Guava Accessions Research Articles

CHEMICAL AND BIOCHEMICAL CHARACTERIZATION OF GUAVA AND ARAÇÁ FRUITS FROM DIFFERENT REGIONS OF BRAZIL

Guava and araca, species of the Psidium genus, are important options for Brazilian agribusiness, especially the former species, due to their fruit characteristics, such as appearance, taste and richness in minerals and phenolic compounds. These fruits can be consumed in natura or in several processed forms. The active germplasm bank is an important tool for genetic resource characterization and plant breeding studies. Sixty guava and ten araca accessions of the Psidium active germplasm, sampled in 44 different Brazilian regions and grown at Embrapa Semiarid, were chemically and biochemically characterized in order to support breeding programs. The accessions were grown in a randomized block design, with two replications and three plants/plot. The sugar, proteins, soluble solids, titratable acidity, calcium, magnesium, iron and phosphorus contents were determined. Large variations were observed in the analyzed compounds, which could be attributed to the diversity of genotypes and also to the environmental conditions, which affect the plant metabolism. The high variability observed in most parameters of the accessions is an important factor for the improvement of these species. Most guava accessions showed higher titratable acidity and soluble solids than those found in commercial cultivars and, in araca, these levels were even higher, which makes them promising for commercial exploitation. Moreover, fruits of the guava and araca accessions present good sources of sugars and minerals. Special attention should be given to some guava and araca accessions from Maranhao and Pernambuco States, respectively, which showed high levels for titratable acidity, soluble solids, SS/TA ratio, total soluble sugars, calcium, magnesium and iron, should be targets of breeding programs for new Psidium cultivars.

Similaridade genética entre acessos de goiabeiras e araçazeiros baseada em marcadores moleculares AFLP

Espécies do gênero Psidium, como goiabeira e araçazeiros, são economicamente importantes e têm como área de diversidade genética primária o Brasil. Foram determinadas as relações genéticas, com base no marcador AFLP, para acessos do Banco Ativo de Germoplasma (BAG) de Psidium da Embrapa Semiárido, para orientar trabalhos de melhoramento e de manejo de recursos genéticos do gênero. Foram analisados 88 acessos, sendo 64 de goiabeira e 24 de araçazeiros, coletados em dez Estados brasileiros, adotando-se para agrupamento o dendrograma UPGMA, considerando a matriz de similaridade do coeficiente de Jaccard de 149 bandas polimórficas de AFLP de 16 combinações dos iniciadores EcoRI e MseI. A análise da variância de dados moleculares foi realizada considerando a variação entre e dentro das populações de goiabeira dos dez Estados. O dendrograma apresentou boa definição, com coeficiente de correlação cofenética de 0,94. Foram observados dois grandes grupos: um formado por acessos de goiabeira e outro com acessos de araçazeiros, com inclusão de alguns acessos de goiabeira. Foram observados agrupamentos específicos no dendograma apenas para os indivíduos de goiabeira coletados em Goiás e Roraima. Os acessos estudados apresentaram similaridade variando de 28 a 98%, evidenciando a alta variabilidade genética dos mesmos. A variação entre acessos foi estimada em 0,16 (ΦST), indicando diferenciação genética moderada entre as populações de goiabeira dos dez Estados. Para aumentar a variabilidade genética do BAG estudado, sugere-se a coleta de um número maior de acessos nos Estados de Goiás e Roraima, dado o alto índice de similaridade entre os acessos provenientes destes Estados, bem como coletas amplas em outros Estados brasileiros. Sugerem-se ainda cruzamentos entre os poucos acessos de goiabeira posicionados no grupo dos araçazeiros para o desenvolvimento de híbridos interespecificos no gênero Psidium.

Antioxidant content in guava (Psidium guajava) and araçá (Psidiumspp.) germplasm from different Brazilian regions

Guava (Psidium guajava) and araçá (Psidiumspp.) plants are important for the Brazilian economy, as their fruit is both accepted by the consumers, and makes a beneficial contribution to the human diet thanks to their content in vitamin C, carotenoids and phenolic compounds. Here, we report the content in the fruit of free ascorbic acid, lycopene, β-carotene, flavonoids and phenolic compounds, and the total antioxidant activity present in a collection of guava and araçá accessions curated at the Embrapa Semiarido germplasm bank. Guava fruits with a red-coloured pulp flesh contained a significant amount of carotenoids, especially lycopene, and a high concentration of phenolic compounds. These compounds were largely responsible for the antioxidant activity of the araçá accessions. Among the guava accessions, phenolic compounds were also responsible for the antioxidant activity. High levels of free ascorbic acid were present in most accessions. In both guava and araçá, there is substantial potential to develop cultivars with a good level of consumer acceptability.

Marcadores moleculares RAPD e descritores morfológicos na avaliação da diversidade genética de goiabeiras (Psidium guajava L.)

The knowledge of the genetic and phenotypic variability among different accessions of guava is important for supporting improvement programs of this specie in northern Rio de Janeiro state, which needs new cultivars able to generate income for local farmers. This work aimed to evaluate the genetic divergence among six cultivars and 19 accessions of guava via RAPD molecular markers and morphological characteristics. One hundred and seventeen polymorphic markers were obtained from 28 primers. The results showed a partial agreement between the methods of studied groupings, with the formation of 12 groups. The accessions ‘Vita 3’and ‘6’ were the most divergent, showing genetic distance of 0.663. The comparative analysis of groupings showed that RAPD markers and morphological descriptors were effective in discriminating the accessions and to show potential genetic variability useful in genetic improvement programs.

USE OF MICROSATELLITE MARKERS TO CHARACTERIZE GENETIC DIVERSITY OF SELECTED ACCESSIONS OF GUAVA (PSIDIUM GUAJAVA) IN THE UNITED STATES

Guava (Psidium guajava L., Myrtaceae family) is one of the most nutritious fruits and has gained nutraceutical importance in recent years. In this study, microsatellite markers were used to characterize the diversity of guava germplasm in the United States. Seven PCR primers amplifying fourteen previously developed microsatellite loci were used to identify and characterize 13 guava accessions. Microsatellite alleles were detected using WellRED fluorescent-labeled primers and capillary electrophoresis. Data were analyzed using the CEQ 8000 Fragment Analysis software and allele frequencies were calculated as co-dominant markers using POPGENE software. Genetic relationships between individuals were analyzed using Nei's index of genetic distance. All primers successfully generated amplicons. Allelic variation was observed in each of the cultivars irrespective of geographic origin. A total of seven alleles were detected ranging from a minimum of two (mPgCIR01 and mPgCIR07) to a maximum of seven (mPgCIR16 and mPgCIR21). Expected heterozygosity values for individual loci ranged from 0.14 to 0.80 with an average of 0.61. This study indicated that microsatellite markers could serve as a useful tool in the characterization of genetic diversity, which is essential for the selection of parents for guava improvement programs.

GENETIC DIVERSITY OF MEXICAN GUAVA GERMPLASM EVALUATED USING AFLP AND SSR MARKERS

In Mexico, guava (Psidium guajava) is grown on more than 20,000 ha. Significant morphological and biochemical variation among and between guava orchards of Mexico have been previously observed. The goal of this work was to evaluate the diversity of Mexican guava maintained on the ex situ germplasm bank of INIFAP using 9 AFLP primer combinations and 6 SSR loci. In this analysis, 68 accessions from 12 different regions of Mexico were analyzed, with six accessions from Venezuela and two from Cuba included as references. In the AFLP profiling, a total of 335 bands were identified, of which 71.9% were polymorphic. Specific region-bands were not observed. The similarity index varied from 0.46 to 0.90, with accessions from Aguascalientes and Guanajuato showing the greatest similarity. The SSR marker analysis revealed a total of 101 alleles. The number of alleles per locus ranged from 12 to 25 and averaged 17. The microsatellite mPgCIR161 revealed the highest number of alleles. The AFLP- and SSR-based dendrogram grouped guava accessions into four groups, with other diverse accessions failing to cluster. Most Mexican accessions were in groups B and C, while Venezuelan cultivars were placed in group E. The results show that Mexican guava germplasm is diverse and that a more detailed analysis is needed in order to determine the level of genetic variability for conservation, management, and development of new varieties.

PROSPECTING AND MORPHOLOGICAL CHARACTERIZATION OF BRAZILIAN PSIDIUM GERMPLASM

A large germplasm prospecting expedition was carried out in different ecoregions in ten Brazilian States in order collect and characterize Psidium guajava L. and another Psidium species, known as araca. Ecogeographic sampling areas were defined based on eco-geographical zoning and vegetation maps. The accessions were characterized for 40 descriptors, according to the International Union for the Protection of New Varieties of Plants guidelines. One hundred and nineteen guava accessions and 40 araca accessions araca were sampled and characterized in 35 different Brazilian ecoregions. The most invariable descriptors for both guava and araca were color of young shoots, leaf pubescence on lower side, leaf blade length and width, leaf variegation, fruit surface relief, fruit longitudinal ridges and grooves and evenness of fruit flesh color. The large majority of araca accessions presented widely spaced leaf veins, contrasting with the guava accessions that presented medium to close spacing. Most fruits of araca accessions were classified as small, while most fruits of guava accessions were grouped into the class of medium size. For the fruit flesh color, 91% araca were grouped as cream and white, while 58% guava accessions presented pale pink, pink and dark pink coloring. These fruit differences among wild Psidium species and guava suggested that the fruit traits have been the most altered trait by artificial selection.

COMPARISON OF THE POLYMORPHISM LEVEL, DISCRIMINATING CAPACITY AND INFORMATIVENESS OF MORPHO-AGRONOMIC TRAITS AND MOLECULAR MARKERS IN GUAVA (PSIDIUM GUAJAVA L.)

Agro-morphologic traits and molecular markers were compared in terms of their polymorphism level, discriminating power, and informativeness for 23 genotypes assembled in the Cuban guava germplasm collection. AFLP and SSR markers were powerful techniques for guava discrimination and variety identification, but the high level of polymorphic loci detected by the dominant AFLP marker highlights the discriminating capacity of this genetic marker. With a single AFLP primer combination all of the individuals were identified, while only a few genotypes can be differentiated with a single SSR primer combination or by morphological variables. The higher values of expected heterozygosity were detected by SSR. This value doubled the one obtained with AFLP, and reflects the high level of informativeness of this marker, due to the multiallelic and co-dominant nature of SSR; which makes them suitable for diversity studies. The morphologic diversity index provided a good estimate of diversity among guava accessions when phenotypic traits of high heritability were used, and it was comparable with the expected heterozygosity scored with DNA markers. The value of this index was the lowest. The assay efficiency index (A i ) and marker index (MI) had the same pattern of variation than discrimination capacity (D), number of banding pattern (I), number of unique banding pattern (I u ) and number of effective pattern (P) for both molecular markers. Then, these indexes are probably indicators of the discriminating capacity in guava.

EVALUATION OF MEXICAN GUAVA GERMPLASM AGAINST ROOT KNOT NEMATODES

Root knot nematodes (Meloidogyne spp.) are one of the main phytosanitary problems of guava orchards in Mexico. At Calvillo, Aguascalientes, almost 90% of the seven-thousand hectares cultivated with guava are infested with nematodes. Although there are chemical and biological strategies to manage this problem, genetic resistance of native guava germplasm under cultivation has never been studied. The purpose of the present study was to determine the degree of susceptibility of a group of guava selections included at the germplasm bank of INIFAP as well as other guava accessions. Air-layering plants of the selections 10, 12, 20, 45, 46, 48, 106, 115, 117, and 118 were obtained, and then placed in pots of 12 kg of capacity. Plants were inoculated with 12 ml J2 plus nematode eggs collected at infested guava orchards of Aguascalientes, Michoacan, and Zacatecas. Results using air-layering plants showed that selections 46, 106, and 45 were more tolerant with 26, 35, and 35% of root damaged, respectively, while the most susceptible was selection 48 with 70% of the roots showing galls. In the group of guava seedlings, four accessions (51, 58, Boyaca, and Brazil) showed the highest gall numbers per centimeter of root, whereas the least affected were selection 42 and a Psidium spp. This study provides evidence that guava genetic resistance to nematodes could be present in the germplasm under study, and could be used as rootstocks or hybridization in future works.

RELATIONSHIP BETWEEN ECOGEOGRAPHIC SAMPLING AND PHENOTYPIC DIVERSITY OF BRAZILIAN PSIDIUM GERMPLASM BASED ON CATEGORICAL DESCRIPTORS

Relationships between eco-geographic origin and phenotypic variation were established for 143 Psidium accessions, including (a general term for wild-growing Psidium spp. in Brazil) and guava (P. guajava) species, sampled in 31 different eco-geographic regions of ten Brazilian States. The accessions were characterized for 35 categorical traits according to the International Union for the Protection of New Varieties of Plants (UPOV) descriptors for P. guajava. The correlation between the cophenetic values and the simple matching matrices was 0.55, and the badness-of-fit of the multidimensional scaling was 0.30. Eighty-eight percent of the araca accessions were grouped together and they clustered according to ecogeographic regions. Clusters of guava accessions were verified only in collections from four Brazilian States, and did not present clustering by specific ecogeographic regions. It was expected that the capturing of rare alleles and the enhancement of the genetic variability of Psidium germplasm could be achieved by sampling accessions according to predefined geographical areas, even for guava germplasm.

ASSESSMENT OF THE VARIABILITY OF VENEZUELAN GUAVA LANDRACES BY MICROSATELLITES

Guava is one of the neotropical fruits with major economic value in the world. In spite of the former tradition of crop growth and consumption of guava in Venezuela, its cultivation has been performed carelessly, since an appropriate management of the crop taking into account recent advances in modern agriculture has not been carried out. In addition, research in the field is scarce in the country, with the exception of continuous and successful efforts in the field of phytopathology. Rational programs of genetic improvement have not been performed so far, and there are no germplasm banks that may account for the diversity that Venezuela possesses. In this way, neither the commercially cultivated guavas nor the guava landraces have been characterized phenotypically or genotypically, ignoring the number and variability of all the varieties and types present in the country. In the present research, we evaluated the genotypic variability of Venezuelan guava landraces using SSR markers. To attain this goal, 31 guava accessions from different regions of Venezuela were selected, which now belong to a recently established ex situ germplasm facility of Myrtaceae at Universidad de Los Andes. All samples were evaluated for 16 microsatellite loci, using primers specific for guava. All evaluated loci were highly polymorphic, observing up to 100% of polymorphism and detecting several alleles per locus. These results reveal the great genetic diversity of the natural population of P. guajava in Venezuela, which seems to be associated with its geographical distribution. Finally, these microsatellites allowed us to characterize genetically the accessions of the germplasm bank, which in the future will enable the monitoring, genotyping and selection of specific individuals during the development of coherent programs of genetic improvement.

SIMPLE SEQUENCE REPEATS (SSRS) FOR DIVERSITY CHARACTERIZATION OF GUAVA (PSIDIUM GUAJAVA L.)

Guava (Psidium guajava L.) is one of the economically most important fruit trees of the Myrtaceae. Until nowadays, guava breeding programs in Cuba have been limited to the selection and introduction of genotypes with important agronomic characteristics, but focussed studies on genetic diversity which is very important for the identification of potential parents for breeding programs, had not been undertaken. The utilization of microsatellite (SSR) markers for guava germplasm characterization and gene bank management was the main objective of this work. A total of 34 different SSR alleles ranging from three to seven per locus were detected in the examined genotypes with an average number of putative alleles per locus of 4.57. Out of these, twenty-four alleles were classified as common alleles, out of which 10 were widespread and 14 sporadic. Ten alleles were classified as rare, from which 7 were sporadic and 3 localised. For all SSR loci, a major number of homozygote genotypes were identified, except for the SSR locus mPgCIR09. This result reflected the medium to low levels of heterozygosis detected, which ranged from 0.08 to 0.54 with 0.38 as the total average for this parameter. Genotypes showing cultivar-specific markers were 'Dario 19-2'; 'Belic L-98'; 'BG 76-23'; 'Belic L-205' and 'Microguayaba'. These could be important materials for conservation purposes. The high number of common alleles detected suggested that most of the plant material analyzed shares a common genetic ancestor. The microsatellites evaluated could play an important role in the identification of guava accessions representing an interesting gene pool for ex situ maintenance.

ASSESSMENT OF GENETIC DIVERSITY OF MEXICAN GUAVA GERMPLASM USING DNA MOLECULAR MARKERS

In Mexico, more than 20,000 ha are used to produce guava. Significant morphological and biochemical variation among and between guava (Psidium guajava L.) orchards of Mexico have been previously observed. The aim of this work was to evaluate the diversity of guava from different parts of Central and Northern Mexico by DNA markers, using 6 SSR loci and 5 AFLP primer combinations in an automatic sequencer. In this analysis a total of 57 individual accessions (maintained at the INIFAP Pabellon Campus in Aguascalientes) from 10 different regions of Mexico were included. As a result of AFLP profiling, a total of 233 bands were identified, of which 82% were polymorphic, but region-specific bands were not observed. The similarity index varied from 0.64 to 0.97, being most similar for samples from Aguascalientes and Guanajuato. By SSR marker analysis, a total of 79 alleles were identified. The observed number of alleles per locus varied from 8 to 21 with an average of 13 alleles per locus considering samples from all regions. The microsatellite mPgCIR161 revealed the highest frequency of homozygosity. The AFLP- and SSR-based dendrogram clusters the analyzed guava accessions into 2 main groups with at least 5 different sub-clusters without specific separation based on the region of origin. The results show that Mexican guava is diverse and that a more detailed analysis is needed in order to determine the level of genetic variability for conservation, management, and development of new varieties.

Resistência de goiabeiras e araçazeiros a Meloidogyne mayaguensis

O objetivo deste trabalho foi identificar espécies de Myrtaceae resistentes a Meloidogyne mayaguensis. Acessos de araçazeiros e goiabeiras da Coleção de Plantas Frutíferas Nativas e Exóticas da Unesp/FCAV e acessos de araçazeiro de fragmentos de matas nativas do Nordeste do Estado de São Paulo e Triângulo Mineiro foram testados quanto à resistência ao nematódeo. As mudas receberam 4.000 ovos e juvenis de segundo estádio de M. mayaguensis por planta e foram conduzidas em casa de vegetação. Aos 150 dias, os genótipos foram avaliados quanto à resistência ao nematódeo com base no fator de reprodução. Três acessos de Psidium e um de Eugenia foram resistentes a M. mayaguensis.

Preliminary characterization of Psidium germplasm in different Brazilian ecogeographic regions

The objective of this work was to characterize 119 accessions of guava and 40 accessions of "araçá" sampled in 35 Brazilian ecoregions, according to the International Union for the Protection of New Varieties of Plants (UPOV) descriptors. The majority of "araçá" accessions presented wide spacing of leaf veins, while guava accessions presented medium to close spacing. Most fruits of "araçá" accessions were classified as small, contrasting with medium to large fruits of guava accessions. Most of "araçá" accessions (91%) presented white flesh fruit color, while 58% of guava accessions presented pale pink, pink and dark pink colors. Fruit differences among wild and cultivated Psidium species indicate fruit as the most altered trait under artificial selection.

CHARACTERIZATION OF GUAVA ACCESSIONS BY SSR MARKERS, EXTENSION OF THE MOLECULAR LINKAGE MAP, AND MAPPING OF QTLS FOR VEGETATIVE AND REPRODUCTIVE CHARACTERS

The guava accessions assembled in the Cuban germplasm collection at Alquizar (Havana Province) were previously characterized by phenotypic descriptors as well as by AFLP DNA markers (Rodriguez et al., 2004; Valdes-Infante et al., 2003). Here, SSR DNA markers were applied in the establishment of phylogenetic relationships. Furthermore, three guava mapping populations were produced by controlled crosses with the dwarf cultivar 'Enana Roja cubana' as the female parent. Based on segregating AFLP markers, an integrated molecular linkage map of guava was constructed for the first mapping population MP1 under investigation. The previously published linkage map (Valdes-Infante et al., 2003) was extended by arranging a total of 220 markers into 11 linkage groups possibly representing the 11 chromosomes (2n = 22) of the guava genome with 11 to 30 markers per linkage group and a total genome length of 1379 cM. QTL analysis for vegetative characters identified a total of fifteen loci contributing to leaf length, leaf width, petiole length, height, and growth rates for diameter and height. The QTL analysis for fruit characters resulted in the identification of loci such as fruit weight, acidity, total soluble solids, vitamin C content, and pulp thickness. (Resume d'auteur)

Identification and Characterization of Pestalotiopsis spp. Causing Scab Disease of Guava, Psidium guajava, in Hawaii.

Guava is one of the most widely grown plants in the tropics; however, it is affected by many fruit rot diseases. Fruit diseases decrease the marketability of fresh fruit and fruit for processing. A survey of scab disease was conducted at the USDA/ARS Tropical Plant Genetic Resource Management Unit in Hilo, HI, where more than 50 accessions of guava are grown. Symptoms observed were gray/light brown lesions surrounded by dark brown borders on leaves and brown, raised, corky, necrotic lesions on the exocarp of fruit which progressed as the fruits matured. Seventeen isolates from infected fruit, six isolates from lesions on leaves, and nine isolates from additional crops surrounding the guava trees were collected. The main fungi consistently isolated from symptomatic leaves and fruit were Pestalotiopsis spp. Morphology, colony characteristics, and pathogenicity of the isolates were examined and potential sources of host resistance were identified for germplasm characterization studies. Molecular methods were used to identify four Pestalotiopsis taxa (P. clavispora, P. microspora, P. sp. GJ-1, and P. disseminata) on guava in Hawaii. To our knowledge, this is the first report of traditional and molecular methods of identification and characterization being used for fungal pathogens of guava in Hawaii.

Variations in the yield and fruit characters of some guava (Psidium guajava L) accessions in Ibadan, Southwestern Nigeria

A germplasm collection block of guava containing nine accessions was established in Ibadan to assess variations in metrical, visual and other fruit yield characters for the purpose of selection for good quality fruit. The results showed that four years after planting only accessions TB85/2885 and TB85/2887 had high survival percentages of 90% and 86% respectively. Most of the accessions produced fruits two years after planting. The accessions were significantly different with regards to fruit yield and metrical characters. Based on harvest duration, two groups of guava were identified – early fruiting (July-September) and late fruiting (August-October). The harvest duration varied among accessions from four weeks to nine weeks. All accessions were inferior to the improved varieties in terms of small fruit size and low fruit/seed weight proportion. Nevertheless, TB85/2885 may be selected among the accessions for its good survival on poor soil, big fruits, high fruit/seed weight proportion, long fruiting duration as well as availability of its fruits off-season. Key Words: Accessions; guava; harvest duration;, metrical characters; percentage survival Moor J. Agric. Res. Vol.4(1) 2003: 71-77