Effects of Meloidogyne incognita on the Yield and Quality of Sweet Potato in the Humid Lowlands of Papua New Guinea
DOI:
https://doi.org/10.32945/atr3716.2015Keywords:
Abstract
Field experiments were conducted in 2012 and 2013 to study the effects of inoculum densities of Meloidogyne incognita applied at 10, 100, 1000, 5000, and 10000 juveniles/eggs per 500 cm3 along with un- inoculated control treatments, on a susceptible sweet potato variety, K9. At the highest initial inoculum (Pi), an average marketable tuber yield of 991 kg ha-1 was recorded compared to 3495.5 kg ha-1 from un-inoculated control, accounting for 72% relative yield reduction. Significant (p<0.05) yield reduction of 37% was also recorded from the lowest Pi of 10 juveniles/500 cm3. Probit analysis projected that 50% loss to marketable 3 tubers are likely to occur at populations as low as 40 nematodes/500 cm3. There was a high positive correlation (r=0.87**) between percentage relative yield loss and initial inoculum densities.
There was significant (p<0.05) impairment in marketable tuber quality with 4% cracking at 10 M. incognita per 500 cm3, increasing to 37% at the highest Pi of 10,000. Highly significant positive correlations were also observed for cracked tubers (r=0.93**) and non-marketable tubers (r=0.96**), when tested against the Pi densities of M. incognita. Nematode population was monitored during the cropping season revealed an overall significant increase (p<0.05) in juvenile populations at mid-season (60 days after inoculation) from the initial inoculum populations. A reverse in trend of juvenile numbers was observed at harvest (120 DAI).
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