Evaluation of Yield and Quality of Peach Fruit (Prunus persica var Red Top) Cultivated under Split Roots System, Inoculated with Fungi and Irrigated with different Levels

Water scarcity is one of the most important limiting factors threatening the production of horticultural crops. Approximately, 45% of the world's arable land is subject to permanent or intermittent water shortages, and approximately 50% of the world's annual yield is lost due to drought. Due to climate changes, especially the increase temperature and decrease rainfall in recent years in Iran, most of the gardens are facing limited water resources. In order to reduce water stress, increasing water use efficiency by naval technics seems to be crucial. Peach fruit growth mainly depends on adequate water supply. Therefore, water stress reduces the growth of the fleshy part and the quality of the peach fruits. Split root means placing a part of the root in different conditions compared to the remains of the root. Studies on split root culture were done in the laboratory for the first time. Increasing water holding capacity by split root system may improve soil- plant water availability. Furthermore, many studies indicated that Mycorrhiza and Trichoderma fungi improve the absorption of water and nutrients by plant. Increasing the absorption of water and nutrients leads to increasing growth and yield. The aim of this research was to improve the water efficiency and the use of low-yielding lands by placing a bag containing pumice and inoculating the roots with fungi.
This experiment was performed as a factorial experiment based on randomized complete blocks design with three replications for two years. Treatments included placing the bag close to the trunk of peach trees in three levels (without bag, one bag and two bags), different levels of irrigation (50, 75 and 100% of field capacity) and root inoculation treatments with mycorrhiza, Trichoderma fungi and control without fungus. Redtop peaches grafted on GF677 rootstock were planted in May 2018. The bags were placed at a depth of 60 cm and at a distance of 40 and 60 cm from the tree trunk. The bags size was 40 liters filled with pumice. At 20 cm from the top of the bag, three holes were made to remove excess water from that part and as a signal to cause the root to move towards the bag. For plants treated with mycorrhiza, 250 g of Mycorrhiza glomus was mixed and for plants treated with Trichoderma, 4.5 g of Trichoderma harizanium was mixed with pumice in the bag. In treatments with no bag placement, the plant roots were inoculated with fungi. Characteristics such as relative water content (RWC), yield, total soluble solids (TSS), titratable acidity (TA), TSS/TA, total phenol and fruit anthocyanin were measured at the end of growing season. Fruit skin color characteristics including L*, a*, b*, Chroma and Hue were measured with a colorimeter. Statistical analysis was performed by SAS software version 9.1. Mean data were compared using Duncan's multiple range test. drawing diagrams done by Excel software.
 
The results showed that bag placement increased RWC. The highest RWC of leaf was measured in the treatment of placing two bags, 75% irrigation and root inoculation with Trichoderma fungus. In the main effect of bag placement, irrigation levels and root inoculation, the highest RWC of leaf was observed in placing a bag, 100% irrigation and root inoculation with Trichoderma fungus, respectively. The treatment one bag, 100% irrigation and root inoculation with mycorrhiza improved vegetative growth and produced the largest trunk diameter.  Yield in terms of fresh weight of fruit in two-bag placement, 100% irrigation and root inoculation with mycorrhiza was increased by 1.8 compared to the control. The highest TA was measured in the treatment of placing a bag, 50% irrigation and root inoculation with mycorrhizal fungus. Treatment without bag placement, 75% irrigation and without fungus inoculation had the highest total soluble solids and TSS/TA of fruit. The index ratio of TSS/TA is used to determine the taste of the fruit. The highest total phenol and anthocyanin of fruit was observed in treatments without bag under 50% irrigation levels. One bag placement, 75% irrigation without fungal inoculation treatment and no bag placement treatment, 50% irrigation, mycorrhiza inoculation caused the a* and L* of the fruit skin increased. The interaction effect of the three factors of bag placement, irrigation levels and root inoculation with fungus had no significant effect on Hue and b*.
The results of this experiment showed that water consumption can be reduced by placing a bag. The finding of the experiment led to the conclusion that a bag placement treatment, 75% irrigation and inoculation with mycorrhizal fungus improve fruit yield and quality of peach trees
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