نشریه پژوهش های کاربردی در گیاه پزشکی
سال یازدهم شماره 4 (زمستان 1401)

In this study, genetic diversity of 70 isolates of Colletotrichum fructicola obtained from the leaf spot symptoms on a variety of cultivated and wild plants in different regions of three northern provinces of Iran, including Guilan, Mazandaran and Golestan, was investigated using the ISSR molecular marker. Cluster analysis of the results of DNA fingerprinting using five ISSR primers for 70 isolates of C. fructicola cleraly reverlaed genetic diversity among the isolates. Based on this, 70 isolates were differentiated into eight colonal lineages. These results showed that there is a high level of genetic diversity among isolates of this fungal species. No direct correlation between DNA fingerprinting groups and geographical origin and host of the isolates was observed. In order to evaluate the efficiency of ISSR molecular marker in differentiating C. fructicola isolates from isolates of some close and dominant species of the genus Colletotrichum, DNA fingerprinting using this molecular marker for 89 isolates including 85 C. fructicola isolates, two C. gloeosporioides isolates, one isolate for each of C. aenigma and C. karstii was performed. Based on the comparison of the DNA fingerprinting pattern and the drawn phenogram, 89 isolates were placed in four main groups (A-D) at the genetic similarity level of 70%. So that the isolates of colonal lineages A-D belonged to C. karstii, C. fructicola, C. gloeosporioides and C. aenigma species, respectively. To ensure the accuracy of the identification, 28 isolates from different clonal lineages were selected as representatives for molecular identification based on the sequencing of the beta-tubulin (TUB2) gene region and the APN2/MAT1 (ApMAT) intergenic space. Phylogenetic analysis showed the accuracy of identification and the efficiency of ISSR molecular marker as a useful tool in grouping and separating the dominant species of the genus Colletotrichum.

The green lacewing, Chrysoperla carnea, plays an important role in biological control of various aphid species. In this study, the functional responses of the second and third instar larvae of C. carnea were studied on the citrus aphid, Aphis spiraecola and melon aphid, A. gossypii. The experiments were carried out on orange (cv. Thompson Navel) leaves in a growth chamber at 27 ± 2°C, 65 ± 5% RH and a photoperiod of 16 L: 8 D h. Different densities of the preys were offered to the predators, and the number of consumed preys was calculated after 24 h. Based on the logistic regression analysis, both second and third larval instars of the predator exhibited a Type II functional response to both aphid species. With increasing of the larval instar, the attack rate (a) of the predator on A. spiraecola was significantly increased and the handling time (Th) decreased. Attack rate of second larval instar of the predator on A. gossypii was significantly higher than that on A. spiraecola. Furthermore, the third instar larvae fed on A. gossypii showed significantly lower handling time and higher attack rate compared to A. spiraecola. The results of this study revealed that the larvae of C. carnea, especially the third instar, had a good predation potential in controlling A. spiraecola and A. gossypii. However, further field-based studies are needed for a comprehensive estimation of biocontrol abilities of C. carnea toward these two aphids on the citrus.

Tomato leaf miner, Tuta absoluta, is one of the most detrimental biological agents in tomato cultivation, and there have been many reports of its worldwide resistance to various insecticides. This study aimed to evaluate the resistance of six T. absoluta populations collected from four provinces of Iran, including Ardabil, Tehran, Alborz, and Khuzestan to the widely-used insecticide indoxacarb. Leaf-dipping method bioassay was performed against the second-instar larvae. Estimated 72 h-LC50 values had not any overlapping between their 95% confidence intervals in all populations, indicating the presence of significant resistance in six populations compared to the susceptible one. The highest to lowest resistance ratios were obtained for the populations of Ziba Shahr (25.83), Mohammad Shahr (13.08), Parsabad Moghan (8.68), Safiabad (8.52), Ardabil (4.23), and Benoot-e Bala (2.19), respectively. The indoxacarb mixed with azadirachtin at the LC10: LC10 ratio showed an additive effect, while the LC25: LC25 ratio showed a synergistic effect. Also, the larval mortality caused by a mixture of LC25 values of indoxacarb and azadirachtin was significantly higher than mortality due to their separately used LC50 values in the susceptible population. In conclusion, some indoxacarb-resistant levels were documented in field second-instar larvae of T. absoluta. However, adding azadirachtin enhanced insecticidal efficiency of indoxacarb, which may be applicable in the suitable and safe management of this detrimental insect pest.