Pathogenicty of Pratylenchus delattrei Luc, 1958 to crossandra with special reference to biochemical alterations Vadivelu Sivagami, Muthukrishnan T. S. Tamilnadu Agricultural University, Coimbatore-641 003. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract Pratylenchus delattrei Luc, 1958 is one of the important plant parasitic nematodes in Tamilnadu, particularly on Crossandra, an ornamental crop which is cultivated,in several parts of the State. The observations made on the effect of higher levels of nematode population on plant growth and their effect on major and minor elements, carbohydrate level in the leaves and free sugars, amino acids, peroxidase and B-glucosidase activity and phenolic content of roots are presented in the paper. The plants inoculated with 1000 and 5000 nematodes at the time of planting exhibited foliage discolouration and chlorotic symptoms in 35–40 days and 20–27 days respectively. Reduction in shoot length, shoot weight, root length and root weight and the total number of roots in the infected plants (22.7–47.1, 80.0–95.4; 65.1–93.1, 84.9–97.8 and 69.1–92.6 per cent respectively) was also noticed. The plants treated with 5000 nematodes failed to produce the flower spikes, while those inoculated with 1000 nematodes produced 1.7 spikes and 25 flowers per plant in contrast to 9 spikes and a total 104 flowers developed in healthy plants. The leaves of the nematode infected plants exhibited deficiency in nitrogen (22.4–59.0% and increase in phosphorus and potassium (11.5–45.4 and 70.0–137.3%). Among the micronutrient elements, increase in zinc (8.8 and 42.5 per cent) and copper (66.0 and 108 percent) and decrease in the iron (12.0 and 24.0 per cent) and manganese (24.2 and 36.8 per cent) content were noticed in the leaves. A reduction of 30 and 15 per cent in the carbohydrate was also noted. The details on total free sugars, the total amino acid and the orthodihydroxy and total phenolic contents of the nematode inoculated plant roots are also furnished. Top |