJ, Brazil). The variable measured in the 40 genotypes was dry matter yield (DMY) at 2009, 2010 and 2011 in a field study designed as randomized block design with two replicates. Each sample was grown in different environment condition. The stability methods tested were the Yates and Cochran’s, Plaisted and Peterson’s, Wricke’s ecovalence, Annicchiarico’s, Lin and Binns’ and Kang and Phan’s. Results indicated that cutting (E) and genotypes (G) influenced significantly on the performance of dry matter yield. The non-parametric stability methods were effective for the evaluation of stability in dry matter yield. Genotypes Mercker, Pinda-México, Mercker 86-México, Guaçu/IZ, Mercker Pinda, P-241-Piracicaba and Cubano Pinda were stable stability dry matter yield. Hence, there are genotypes may be exploited in future breeding programmes in order to improve productivity of upland elephant grass over environment.