Effect of plant growth regulators on two different types of eggplant flowers regarding style length and fruit setting

Aim of study: (i) to explore differences between eggplant flowers capable of setting fruit including long (LGs) and medium style flowers (MEs) and those which suffer from severe problems with fertility and fruit setting including short style ones (SRTs); (ii) to study the effect of plant growth regulators on floral morphology and fruit setting. Area of study: Isfahan University of Technology, Isfahan, Iran, 2017 and 2018. Material and methods: First the floral morphology and initial fruit setting of 13 eggplant genotypes from Iran were investigated. Then the differences between LGs and SRTs of two genotypes were explored. Finally, the effect of 1-naphthaleneacetic acid (NAA) and spermidine (Spd) on floral morphology and initial and final fruit setting of these two genotypes was determined. Main results: Results showed SRTs were not capable of fruit setting. Compared to SRTs, LGs had larger central canals, higher protein, total sugar, reducing sugar and K concentrations, as well as longer polar axis and pollen tubes and greater pollen viability. Although 1.5 mM Spd and 20 mg L-1 NAA resulted in increasing of LGs and MEs, and also total initial fruit set, surprisingly, no significant differences were observed in the final yield and final fruit set between the control and these treatments. Researching highlights: Since the rate of fruit dropping was higher in those treatments compared to the control, plants with more SRTs likely regulate their final load by abscising their flowers, and plants with more LGs regulate them by abscising their fruits