No abstract

Seventeen varieties of sugarbeet either as monogerm or multigerm were screened for their productivity and susceptibility or resistance against the infection by Meloidogyne javanica. All the tested varieties varied in the degree of nematode development and reproduction. Statistical differences in sugarbeet varieties are found between infected and non infected plants in yields of roots, leaves and sugar except, Barca, Pamela and Toro varieties which were not significantly damaged in all these parameters. All evaluated sugarbeet varieties were also significant decreased in percentages of sucrose, total soluble solids and purity except, Esperanza and Toro varieties which were not significantly decreased in total soluble solids and purity percentages, respectively. Four host categories systems were suggested in this study. Root damage index is an average of gall index, gall size and gall area. The combination of the nematode reproduction and root damage index is termed as susceptibility rate. Host vigor percentage is an average of root yield potential and sucrose and total soluble solids percentages. However, host-parasite index as a new term is suggested which expresses the amount of crop damage in yields (roots, leaves and sugar) and quality characters (sucrose, total soluble solids and purity percentages) by nematode infection. The host-parasite index is more suitable because of the generally high correlation between these parameters and crop damage. Thus the Barca and Gloria varieties were rated as a tolerant and Hilma and Helios as highly susceptible, 8 as moderately susceptible and 5 as low susceptible to M. javanica root-knot nematode infection in this investigation.

The host suitability of the ten sugarbeet varieties of monogerm (i.e., Estaban, Francescan, Sander, Sible and Univers) and multigerm (i.e., Heba, Lilly, Mammut, Mirados and Oscarpoly) to M. incognita infection was conducted under greenhouses condition. Results revealed that all yield characters (root, top and sugar yields) and quality characters, (sucrose, total soluble solids and purity %) of such screened sugarbeet variety were obviously diminished by M. incognita infection to great extort. The degree of susceptibility/ resistance of these sugarbeet varieties evaluated according to modified host parasite index (MHPI) scale which was used as a new and suitable scale (special technique) to assess host (sugarbeet plant) reaction. The MHPI is calculated by dividing a gross average of reduction percentages in all yield and quality characters by the susceptibility rate. It could be ranked as standardization of host suitability technique and reporting of resistance of sugarbeet to root-knot nematodes. On this basis, the screened sugarbeet varieties are categorized into three groups, two varieties are as tolerant host (Heba and Sible), four as low susceptible (Estaban, Lilly, Mirador and Sandor) and four as moderately susceptible (Francescan, Mammut, Oscarpoly and Univers) against root-knot nematode, M. incognita. So, they could be Heba (as multigerm) and Sible (as monogerm) varieties recommended as excellent commercial varieties in Egypt, and could be introduced in integrated pest management (IPM) for controlling root-knot nematodes.

No abstract

No abstract