Estabilidade e adaptabilidade de clones de pennisetum sp. Sob pastejo. Mancha ocular

The work was conducted at the Experimental Station of Itambé, of the Pernambuco State Agricultural Research Enterprise, to evaluate the adaptability and stability of Pennisetum sp. clones under pasture and Helminthosporium sp. incidence. The experimental design was randomized blocks, with 5 replicates and 16 treatments. Plots measured 5x5 m with one meter between rows spacing. Helminthosporium sp. incidence was studied by note scale according to spot presence on the leaves of the studied genotypes. With regards to genotype adaptability, Mineirão (0.31), Taiwan A 25 P 18 (0.50), SEA P 36 (0.28), SEA P 37 (0.38) and Gigante de Pinda P 73 (0.46) had regression coefficients below population average (β 1i ), indicating unfavorable environment adaptability. Genotypes Pusa Napier 1 P 25 (1.58), Pusa Napier 1 P 27 (1.55), Pusa Napier 1 P 28 (1.47), Pusa Napier 1 P 32 (1.28), Pusa Napier 1 P 33 (1.22), SEA P 35 (1.60), HV 241 (1.41) and Pioneiro (1.36) had better response in favorable environments, and Pusa Napier 1 P 31 and Roxo de Botucatu P 80 had ample adaptability. Hybrid HV 241 and Pioneiro had significant deviations from regression by the F test (p<0.05), indicating instability and unpredictability to environmental alterations. Genotypes Pusa Napier 1 P 31 and Roxo de Botucatu P 80 had ample adaptability, with resistance to Helminthosporium sp. and stable behavior at the Forest Zone of Pernambuco.Foi realizado um trabalho na Estação Experi- mental de Itambé, do Instituto Agronômico de Pernambuco-IPA, com o objetivo de avaliar a adaptabilidade e estabilidade de clones de Pennisetum sp. sob pastejo, considerando a incidência de Helminthosporium sp. O deline- amento experimental foi de blocos ao acaso com cinco repetições e 16 tratamentos. As parcelas mediam 5x5 m com espaçamento de um metro entre linhas. A incidência de Helminthosporium sp. foi estudada por uma escala de notas confor- me a presença de manchas nas folhas dos genótipos testados. Com relação à adaptabilidade dos genótipos, o Mineirão (0,31), Taiwan A 25 P 18 (0,50), SEA P 36 (0,28), SEA P 37 (0,38) e Gigante de Pinda P 73 (0,46) apresentaram coefi- cientes de regressão abaixo da média populacional (β 1i ), indicando adaptabilidade a ambientes desfavoráveis. Os genótipos Pusa Napier 1 P 25 (1,58), Pusa Napier 1 P 27 (1,55), Pusa Napier 1 P 28 (1,47), Pusa Napier 1 P 32 (1,28), Pusa Napier 1 P 33 (1,22), SEA P 35 (1,60), HV 241 (1,41) e Pioneiro (1,36) responderam melhor em ambientes favoráveis, e o Pusa Napier 1 P 31 e Roxo de Botucatu P 80 apresentaram ampla adaptabilidade. O híbrido HV 241 e o Pioneiro apresentaram desvios significativos da regressão pelo teste F (p