Abstract:
Relationships between population densities of different nematode species at harvest and yield of maize were examined for 4 cropping sequences on sandy loam soil in Ismailia, Egypt. Correlations calculated
between the total plant-parasitic nematode population densities and yield were not significant for individual cropping sequences tested; whereas among the individual genera, population densities of Helicotylenchus
pseudorobustus only had significant (P=0.05) negative correlation with yield in two cropping sequences. Log-transformed nematode densities, however, revealed additional negative correlation between maize yield and density of Heterodera zeae. The general relationship was described by Y = 409.1283 - 1.2113 X1 - -0.7330 X2 + 0.2430 X3 + 0.2429X4 where Y = yield or ear weight (g/plant), X1, X2, X3 and X4 nematode population densities of Helicotylenchus pseudorobustus, Heterodera zeae juveniles, Pratylenchus brachyurus and Tylenchorhynchus latusper 100 cm3 soil at harvest; respectively (P = 0.0628). Accordingly, maize yield loss estimate caused by the nematodes was 63 g/plant. At harvest, no significant correlations were found between population densities of the different nematode species in each site including a cropping sequence. Yield components of individual maize cv. Giza 2 plants were more than that produced by cv. Double hybrid 202.
