Dry Matter and Oil Accumulation in Fruit of Some Olive Promising Genotypes under Sarpol-e Zahab Environmental Conditions in Iran

This research was conducted for evaluating the tend of dry matter and oil accumulation in fruits of seven olive promising genotypes under climatic conditions of Dallaho olive research station in Sarpol-e Zahab, in Kermanshah province, Iran, in 2018 and 2019 growing seasons. Ten years old trees of seven olive promising genotypes; D1, Dd1, Gw, Ps1, Bn3, Bn6 and Ds3 were planted using randomized complete block design with 3 replications. The results showed that oil accumulation in olive genotype commenced from July and reached to maximal content in November. The oil accumulation was continuous in fruits and gradually increased in all of genotypes. D1 and Bn3 promising genotypes had the highest oil content in dry matter, and the maximum dry matter was observed in Gw and Dd1. The results of this research revealed that olive promising genotypes had different responses in warm climatic conditions, and oil accumulation was influenced by temperature.

Olive tree (Olea europaea L.) is an evergreen and native plant to the Mediterranean regions. The appropriate area for olive cultivation for oil production has moderate winters and long and dry summers. In high temperatures and intensive radiation, olive trees indicate 80% reduction in leaves photosynthesis (Bongi and Long, 1987). In high temperature and water shortage, fruit and oil quality in olive trees decrease (Saadato et al., 2013). The precursor of oil biosynthesis in olive fruits is carbohydrate (Conde et al., 2008). The semi-arid and arid weather during fruit growth and oil accumulation necessitate the selection of tolerant olive cultivars. The dry matter and oil accumulation strongly depend upon climatic condition and olive cultivars, therefore the choice of the most promising tolerant cultivars that perform successful, under stressful conditions, is inevitable to achieve the high quality olive fruit and oil. 

This study was carried out in Dallaho olive research station (34º 30′ 34′′ N, 45º 51′ 53′′ E, and 580m above sea level) in Sarpolezahab in Kermanshah province in Iran in 2018 and 2019 growing seasons. Ten years old tress of seven olive promising cultivars (D1, Dd1, Gw, Ps1, Bn3, Bn6 and Ds3 were evaluated using randomized complete block design with three replications. In two consecutive years, 2018 and 2019, fruit harvesting was carried out in two weeks intervals from July to November. Dry matter was measured following by Anonymous (1997) and oil content was determined following Dag et al. (2011). Combined analysis of variance was performed using SAS software. Duncan’s Multiple Range Test was employed for mean comparison. Figures were depicted using Excel software. 

The highest oil contente in dry matter belonged to D1 and Bn3 promising genotypes. The highest dry matter was observed in Gw and Dd1 promising genotypes. As harvest date delayed, oil content in dry matter increased, and in September until final harvest in November, the highest oil content in dry and fresh matters was obtained. The oil content is sensitive to temperature variation and by increasing temperature from 16 ºC to 32 ºC, oil content decreased (Borges et al., 2017).The reduction of pomological traits in olive in high temperature conditions is due to enhancement of respiration, oxidative disturbance and reduction of photosynthesis efficiency (Neves et al., 2019). Different olive promising genotypes due to expression of heat shock proteins had different levels of tolerance against high temperature (Nissim et al., 2020). During this research, the mean maximum and minimum temperatures were more than 40 ℃ and 30 ℃ in June, July and August, and the high temperature was accompanied by reduction in relative humidity. The results indicated that maximum and minimum temperatures had negative effects on oil content of some olive promising genotypes.