Root Gall Index Research Articles

Efficacy of Resistance to Root-knot Nematode in Snap Beans1

Abstract Four snap bean (Phaseolus vulgaris L.) breeding lines, resistant PI 165426, and 2 susceptible commercial cultivars were tested for resistance to root galling and root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) reproduction under greenhouse and field conditions. Root gall indices, reproduction indices, and numbers of eggs/g of root were significantly less on resistant lines than on ‘White Seeded Provider’ in 2 greenhouse tests. In field tests, soil treatment with the nematicide DBCP resulted in significant control. In nontreated plots, resistant bean lines had less root galls than ‘Early Gallatin’. Plots planted with resistant lines had fewer M. incognita larvae than those with ‘Early Gallatin’. Mean yield of pods from resistant lines in nontreated soil was about 3 times the yield of ‘Early Gallatin’. Yield of pods from treated and nontreated subplots were not significantly different. These results indicate that resistance is equivalent to soil fumigation for root-knot nematode control in snap beans.

Zur Wirkung von Nemacur- und Temik-Granulaten auf Wurzelgallen-Nematoden (Meloidogyne spp.) bei der Tomate

The susceptibility of the two single populations of root-knot nematodes invading tomato roots,Meloidogyne javanica andM. incognita acrita, in comparison with a mixed population of the two species was investigated to the granular nematicides, Nemacur and Temik. Root-gall indices ofM. incognita acrita were reduced more than ofM. javanica. In addition, root-gall indices of the mixed population and a single population,M. incognita acrita, were the same.

Methods for Screening Snap Beans for Resistance to Root-knot Nematodes1

Abstract A method was developed to evaluate snap beans, Phaseolus vulgaris L., for resistance to root-knot nematodes, Meloidogyne spp., which permits selected plants to survive, making either hybridizations or seed increase possible in the same generation. Nematode inoculum are added to commercial potting medium in greenhouse benches and snap beans are grown either in peat or clay pots filled with uninoculated soil and buried in the inoculated media. Roots protruding through holes in the bottom of the pots are evaluated for root gall and reproduction indices.

EFFECTS OF D-D AND OXAMYL USED ALONE AND IN COMBINATION ON TOMATO PRODUCTION AND THE VERTICAL DISTRIBUTION OF ROOT-KNOT NEMATODE EM GREENHOUSE SOIL

A combined treatment of D-D plus two foliar applications of oxamyl did not increase the depth or duration of control of Meloidogyne incognita in greenhouse soil even though it did reduce the root-gall index in both spring and fall crops and increase the number and average weight of fruit in the fall crop over that obtained using D-D alone. Oxamyl-only treatments failed to increase tomato production, in the spring crop, over that obtained in the check although the root-gall indices were reduced. In the fall crop, only the oxamyl drench treatment reduced the root-gall index, while both the drench and foliar treatments increased tomato production over the check, the drench treatment being superior.

VERTICAL MOVEMENT AND DISTRIBUTION OF MELOIDOGYNE INCOGNITA (NEMATODEA) UNDER TOMATO IN A SANDY LOAM GREENHOUSE SOIL

The southern root-knot nematode, Meloidogyne incognita (Kofoid and White 1919) Chitwood 1949, escaped control by steam, Vorlex, or a combination of both at soil depths below 100 cm in naturally infested sandy loam greenhouse soil. Nematodes moved upward to infest the subsequent crop. In microplot studies M. incognita moved rapidly in both directions through a soil depth of 150 cm. High nematode population densities and root gall indices on tomato (Lycopersicon esculentum Mill.) roots were recorded through depths of 150 cm in soil inoculated with 4,400 M. incognita/kg in the top 30 cm or 120–135 cm below the surface. In the top 30 cm of soil this initial population density reduced tomato yield by 20% in the first crop and 70% in the second. Similar population densities 120–135 cm from the soil surface reduced tomato yield by 11% in the first crop and 59% in the second.