Selection of resistant upland cotton genotypes challenged with aggressive isolates of Meloidogyne incognita race 3
¹Centro Universitário Fundação Assis Gurgacz, Avenida Ministro Cirne Lima, 2565, Jardim Coopagro, 85.903-590, Toledo, Paraná, Brasil
²Centro Nacional de Recursos Genéticos e Biotecnologia, Parque Estação Biológica, PqEB, Av. W5 Norte, Brasília, Distrito Federal, 70770-917, Brasil
³Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Fitopatologia, Campus Darcy Ribeiro, Asa Norte, 70.910-900, Brasília, Distrito Federal, Brasil
⁴Universidade Federal do Paraná, R. Pioneiro 2153, Jardim Dallas, 85950-000, Palotina, Paraná, Brasil
⁵Instituto Matogrossense do Algodão, Departamento de Fitopatologia, Estrada Br 070, S/N Zona Rural, 78.850-000, Primavera do Leste, Mato Grosso, Brasil
*Correspondence: cfurla@hotmail.com
Abstract:
This
study aimed to select populations of M. incognita race 3 for screening cotton genotypes as part of a breeding program for the
development of resistant cotton cultivars. Five isolates of M. incognita race 3, collected in
Western Paraná, Brazil, were tested for virulence and aggressiveness against
the cotton cultivars FM966 (susceptible), IAC 24 (resistant), CD 409, and FMT
701 (moderately resistants) under greenhouse conditions, and following a
factorial design with five replicates. Thirty-one cotton genotypes were
screened against the three most aggressive isolates of M. incognita race 3 tested before and kept under greenhouse
conditions following a factorial design with five replicates. Experiments run
under greenhouse conditions had single cotton plants inoculated with 5,000
eggs/J2 of M. incognita and were
assessed at 120 days after inoculation considering the variables gall index,
egg mass index, total eggs, and reproduction factor. The same genotypes tested
under greenhouse conditions were also grown in a field infested with M. incognita race 3 in a randomized
block design with 10 replicates. In the field, the M. incognita population was monitored by the quantification of
J2 forms in soil samples collected before sowing, 60 days after sowing (DAS),
and 120 DAS. A gall index score was used to evaluate the roots of cotton
genotypes at 120 DAS. The isolate from Umuarama was the most aggressive,
followed by Moreira Sales and Iporã. The genotypes CD 05-419, CD 05-945,
CD 05-1087, and CD 05-1170 showed resistance against M. incognita race 3 under greenhouse
and field conditions.
Key words:
aggressiveness, genetic resistance, Gossypium hirsutum, root-knot nematode, virulence