گونه‌های شایع نماتدهای مولد زخم ریشه (pratylenchus thornei و p. neglectus) در مزارع گندم و جو استان خوزستان و وضعیت آلودگی مزارع به آن‌ها

استان خوزستان جایگاه اول تولید گندم در کشور را دارد. نماتدهای مولد زخم ریشه (.pratylenchus spp) از نماتدهای انگل گیاهی هستند که شامل چندین گونه نزدیک به هم بوده و دارای اهمیت اقتصادی روی غلات هستند. به منظور بررسی وجود آنها در طی اواخر دوره داشت سال‌های 90-1387، 200 نمونه خاک و ریشه از مزارع گندم و جو استان جمع‌آوری و نسبت به آلودگی به نماتدهای مولد زخم ریشه بررسی شدند. براساس نتایج، 37 درصد از مزارع گندم بررسی شده در شهرستان‌های امیدیه، اندیکا، اندیمشک، اهواز، ایذه، باغملک، بهبهان، دزفول، دشت‌آزادگان، رامشیر، رامهرمز، شادگان، شوش، شوشتر، گتوند، لالی و هویزه با متوسط میزان جمعیت به ترتیب 39 نماتد در گرم ریشه و 101 نماتد در 250 سانتی‌متر مکعب خاک به گونه‌های p. neglectus (18 درصد)، pratylenchus thornei  (62 درصد) و مخلوط دو گونه (20 درصد) آلوده بودند. همچنین 42 درصد از مزارع جو بررسی شده در شهرستان‌های امیدیه، اندیکا، ایذه، باغملک، رامهرمز و لالی با متوسط میزان جمعیت به ترتیب 9 نماتد در گرم ریشه و 72 نماتد در 250 سانتی‌متر مکعب خاک به این نماتدها آلوده بودند. آلودگی به نماتدهای زخم ریشه در مزارع گندم بیشتر شهرستان‌های استان به جز باغملک، خرمشهر، هفتگل و هندیجان و در مزارع جو شهرستان‌های امیدیه، اندیکا، ایذه، باغملک، رامهرمز و لالی مشاهده شد. 10 درصد از مزارع نمونه‌برداری شده دارای جمعیت‌ بالای 21 نماتد در گرم خاک بودند که امکان وقوع خسارت به محصول بسیار محتمل است.

The prevalence of root lesion nematodes (Pratylenchus thornei & P. neglectus) in wheat and barley fields in Khuzestan province, as well as the contamination status of these fields

Background and ObjectivesIran’s Khuzestan province ranks first in wheat production. Rootlesion nematodes (RLN) are a group of plant parasitic nematodes that includes several closely related species of economically significant cereals. There have been eight species of RLN recorded for small grains. Four species (P. thornei, P. crenatus, P. neglectus and P. penetrans) are found worldwide, particularly in temperate zones. P. neglectus, P. thornei, P. pseudopratensis and P. penetrans prevalent in Iranian wheat fields. However, there is insufficient information regarding the status of RLN in the province of Khuzestan’s cereal fields. The objective of this study was to determine the occurrence, distribution and population density of RLN in wheat and barley fields in Khuzestan province.Material and MethodsA survey was conducted over three years (20082011), where 169 wheat and 31 barley fields were inspected and sampled in 21 regions during the grain filling and harvesting periods in the Khuzestan province of Iran. A stereomicroscope was used to examine the root tissue of 10 wheat and barley plant samples for disease symptoms. The Whitehead tray method was employed to process 250 cm3 of soil from each collected soil sample. The RLN species were identified using morphological and morphometric characteristics. ArcGIS 9.3 software was utilized to map the distribution of RLN on the map of Khuzestan.ResultsResults indicated that 37% of wheat fields in the regions of Ahvaz, Andika, Andimeshk, Baghmalek, Behbahan, Dashte Azadegan, Dezful, Gotvand, Hoveyzeh, Izeh, Lali, Omidiyeh, Ramshir, Ramhormoz, Shadegan, Shushtar, and Shush were infested with P. thornei and P. neglectus, with mean population densities of 39 and 101 nematodes per gram of root and 250 cm3 of soil, respectively. In addition, 42% of barley fields in Andika, Baghmalek, Izeh, Lali, Omidiyeh, and Ramhormoz were infested with the nematode, with mean population densities of 9 and 72 nematodes per gram of root and 250 cm3 of soil, respectively. The regions with the highest and lowest nematode populations were Shush, Shusthar, Baghmalek, and Hendijan, with densities of 1,334, 904, 11, and 100 per 250 cm3 of soil, respectively. Ten percent of the surviving fields exhibited nematode populations exceeding 12 per gram of soil, which is extremely likely to cause cereal crop damage.DiscussionPratylenchus thornei, P. neglectus, and a mix of the two species were observed in 62, 18, and 20% of the surveyed fields in Khuzestan, respectively. In both wheat and barley fields, P. thornei was the dominant species. Globally, P. thornei is deemed more dangerous than P. neglectus. This is the first report of the presence of root lesion nematodes in wheat and barley fields in Khuzestan province, with contamination rates of 37 and 42%, respectively. Disease incidence was higher in irrigated fields than in rainfed fields, indicating that soil moisture and nutrients positively influence the nematode population. The nematode population density was higher in wheat fields than in barley fields, confirming that barley is a poor host for RLN. The economic damage thresholds for P. thornei and P. neglectus on wheat have been reported to be 12 nematodes per gram of soil in various parts of the world. The most important management practice is the use of resistant and tolerant wheat varieties to RLN.