Screening of Tolerance of Plum Cultivars to the Plum Moth Grapholita funebrana (Treitschke)

Document Type : Full Paper

Authors

• Masoud Latifian ¹
• Mohieddin Pirkhezri ²
• Razieh Ghaemi ³

¹ Agricultural Research, Education and Extension Organization, Horticultural Sciences Research Institute, Temperate Fruits Research Center, Karaj.Iran

² Agricultural Research Education and Extension Organization .Horticultural Science Research Institute,Temperate Fruits Research Center, Karaj, Iran

³ Agricultural Research, Education and Extension Organization, Horticultural Sciences Research Institute, Temperate Fruits Research Center, Karaj. Iran,

Abstract

Keywords

• Larvae
• Injury
• Strees Suceptibility
• Plant defence

Main Subjects

• Fruit Science

Extended Abstract

Introduction

    Plum fruit moth, Grapholita funebrana, is one of the most important plum (Prunus domestica) pests. The larva of this pest feeds on the flesh of the fruit. Larvae-infested fruits contain a dense mass of black excrement, which greatly reduces the economic value of the product. The damage rate of this pest is reported 30 to 70 percent. The advantages of using resistant plum cultivars can be mentioned by reducing the cost of purchasing pest control inputs and increasing yield per unit area. Consequently, the introduction of plum cultivars tolerant to plum moth is an important and necessary step in the good management of this pest in the country.

Materials and methods

This project was carried out in the collection garden of the temperate and cold-season fruit research institute located in the city of Kamalshahr, Karaj, from 2019 to 2021.To carry out this project, 26 promising plum cultivars and genotypes named Kh-Mashhad, Sosormi, G-balck, G98, Mortini, Anjelo, Songhor abadi, Ghomi, Kermanshah, Black Amber, G99, Geontype 19, Feriyar, Zard Kordestane, Black star, Ghalo, Bokhara, Queen roza, Laroda, Gr-Rezaeyeh, Gholaman, Zojelo, Uromieh 20, Santarza, G-Malayer and G100 were used. Estimation of the percentage of infection with plum larvae was done at the peak of its activity, i.e., in the middle of May, every ten days until the end of October.Twenty randomly selected fruits from four trees of each genotype in four directions (south, north, east and west) of each tree were harvested and transferred to the laboratory. The fruits were chopped and the number of healthy and infected fruits was counted on the basis of the presence or absence of larvae or their remnants. The number of active larvae inside the fruits was counted separately. After estimating the injury percentage and the effective larval population, strees susceptibility, stress tolerance, damage and tolerance indices, were also calculated for each cultivar. To examine the quantitative and qualitative characteristics of the fruit, 10 ripe fruits from each tree were transferred to the laboratory. Time series models were utilized to study the correlation between damage percentage and larval population. The cluster analysis method was used to classify cultivars and genotypes based on the tolerance indices. The degree of the effect of different fruit characteristics on the tolerance level was investigated by calculating the correlation coefficient using the IBM® SPSS 27.0.1 IF026 software.

Results and Discussion

The damaging population of the pest started its activity from the second half of May and gradually the density of the active larvae population on the plum fruit increased. The maximum effective day-larva index in the studied years was in late July to early August. Although this pattern had the same trend in most of the studied cultivars, differences were also observed in some of them. So that in Anjelo, Gholaman, Kh-Kermanshah and Zojelo cultivars the maximum activity of pest larvae was happened with a little delay, in late August to early September, while in some cultivars such as Kermanshah it happened earlier than other cultivars, in late June. In three years of study, Ghalo and Sosormi cultivars have, respectively, the maximum and minimum values of the cross correlation coefficient between the percentage of damage and the population of harmful larvae. Genotypes with toletrance reactions included Gholaman, Faryar, G-Black, Zojelo, Gallo, G-100, Qomi, G98, G99, Mortini, Black Amber and Kermanshah. Among the investigated characters, fruit surface area, sphericity index, average diameter of fruit engineering, fruit size index, fruit length, and fruit width had a positive and significant correlation with tolerance indices. The important point is the extent that defensive traits provide sustainable pest control. Adaptation and selection of defense traits with different types of pests to optimize the breeding process of tolerant cultivars depends on the nature of the damage caused by the pest, whether it is direct feeding damage, visual spoilage, or whether the pest is a disease carrier. Focusing on specific traits that make plants resistant to pests is vital for the development of pest-tolerant fruit tree germplasm.

Conclusion

In general, the germplasms of Queen Rosa and Angelo were the most sensitive, and Qomi, Gholaman, Faryar, G-Black, Zoglu, Gallo, G-100, G98, G99, Moretini, Black Amber and Kermanshah were the most tolerant cultivars to plum moth. An advantage of using tolerant cultivars as part of integrated pest management is ecological compatibility with other control tactics. One of the most important tasks for breeders is to find and use the natural diversity of plant defense characters and transfer them to future cultivars to improve the inherent resistance of horticultural products, including plum, against pests. The results of this research are also a part of the breeding program of plum cultivars to develop the cultivation of this product in the country.