Abstract:
Root-lesion nematodes, particularly Pratylenchus neglectus and P. crenatus (PNC), are
widely distributed in New Zealand and cause significant damage to maize roots, reducing crop
productivity. Despite their economic importance, no comprehensive assessment of commercial maize
hybrids’ resistance to PNC has been conducted in the country. Significant variation was observed in
the nematode reproduction factor (Rf) and final population (Pf) among hybrids. In Experiment 1
(initial population (Pi) = 1250 PNC kg⁻¹ soil), Rf ranged from 3.1 in hybrid P8500 to 7.1 in hybrid
P9127, with Pf values ranging from 3863 to 8903 PNC kg⁻¹ soil + roots in 45 days. In Experiment 2
(Pi = 750 PNC kg⁻¹ soil), Rf ranged from 18.4 in hybrid P1613 to 37.5 in hybrid P8805, with Pf
values from 13,784 to 28,426 PNC kg⁻¹ soil + roots in 60 days. These results indicate active
nematode reproduction and substantial hybrid-dependent variation in host response. Experiment 3
examined the impact of varying initial inoculum densities (500, 1000 and 1500 PNC kg⁻¹ soil),
showing a dose-dependent increase in Pf and corresponding root damage. Susceptible hybrid (P9127)
exhibited up to 42% root dry weight and 22% shoot dry weight reductions. This study is the first
systematic evaluation of PNC resistance in New Zealand maize hybrids. It identifies P9127 and P8805
as highly susceptible, and P0891, P8500, and P1613 as moderately resistant. These findings offer
valuable benchmarks for future breeding and support nematode management in New Zealand.
