جستجوی مقالات مرتبط با کلیدواژه "larvae" در نشریات گروه "گیاهپزشکی"

Bean (Phaseolus vulgaris L.) (Fabaceae) is one of the most cultivated plants of legumes in most countries. Several of insects with piercing-sucking mouthparts such as thrips, leafhopper, aphids, and plant bugs are as pest on beans. Thrips can attack beans from the seedlings emerge through to flowering, but it is the damage some do during flowering that has the greatest impact. Thrips tabaci Lindeman 1889, the onion thrips is a cosmopolitan species. It has hundreds of host plants but of these, the economically most important crop plants are onion, cabbage, tobacco, pepper, bean and tomato. Here, population fluctuation and spatial distribution of thrips was investigated in the bean fields of Sanandaj county (Kurdistan province, west of Iran).

Sampling was done from bean leaves from two leaves stage until ending growing season  in the bean fields (bean Canyon variety) located in Arandan village (N 35° 23' 10.96", E 46° 54' 53.16", alt. 1660 m), Sanandaj county during the years 2022 and 2023. Bean leaf was selected as sampling unit. Sampling was done weekly and four rows were sampled each time. A systematic sampling pattern was used to collect the samples. In this way, in the selected rows, 24 plants at the beginning and end of each row were ignored, and the 25th plant of each row was the first plant on which thrips were counted. After that, 24 plants were left and counting was done on the 25th plant after the first plant. In this way, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300 and 325 plants were sampled in each row. Weekly sampling was done in a similar style, but each time, different rows of crops were selected for sampling. Sampling was done weekly, and for this purpose lower, middle and upper leaves were selected from each bean and the leaves were shaken on a white tray and then the thrips were put into Eppendorf containing ethyl alcohol 75%. In order to accurately count thrips, by using a stereomicroscope, some samples were separated and microscopic slides were prepared from some samples and finally the number of samples was recorded. Spatial distribution of adults of thrips was estimated using Taylor’s power law and Iwao’s patchiness regression methods.

The results showed that the population of onion thrips was observed from July and gradually increased and in 2022 its maximum was in the first week of August with an average of 11.65 ± 0.14 thrips and in 2023 its maximum was in the end of week of August with an average of 11.29 ± 0.23 thrips at the sampling unit. In addition, the highest mean number of onion thrips was observed with a significant difference in the lower leaves compared to the middle and upper leaves. The results of the spatial distribution of the pest showed that based on the variance-to-mean ratio, Taylor’s power law and Iwao’s patchiness regression methods, the spatial distribution of onion thrips was clumped, randomized and clumped, respectively. In general, the results showed that the peak of population of onion thrips reaches in early of August. Furthermore, based on goodness of fit, the Iwao’s patchiness method was more suitable than the Taylor’s power law method for estimating the spatial distribution of the pest.

It can be concluded that, at the beginning of the growing season of beans in the field, a low population of onion thrips was activated, and gradually with the warming of the weather and the change of the growing stages of the beans, the population of the pest in the field increased, so that the largest population of onion thrips were observed in the first week of August. In addition, based on the sampling, the highest average number of onion thrips was observed in the lower leaves of beans compared to the middle and upper leaves. The relationship between population fluctuations of onion thrips with average positive temperature was obtained. In examining the spatial distribution pattern with the Iwao’s patchiness method, it was found that the spatial distribution of onion thrips is uniform. Considering the high activity and damage caused by onion thrips on various crops, especially on beans, it is necessary and important to conduct more studies on its various characteristics in various regions and crops of Kurdistan province so that a suitable management plan can be developed to control this pest.

Wheat Triticum aestivum L., is one of the most important and strategic crops in the world. Bread wheat (2n = 6x = 42), belonging to the family Poaceae, which is considered the most diverse and important family of the plant kingdom, produces large edible grains and provides about one-half of humans’ food calories(Wang et al., 2017). A number of pests and diseases attack wheat, out of which nematodes have been considered universally as one of the important microscopic organisms (ref). The Cereal Cyst Nematodes (CCN: Heterodera spp.) have a global distribution and cause significant economic yield losses in many countries of the world (Pariyar et al., 2016). It is known as the first and most important cereal crop in the world and widely consumed by 75 % of world populations (Drikvand et al., 2013).Cereal cyst nematode Heterodera filipjevi has wider distribution, than other species in cereal fields in Iran. In this study, the reaction of 30 wheat cultivars against cyst nematode were evaluated in statistical design in greenhouse and the field. These cultivars planted in growing seasons (2015/2016) in a H. filipjevi-infested field in Agricultural Research Station, Central Kabotrabad area of Isfahan (30°42′ and 34°30′ N latitude and 49°36′ and 55°32′ E longitude), in a completely randomized block design, with three replications, each of which in a four rows of three meter length and 20cm distance.The cereal cyst species were identified based on morphological, morphometric features and molecular characters. The number of cysts, second stage juveniles and eggs were analyzed. Also, reproductive factor and percentage reduction and or increase in cereal cyst nematode population in each treatment were calculated into its initial population. Statistical and clustered analysis data were carried out on by Duncan's multiple range test (DMRT), SAS and SPSS statistical softwares, respectively. The results showed that, in the greenhouse, the lowest brown cyst was in Behrang cultivar with an average of 15 cysts and then Bam cultivar with an average of 15.25 in 200 cc of soil.The lowest number of CCN eggs and second stage juveniles and reproductive factor were of Pyshtaz cultivar with the average of 0.49 per gram of soil. The, cultivars were classified into three ranges of resistant, tolerant and susceptible. In field conditions, the lowest brown cyst was of Bam cultivar with 113.33 per 200 cc of soil. Whereas the lowest numbers of CCN eggs and second stage juveniles and reproductive factors were in Parsi cultivar with 0.69 per gram of soil, fallowed by Aflak cultivar with 1.69 in two different statistically groups. Also, cluster analysis classified the cultivars into three different categories, which also showed remarkable similarities to Duncan's test results. Currently, the resistant and tolerant wheat cultivars to cyst nematode is widely used in many European countries such as the UK, Denmark, France, Sweden and Australia. Row. Therefore, identifying and recognizing resistant genes in the cultivars under study provides a way for the production of resistant transgenic commercial wheat varieties. From our results, we confirmed that wheat accessions Behrang and Bam possess resistance and can subsequently be crossed with high yielding cultivars improving their genetic resistance to CCNs. There is a deal of potential for this study to develop new resistant varieties to H. filipjevi which will have a great value to the agriculture sector in Iran. These resistant cultivars can be used in crop nematode management program and tracking and transferring resistance genes to desirable crop cultivars. Also, in addition to number of cysts, the number of larvae took into screening programs for better susceptibility assessment justifications. It is suggested that Marker-assisted selection will further improve the development of resistant cultivars. Isolation of candidate genes associated with specific markers will greatly facilitate this process. Finding new sources of resistance would be very much demanded to control the different populations especially in areas, where a mixture of Heterodera species occurs. Therefore, wheat origin countries including Iran, Iraq, Syrian and Turkey obtained wild wheat relatives, which is to be screened to the main Heterodera species. Taking advantage of these sources of resistance is necessary to know the reaction of genotypes against CCN species for new resistant gene/s in Iran.

This study was conducted for evaluation of the infestation levels in plants of six commercial cultivars of potato including: Impala, agria, savalan, florida, emeraude and markies to the tomato leafminer, Tuta absoluta (Meyrick) under field condition in Ardabil region during 2013 and 2014. The number of mines and live larvae per plant, the number of mines per leaf, dry weight of foliage and tubers, and the percent reduction in dry weight of foliage and tubers per plant in six potato cultivars were analyzed as a randomized complete block design. Our results indicated that amongst the six tested cultivars, emeraude and markies with the highest number of mines and larvae, and the greatest percent reduction in dry weight of foliage and tubers have the greatest relative suitability to the tomato leafminer. Whereas, florida with the lowest number of mines and larvae, and the lowest percent reduction in dry weight of foliage and tubers had the lowest relative suitability to the tomato leafminer. In savalan, with the medium number of mines and larvae, the percent reduction in dry weight of foliage and tubers was significantly lower than other cultivars (with florida). These results likely reflect the highest relative tolerance of savalan to tomato leafminer among the six tested cultivars of potato. Therefore, savalan (with the highest relative tolerance) and florida (with the least relative suitability) have potential for use in the sustainable management of T. absoluta in potato fields.