Abstract Plant responses to nitrogen supply are dependent on auxin signaling, but much still remains to be elucidated regarding N deficiency in tomato. Thus, the objective of this work was to evaluate how low auxin sensitivity regulates the responses of tomato plants to N deficiency. For this purpose, we used the tomato diageotropica mutant, with low auxin sensitivity, and a near isogenic line cv. Micro-Tom grown in nutrient solutions under absence and presence of nitrogen. Plant height, stem diameter, root and shoot dry mass, area and root density, number of lateral roots, leaf area, chlorophylls and carotenoids content, nitrogen accumulation and nitrogen use efficiency were evaluated. We observed a clear interaction between the tomato genotype and nitrogen. When the plants were grown with nitrogen, ‘Micro-Tom’ showed higher growth than the diageotropica mutant. Under nitrogen deficiency condition, the mutant showed improved growth, nitrogen use efficiency and higher contents of pigments. In general, the low sensitivity to auxin in diageotropica caused reduced growth in both shoot and root. However, the diageotropica tomato showed a positive regulation of the nitrogen use efficiency under nitrogen deficiency. In general, our data revealed that the reduced sensitivity to auxin increased the adaptive capacity to the nitrogen deficiency.

ABSTRACT The cultivation of melon (Cucumis melo L.) in greenhouses has contributed to the increased incidence of fungal diseases, particularly gummy stem blight caused by Didymella bryoniae (Fuckel) Rehm. This disease is currently considered the main disease affecting this crop, causing conditions such as water soaked seedlings, and stem and fruit cankers, reducing productivity and fruit quality. Considering the importance of this disease, the aim of this study was to evaluate the reaction of different C. melo genotypes to D. bryoniae. Sixty-eight different melon genotypes were investigated. Two phenotyping assays were performed to investigate the resistance to the disease, following a randomized block design with four replicates. Subsequently, a new assay was conducted to validate the resistance of the genotypes selected in the previous step, using a randomized block design with three replicates. The plants were inoculated using the toothpick method, and resistance was evaluated according to a grading scale. Also, reaction classes and assay groups were used for classifying the resistance level of the genotype. The JAB-11 and JAB-20 strains were susceptible to the pathogen, as well as the commercial hybrids Louis F1 and Fantasy Fi. The hits AC-29, C160, Charentais Fom 1, PI 420145, PI 482398 and PI 532830 were resistant to D. bryoniae, and could become an important gene source for the development of resistant cultivars.

ABSTRACT The okra (Abelmoschus esculentus L. Moench) is one of the most important vegetables in the world and is a popular food item in many tropical and subtropical countries. Besides its cultivation for fresh consumption, okra also has potential industrial uses. Nonetheless, pests and diseases remain the most damaging factors affecting its crop yield. Among these, root-knot nematodes are the main pests limiting okra production. This study aimed to determine the responses of plant species of the Malvaceae family to Meloidogyne incognita and M. enterolobii root-knot nematodes, and to also assess the compatibility of the same with the okra commercial 'Colhe Bem IAC'. Resistance was evaluated using the reproduction factor in two commercial okra cultivars ('Colhe Bem IAC' and 'Santa Cruz 47'), five cotton (Gossypium hirsutum L.) plant genotypes (PRO 277, IAC 29-233, PR 136, IAC 24, and IAC 03-979), and vinagreira (Hibiscus sabdariffa L.) Other resistance-related traits measured were the percentage of healing, plant height, root length, rootstock stem diameter, scion stem diameter, number of leaves, total fresh weight, and fresh weight of the scion, rootstock, and root parts. While the cotton and vinagreira genotypes tested were resistant to both species of nematodes, okra cultivars were not. The okra, however, showed successful adaptation to grafting, which may offer an important physical resistance against attacks by root-knot nematodes, while vinagreira showed the greatest potential for use as rootstock for protecting okra crops.

Devido ao severo ataque de nematoides na cultura do meloeiro rendilhado sob ambiente protegido, este trabalho teve por objetivo selecionar porta-enxertos resistentes a Meloidogyne incognitae M. javanica. O experimento foi conduzido em casa de vegetação, de outubro de 2010 a abril de 2011, em Jaboticabal-SP. Foram avaliados 33 porta-enxertos; melões: CNPH 01-930 (Cucumis melo var. flexuosus), CNPH 01-962, CNPH 01-963 (Cucumis melo var. conomon), cvs. Gaúcho Redondo, Gaúcho Comprido, Redondo Amarelo, Gulfcoast, Chilton, Bônus n° 2, Fantasy; melancias: cv. Charleston Gray, Progênie da Coréia (Citrullus lanatus); abóboras: cvs. Mra. Ma, Ornamental, Howden, Mammoth, Kururu, Goianinha (Cucurbita moschata); cabaça: Abóbora de Porco, cvs. Maranhão, Brasileirinha (Lagenaria siceraria); moranga: cv. Pataca Gigante (Cucurbita maxima); pepinos: cvs. Caipira, Branco Meio-Comprido, Curumim (Cucumis sativus); buchas: Metro, Semente Branca, Semente Preta (Luffa cylindrica); abóbora d'água (Benincasa hispida); abóbora porta-enxerto: Híbrido cv. Keij; quiabo de Metro (Trichosanthes cucumerins) e Cruá (Sicana odorifera). Para avaliar a resistência de plantas, as mudas foram transplantadas para vasos e inoculados com 3.000 ovos e juvenis de M. incognita via sistema radicular. Aos 50 dias após a inoculação, foi realizada avaliação da resistência das plantas, com base no fator de reprodução do nematoide. Foram realizados os mesmos procedimentos para as duas espécies de nematoides. Nos porta-enxertos resistentes aos nematoides foram realizadas enxertias, com os melões rendilhados 'Bônus n° 2' e 'Fantasy'. CNPH 01-962, CNPH 01-963 e melão 'Gaúcho Redondo' foram resistentes a M. incognita. Melão 'Redondo Amarelo', melancia 'Charleston Gray', Progênie da Coréia, e Trichosanthes cucumerins, foram resistentes a M. javanica. Benincasa hispida foi resistente a ambas as espécies. As compatibilidades de enxertia entre os porta-enxertos resistentes e os melões rendilhados 'Bônus no 2' e 'Fantasy' foram superiores a 98%.

Nematodes severely attack net melon plants under protected cultivation conditions. The objective of this research was to select rootstocks with resistance to Meloidogyne incognita and M. javanica. The experiment was carried out under greenhouse conditions from October 2010 to April 2011 in Jaboticabal, São Paulo state, Brazil. Thirty-three cucurbitaceous genotypes were investigated as rootstocks; melons: CNPH 01-930 (Cucumis melovar. flexuosus), CNPH 01-962, 01-963 CNPH (Cucumis melo var. conomon), cvs. Gaucho Redondo, Gaucho Comprido, Redondo Amarelo, Gulfcoast, Chilton, Bônus no. 2, Fantasy; watermelons: cv. Charleston Gray, Progênie da Coréia (Citrullus lanatus); pumpkins: cvs. Mra. Ma, Ornamental, Howden, Mammoth, Kururu, Goianinha (Cucurbita moschata); gourd: Abóbora de Porco, cvs. Maranhão, Brasileirinha (Lagenaria siceraria); squash: cv. Pataca Gigante (Cucurbita maxima); cucumber: cvs. Caipira, Branco Meio Comprido, Curumim (Cucumis sativus); loofah: Metro, Semente Branca, Semente Preta (Luffa cylindrica); wax gourd (Benincasa hispida); pumpkin rootstock: Hybrid cv. Keij; snake gourd (Trichosanthes cucumerins) and musk cucumber (Sicana odorifera). To evaluate the resistance, seedlings were transplanted to pots and the root inoculated with 3,000 eggs and second stage juveniles of M. incognitaand M. javanica. Fifty days after the inoculation, the plants were evaluated for nematode resistance by means of the reproduction factor. The grafting compatibility between net melon cvs. Bonus no. 2 and Fantasy and the rootstocks previously characterized as resistant were evaluated by means of 60 graftings. CNPH 01-962, CNPH 01-963 and melon 'Gaucho Redondo', were considered resistant to M. incognita. Melon 'Redondo Amarelo', watermelon 'Charleston Gray', watermelon Progênie da Coréia, Trichosanthes cucumerins were considered resistant to M. javanica. Benincasa hispida was resistant to M. javanicaand M. incognita. The compatibility between net melons and resistant rootstocks was higher than 98%.