Orientador: William J. da Silva

Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia

Resumo: Um estudo comparativo envolvendo diferentes mutantes de endosperma de milho e seus correspondentes endospermas normais, foi realizado para analisar o efeito de genes do endosperma na patogenicidade do F. moniliformee. . Os mutantes estudados foram: Shrunken (sh), shrunken-2 (sh2), floury...

Resumo: Um estudo comparativo envolvendo diferentes mutantes de endosperma de milho e seus correspondentes endospermas normais, foi realizado para analisar o efeito de genes do endosperma na patogenicidade do F. moniliformee. . Os mutantes estudados foram: Shrunken (sh), shrunken-2 (sh2), floury (fl) brittle (bt), brittle-2 (bt2) waxy (wx), dull (du), sugary (su),sugary-2 (su2), apaque-2 (o2) e amylose extender (ae). Os efeitos desses genes foram ava1iados em linhagens homozigotas, obtidas de várias popu1ações sintéticas de milho. Os genes mutantes de endosperma foram introduzidos nessas populações através de um esquema de retrocruzamento. Numa primeira fase analisou-se a ocorrência de variantes em diferentes culturas do fungo, isoladas de sementes de milho. Nesse estudo, com 197 culturas, ficou evidenciado que o patógeno ocorre na natureza sob a forma de tipos diferentes, onde predominou o tipo roxo com freqüência de 55%. É provável que esses tipos ocorram na natureza sob a forma de heterocários. Realizou-se um ensaio de campo com delineamento em blocos ao acaso com 4 repetições onde as onze linhagens portadoras dos genes mutantes de endosperma foram autofecundadas,e em seguida suas espigas inoculadas com F. moniliforme . As sementes colhidas nesse ensaio foram utilizadas para os estudos do presente trabalho

Abstract: A comparative study involving 11 different endosperm mutants of maize and their correspondent normal counterparts was carried out to study the effect of endosperm mutant genes on pathogenicity of F. moniliforme. The following mutants were studied: Shrunken (sh), shrunken-2 (sh2), floury...

Abstract: A comparative study involving 11 different endosperm mutants of maize and their correspondent normal counterparts was carried out to study the effect of endosperm mutant genes on pathogenicity of F. moniliforme. The following mutants were studied: Shrunken (sh), shrunken-2 (sh2), floury (fl), brittle (bt) brittle-2 (bt2), waxy (wx), dull (du), sugary (su), sugary-2 (su2), opaque-2 (o2) and amylose extender (ae). Those genes were introduced in several synthetic varieties through a backcross procedure and were studied in S5 inbred lines derived from them. In a preliminary step it was studied the presence of variants among cultures of F. moniliforme isolated from corn seeds. It was found that the pathogen occur in nature with different types being predominant the purple type. Apparently the types occur in nature by heterocaryosis. A randomized complete block experiment involving 11 inbred lines segregating only for the endosperm gene, with 5 replications, was planted at the experimental field. At flowering the 10 m long plots were selfed and the segregating ears were artificially inoculated with spores from a purple colony of F. moniliforme. The study of seed pathogenicity was carried out by the isolation of the fungus from 11 endosperm and their normal kernels of the segregating ears. Mutants and their normal kernels of the segregating ears. Two tests were made. One, with deep-freezing treatment at -19ºC and the other with intact seeds