Resistência de campo ao vírus da queima-do-broto em genótipos de soja resistentes a insetos Field resistence to brazilian bud blight in soybean genotypes resistant to insects

• Main Authors: André Luiz Lourenção, Álvaro Santos Costa, Manoel Albino Coelho de Miranda
• Format: Article
• Language: English
• Published: Instituto Agronômico de Campinas 1989-01-01
• Series: Bragantia
• Subjects: Glycine max (L) Merrill; resistência a insetos; vírus da queima-do-broto; tripes; Frankliniella; Glycine max (L.) Merrill; resistance to insects; thrips
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051989000200006

Avaliou-se o comportamento de trinta e seis genótipos de soja em relação à incidência da queima-do-broto em condições de campo, no Centro Experimental de Campinas (IAC), no ano agrícola 1985/86. A infecção variou de 13 a 92%, destacando-se PI 227687 (13%), IAC 73-228 (25%), IAC 80-1177 (36%), IAC 80-1191 e IAC 84-20-1 (38%) e PI 274453 (40%) com os menores índices da doença. Os cinco genótipos menos infectados, mais a linhagem IAC 79-1823 e os cultivares IAC 9, IAC 10, IAC 12, Santa Rosa, Cristalina e IAC Foscarin-31, inoculados mecanicamente em casa de vegetação com diferentes isolados do vírus, não mostraram nível de resistência semelhante ao observado em campo; nesse teste, a infecção variou de 45 a 90%, tendo o melhor tratamento do experimento de campo (PI 227687) apresentado 90% de infecção. Há indicação, portanto, que a menor infecção observada nos genótipos no experimento de exposição natural seja resistência de campo, relacionada com a interação planta-tripes vetor.<br>Brazilian bud blight, a soybean disease caused by the tobacco streak virus, is prevalent in a few areas in the States of Paraná and São Paulo. Although the virus is seed-transmitted, outbreaks of the disease are related to the presence of virus in donor plants in the weed vegetation and not to seed sources. Species of Frankliniella act as vectors. Thirty six soybean genotypes, about half of them known to have varying degrees of resistance to insects, were evaluated when exposed to natural infection by bud blight in five replicated plots sown in an area where medium to severe outbreaks of the virus had occurred in previous years. Incidence of bud blight was high in the experiment and reached 90% infection for some of the genotypes. Best genotypes for resistance to bud blight were PI 227687 (13% infection), IAC 73-228 (25%), IAC 80-1177 (36%), IAC 80-1191 and IAC 84-20-1 (both 38%), and PI 274453 (40%). The best five most resistant genotypes mentioned above plus seven others were also screened by mechanical inoculation of greenhouse plants with five isolates of the soybean bud blight virus. The results were not parallel to those read in the field exposure test. Thus, the response of PI 227687, IAC 73-228 and probably those of some of the other best genotypes are not considered the result of plant resistance to the virus, but rather as field resistance related to the interaction plant/thrips vector.