Mecanismo genético de resistência em três cultivares de algodoeiro a Xanthomonas axonopodis pv. malvacearum

Abstract

Mecanismo genético de resistência em três cultivares de algodoeiro a Xanthomonas axonopodis pv. malvacearum. Fitopatologia Brasileira 30:647-649. 2005 RESUMOA mancha angular do algodoeiro (Gossypium hirsutum) causada por Xanthomonas axonopodis pv. malvacearum (Xam) é uma doença de importância econômica para o Brasil, e sua severidade depende de fatores climáticos e da cultivar. A doença não é controlada por produtos químicos sendo que seu controle depende da utilização de sementes sadias, e resistência varietal. DeltaOPAL, EPAMIG Liça, e Fibermax 986 são importantes fontes de resistência a Xam, pois além de resistência, apresentam boas características agronômicas. O objetivo do presente trabalho foi estudar o mecanismo de resistência à mancha angular envolvendo cruzamentos entre as três cultivares resistentes e a suscetível BRS Ita 90, em casa de vegetação. Populações parentais, F1 e F2 foram avaliadas após inoculação com um isolado agressivo de Xam. As três cultivares apresentaram mecanismos diferentes de resistência. Nas cultivares DeltaOPAL e EPAMIG Liça a resistência é conferida por um gene dominante, enquanto que em Fibermax 986, a resistência é dada por dois genes dominantes, independentes e complementares.Palavras-chave adicionais: Gossypium hirsutum, mancha angular, bacteriose.ABSTRACT Genetic mechanism of resistance to Xanthomonas axonopodis pv. malvacearum in three cotton cultivars Angular leaf spot of cotton (Gossypium hirsutum) caused by Xanthomonas axonopodis pv. malvacearum (Xam) is an economically important disease in Brazil. The severity of the disease depends on climatic conditions and the type of cultivar. The disease is not satisfactorily controlled by the use of chemicals, but with control depending basically on the use of healthy seed and resistant varieties. Cultivars DeltaOPAL, EPAMIG Liça and Fibermax 986 are the best sources of resistance to Xam, since besides resistance, these cultivars possess desirable agronomic characteristics. The objective of the present investigation was to verify the mechanism of resistance to angular leaf spot in these three resistant cotton cultivars by crossing them with the susceptible cultivar BRS Ita 90, under glasshouse conditions. Parental populations F1 and F2 were evaluated in the glasshouse after inoculation with an aggressive isolate of Xam. All the three of the cultivars revealed different mechanisms of resistance. In cvs. DeltaOPAL and EPAMIG Liça, resistance is governed by one dominant gene, whereas in cv. Fibermax 986, the resistance is governed by two dominant, independent and complementary genes.Additional keywords: Gossypium hirsutum, angular leaf spot, black arm. 647 Fitopatol. bras. 30(6), nov -dez 2005

Search for a Microsatellite Marker Linked with Resistance Gene to <i>Xanthomonas axonopodis</i> pv. <i>malvacearum</i> in Brazilian Cotton

“…Analysis of the F 2 populations derived from the cross DELTAOPAL × BRS ITA 90, yielded a segregation ratio of 3R:1S suggesting the presence of a single dominant gene for resistance to Xam [3]. Out of the 220 microsatellite primers tested, only one (Primer BNL 2634.…”

“…Nineteen races of the pathogen currently are recognized in the USA [1,3]. In Brazil, although sources of resistance like cvs.…”

Inheritance of resistance to cotton blue disease

“…In the same way, the cotton plants resistance to angular leaf spot, caused by Xanthomonas axonopodis pv. malvacearum bacterium, is controlled by one dominant gene in Delta Opal and Epamig Liça cultivars, and by two dominant genes in Fibermax 986 cultivar (Zandoná et al, 2005). Metha & Arias (2001) have studied F 2 e F 2:3 populations descending from the crosses: 'PR 94-82' (R) x 'IAPAR 71' (S), 'PR 94-215' (R) x 'IAPAR 71' (S) and 'CNPA PRECOCE 2' (R) x 'IAPAR 71' (S).…”