A survey of guava orchards of Uttarakhand, Uttar Pradesh and Haryana states in northern India to assess the spread of root-knot nematodes

Guava is an important commercial fruit crop grown in the subtropical and tropical regions of the world. India is world’s largest guava producer and accounts for 45.22% of global production. Recent reports from several parts of India suggest that guava orchards are infested with root-knot nematodes (RKNs) Meloidogyne enterolobii , M. incognita and M. javanica . However, limited information is available on the RKNs affecting guava in the northern states of India. Here, we surveyed 25 orchards in three important guava-producing north-Indian states of Uttarakhand, Uttar Pradesh and Haryana. Eleven samples were positive for RKN, whereas fourteen contained no RKN. All six samples from Uttarakhand, four out of fourteen orchards of Haryana, and one out of five surveyed orchards in Uttar Pradesh showed RKN infection. The infected young plants did not show disease symptoms, but the older plants showed yellowing and browning of the leaves with necrosis in the margins, stunted plant growth, drooping of leaves with bare twigs, and roots with simple and compound galls depending on the severity of the infection. Morphological identification by observing the RKN female’s posterior cuticular patterns and molecular identification using species-specific markers confirmed the identity of the nematode species as M. enterolobii . Our study confirms the presence of M. enterolobii in previously unreported areas of the north Indian states of Uttarakhand, Uttar Pradesh and Haryana. More information on the extent of the spread of M. enterolobii must be generated and used to prevent the further spread of this nematode to newer areas.