Pathogenic Variability of Meloidogyne incognita Populations Occurring in Pepper-Production Greenhouses in Israel Toward Me1, Me3 and N Pepper Resistance Genes

Abstract

Natural variation in the root-knot nematode Meloidogyne incognita is problematic for breeding programs: populations possessing similar morphological characteristics can produce different reactions on the same host. We collected 30 widely dispersed M. incognita populations from protected pepper production systems in major pepper-growing regions of Israel and accurately identified their virulence characteristics by modified differential host test in a growth chamber on tomato, tobacco, cotton, melon, pepper, and peanut. Galling indices and reproduction were determined on the different hosts. All populations fit the published scheme for M. incognita race 2, except for reproduction on cotton plants by five out of 25 tested M. incognita populations, indicating host-range variations. Reaction of three genes that confer resistance to M. incognita-Me1, Me3 and N-to the collected populations was evaluated. Several M. incognita populations induced galling and reproduced successfully on pepper genotypes carrying Me3 and N, whereas plant resistance conferred by Me1 was more robust for all examined populations. Moreover, the effect of genetic background on Me1 resistance demonstrated a relative advantage of several genotypes in nematode infestations. Efficiency of Me3 under local nematode infestation was further studied with a homozygous line carrying two Me3 alleles. Reproduction of virulent populations on the homozygotes (Me3/Me3) and heterozygotes (Me3/Me3⁺) was similar, suggesting a limited quantitative effect of Me3. These results present the first characterization of host range, reproduction, and molecular aspects of M. incognita from Israel and highlight the importance of taking a multidimensional approach in pepper-breeding programs for resistance to M. incognita.