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Project description

Implementation value of root-galling resistance and reproduction resistance for root-knot nematode management in dry beans. (02CC012)
Program UC IPM competitive research grants program
Principal
investigator
P.A. Roberts, Nematology, UC Riverside
Host/habitat Beans
Pest Root-Knot Nematode Meloidogyne spp.
Discipline Nematology
Review
panel
Cultural Controls
Start year (duration)  2002 (Three Years)
Objectives Quantify the protective value of different resistance traits that block root-galling and (or) reproduction of root-knot nematodes in limiting yield loss in lima and cowpea (blackeyes) dry bean production.

Final report The protective value of resistance traits to root-knot nematodes for yield of lima and blackeyed beans has been quantified. Field experiments to generate damage functions by assessing growth and yield of each variety in plots with zero to high nematode levels were conducted at the South Coast Research and Extension Center, Tustin. In 2002, three sites were planted with susceptible tomato and inoculated with a different nematode species or population (collected from California bean growing areas). Each site included eight inoculation rates replicated in a grid of 144 plots. In 2003, lima and blackeye varieties carrying different resistance genes were grown on the 432 plots. Grain yields regressed on nematode levels in soil provided damage functions for vine and bush limas. Lima genes for galling and reproduction resistance appeared similarly effective in protecting from nematode damage, but not as effective as the two genes in combination. 372 subplots with inoculated tomatoes were set up during 2003 on adjacent sites as in 2002. In 2004, four near-isogenic blackeye genotypes (each with a different resistance gene, plus susceptible check) were grown on these subplots to generate damage functions. Late planting prevented grain yield determination, but top growth weights recorded were used to index genotype differences in response to nematode levels in soil at planting. Large biomass differences were found due to effects of the resistance genes. In 2005, the blackeye experiment was repeated with an earlier planting date and grain yield determinations were made. The lima bean lines were tested again in 2005 using comparisons of grain yield in fumigated and non-treated plots, and the results of the 2003 experiments were confirmed. These findings provide an objective basis for prioritizing resistance traits to be bred into new lima and blackeye bean varieties for California growers.

Third-year
progress
The protective value of resistance traits to root-knot nematodes for yield of lima and blackeyed beans is being quantified. Field experiments to generate damage functions by assessing growth and yield of each variety in plots with zero to high nematode levels were set up at the South Coast Research and Extension Center, Tustin. In 2002, three sites were planted with susceptible tomato and inoculated with a different nematode species or population (collected from California bean growing areas). Each site included eight inoculation rates replicated in a grid of 144 plots. In 2003, lima and blackeye varieties carrying different resistance genes were grown on the 432 plots. Grain yields regressed on nematode levels in soil provided damage functions for vine and bush limas. Lima genes for galling and reproduction resistance appeared similarly effective in protecting from nematode damage, but not as effective as the two genes in combination. 372 subplots with inoculated tomatoes were set up during 2003 on adjacent sites as in 2002. In 2004, four near-isogenic blackeye genotypes (each with a different resistance gene, plus susceptible check) were grown on these subplots to generate damage functions. Late planting prevented grain yield determination but top growth weights recorded in December were used to index genotype differences in response to nematode levels in soil at planting. Large biomass differences were found due to effects of the resistance genes. At harvest soil samples and data analysis from 2004 are in progress. A repeat experiment in 2005 will be used to obtain blackeye grain yields.

Second-year
progress
Lima and black-eyed bean varieties of similar genetic background carrying different resistance genes grown on the 432 plots were harvested in November 2003, and the tops transported to Riverside for drying and threshing. Yield determinations from threshed and cleaned seed are currently being determined. Initial observations show large yield differences due to effects of the resistance genes. Root samples collected from all plots at harvest were indexed for nematode galling and infection. Regressions of galling on initial population densities revealed large differences in plant response due to resistance gene effects. In preparation for a second series of damage function experiments in 2004, an exact duplication of 432 subplots was set up during spring and summer 2003 on adjacent sites. Complementary greenhouse testing of the same bean varieties is in progress, to provide comparison data under controlled conditions.

First-year
progress
Both field experiments and greenhouse experiments are being conducted in an effort to quantify the protective value of different resistance traits to root-knot nematodes in Lima beans and Blackeyed beans. The experiments are designed to generate damage functions for different bean varieties carrying different nematode resistance genes. The growth and yield of each variety is being compared over a range of from zero to very high nematode infestation levels. The bean varieties that produce the highest relative yields under high nematode pressure should represent those with the greatest tolerance to nematode attack. Field experiments were set up at the South Coast Research and Extension Center, Tustin. Three separate sites were inoculated during the summer and fall, 2002 each with a different root-knot nematode species or population. Nematode populations were collected from California bean growing areas, and were chosen for their known reaction to different Lima and Blackeye resistance genes. Each site included a series of eight inoculation rates, repeated eighteen times per site to establish a grid of 144 sub-plots. Each sub-plot was planted to nematode susceptible processing tomato to allow nematode reproduction and provide uniform cropping. Lima and Blackeyed bean varieties carrying different resistance genes are being multiplied in greenhouse isolations during the winter, to provide enough planting seed for measuring nematode tolerance in the field plots in Spring and Summer of 2003. A complementary testing of the same bean varieties has been initiated in the greenhouse, to provide comparison data under controlled conditions.

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