DNA CONTENT AND VARIATION IN CHROMOSOME-NUMBER IN PLANT-CELLS AFFECTED BY MELOIDOGYNE-INCOGNITA AND M-ARENARIA

DNA content of Meloidogyne-induced giant cell nuclei in four host species was determined by Feulgen microspectrophotometry. Nuclei from mature giant cells in pea and tomato averaged 15.8 and 14.2 times more DNA, respectively, than the 2C values from uninfected root-tip nuclei. Nuclei from broad bean and lettuce showed a mean increase in DNA content of 8.3- and 6.5-fold, respectively, when compared to the 2C values of uninfected root tip nuclei. DNA content of giant cell nuclei was highly variable (coefficients of variation > 41%), while DNA content of root tip cells showed little variation (coefficients of variation < 8%). Mean DNA content in giant cell nuclei from peas increased linearly from the time of inoculation until development of mature female nematodes, 3 wk after inoculation. In giant cells from lettuce, DNA content per nucleus increased 6.5-fold during the first week after inoculation with no further increase later on. Cytogenetic studies of pea giant cells showed that the majority of the nuclei were aneuploid with chromosome counts ranging from 15 (2n = 14) to over 100. Also observed were lagging chromosomes and chromatin bridges between giant cell nuclei, which could generate the observed aneuploidy.