Disease epidemics of early and late leaf spots (ELS and LLS, respectively) are affected by weather patterns such as hot and wet conditions, making them prevalent in the Guinea and Sudan Savanna zones of Nigeria. The objective of this research was to determine the genetic diversity and stability of groundnut ( Arachis hypogaea
L.) mini-core collections for ELS and LLS in Nigeria. The collections were evaluated at Bayero University Kano (2015, 2016 and 2017) and Minjibir (2017) during the rainy seasons. The data collected were analysed by a mixed model and Cluster analysis was carried out to summarise relationships among the mini-core collections. Significant differences were observed between the lines for kernel yield, ELS and LLS resistance. The highest kernel yield was recorded by ICG 12988 (1225 kg ha-1
). The highest yielding check variety was Samnut 24, with a kernel yield of 805 kg ha-1
. Lines with low ratings for ELS and LLS were in cluster one but had the lowest mean kernel yield; followed by Cluster 2 with a similar trend. Two lines, ICG 12988 and ICG 12989, were grouped in Cluster 10, which had the highest mean yield (1107 kg ha-1), with ELS and LLS rating of 3 and 4, respectively. Check varieties such as Samnut 22, 24 and 25 were grouped in Cluster 9 and are moderately tolerant to leaf spots; while Samnut 26, which is a more recent improved variety was in Cluster 7 with moderate resistance to leaf spots. There was a significant line × environment interaction for kernel yield. ICG 12988 and ICG 12989 were highly unstable; while ICG 2019 was the most stable line followed by ICG 12697, ICG 3312 and ICG 8567. In general, results of the current study show a linkage between kernel yield and leaf spots diseases. Therefore, special breeding techniques such as backcrossing or marker-assisted backcrossing are required to improve lines identified with low yield but high resistance or high yield with low resistance.