Growth charts of root knots and giant cells caused by Meloidogyne incognita in susceptible tomato roots in vit

Abstract

In this study, a repeatable and compatible interaction system between Meloidogyne incognita and tomato plants was firstly established by artificially inoculating sterilized second stage juvenile(J2) of M. incognita into root tips of 15-day tomato plant in vitro. Egg masses of female nematodes were obviously seen on root-knots after inoculation for 30 days at 27°C in a growth chamber. Then, growth charts of root-knots and giant cells caused by M. incognita in tomato roots in vitro were studied as follows: Ten inoculated root tips were observed and collected each day for studying growth charts of root knots and giant cells by paraffin sections during 28 days after inoculation (dai). The biggest diameter of each-day root-knot and its giant cell size were measured. Totally, 280 effective root-knots and their giant cells in 1680 paraffin sections were studied. Growth charts drawn by the software of SAS (system for windows 9.0) indicated that the biggest diameter of root knot became bigger and bigger during the first 20 dai, and then keep almost the same size from 24 to 28 dai; meanwhile, its giant cell size became bigger and bigger in the first 14 dai, and then keep almost the same size from 14dai to 20 dai, at last became smaller and smaller after 20 dai. To be surprised, no giant cells were seen at 28 dai, while the female nematodes were seen with their egg masses in tomato root tissue. To our knowledge, it is a first report on 28- day growth charts of root knots and giant cells caused by M. incognita in tomato roots.