Exploring Citrus Nematodes and its Antagonists in Citrus Growing Areas of Punjab, Pakistan

Abstract

Citrus nematode (Tylenchulus semipenetrans) is a major threat to the citrus industry in Pakistan. During 2019-20, a survey was carried out for citrus nematode and its antagonists in citrus orchards (Both healthy and declining trees were samples) of Punjab, Pakistan. Bhalwal, Shahpur, Sillanwali, Kotmomin, Sargodha, Quaidabad, Jhang, and Rahim Yar Khan were surveyed for disease incidence, prevalence, and association of T. semipenetrans. Maximum disease prevalence (100%) was recorded in Rahim Yar Khan while minimum (20%) in Bhalwal and Kotmomin. Maximum slow decline with 80% field incidence was observed in Rahim Yar Khan while a minimum of 20% in Quaidabad.  Soil and root samples were used for nematode extraction using Baerman's funnel method and the Whitehead Hemming tray method. A maximum number of J2s/100ml of soil were observed in soil samples taken from Rahim Yar Khan (1674) followed by Shahpur (1534), Qaidabad (1432), Sargodha (1347), and Bhalwal (1172). The highest number of nematode females per gram of root were recorded in Rahim Yar Khan (652) followed by Quaidabad (611), Bhalwal (490), Kotmomin (421), Sillanwali (387). Isolation of different fungal and bacterial antagonist isolates was also done by soil dilution plate technique using nutrient agar media and potato dextrose agar media. Identification of fungal antagonists was made on colony growth, color, and spore structure. Bacterial identification was also done on morphological characters and gram tests. Trichoderma harzianum, Trichoderma viride, Trichoderma koningii Trichoderma atroviride, Pseudomonas fluorescens, Pseudomonas putida, Bacillus cereus and Bacillus subtilis were found associated.