Characteristics of Progeny Obtained from the Cross between Geraniums (<b><i>Pelargonium×hortorum</i></b>) and Wild Species in Section <i><b>Ciconium</i></b>, Including Heat Tolerance and Odor of Leaves

In order to develop new geranium cultivars with characteristics not found in existing cultivars, such as heat tolerance and odorless leaves, intercrosses between geranium and four wild species of section <i>Ciconium</i> were carried out. The intercrosses between geranium and <i>P. frutetorum, P. inquinans</i>, and <i>P. salmoneum</i> showed relatively high compatibility, regardless of the seed parent. Their F₁ plants grew vigorously and developed normally. On the contrary, some F₁ plants derived from the intercross with <i>P. acetosum</i> developed chlorosis and variegation in the leaves, with many plants dying in the early stage of growth. However, the F₁ plants that survived showed high pollen fertility, and F₂ and BC₁ generations could be obtained easily. Some F₂ plants showed odorless, and all BC₁ plants had non-trichome leaves. Heat tolerance trial was carried out in a greenhouse from spring to autumn using all plants of F₁, F₂ and BC₁ obtained from backcrossing to geranium. Favorable plants with an increased number of flowering peduncles even in summer were selected from the BC₁ plants derived from <i>P. frutetorum, P. acetosum</i>, and <i>P. salmoneum</i>. These progeny can be used as breeding material for producing promising new heat-tolerant geraniums with odorless leaves.