Hamisu H.S.^1,, Ishiyaku M.F.², Mohammed S.M.², Umar L.M.², Abdulmalik. M.M.², Umeh P.P.², Yakasai A.S.³, Sa’idu G.², Hudu M.¹, Kala A.I.¹, Abdullahi A.K¹, Yakub A.M.¹

Tomato is a self-pollinating crop and relatively easy to cross, producing around 25-50 seeds per fruit. Despite its ease of crossing, specific periods and conditions for crossing tomatoes remained undocumented in Nigeria. Therefore, there is a need to investigate the appropriate period and time for crossing tomatoes with an acceptable percentage fruit set under contrasting conditions for a tomato breeding program. It is also vital to understand the nature and magnitude of genetic variability for various traits under hot dry and wet humid conditions. Screen house experiments were conducted in a completely randomized design with three repetitions under dry hot (37.18^oC/28.65^oC and 19.27%) and wet humid (29.71^oC/24.53^oC and 75.13%) conditions in the year 2022 to develop eight sets of F₁, BCP₁ and BCP₂ crosses. Eight traits were recorded on five plants for days to flowering, number of pollinated flowers, number of fruits set, percentage fruits set, number of aborted flowers, days to maturity, number of seeds per fruit and number of fruits without seeds. The results revealed significant mean squares and high genotypic variance compared to environmental variance under both conditions for all studied traits, suggesting high genetic variability for the traits. High broad-sense heritability was recorded for all traits, showing that environmental factors have less influence on the expression of these traits. BCP₁ and BCP₂ crosses flowered early and produced the highest number of fruits set, percentage fruits set, number of seeds per fruit, but had minimum number of aborted flowers and number of fruits without seeds under wet humid conditions because of low day and night temperatures compared to F₁ crosses under dry hot conditions. Number of pollinated flowers shows a highly significant positive correlation at genotypic and phenotypic levels with number of fruits set, percentage of fruit set and number of aborted flowers. Based on the results of the study, it is recommended to cross tomatoes in wet humid (September) conditions to achieve a higher percentage of fruits set, number of seeds per fruit, with a minimum number of aborted flowers and fruits without seeds. However, early morning pollination should be avoided under wet humid conditions due to the inability of the flowers to release sufficient pollen because of high humidity.

Crossability, Fruit set, heritability, GCV, PCV