ABSTRACT: Genetically diverse interspecific hybrids of Vitis were selected for resistance to Pratylenchus brachyurus. Three segregating populations with 57 hybrid crosses were evaluated. The parents included Vitis romanetiiC166-043 × 07355-075, 06354-047 × Cereza and 06354-047 × Nocera, selected from the germplasm bank at the University of California, Davis, the United States. The experiment was arranged in a randomized block design, with three replications and three plants per plot. Root mass, nematodes per gram of root and reproduction factor were determined and used as quantitative variables; 16 multi categoric descriptors were also evaluated. The traits were analyzed using the Ward-Modified Location Model procedure (Ward-MLM) for the composition of genotype groups. Genetic parameters and prediction of genetic values by Restricted Maximum Likelihood / Best Linear Unbiased Prediction (REML / BLUP) were assessed. The Ward-MLM classification strategy supported the formation of three homogeneous groups. Group I comprised 13 hybrids; Group II, 26 hybrids; and Group III, 18 hybrids. Groups II and III contained hybrids resistant to P. brachyurus. High broad sense heritability values were found for root mass, reproduction factor and nematodes per gram of root, which provided genetic gain and allowed selection of resistant genotypes available for cloning, since the total genetic variance occurred due to the dominance effects. Of the 57 genotypes assessed, those with the lowest genotypic values for reproduction factor were selected as resistant, including: CH3.2, CH3.23, CH3.8, CH3.37, CH3.38, CH3.41, CH3.36, CH2.1, CH2.7, CH1.1, CH1.3 and CH1.2.

ABSTRACT. Since 2001, the disease known as 'guava decline', resulting from the interaction between the phytonematode Meloidogyne enterolobii and the fungus Fusarium solanie, has caused direct and indirect economic losses to the entire guava production chain. Given the lack of sources of resistance in guava genotypes, interspecific hybrids of Psidium spp. were obtained for resistance to the nematode M. enterolobii. To classify the level of resistance of the interspecific hybrids, we evaluated the plant classification methodologies proposed by Oostenbrink (1966) and Moura and Régis (1987). Estimates of genetic parameters were obtained using the REML/BLUP approach. Interspecific hybrids resistant to M. enterolobii were selected that can be used as rootstocks or in new crosses for the development of the guava breeding program.

RESUMO: Este trabalho teve por objetivo avaliar a resistência de genótipos de P. cattleyanum a M. enterolobii. O experimento foi conduzido em DIC, com seis tratamentos, constituídospor cinco genótipos de P. cattleyanum, pela goiabeira 'Paluma' (testemunha) e oito repetições constituídas por clones desses genótipos. A classificação quanto à resistência foi determinada de acordo com o fator de reprodução (FR), avaliado aos 135 dias após inoculação com o nematoide. Os genótipos de P. cattleyanum avaliados foram resistentes a M. enterolobii com FR iguais ou inferiores a 0,2.

ABSTRACT: This research aimed to evaluate genotypes of P. cattleyanum by resistance to M. enterolobii. The experiment was conducted in a completely randomized design with six treatments, consisting of five genotypes of P. cattleyanum and guava 'Paluma' (control) and eight replicates. Genotypes classification for resistance was determined by the reproduction factor (RF), evaluated at 135 days after inoculation with the nematode. Genotypes of P. cattleyanum were considered as resistant once reproduction factors evaluated had less than or equal to 0.2.

O declínio da goiabeira, uma doença complexa envolvendo Meloidogyne enterolobii e Fusarium solani, tem causado grandes prejuízos diretos para os produtores brasileiros. Apesar de várias estratégias terem sido discutidas para o controle do nematoide, a utilização de matéria orgânica adicionada ao solo é atualmente a melhor abordagem para conviver com essa doença. Para avaliar a dose adequada de farinha de carne e ossos (FCO) a ser incorporada ao solo, mudas de goiabeira inoculadas com M. enterolobii foram tratadas com 1-5% v/v da FCO. Noventa dias após foram avaliadas variáveis relacionadas à reprodução do nematoide e ao desenvolvimento das plantas, indicando um possível efeito nematicida da FCO a 3%. Outro experimento avaliou variáveis relacionadas ao nematoide e à planta 90 dias após o tratamento das mudas com FCO, quitosana, casca de camarão e torta de nem a 3%, 0,05%, 2% e 0,1% v/v, respectivamente. A FCO reduziu a reprodução do nematoide, destacando-se em relação aos demais tratamentos. Esta dosagem de FCO foi convertida para 25 kg planta-1 e avaliada em três regimes de aplicação (mensal, bimestral ou trimestral), por seis meses, em pomar de goiaba acometido pelo declínio. As variáveis avaliadas foram densidade no solo de unidades formadoras de colônia (UFC) de bactérias e fungos, e a densidade no solo e/ou raiz de M. enterolobii, Helicotylenchus sp., e de diferentes grupos tróficos de nematoides. Em todos os três regimes de aplicação a FCO reduziu todos os nematoides parasitas de plantas no solo e o número de UFC de fungos, e promoveu aumento no número de UFC de bactérias e nematoides bacteriofagos.

Guava decline is a complex disease involving Meloidogyne enterolobii and Fusarium solani and it has caused major direct losses to Brazilian growers. Although several strategies have been sought to control the nematode, the use of organic soil amendments is currently the best approach to manage this disease. To assess the best amount of meat and bone meal (MBM) to be incorporated into the soil, guava seedlings inoculated with M. enterolobii were treated with 1-5% v/v of the MBM. Ninety days later variables related to nematode reproduction and plant development were evaluated, which indicated a potential nematicidal effect of the MBM at 3%. Another experiment assessed nematode- and plant-related variables 90 days after treatment of the seedlings with MBM, chitosan, shrimp shell or neem cake at 3%, 0.05%, 2% and 0.1% v/v, respectively. The MBM ranked first, reducing nematode reproduction. This MBM rate was converted to 25 kg/tree and assessed in three application regimes (monthly, bimonthly or trimonthly), for six months, in an orchard affected by guava decline. The variables assessed were soil density of colony forming units (CFU) of bacteria and fungus, and soil and/or root density of M. enterolobii, Helicotylenchus sp., and of different nematode trophic groups. In all three application regimes the MBM reduced all plant-parasitic nematodes in the soil and the fungus CFUs. It also promoted an increase in bacterial CFU and bacterivorous nematodes.

Buscando o controle biológico do declínio da goiabeira, foram obtidos 120 isolados de rizobactérias de goiabeiras assintomáticas, localizadas em pomares infestados por M. enterolobii. Dos 120 isolados, 44 foram avaliados em seu potencial para reduzir o nível populacional do nematoide. Para cada isolado, seis estacas vegetativas de goiabeira foram embebidas com suspensão bacteriana por 8 horas e transplantadas para sacolas de 5 L. Após o desenvolvimento das raízes, as mudas foram submetidas à inoculação com 2.000 ovos de M. enterolobii e mantidas por quatro meses em casa de vegetação. Mudas submetidas à inoculação com água, com ou sem M. enterolobii, serviram como controles. Os 46 tratamentos foram equivalentes nas cinco variáveis que avaliaram o desenvolvimento das plantas. Várias rizobactérias reduziram (p<0,05) a população final do nematoide (PF), PF/g de raiz e fator de reprodução, embora em níveis insatisfatórios. Posteriormente, um experimento bianual foi estabelecido em um pomar afetado pelo declínio da goiabeira, no qual três rizobactérias foram comparadas com os produtos biológicos Nemat® e Nemaplus® em sua capacidade de reduzir o parasitismo pelo nematoide e aumentar a produtividade da goiabeira. Sete aplicações bimensais desses tratamentos não reduziram o parasitismo pelo nematoide e não houve aumento de produtividade. A morte de algumas plantas levou à finalização antecipada do experimento após a primeira colheita. Em conclusão, aplicações de rizobactérias parecem incapazes de diminuir o parasitismo por M. enterolobii, e menos ainda reduzir a extensa necrose radicular e o estresse fisiológico ocorrido nas árvores afetadas pelo declínio de goiabeira.

In an effort to devise a biological strategy to control guava decline, 120 rhizobacteria isolates were obtained from symptomless guava trees located in Meloidogyne enterolobii-infested orchards. Of those isolates, 44 were assessed for their potential to reduce nematode's reproduction: for each isolate, six guava stem cuttings were embedded for eight hours with bacterial suspension and transplanted. Upon development of the roots, the plants were inoculated with 2000 nematode eggs and allowed to grow for four months under greenhouse. Seedlings embedded with water, inoculated or not with the nematode, served as controls. All treatments were equivalent in the five variables that assessed plant development. Several rhizobacteria reduced (p<0.05) the final nematode population (Fp), Fp/gram of root and reproduction factor, although not to satisfactory levels. Subsequently, a two-year experiment was set up in a guava orchard affected by guava decline, in which three of the most effective rhizobacterial isolates were compared with the biological products Nemat® and Nemaplus® for their ability to reduce variables related to nematode parasitism and increase guava productivity. Seven bimonthly applications of these treatments under the tree canopy were unable to reduce nematode parasitism and increase productivity. The decline and death of some plants forced the experiment to be stopped after the first harvest. In conclusion, rhizobacteria applications seem unable to reduce the parasitism of M. enterolobii on guava plants, and even less to reduce the extensive root decay or alleviate the physiological stress suffered by trees affected by guava decline.

Foi avaliado o efeito de três concentrações de auxina (0, 2.000 e 6.000 ppm) (ácido indol-bultírico - AIB) para induzir a formação de raízes adventícias em três tipos de estacas caulinares (herbáceas, semilenhosas e lenhosas) de malvavisco (Malvaviscus arboreus Cav.). As estacas foram cortadas em bisel, com aproximadamente 12 cm cada, tratadas com o fungicida benomyl e, posteriormente, com AIB. As avaliações foram feitas 30 dias após o plantio, sendo avaliado o aparecimento ou não de calos, raízes e brotações. Entre as estacas, as lenhosas apresentaram melhor capacidade regenerativa, atingindo o máximo de tecido caloso, enraizamento e brotação, independentemente da concentração de AIB utilizada. No tratamento com AIB na concentração de 2.000 ppm, em estacas herbáceas e lenhosas, obtiveram-se melhores resultados para enraizamento.

The study evaluated the effect of three concentrations of auxin (0; 2,000 and 6,000 ppm) (indolbutiric acid - IBA) in inducing the formation of adventitious roots in three types of stem stakes (herbaceous, woody and semi-woody) of wax mallow (Malvaviscus arboreus Cav.). The stakes were cut into a bezel angle, with approximately 12 cm each, treated with the fungicide Benlate and later with IBA. The assessments were made 30 days after planting, evaluating the appearance or absence of calluses, roots and shoots. Among the stakes, the woody ones showed the best regenerative capacity, reaching the maximum corpus callosum, rooting and shooting, regardless of IBA concentration. In the treatment with 2000 ppm IBA concentration, herbaceous and woody stakes showed the best results for rooting.