Inheritance of Resistance to Meloidoygne incognita in Primitive Cotton Accessions from Mexico

摘要

Few sources of resistance to root-knot nematodes (Meloidogyne incognita) in upland cotton (Gossypium hirsutum) have been utilized to develop resistant cultivars, making this resistance vulnerable to virulence in the pathogen population.The objectives of this study were to determine the inheritance of resistance in ?ve primitive accessions of G.hirsutum (TX1174, TX1440, TX2076, TX2079, and TX2107) and to determine allelic relations with the genes for resistance in the genotypes Clevewilt-6 (CW) and Wild Mexico Jack Jones (WMJJ).A half-diallel experimental design was used to create 28 populations from crosses among these seven sources of resistance and the susceptible cultivar DeltaPine 90 (DP90).Resistance to M.incognita was measured as eggs per g roots in the parents, F1 and F2 generations of each cross.The resistance in CW and WMJJ was inherited as recessive traits, as reported previously for CW, whereasthe resistance in the TX accessions was inheritedas a dominant trait.Chi square analysis of segregationof resistance in the F2 was used to estimate the numbers of genes that conditioned resistance.Resistance in CW and WMJJ appeared to be a multigenic trait whereas the resistance in the TX accessions best ?t either a one or two gene model.The TX accessions were screened with nine SSR markers linked to resistance loci in other cotton genotypes.The TX accessions lacked the allele ampli?ed by SSR marker CR316 and linked to resistance in CWand other resistant genotypes derived from this source.Four of ?ve TX genotypes lacked the ampli?cation products from the marker BNL1231 that is also associated with the resistant allele on Chromosome 11 in WMJJ,CW, NemX,M120RNR andAuburn634 RNR.However, all?ve TXgenotypesproducedthesameampli?cationproducts from three SSR markers linked to the resistant allele on Chromosome 14 in M120 RNR and M240 RNR.The TX accessions have unique resistance genes that are likely to be useful in efforts to develop resistant cotton cultivars with increased durability.