التشخيص المظهري و الجزيئي لمسبب مرض التدهور البطيء Tylenchulus semipenetrans و مكافحتها كيميائيا واحيائيا

Morphological and molecular diagnosis of the causative agent of slow decline disease caused by Tylenchulus semipenetrans and its chemical

A field study was conducted in the holy city of Karbala in the year 2021-2022 to find out about the genus Tylenchulus semipenetrans that causes citrus deterioration in the governorate and to find out the most important causes leading to this deterioration. This study included orchards and areas of Karbala governorate and a number of nurseries with five/six samples per area. The study focused on the symptoms of infection with citrus deterioration nematode, as the percentage of infection varied according to the studied orchards and the number of samples bearing the manifestations of infection, whether on the shoot or root, depending on the samples bearing the infection. The highest percentage of infection in home gardens was for each of Al-Amel neighborhood and orchards in Al-Hindiya district with a rate of 83.3%, followed by Aoun area with a rate of 66.6%, Al-Husayniyyah area with a rate of 60%, Al-Boubiyat area with a rate of 51.5%, and Al-Haydariyat area with a rate of 40%. While the highest severity of the infection was in the orchards of Al-Hindiya district and Al-Amil district with a rate of 83.3%, followed by the Aoun region with an infection severity of 53.3% The severity of the injury varied until it reached the lowest severity in the Al-Hur Al-Saghirad region, which amounted to 1.2%.
The morphological and molecular diagnosis using the polymerase chain reaction (PCR) technique confirmed the infection of citrus trees with the genus Tylenchulus semipenetrans. This is the first molecular diagnosis of this genus at the national level
The results of the field experiments showed that the vermocompost fertilizer increased the plant content of the total chlorophyll of trees, reaching SPAD44.20, followed by the biological pesticide Verox by 39.23 SPAD units, followed by the organic pesticide Tondexir by 25.13 SPAD units, and the other organic pesticide Palizin by 22.55 SPAD units. 23.16 SPAD units compared to the SPAD control treatment. 28.36
The results of laboratory experiments in the percentage of hatching eggs of slow deterioration nematodes on citrus indicated the superiority of the chemical pesticide Tendro by 4.21%, followed by the combined complementary pesticide treatment by 4.80%, while the biological pesticide Verox gave a percentage of 16.13%, followed by the treatment of organic pesticides Tondaxer and Pazilin B, 48.53%, 36.70% over which were significantly different from the 100% control treatment.
The results of field control showed a significant decrease in the number of egg mases (egg sacs) of the nematode Tylenchulus semipenetrans until it reached the lowest level in the combined integrated treatment, as the effect of the use of biological and organic pesticides in reducing the numbers of females compared to the contaminated treatment (control) in one cm of the root and at a lower concentration It is recommended that the pesticides with effective concentrations in the laboratory showed high efficiency in reducing the number of females in the soil and root, as the chemical pesticide treatment reached 3.50 females per one cm of root, followed by the complementary treatment with a ratio of 5.33 females per one cm/root and a ratio of 6.50 females per one cm of root. For biological and chemical pesticides with a treatment rate of 3.50 and organic fertilizer The organic fertilizer Vermocompost with a treatment rate of 7.50, the organic pesticide Tondxir with a treatment rate of 10, and the pesticide Pazilin with a treatment rate of 9.66, while the pesticide mixing treatment with a rate of 5.33 showed high efficiency in reducing the population of nematodes, and this is an indication of the possibility of including it in the integrated control programs for this pest.
The field control results showed the effect of the chemical substance of Tendro, the biological of Verox, and the organic pesticides of Tondxir and Pazilin, on reducing the numbers of females in one cm of roots and the number of egg sacs in the soil, which led to a significant decrease in the number of egg sacs and females in one cm of root, as the three-leaved cultivar outperformed The local variety, as the lowest percentage in egg sac numbers in the integrated combined treatment of the three-leaved cultivar was 2.66, while the local variety was 5.33.