Re-Emergence of Wheat Seed Gall Nematode (Anguina tritici) in Punjab, Pakistan

In order to record the incidence of ear cockle of wheat in Sargodha division, fields were randomly selected from 14 tehsils of four districts (Sargodha, Khushab, Bhakkar and Mianwali) of Sargodha division of the Punjab province. A total of 149 villages were visited and from each tehsil of each district 10-11 fields were randomly selected. The fields were visited only once during the survey when the crop was at actively growth stage. From each field four quadrates of 1 m2 each were taken and total numbers of healthy and infected plants were counted. The incidence in each field was determined by the method described by Mukhtar et al. (2017). During surveys different factors i.e. age of crop, variety cultivated, area under cultivation, date of sowing, number of irrigations, fertilizers and pesticides were also recorded. Similarly, incidence in each field of each district was recorded and the individual incidence in each tehsil and district was calculated. The prevalence of seed gall nematode in each tehsil and district was determined as described by Fateh et al. (2017). The incidence on each cultivar in each district and overall incidence on each cultivar was also calculated. All the graphs were made in Microsoft Excel 2007.

The overall incidence of ear cockle of wheat in Sargodha division was found to be 1.2% while the overall prevalence was 27%. As regards districts, the maximum incidence was recorded in district Bhakkar followed by Khushab. Similarly, the maximum prevalence was observed in district Bhakkar followed by Sargodha while it was the minimum in district Khushab as shown in Table I, which also shows Tehsil-wise incidence and prevalence in the four districts. The incidence of the nematode was found variable on different cultivars. The maximum incidence was recorded on cultivar Chakwal-50 followed by Faisalabad-2008 and Lasani-2008 whereas the minimum incidence was observed on cultivars Punjab-2011 and Millat-2011. No incidence of the nematode was recorded on Shafaq-2006 and Aas-2011 cultivars as shown in Table II. The variety wise incidence in the four districts has also been given in Table II.

SGD, Sargodha; KSB, Khushab; BKR, Bhakkar; MWL, Mianwali.

Anguina tritici was the first plant parasitic nematode to be discovered in England by Needham. Since its first report in 1743, the nematode was subsequently found in numerous countries and states of the world on wheat (Al-Talib et al., 1986; Brown, 1987; Gotke and Swarup, 1988; Esser et al., 1991; Kalha et al., 1992; Nath and Patkak, 1993; Riley and Reardon, 1995; CABI/EPPO, 2002; EPPO, 2014, 2015; Mohamedova and Piperkova, 2013; PERAL, 2015). In the present survey incidence of ear cockle was observed up to 1.5% in Sargodha division. Incidence of ear cockle is affected by many factors. Midha and Swarup (1972) reported that the larval population of the nematode affects the infection and incidence. The depth of galls in the soil has also been found to affect the symptom expression. Midha and Swarup (1972) reported maximum ear cockle symptoms when the galls and seeds were placed at a soil depth of 2 cm. Leukel (1924) had earlier reported a decrease in infection when the galls were placed deeper than the seeds. The disease is favored by cool and moist weather. As the wheat plants grow more rapidly in hot weather so they can escape the susceptible period more quickly. The release of juveniles from the galls has been reported to be influenced by soil moisture and temperature and also the thickness of gall’s walls (Leukel, 1924). Cairne (1926) recorded that germination of wheat seed always preceded the release of juveniles from galls. Pathak and Swarup (1983) agreed with Cairne (1926) when they observed that wheat seeds normally start sprouting within three days after planting and the earliest release of juveniles from galls occurs on the 4th day under alternate drying and welting conditions. Pathak and Swarup (1983) also observed that the number of tillers infected with juveniles had a relation with the inoculum level, number and size of galls produced.

Similarly, the main source of disease spread is the infected seeds. Modern agricultural practices, including use of clean seed and crop rotation, have all but eliminated A. tritici in countries which have adopted these practices, and the nematode has not been found in the United States since 1975 (PERAL, 2015). However, A. tritici is still a problem in third world countries where such practices are not widely adapted. In addition, trade issues have arisen due to conflicting records of A. tritici in the United States (PERAL, 2015). A. tritici has been listed as a harmful organism in 21 countries (USDA-PCIT, 2016). There may be trade implications with these countries due to historical records showing the presence of the nematode and/or if A. tritici is discovered again. Brazil has halted shipments of U.S. wheat based on general literature describing the nematode as “widespread in the United States” (PERAL, 2015).

Cultural practices have also affected incidence of seed gall nematode. The incidence was less or no-where the farmers followed crop rotation. Due to crop rotation the nematodes in the soil die and could not cause infection in the following season. Varieties also affect incidence of ear cockle (Anwar et al., 2011). The incidence was low on resistant varieties while it was higher on susceptible varieties. Midha and Swarup (1972) could not obtain ear cockle infection on two wheat varieties Sonara 64 and C591.

It is concluded that wheat seed gall nematode (Anguina tritici) was found prevalent throughout Sargodha division and the incidence was quite low. It is, therefore, imperative to keep the nematode under constant surveillance and to adopt stringent control strategies to prevent this nematode from becoming a threat to wheat. As no incidence of the nematode was recorded on Shafaq-2006 and Aas-2011 cultivars, therefore, cultivation of these cultivars should be encouraged.

The authors declare that there is no conflict of interests regarding the publication of this article.