Effect of Fruit Pruning on Qualitative and Performance Indices of Two Bell Pepper Cultivars (Capsicum annuum L.)

Bell pepper is a popular agricultural product, not only for its economic value but also for the nutritional value of its fruits, which are enriched source of natural colors and antioxidant compounds. During developmental stages, the pepper fruit serves as a significant carbon sink, exerting a notable influence on the growth and carbon levels of adjacent organs including buds, flowers, and immature fruits. The occurrence of abortion and the abscission of flowers and immature fruits can lead to substantial alterations in crop output during the growth cycle. The fruiting patterns are influenced by both environmental conditions and the quantity of fruits. When specific fruits attain ripeness, their rate of sink power decelerates. Consequently, a novel fruit set initiates its growth, thereby initiating a fresh cycle of fruit production. Consequently, the presence of unpruned plants leads to flash fruiting, characterized by periodic variations in fruit output, thereby constituting a significant challenge in greenhouse cultivation of bell pepper. The purpose of the current experiment was to investigate the effect of fruit pruning and harvest sequence on the yield and qualitative characteristics of two common bell pepper cultivars grown under greenhouse condition.

This study was conducted in a greenhouse located in the east of Isfahan during 2019. A factorial experiment was carried out based on completely randomized design with four replications. The experiment factors included a) fruit pruning at four levels: Non-pruning (control), and 10%, 20% and 30% pruning, b) pepper cultivar at two levels: Lumos yellow cultivar (from Syngenta company) and Lorka red cultivar (from Seminis company) and c) harvest sequence at four levels: first, second, third and fourth. Seeds sowing was done on October 23, 2019. Seeds were sown in transplant trays filled with a mixture of peat moss and perlite. Subsequently, on December 1, 2019, seedlings were transferred to the primary substrate, when they had developed four to six true leaves. The individuals were relocated to the greenhouse. During this period, the pepper plants were pruned and secured to the taut wires of the trellis. Furthermore, the greenhouse temperature was adjusted on 26-28 °C as day temperature and 16-18 °C as night temperature. Irrigation was implemented in a strip-wise manner. During this research, the effect of fruit pruning and cultivar on morpho-physiological traits and also, the effect of fruit pruning and harvest sequence on performance characteristics of pepper plant were investigated.

Results indicated that pruning 10 % led to an increase in seed weight, flesh thickness and L* color index of yellow cultivar. The effect of pruning on fruit weight of yellow cultivar during successive harvests revealed that unpruned plants had relatively acceptable fruit weight on first harvest, but the weight of the fruits decreased over the time during subsequent harvests, indicating when fruit pruning is not done the number of fruits increases, and as a result, the weight of each fruit decreases. While, pruning 30% was able to maintain the fruit weight from the first harvest to the fourth harvest. Maintaining the fruit weight during successive harvests is highly important for pepper farmers. Reduction of fruit number through the pruning leads to prevention of fruit weight loss during successive harvests followed by higher fruits marketability. The effect of pruning on fruit weight of red cultivar during different harvests revealed that unpruned and pruned plants at 10 % level did not produce any fruits at first harvest, and fruit production initiated at second harvest leading to lower yield performance. The highest fruit diameter of yellow cultivar during successive harvests was recorded at pruning 30 %. Also, the highest fruit length of red cultivar was measured at first harvest and pruning 30 %. All pruning levels increased the total weight of first grade fruits of red cultivar, so that the lowest value of this trait was recorded in unpruned plants.  

Fruit pruning appears to improve the source/sink relationship in pepper by increasing fruit yield and weight as well as fruit qualitative characteristics so that the red cultivar outperformed the yellow cultivar in most growth and qualitative traits, and pruning 10 and 20 % were more positively effective on fruit firmness and size (diameter and length) comparing to other levels. Based on results, it is recommendable to conduct pruning at levels of 10 and 20 % on two bell pepper cultivars, namely yellow (Lumos) and red (Lorka), in order to enhance the fruit yield and qualitative characteristics.