شناسایی و توصیف Aphelenchoides besseyi Christie, 1942 (Nematoda: Aphelenchoidea) عامل نوک سفیدی برنج در استان فارس

During October 2017, plants with leaves showing white tip symptoms, as well as with darkened crowns were observed in a rice field in Kamfiruz country, Fars province, southern Iran. Several pieces of crown tissue were cultured on potato-dextrose-agar (PDA) medium. After 48 hours, structures typical of Fusarium fungus and also high numbers of a nematode colonized the medium. After extraction with tray method, and regarding morphological and morphometric characters, the population of nematode was identified as A. besseyi. This species has already been collected and identified from inside tissues of rice and strawberry, as well as from the rhizosphere of citrus trees and saffron plants in Iran, but morphological and morphometric characterization of these populations never presented so far. In this population, females body slender, generally straight, 606-828µm. Cuticle weakly annulated, Lateral field with 4 longitudinal incisures. Lip region rounded, offset. Stylet 9.9-13µm. Hemizonid one annulus posterior to excretory pore, often indistinct. Pharyngeal gland lobe overlap intestine dorsally; three gland nuclei arranged ordinary in a straight line. Ovary outstretched anteriorly until reaching near pharyngeal gland lobe, vagina relatively sclerotized and slightly directed anteriorly; vulva with slightly raised protuberant lips. Post-vulval uterine sac 43-63 µm, ca 2.5-3.5 times of vulval body diameter and 21-50% of the vulva-anus distance. Tail convex-conoid, straight or slightly curved ventrally; terminus bearing a mucro with 3, or rarely 4 pointed processes. Males body J-shaped, 552-630 µm. Testis single, anteriorly outstretched, or reflexed in some specimens. Cloacal lips slightly raised. Spicules without distinct apex and with normal rostrum; gubernaculum and bursa absent. Three pairs of subventral caudal papilla present: first pair located just posterior to cloaca, second pair slightly posterior to mid-tail region and third pair subterminal. Tail conoid, curved ventrally; terminal mucro similar to female in shape, but with smaller processes.