Putative paternal factors controlling chilling tolerance in Korean market-type cucumber (Cucumis sativus L.)

Chilling temperatures (<10°C) may cause damages in cucumber plants (Cucumis sativus L.) during winter and early spring seasons. Inheritance of chilling injury in U.S. processing cucumber is controlled by cytoplasmic (maternally) and nuclear factors. To understand inheritance of chilling injury in Korean market-type cucumber, reciprocal crosses between chilling tolerant (CT1) and susceptible (CT4) lines produced F₁ (CT1×CT4) and F₁ (CT4×CT1) progenies. Reciprocal F₂ (CT1×CT4) and F₂ (CT4×CT1) populations were subsequently derived. Seedlings in the first true leaf stage were subjected to 4°C for 8h (08:00 to 16:00) and damage level was assessed visually using 1 (no damage) to 5 (severe damage) rating scale. Means of damage rating for reciprocal F₁ (CT1×CT4) and F₁ (CT4×CT1) progenies were 1.1 and 1.1, respectively. This indicates that tolerance for chilling stress at 4°C in this germplasm is dominant. However, means of damage for F₂ (CT1×CT4) progenies and F₂ (CT4×CT1) progenies were 3.2 and 1.2, respectively. These data indicate that genetic control of chilling injury in these progenies is paternal. Based on the data, we hypothesize that line CT1 possesses a dominant nuclear factor that conditions chilling tolerance in both reciprocal F₁s and a paternal factor(s) that lead chilling tolerance only in F₂ (CT4×CT1). These putative nuclear and paternal genetic factors are designated as Ch-1 and Ch-p, respectively.