ResumoMétodos de fácil execução, rápidos e não destrutivos, que possibilitem estimar a área foliar com precisão, são importantes para avaliar o crescimento das plantas nas condições de campo. Objetivou-se no presente trabalho, ajustar equações para estimar a área do limbo foliar e a área das folhas do girassol, em função das medidas lineares do limbo e do número de folhas por planta, incluindo a verificação da possibilidade de modelos comuns para as cultivares BR-122 e M-734. Seis plantas de cada cultivar nos estádios de início de florescimento e de florescimento pleno foram coletadas. As áreas dos limbos foliares foram determinadas por método direto. Foram medidos o comprimento ao longo da nervura principal e a largura de forma perpendicular à inserção do limbo no pecíolo. Foram ajustados os modelos linear, quadrático, cúbico, exponencial e potencial. Os modelos potenciais Ŷ i = 1,6329X i 1,7164 e Ŷ i = 0,5405X i 1,0212 com a utilização, respectivamente, das medidas da largura e do produto largura e comprimento são os mais adequados para estimar a área do limbo foliar do girassol. O modelo Ŷ i = 5,1014X i 2,4383 permite estimar com precisão a área foliar total do girassol em função do número de folhas por planta. A precisão das equações ajustadas para as estimativas da área do limbo foliar ou de folhas por planta não é reduzida quando se ajustam modelos comuns às cultivares BR-122 e M-734.Palavras-chave: Helianthus annuus L., crescimento de planta, alometria.Estimates of sunflower leaf area by a non-destructive method Abstract Simple, rapid, and non-destructive methods that help to estimate leaf area accurately are very important to assess plant growth under field conditions. The objective of this study was to adjust equations to estimate the area of a single sunflower leaf and also the area of total leaves per plant as a function of linear measurements of them. It was also verified the possibility of using common models for the sunflower cultivars BR-122 and M-734. Six plants of each cultivar in the early stage of flowering and full flowering were harvested. The area of each leaf was determined by the direct method. The length along the midrib and the width perpendicular to leaf insertion in the petiole were determined. Linear, quadratic, cubic, exponential, and potential models were adjusted. The potential models Ŷ i = 1.6329X i 1,7164 and Ŷ i = 0.5405X i 1,0212 using the width measurements and width x length, respectively, were the most adequate to estimate the leaf area. The model Ŷ i = 5.1014X i 2,4383 allowed to precisely estimate the total leaf area according to the number of leaves per plant. The accuracy of the adjusted equations to estimate each leaf are and total leaves area was not reduced when common models were adjusted to the two cultivars used.Key words: Helianthus annuus L., plant growth, allometry.O girassol (Helianthus annuus L.) é uma planta caracterizada por sua versatilidade industrial e adaptabilidade climática. Considerada uma das principais oleaginosas do mundo, responde por aproximadam...

Brazil is the world’s biggest producer of sugarcane (Saccharum spp. hybrids). Pokkah boeng is an important fungal disease in this crop caused by members of the Fusarium fujikuroi species complex (FFSC) and characterized by deformation of the aerial part of the plant and stem rot. While the occurrence of symptoms has been reported in plantations in Brazil, no official reports of the disease exist. In this study, species of the FFSC were identified that are associated with sugarcane plants with symptoms of pokkah boeng in Brazil. This was achieved using two‐loci molecular phylogeny, sexual compatibility and analysis of morphological markers. The ability of strains to cause disease in plants of sugarcane, maize, sorghum and millet was also evaluated. The 39 isolates studied were identified as F. sacchari, F. proliferatum and another, still unknown, phylogenetic lineage that is sister to F. andiyazi. Crossing field isolates of F. sacchari and F. proliferatum with their respective tester strains produced fertile perithecia and viable ascospores. All three species induced symptoms of pokkah boeng on inoculated sugarcane plants and caused stem rot in maize, sorghum and millet. Symptoms on sugarcane are chlorosis and necrosis of leaves, punctured lesions, twisted leaves, reduction of the total leaf area, death of the top of the plant and stalk rot. The findings confirmed the aetiology of the disease in Brazil, generated basic knowledge for the development of strategies for diagnosis and monitoring of the disease and support breeding programmes for selecting resistant germplasm.

Cultivation of sugarcane for the production of sugar and alcohol is of outstanding economic importance for Brazil, being the largest producer of this crop worldwide (CONAB, 2019). Red rot is one of the main diseases of sugarcane, first reported in 1893 in Java and Indonesia, and is still a major problem in countries like India, Indonesia, and Pakistan (Kumar et al., 2010;Malathi et al., 2011). The aetiological agent of this disease is known as Colletotrichum falcatum, a member of the Colletotrichum graminicola species complex (CGSC), which contains several important grass pathogens Crouch et al., 2006).C. falcatum can infect the plant through natural openings and injuries caused by improper handling of the blades during planting, or by the sugarcane borer, Diatrea saccharalis (Lepidoptera: Crambidae), leading to the borer-rot disease complex (Peñaflor & Bento, 2019;Viswanathan & Samiyappan, 2000). Plants show characteristic symptoms of discolouration, drying, and reddish spots on the leaves,

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The north‐east of Brazil is one of the most important melon‐producing regions in the world. Crop yield is often reduced by the occurrence of a root rot disease, caused by Fusarium species. The present study aimed to characterize a collection of 31 isolates with morphological markers of F. solani obtained from melon plants with symptoms of root rot by phylogenetic analysis of the barcode regions EF‐1α and RPB2, and to verify their pathogenicity to melon plantlets. Phylogenetic analysis showed that 29 isolates grouped with reference material of Fusarium falciforme (FSSC 3 + 4) and two with F. suttonianum (FSSC 20). The pathogenicity test showed that isolates of both species cause root rot in melon plants, with no significant difference of virulence between isolates and species with both methodologies used (infested toothpick and infested rice). Melon plants expressed first symptoms 15 days after inoculation, showing yellowing and wilting, with later tipping and rot. To our knowledge, this is the first report of the occurrence of these species causing root rot in muskmelon in Brazil. Our results support monitoring of causal agents of melon fusarioses and will be useful for breeding programmes in the search for plant material with resistance to Fusarium rot.

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