Resistência à antracnose do colmo em milho: escala de avaliação, marcador molecular e correlação da severidade entre colmo e folha

• Autor(a) principal: Nicoli, Alessandro
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1060
• topic: Doença antracnose; Zea mays; Resistência; Marcador SNP; Anthracnose disease; Zea mays; Resistance; SNP marker; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Maize (Zea mays L.) is an important crop in world agriculture, but its production is limited by several factors, including diseases. Anthracnose stalk rot caused by Colletotrichum graminicola is one of the widely distributed diseases in corn, causing plant lodging or premature death and reduced quality and grain weight. Estimate the intensity of this disease is very important to evaluate the different control measures, such as genetic resistance. With this, were validated a diagrammatic scale, containing illustrations of stalk internode with eight severity levels. With the scale, the assessments perfomed by all raters were closer to the actual value and most deviations in errors were concentrated in the range of 10%. Moreover, when checking the reliability of the estimate of disease severity, 100% of the comparisons resulted in R2 > 0.90. The scale proposed improved accuracy, precision and reproducibility of the estimates of anthracnose stalk rot severity and may be recommended for plant breeding for resistance, epidemiological studies, characterization of isolates of C. graminicola and other studies involving this pathosystem. To identify molecular markers SNP (Single Nucleotide Polymorphism) associated with resistance to anthracnose stalk rot, F2:3 progenies were phenotyped in the field, where were selected 20 resistant and 20 susceptible progenies to disease. At greenhouse, plants with severity ≤ 18.8% (within the 19 resistant progenies) and severity ≥ 56.3 % (within the 20 susceptible progenies), in addition hybrid, were selected for DNA extraction and genotyping. Linear regression analysis was performed to identify markers significantly associated with resistance to anthracnose stalk rot. Eight SNP markers with additive genetic effect and four with dominance genetic effect were detected associated with resistance to anthracnose stalk rot. The additive effects explained between 18 and 23% of the phenotypic variation and the dominance effects explained between 18 and 35%. Future studies should be conducted to validate these markers, checking the potential in use marker- assisted selection in maize breeding programs. Aiming to compare the reaction of the leaf and stalk of maize to anthracnose, five experiments were conducted at greenhouse to evaluate anthracnose leaf blight and five to anthracnose stalk rot. The correlation was positive and significant only for the most susceptible hybrids BRS1010 and P3862, however, for the most resistant hybrids 2B710, 2B707 and P30F35, there were no correlation. The results indicated that the genotypes more resistant to anthracnose have no correlation between reaction in the leaf and stalk, evidencing the lack of relationship in resistance mechanisms between these two organs. With this, it is recommended to first verify the reaction of leaf and stalk for adoption of maize cultivars in regions and seasons where the disease occurs. Based on the results, verify that studies of resistance inheritance to anthracnose and about physiological races of C. graminicola should be conducted to leaf and stalk separately. Furthermore, verify that per genetic breeding, cultivars with resistance to anthracnose leaf blight and anthracnose stalk rot can be developed.