RESISTANCE OF AUTOTETRAPLOID AND ALLOTETRAPLOID TRITICEAE SPECIES ANDACCESSIONS TO MELOIDOGYNE-CHITWOODI BASED ON GENOME COMPOSITION

The Columbia root-knot nematode Meloidogyne chitwoodi parasitizes seve ral plant species, including grasses that have been developed for semi arid environments, and substantially reduces the productivity of cerea ls and the longevity of perennial grasses growing under semiarid condi tions throughout the intermountain region. Thirty-two auto- and allote traploid (2n = 28) taxa in the perennial Triticeae were evaluated as p ossible sources of resistance to M. chitwoodi. Low levels of root gall ing were observed on roots of all accessions; root-gall indices ranged from 0 (no galls) to 1.95 in the grasses compared to 4.67 for the sus ceptible 'Ranger' alfalfa check on a scale of 1 to 6. Even though the gall ratings were low, significant (P < 0.01) differences among access ions of the same species, among species, and among genera with differe nt genomes were observed. Within the reproductive indices, which range d from 0.01 to 1.20 in the grasses compared to 65.38 for the alfalfa c heck, there was no difference among genera with different genomes and accessions within the same species and genome; however, there was a si gnificant (P < 0.05) difference among species with the same genomes. T his variation can be traced to Thinopyrum nodosum (Jaaska-19), which w as the only accession with a reproductive factor greater than 1.00. Ba sed on the data, all auto- and allotetraploids are considered resistan t to M. chitwoodi.