Use of immunostrips for the rapid detection of citrus Phytophthora disease

Punjab is leader of Kinnow mandarin producer in India. Its commercial cultivation has brought the “Gold Revolution” in state. Of the various pathological problems, citrus foot rot/gummosis (Phytophthora parasitica) is the major constraint causing moderate to heavy destruction of Kinnow plants in nurseries and orchards. Field and laboratory diagnostics tools available for detection of this pathogen are laborious and time consuming. The development of Immunostrips ELISA has created rapid detection of Phytophthora under field conditions. During the present investigation efforts were made to standardize the quick detection method using Phytophthora Immunostrips (agDia, Elkhart, USA). The soil samples from different citrus groves were collected. Composite soil sample (1.5 gm) was extracted in a mesh pouch filled with the extraction buffer, followed by inserting an Immunostrip into soil extract. Positive result was indicated by development of red test line below the control line. Out of the 100 samples, 33 were found positive for citrus Phytophthora disease. Of the 39 field grown Kinnow plants, 12 were found positive whereas in Sweet orange, out of the 35 plants, 17 were positive for Phytophthora disease. All the 8 samples of Kinnow plants multiplied in screen house were found negative whereas in the field nursery beds, out of the 18 samples, 4 were found positive. This study showed that immunostrips assays can be exploited for the rapid and mass detection of citrus Phytophthora disease.