Includes bibliographical references and index.

Khasi Mandarin (Citrus reticulata Blanco) belonging to the family rutaceae is one of the most economically important and worldwide accepted fruit. Numerous pests and pathogens hinder the yield of Khasi Mandarin in Meghalaya. Plant Parasitic Nematodes (PPNs) are one of them. However, PPNs which act as hidden enemy are often neglected by farmers due to lack of information and their hidden character. The goal of the current study is to understand the distribution and community structure of nematodes associated with Khasi Mandarin (Citrus reticulata Blanco) in ten localities in Meghalaya. Soil samples were collected from ten localities viz., Bhoirymbong, Umdenlang, Umsohme, Sohkhwai, Mawphu, Nongjrong, Saipung, Narwan, Shangpung and Nartiang. Examination of these soil samples revealed that there were five genera of PPNs associated with Khasi Mandarin. The five genera were Tylenchulus sp., Helicotylenchus sp., Hoplolaimus sp., Criconema sp. and Xiphinema sp. According to the community study, it was revealed that citrus nematode Tylenchulus sp. ranked first in having the highest absolute frequency (100%) from most of the localities, while the lowest absolute frequency (40%) was found in three PPNs viz., Hoplolaimus sp., Criconema sp. and Xiphinema sp. The highest relative frequency (41.66%) was also found in citrus nematode from two localities i.e., Umdenlang and Umsohme. However, the lowest relative frequency (12.5%) was found in Xiphinema sp. from Shangpung locality. Citrus nematode from Sohkhwai locality had the highest absolute density (51.5%) whereas Criconema sp. from the Nartiang locality had the lowest (1.8%). Citrus nematode had the highest relative density (70.95%) from Umsohme locality, while Criconema sp. had the lowest relative density (2.43%) from Sohkhwai locality. Citrus nematodes from Umsohme locality had the highest recorded prominence value (497.15). However, Criconema sp. from Sohkhwai locality had the lowest prominence value (7.89). Simpson’s index was also highest (0.87) in citrus nematode, while the lowest (0.6) was found in Criconema sp. The highest Shannon diversity index (2.15) was also found in citrus nematode, likewise the lowest Shannon diversity index (1.22) was also found in Criconema sp. It was also revealed that pH exhibited a negative correlation with four PPNs viz., Helicotylenchus sp., Hoplolaimus sp., Criconema sp. and Xiphinema sp., while a positive correlation was found with citrus nematode. Soil moisture availability also had a positive correlation with the total nematode count. In relation with soil texture, citrus nematode was found highest in number in clay soil while other PPNs was found highest in sandy loam soil.