Comparison of Photosynthetic Characteristics and Reproductive Traits of Winter Squash (<i>Cucurbita maxima </i>L.) Between Cultivars

Abstract

The production of winter squash used vertical trellising was popular in the greenhouse for easy to manage growth and fruiting. This study investigated the photosynthetic characteristics of six winter squash cultivars to explore the differences in crop production efficiency between cultivars by vertical trellising cultivation. Plant growth, photosynthetic characteristics and fruit quality of winter squash cultivars ‘Black lamp’, ‘Tastemaker’, ‘East elite’, ‘Julius’, ‘Sugar’ and ‘Lyric’ were surveyed. The photosynthetic rate (Pn) was measured on the 70^th day after planting. We selected the three leaves above the fruit in which to compare the Pn between cultivars, and surveyed all leaves on ‘Black lamp’ and ‘East elite’ in order to make a comparison between nodes. The Pn values of ‘Black lamp’, ‘East elite’, ‘Lyric’ and ‘Tastemaker’ were significantly higher, at 14.02, 13.06, 12.33 and 12.19 μmol CO₂/m²∙s, respectively. The Pn of the leaves on 5–8^th nodes decreased significantly, and the Pn of the 1^st–5^th nodes up to the fruit also decreased. With regards to reproductive traits, the first pistillate flowers of ‘East elite’ and ‘Black lamp’ bloomed on the 30^th day after planting, while the other cultivars bloomed on the 35–37^th day after planting. The six cultivars were classified according to the size of the fruit on the 48^th day after pollination: ‘Lyric’ and ‘Tastemaker’ were classified into the largest group, at 1203 and 1106 cm³, respectively; the second group contained ‘East elite’ and ‘Julius’, at 870 and 687 cm³; while ‘Sugar’ and ‘Black lamp’ were in the smallest group, at 353 and 217 cm³, respectively. The soluble sugar and total soluble solid (TSS) contents of ‘East elite’ were significantly elevated, their values being 630.6 g/kg and 13.3%, respectively. The starch content of ‘Lyric’ was the highest at 193.7 g/kg. "Black Light" was a fruit-number type, and the increase in fruit number could increase the yield/plant; "East elite" was a fruit-weight type, and the yield per plant was related to the weight of a single fruit. The influence of the unit leaf of “Black Lamp” on the fruit fresh weight was the lowest performance in the reproductive growth. In order to increase productivity of small fruit such as ‘Black lamp’ western pumpkin, the balance between the vegetative growth and the reproductive growth was necessary to be improved.