Citation: Mou, B. Screening for resistance to leafminer in spinach. HortScience Vol. 43(6) October 2008.
Interpretive Summary: Leafminer is a major insect pest of many important crops including spinach. Resistant cultivars are the most economical means of insect control. We screened 345 spinach accessions for leafminer resistance. The accessions differed in sting density, mine density, and other resistant traits. The string result from the field was highly correlated with the result from the insect cage, demonstrating that a cage test can be used to screen for leafminer resistance in the field. Results suggest that leafminer flies prefer certain spinach accessions to lay their eggs. Sting density and mine density were not correlated, which suggests that these two traits are under different genetic control and can be improved independently. These findings demonstrate that breeding of spinach for leafminer resistance is feasible.
Technical Abstract: Leafminer (Liriomyza spp.) is a major insect pest of many important agricultural crops including spinach (Spinacia oleracea). The purposes of the present experiments were to evaluate differences in spinach genotypes to leafminer damage, to compare results obtained from insect cages and from the field, and to study the association among different resistant traits. We screened 345 spinach genotypes for leafminer resistance in an outdoor insect cage and in the field. Significant genotypic differences were found for leafminer stings per unit leaf area, mines per plant, and mines per 100 g plant weight. The sting results from the field was highly correlated (r = 0.770) with the result from the insect cage, demonstrating that a cage test could be used to screen for leafminer resistance in the field. Mines per plant were not correlated with plant weight, suggesting that leafminer flies did not lay their eggs randomly and oviposition-nonpreference occurred in these plants. Stings per unit leaf area was not correlated with mines per plant or per 100 g plant weight, which suggests that feeding non-preference does not necessarily mean oviposition-nonpreference for spinach genotype and these two traits can be improved independently. These findings suggest that genetic improvement of spinach for leafminer resistance is feasible.