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INHERITANCE OF RESISTANCE OF ‘SALINAS 88’ LETTUCE TO THE ROOT-KNOT NEMATODE Meloidogyne incognita (Kofoid & White) Chitwood

2008; UNIVERSIDADE FEDERAL DE PELOTAS; Volume: 14; Issue: 2 Linguagem: Inglês

10.18539/cast.v14i2.1912

2317-2436

José Luiz Sandes de Carvalho Filho, L.A.A. Gomes, Juliana Nogueira Westerich, Wilson Roberto Maluf, Vicente Paulo Campos, Sindynara Ferreira,

Legume Nitrogen Fixing Symbiosis

Este estudo observou o modo de heranca da resistencia da alface ‘Salinas 88’ ao nematoide das galhas Meloidogyne incognita raca 1 ( Kofoid & White) Chitwood . Os tratamentos envolveram as linhas parentais ‘Regina 71’ (P 2 , suscetivel) e ‘Salinas 88’ (P 1 , resistente), assim como as geracoes F 1 (P 1 xP 2 ) e F 2 (P 1 xP 2 ). O experimento foi conduzido em delineamento em blocos casualizados com cinco repeticoes. Foram avaliadas plantas individuais com uma escala de notas de 1 (=resistente) a 5(=suscetivel), 45 dias apos a inoculacao com o patogeno , de cada planta foi avaliada a nota para numero de galhas (GNS), nota para massas de ovos (ENS) e incidencia de galhas (OGI) por sistema radicular. A hipotese de heranca monogenica nao foi rejeitada (ate o limite de significância do c 2 ) para OGI e GNS, indicando que a resistencia pode estar sob controle de um unico locus genico. Resultado divergente foi encontrado para o teste de c 2 para ENS, em que a hipotese de heranca monogencida foi rejeitada. Isso indica que se em ‘Salinas 88’ existe a presenca de um gene para a resistencia ao nematoide, ele pode esta sendo influenciado pela presenca de genes modificadores adicionais. O teste de maxima verossimilhanca evidenciou a presenca de um gene maior com dominância parcial (na direcao de maior nivel de resistencia) e a acao de genes modificadores . Palavras-chave: Lactuca sativa L., heranca, herdabilidade , nematoide das galhas. ABSTRACT This study looked into the inheritance mode of resistance of ‘Salinas 88’ lettuce to the root-knot nematode Meloidogyne incognita race 1 ( Kofoid & White) Chitwood . The treatments involved the parental lines ‘Regina 71’ (P2, nematode susceptible) and ‘Salinas 88’ (P1, nematode resistant), as well as the F 1 ( P 1 xP 2 ) and F 2 (P 1 xP 2 ) generations. The experiment had a randomized complete block design with five replications. Altogether, 37 plants from ‘Regina 71’, 40 from ‘Salinas 88’, 40 from the F 1 generation and 181 from the F 2 generation were evaluated. Individual plants were evaluated with a score grades from 1(=resistant) to 5(=susceptible), 45 days after infestation with the pathogen, for gall number scores (GNS), eggmass number scores( ENS), and overall gall incidence (OGI) on the root system. Broad-sense heritabilities for GNS, ENS and OGI were estimated at 16.3%, 57.4% and 21.5%, respectively. The estimates of the mean degrees of dominance indicated partial dominance in the direction of a higher resistance. The monogenic hipothesis of inheritance was not rejected (at the limit of c 2 test significance) for OGI and GNS, indicating that that resistance may be under control of a single gene locus. Divergent c 2 tests performed for ENS rejected the hipothesis of monogenic inheritance, indicating that, if a major gene for nematode resistance is present in 'Salinas-88', its action may be influenced by the action of additional modifier genes. The test of maximum likelihood provided evidence both for the presence of one major gene with with partial dominance (in the direction of higher levels of resistance) and for the action of modifier polygenes . Key words: Lactuca sativa L., inheritance, heritability, root-knot nematode.