EFFECT OF FOLIAR SPRAY WITH SOME SILICON SOURCES AND PACLOBUTRAZOL ON GROWTH, YIELD AND FRUIT QUALITY OF SWEET PEPPER (CAPSICUM ANNUUM L.) PLANTS UNDER HIGH-TEMPERATURE CONDITIONS

This study was carried out during the two late-summer seasons of 2016 and 2017 at Sids Horticulture Research Station, Beni Sueif Governorate, Agriculture Research Center, Egypt. The objectives of this study were to investigate the effect of foliar spraying with five silicon sources i.e. sodium meta silicate, potassium silicate, kaolin clay particle film, fine crushed of the raw silicon and sunless, in addition paclobutrazol compound at two rates as well as the control treatment (spraying with tap water) under the two late summer seasons condition on the vegetative growth parameters, fruit set %, average fruit weight, yield and its components, fruit quality and some chemical contents in sweet pepper leaves. The experimental design was a randomized complete block containing eight treatments with three replications. Pepper seedlings of Super Star F1 hybrid were transplanted in the 1st week of May during the two late-summer seasons, respectively. The results showed that the most estimated parameters were significantly affected with silicon sources and paclobutrazol treatments as foliar applications; the superiority effect of the treatments was recorded by using kaolin (Aluminumsilicate) followed by potassium silicate and paclobutrazol at a rate of 50 mg/ L as well as sunless respectively, which led to obtaining the highest significant increase in all the previous studied traits under high-temperature stress condition. The remarkable of treated sweet pepper plants with kaolin material leading to increasing in the total yield and decreasing un-marketable yield (ton/ fed.) based on decreasing the injuries of sunburn on pepper fruits as a disorder disease compared with the control treatment. The severity of this disease which increases under the conditions of the late summer season characterize with the high-temperature stress led to sun scale injury at this time of the season, because of the increases of ultraviolet and infrared radiation which prevailing during this critical period of the late summer season, causes serious physiological diseases sun scale or sunburn on pepper fruits, for that the study recommend spraying pepper plants grown under high-temperature stress with any one of the previous mentioned silicon sources, particularly using kaolin compound which applied after 30 days from transplanting and repeated at 15-day intervals at four times to obtain the highest yield, best quality and highest net return, because it is the preferable are comparing to the other treatments.