A determination of genotypes' rank in different environments is used as a non-parametric method to study stability in plant breeding. The stable genotype shows the same ranks across different environments and has a minimum rank variance in varying environments. The truth of statistical assumptions in non-parametric methods is not necessary and therefore with an easy application, one can determine the stability of genotypes. This study was carried out to determine the ranks of 10 corn (Zea mays L.) hybrids across eleven environments during the years 2000-2002. A randomized complete block design with four replications was employed. The results of Huhn and Nassar's non-parametric statistics as well as NP(1), NP(5) and NP(4), indicated that hybrids 8 and 6 were the most stable ones. Also the results of Nassar and Huhn's non-parametric statistics revealed that on the basis of the bidirectional diagram with a mean yield hybrid 8 which is placed in the first position, had a high stability. Hybrids 2, 7 and 1 were placed in the second position and had a high sensitivity to environmental changes, and also had a high yield in favorable environments. Hybrids 6, 9 and 10 were placed in the third position and showed a weak adaptation in all environments. The other hybrids were placed in the fourth position with a middle adaptation with a yield lower than the total mean. According to these configurations, the genotypes witch were placed in the first position, can be considered as stable and well adapted to all environments. For recognition of the adaptability, and had a preeminent position as related to other non-parametric statistics.
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