Péricles de Albuquerque Melo Filho

Allelopathy, an alternative tool to improve cropping systems. A review

Known since ancient times, the phenomenon of allelopathy has recently received greater attention from researchers and farmers worldwide. Crop failures and low yields caused by the reseeding, overseeding, crop rotation and replanting of fruit trees in orchards are believed to be caused by allelopathic activity. Moreover, the expensive and environmentally impacting herbicides for weed control have motivated studies directed at developing cheaper, environmentally-friendly alternatives. Despite the difficulties in separating chemical interference from other mechanisms, more modern approaches have produced consistent and conclusive data on this topic. The release and dynamics of allelochemicals in the soil are discussed herein. Examples of allelopathic crops, the allelochemicals produced and their uses in cropping systems are also presented along with current research trends regarding allelopathy.

Plant Promoters: An Approach of Structure and Function

With current advances in genomics, several technological processes have been generated, resulting in improvement in different segments of molecular research involving prokaryotic and eukaryotic systems. A widely used contribution is the identification of new genes and their functions, which has led to the elucidation of several issues concerning cell regulation and interactions. For this, increase in the knowledge generated from the identification of promoters becomes considerably relevant, especially considering that to generate new technological processes, such as genetically modified organisms, the availability of promoters that regulate the expression of new genes is still limited. Considering that this issue is essential for biotechnologists, this paper presents an updated review of promoters, from their structure to expression, and focuses on the knowledge already available in eukaryotic systems. Information on current promoters and methodologies available for studying their expression are also reported.

Physiological and biochemical responses of peanut genotypes to water deficit

Abstract The effects of drought on water relations, gas exchanges, solutes accumulation, and catalase (CAT), ascorbato peroxidase (APX), and guaiacol peroxidase (GPX) activities were studied in five Arachis genotypes, grown under control or withholding water conditions. Drought stress reduced plant growth of all genotypes; the genotypes A. duranensis 7988 and A. stenosperma SV2411 being characterized as the most drought-sensitive and A. ipaensis as the most drought-tolerant. Data of transpiration and stomatal conductance confirmed the findings that A. ipaensis was more tolerant to drought conditions. Water deficit increased organic solutes content and reduced leaf water potential in all genotypes. The data suggest that solutes accumulation in roots may, at least in part, explain the greater tolerance of A. ipaensis to drought stress. CAT activity showed a significant increase in stressed leaves of sensitive genotypes. APX and GPX activities either increased or were not affected by drought in leaves of all genotypes.

Detection of three Allexivirus species infecting garlic in Brazil

Garlic viruses often occur in mixed infections under field conditions. In this study, garlic samples collected in three geographical areas of Brazil were tested by Dot-ELISA for the detection of allexiviruses using monoclonal specific antibodies to detect Garlic virus A (GarV-A), Garlic virus B (GarV-B), Garlic virus C (GarV-C) and a polyclonal antiserum able to detect the three virus species mentioned plus Garlic virus D (GarV-D). The detected viruses were biologically isolated by successive passages through Chenopodium quinoa. Reverse Transcriptase Polimerase Chain Reaction (RT-PCR) was performed using primers designed from specific regions of the coat protein genes of Japanese allexiviruses available in the Genetic Bank of National Center of Biotechnology Information (NCBI). By these procedures, individual garlic virus genomes were isolated and sequenced. The nucleotide and amino acid sequence analysis and the one with serological data revealed the presence of three distinct allexiviruses GarV-C, GarV-D and a recently described allexivirus, named Garlic mite-borne filamentous virus (GarMbFV), in Brazil.

Yield of advanced lines of peanut under rainfed conditions in northeast Brazil

Eleven upright and runner peanut advanced lines were conducted conditions in four states located in the northeast region aiming to evaluate their pod and seed yield. Assays were carried out in the agricultural year 2005/2007 in the states of Pernambuco (Araripina and Parnamirim), Sergipe (Lagarto), Bahia (Cruz das Almas and Caetite) and Paraiba (Campina Grande and Itabaiana). A completely randomized block experimental design with five replications was used with 13 treatments (8 upright and 5 runner genotypes). The analyzed variables were pod and seed yields. Individual and joint variance analysis were carried out and Tukey (p < 0.05) test was used to compare treatments. The BR 1 cultivar was adopted as a control. The highest pod and seed yields were obtained by LN-1B, with 2,450 and 1,665 kg ha-1, respectively, overcoming the mean of upright lines in 22 and 21%, and of the BR 1 cv. in 11 and 10%. As to runner lines, the pod and seed yields were not satisfactory under the conditions, however, LI-3, LI-5 and LI-1 overcame the group, with 1,722 and 1,154 kg ha-1, corresponding to 9.8 and 10% over general mean, respectively.

Mudanças bioquímicas em genótipos de amendoim submetidos a déficit hídrico moderado

Five peanut genotypes, with different growth habits were submitted to moderate water stress in a greenhouse for seven days. Seeds were planted in 15-litre pots containing soil and a substrate (Plantmax®), both optimized for the crop. The adopted experimental design was completely randomized, using a 5 x 2 bi-factorial scheme(5 genotypes × 2 water treatments) with five replications. The enzymatic activities of SOD, CAT, APX and GPX were analyzed, as well as the carbohydrate, starch and proline. An increased activity was shown in SOD and CAT enzymes for all genotypes submitted to water stress, in both leaf and root, especially in the 55 437 and BR1 cultivars and also in LBM Branco line. Proline accumulation and reduced starch were verified in all stressed genotypes, but carbohydrate content was increased just in tolerant materials. Based on results, 55 437 and BR1 were more tolerant to water stress, followed by LBM Branco. The LBR Branco shows intermediate behavior and LViPE- 06 was more sensitive.

Viral reinfection affecting bulb production in garlic after seven years of cultivation under field conditions

Six sequential field experiments were conducted from 1999 to 2002 to evaluate virus reinfection in garlic cv. Amarante and its effect on bulb production. The treatments in the year 1999 were: T1 – virus-free garlic-seed obtained by thermotherapy and meristem-tip culture and indexed for virus by immuno-sorbent electron microscopy (ISEM) under its first field cycle; T2, T3 and T4 – garlic-seed in the second, third and fourth field cycles, respectively; and C – standard garlic-seed from the grower (with no control of virus infection) as a control. In the years 2000 to 2002, a new plot of virus-free seed was added to the experiment and cloves from the previous treatments were again grown under field conditions. In the fourth year of experiments, the treatments comprised T1 (virus-free garlic seeds under the first field cycle) to T7 (garlic-seed in the sixth field cycle) and C. Two experiments were conducted in the years 1999 and 2000, at two locations and in the years 2001 and 2002 only one experiment per year at one location. The combined analysis of variance for all experiments indicated a significant difference between the treatments for plant height and yield. The bulbs were classified into commercial classes according the Brazilian regulation and the commercial classes 4–7 were 72 %, 60%, 59%, 53% and 35% of the total number of bulbs harvested, from T1 to T5, respectively. Virus reinfection at the end of the second field cycle, determined by serology using antisera against the most common viruses of garlic in Brazil reached 83%. Treatments T1–T7 yielded 118%, 79%, 57%, 51%, 39%, 33% and 31% higher than the control.

Características agronômicas e índice de colheita de diferentes genótipos de amendoim submetidos a estresse hídrico

Upright and runner peanut genotypes were subjected to 27 days of water suspension, starting at vegetative phase and evaluated for their agronomical components and harvest index. The trail was carried out in a greenhouse using a completely randomized design, with factorial scheme 8 x 2 (genotypes x treatment), with five repetitions. The following variables were analysed: dry weight of the plant, dry weight of roots, main stem height, pods plant-1, harvest index and index of tolerance to drought. It was found that upright genotypes had better physiological adjustment when submitted to prolonged water stress, among them genotype 55 437 was more tolerant. All runner genotypes were sensitive to water stress, however LViPE-06 was less sensitive revealing as a promising material for the generation of divergent population.

Classificação de germoplasma de Dioscorea sp. através da análise das componentes principais

Interspecific classification m Dioscorea germplasm was made aiming to characterize them by morphological descriptors and classify by principal component analysis. Eleven accesses belonging to Universidade Federal Rural de Pernambuco Brasil (UFRPE Germplasm Collection) were studied. Fourteen descriptors were chosen for each access: leaf color and shape, petiole pigment, stem color and shape, presence and color of membranes, presence of good, presence of aerial tubers, tuber shape, presence of roots m lhe tuber, pigment in lhe tuber and leaf length and width. It was observed that leaf length and width provided high contribution on lhe access discriminations. The accumulated variance to the 1st and 2nd principal components were 89% of the whole variation. Six groups were made up representing Dioscorea accesses.

Correlations and path analysis of peanut traits associated with the peg

By correlation and path-coefficient analysis, the most relevant traits for selection for peanut pod yield were identified among the following: total number of pegs (TNP), number of pegs in the lower third of the plant (NPLTh), number of mature pods (NMP), main stem height (MSH), and reproductive efficiency (EF1 and EF2). The trial consisted of 15 F2:3 progenies derived from a cross of variety BR 1 and the advanced line CNPA 280 AM, evaluated in a randomized block design with three replications. The lines with best reproductive efficiency were L.8 and L.11. Path analysis detected a strong direct effect of the number of pegs in the lower plant third on the number of mature pods. This finding justifies the use of the number of pegs in the lower plant third in selection of peanut populations for number of mature pods.