Breeding and agrotechnical modifications of blocky type pepper cultivars adapted for passive protected cultivation under mild winter conditions

The areas of pepper growing in passive protected cultivation regions with mild winter conditions are expanding. Simple plastic-covered structures facilitate protected pepper production during the winter. A typical crop is planted at the middle of the summer and ripe fruits are harvested during the fall, winter and spring seasons. Environmental conditions inside such structures are more extreme than those prevailing in climate-controlled greenhouses or outdoors. During the beginning of the production season when flowering and fruit set occur, the plants are exposed to extremely high day and night temperatures; these can be up to 45 and 25°C, respectively. In order to prevent even higher temperatures shading is applied. In the middle of the season, during the winter, minimum night temperatures are in the range 4-10°C, with infrequent frosts, and insufficient radiation. During this period growth continues and fruits are set, develop and ripen. It is proposed that cultivars which can thrive in such harsh conditions should be bred. Sufficient fruit set must occur under both high and low temperatures. The minimum night temperature for proper fruit set of blocky pepper was thought to be 18°C. Selection from a wide range of genetic variation under low night temperatures, led to the development of cultivars that can set normally shaped fruits at temperatures under 8-10°C. Those cultivars are also characterized with vigorous plants. Such cultivars fail to set under high temperatures during the beginning of the season. Special agrotechniques such as removal of shading, nitrogen starvation, and water stress seem to induce flower development and fruit set under high temperatures. This in turn extended the period of fruit setting, leading to a longer production season, and higher yields. It can be concluded that appropriate genetic advancement through breeding, combined with suitable agrotechnical means, can provide farmers with sustainable production systems.