OCCURRENCE OF LEAF SPOTS CAUSED BY FUNGI AND A BACTERIUM ON COTTON CULTIVARS OCORRÊNCIA DE MANCHAS FOLIARES CAUSADAS POR FUNGOS E BACTÉRIA EM CULTIVARES DE ALGODOEIRO

Abstract

<!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --> <p class="western" align="JUSTIFY"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">The cotton leaf spot diseases caused by fungi and bacteria are a growing problem, leading to an increasing use of fungicides. During the 2000/2001 and 2001/2002 growing seasons, field experiments were carried out in a randomized block design, with five replications, aiming to evaluate the behavior of the cotton cultivars Ita-90, CD-401, CD-402, CD-403, CD-404, Fibermax 986, DeltaOpal, and Facual, as related to leaf spot diseases caused by Stemphylium spp., Alternaria spp., Ramularia areola, and the bacterium Xanthomonas axonopodis pv. malvacearum. The cotton cultivars Ita-90 and Facual were the less susceptible to the Stemphylium/Alternaria complex and R. areola. However, Ita-90 was more susceptible to X. axonopodis pv. Malvacearum. The cultivars with the least incidence of X. axonopodis were CD-403, Fibermax 986, and DeltaOpal. The cotton cultivar Facual presented the lowest yield, while the remaining cultivars showed similar yields.</span></span></p> <p class="western" align="JUSTIFY"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">KEY-WORDS: Xanthomonas axonopodis pv. Malvacearum; Stemphylium spp; Alternaria spp; Ramularia areola.</span></span></p> <!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --><!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --> <p class="western" align="JUSTIFY"><span style="color: #000000;"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">As manchas foliares causadas por fungos e bactérias no algodoeiro são um problema cada vez mais grave, levando à utilização, cada vez maior, de fungicidas para controlá-las. Nas safras de 2000/2001 e 2001/2002, foram realizados experimentos m campo, em delineamento de blocos ao acaso, com cinco epetições, objetivando avaliar o comportamento das cultivares e algodoeiro Ita-90, CD-401, CD-402, CD-403, CD-404, Fibermax 986, DeltaOpal e Facual, quanto à severidade das manchas foliares causadas por Stemphylium spp., Alternaria spp., Ramularia areola e pela bactéria Xanthomonas axonopodis pv. malvacearum. As cultivares Ita-90 e Facual foram as menos sensíveis às manchas foliares do complexo Stemphylium/ Alternaria e ramulária. Ita-90, no entanto, foi a mais sensível à bacteriose causada pela Xanthomonas axonopodis pv. malvacearum. As cultivares com as menores incidências de bacteriose foram CD-403, Fibermax 986 e DeltaOpal. Facual apresentou a menor produtividade de algodão em caroço, enquanto as demais variedades obtiveram produtividades semelhantes entre si.</span></span></span></p> <p class="western" align="JUSTIFY"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">PALAVRAS-CHAVE: Xanthomonas axonopodis pv. malvacearum; Stemphylium spp; Alternaria spp; Ramularia areola.</span></span></p> <!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } -->

Keywords

• Xanthomonas axonopodis pv. malvacearum
• Stemphylium spp
• Alternaria spp
• Ramularia areola