Buckwheat (Fagopyrum esculentum Moench) belongs to the Polygonaceae family and has been widely cultivated due to its high nutritional, nutraceutical, and medicinal properties. Brazil ranks seventh-largest producer, with 66,000 tons produced in 2018. Buckwheat is also valued for its adaptability as a cover crop, in grain fields of soybean (Glycine max (L.) Merr., maize (Zea mays L.), and sorghum (Sorghum bicolor (L.) Moench) (Görgen et al. 2016, Babu et al. 2018) especially in fields highly infested with plant-parasitic nematodes (PPN). PPN cause severe root damage, suppressing plant development and yield production. In October 2018, six samples of roots and soil were collected in symptomatic patches of buckwheat, in Guaíra SP (20° 19' 32"S 48° 13' 15.4"W). Samples were analyzed in the Nematology Laboratory (LabNema), UNESP, Jaboticabal, SP, BR. Plants presented symptoms of yellow leaves and galled and volume-reduced roots. Meloidogyne sp. was found, comprising 6,320 eggs and second-stage juveniles (J2s) from 10 g of root and 1,628 J2s in 100 cm³ of soil. Adult morphological characteristics, isoenzyme phenotype of esterase, and molecular analysis were performed to identify the Meloidogyne species. The perineal patterns presented high and trapezoidal dorsal arch (n=15), and the males showed a trapezoidal labial region, including a high head cap formed by a large round labial disc that is raised above the medial lips and centrally concave (n=15) (Eisenback and Hirscmann 1981). These characteristics are typical in Meloidogyne incognita (Kofoid and White, 1912) Chitwood, 1949 (Nascimento et al., 2020; Eisenback and Hirschmann 1981; Netscher and Taylor 1974). The enzymatic phenotype was performed with females (n=8), and the phenotype I1 was verified, described by Esbenshade and Triantaphyllou (1985) as typical for M. incognita. To confirm the species DNA samples were extracted from individual females (n=6) and PCR with specific primers for M. incognita (Mi-F 5′- GTGAGGATTCAGCTCCCCAG-3′ and Mi-R 5′-ACGAGGAA CATACTTCTCCGTCC-3′) and M. javanica (Treub) Chitwood 1949 (Fjav 5′-GGTGCGCGATTGAACTGAGC-3′ and Rjav 5′-CAG GCCCTTCAGTGGAACTATAC-3′) that amplify SCAR markers described by Meng et al. (2004) and Zijlstra et al. (2000), respectively, and specific primers for M. enterolobii Yang & Eisenback 1983 that amplify rDNA-IGS2 region (Me-F 5′-AACTTTTG TGAAAGTGCCGCTG-3′ and Me-R 5′-TCAGTTCAGGCAGG ATCAACC-3′) described by Long et al. (2006) were tested. A fragment of 955 pb DNA size was amplified in Mi-F/R primer, which confirmed the M. incognita identification (Meng et. al., 2004). The original population was used to execute pathogenicity test. In a greenhouse, single buckwheat seeds (cv. IPR 91 Baili) were sown in six 5L pots filled with autoclaved-soil and inoculated with 3,000 eggs and J2s per pot (n=6) and control (n=6). After 60 days, the nematodes were extracted from roots and the M. incognita was confirmed. An average of 15,738 eggs and J2s were recovered, (reproductive factor = 5.24), which confirmed buckwheat as a host to M. incognita. The inoculated plants showed symptoms as those observed in the field. No symptom or nematode was noted on the control. Meloidogyne incognita has been reported causing high damage to the F. esculentum in California (Gardner and Caswell-Chen 1994) plus several crops in Brazil (Nascimento et al., 2020). However, this is the first report of this nematode infecting buckwheat in Brazil. Given the importance of buckwheat in Brazil, with extensive use as forage, cover crop, and its nutritional properties, this report is essential to specific management measures are adopted to avoid further losses.

A necessidade de conhecer a marcha de absorção do nitrogênio (N) pelo feijoeiro é importante para compreender os desempenhos produtivo e qualitativo dessa cultura.  O objetivo deste estudo foi avaliar a influência da cobertura nitrogenada em função de diferentes estádios fenológicos no desempenho morfoagronômico e produtivo e nas características tecnológicas dos grãos do feijoeiro em sistema de plantio convencional. Utilizou-se o delineamento de blocos casualizados, com quatro repetições. Os tratamentos foram constituídos por doze combinações de fornecimento de N (FN) em cobertura (dose total = 90 kg ha-1 de N) aplicadas nos estádios fenológicos V3, V4 e R5 (V3+V4+R5) do feijoeiro de inverno irrigado: 00+00+00; 30+30+30; 30+60+00; 30+00+60; 60+30+00; 00+60+30; 45+45+00; 00+45+45; 45+00+45; 90+00+00; 00+90+00; e 00+00+90. A fonte de N utilizada foi ureia convencional. Os FN 30+00+60, 00+45+45 e 45+00+45 incrementam a produtividade de grãos e a eficiência agronômica em relação à ausência de N e à aplicação de dose única no estádio fenológico V4. do feijoeiro comum. As maiores produtividades de proteína bruta e o menor tempo para cozimento foram proporcionadas pelos FN 00+45+45, 45+00+45, 90+00+00, 00+90+00 e 00+00+90.Palavras-chave: Phaseolus vulgaris; parcelamento do N; eficiência agronômica; tecnologia dos grãos. NITROGEN TOPDRESSING AT DIFFERENT PHENOLOGICAL STAGES ON COMMON BEAN CHANGES GRAIN YIELD AND QUALITY ABSTRACT: The need to know the nitrogen uptake (N) by common bean is important to understand the productive and qualitative performance of this crop. The objective of this study was to evaluate the influence of nitrogen topdressing as a function of different phenological stages on the morphometric and productive performance, and on the technological characteristics of the bean grains grown under conventional soil preparation. A randomized block design with four replications was used. The treatments were constituted by twelve topdressing N supply combinations (NS) (total dose = 90 kg ha-1 N) applied in the phenological stages V3, V4 and R5 (V3+V4+R5) of irrigated winter bean: 00+00+00; 30+30 +30; 30+60+00; 30+00+60; 60 + 30 + 00; 00+60+30; 45+45+00; 00+45+45; 45+00+45; 90+00+00; 00+90+00; and 00+00+90. The source of N used was conventional urea. NS 30 + 00 + 60, 00 + 45 + 45 and 45 + 00 + 45 increase grain yield and agronomic efficiency in relation to the absence of N and single dose application at V4 phenological stage of common bean. The highest crude protein yields and the shortest cooking time were provided by FN 00+45+45, 45+00+45, 90+00+00, 00+90+00 and 00+00+90.Keywords: Phaseolus vulgaris; N splitting; agronomic efficiency; grains technology.

Um dos fatores responsáveis pela baixa produtividade do feijoeiro é o manejo inadequado da adubação nitrogenada. Objetivou-se avaliar o efeito de fontes e doses de nitrogênio no desempenho agronômico e qualitativo e no retorno econômico relativo do feijoeiro. O experimento foi desenvolvido na safra de inverno na região de Guaíra, SP (20º 22’ 20’’ S, 48º 22’ 10’’ W), utilizando a cultivar Pérola. O solo da área experimental foi classificado como Latossolo Vermelho distrófico (590 g kg-1 de argila). Utilizou-se o delineamento experimental de blocos casualizados, em esquema fatorial 2 x 5, constituído por duas fontes de N (ureia e sulfato de amônio) e cinco doses de N (0, 40, 80, 120 e 160 kg ha-1), em quatro repetições. As variáveis analisadas foram o teor de N foliar, número de vagens por planta, número de grãos por vagem, massa de 100 grãos, produtividade, retorno econômico relativo, teor de proteína dos grãos, tempo de cozimento, relação de hidratação e tempo para máxima hidratação. A massa de 100 grãos, produtividade, teor de proteína bruta dos grãos e relação de hidratação apresentaram diferenças entre as doses de N estudadas. A adubação nitrogenada de cobertura aumenta o desempenho agronômico e qualitativo do feijoeiro, incrementando a produtividade e o teor de proteína bruta dos grãos até as doses de N de 139 e 136 kg ha-1, respectivamente. A fonte de nitrogênio utilizada não altera o desempenho agronômico e qualitativo do feijoeiro, entretanto, a fonte de nitrogênio ureia apresenta maior retorno econômico relativo.