گزارش پیدایش نماتد ساقه و پیاز (Ditylenchus dipsaci) در مزارع پیاز استان فارس

The stem and bulb nematode (Ditylenchus dipsaci) has a wide host range and is one of the most important limiting factors for the production of garlic, onion, alfalfa and some other crops in temperate regions and cool seasons. Symptoms of host plant infection include the growth reduction, twisting and deformation of young leaves (strawberry, onion and garlic), shortening of internodes, bud swelling and its color change from white or cream to light brown (alfalfa) (Fig 1). So far, damage caused by this nematode on alfalfa, garlic and strawberry has been reported from Iran. In the winter and early spring of 2024, symptoms of nematode infection were observed in some garlic and onion fields in Marvdasht city and alfalfa in Arsenjan city in Fars province and nematodes were extracted from the infested tissues of the host plants. The nematodes were fixed with hot formaldehyde-acetic acid-glycerol solution (1:1:4) and transferred to anhydrous glycerol. Microscopic permanent preparations were then made of the onion population. The populations studied were identified on the basis of morphometric and morphological characteristics and identification keys, as D. dipsaci. All characteristics of the studied population are consistent with the original description of D. dipsaci. Comparison of the morphological and morphometric characteristics of the onion population showed that the body length and stylet length, as well as the V index of the female were higher than in the populations of the previous reports on this species from Iran and were 1409 µm, 12.2 µm and 84.4, respectively, compared to 1193, 11.3 and 82 in the potato population, and 1169, 11.1 and 79 in the strawberry population. The body length of males was also higher compared to previous studies (1396 µm in the present study compared to 1104 µm in the potato population and 1183 µm in the strawberry population). This is the first report on the occurrence of stem and bulb nematode in the onion fields of Iran. In this survey, it was also found that stem and bulb nematode is widely distributed in garlic, onion and alfalfa fields in Fars province.