Capsicum chinense is commercially the most important pepper species grown in the Caribbean. It is popularly used to impart pungency and flavor to Caribbean cuisine. However, unlike Capsicum annuum, which is the most commercially exploited domesticated species internationally, C. chinense has not been methodically collected or characterized for systematic improvement through plant breeding. The objectives of the study were to assess the diversity of C. chinense and its structure within the Caribbean basin and to determine its phylogenetic relationship to groups within South America. DNA isolated from 201 accessions of C. chinense, representing geographical regions where the species is found, were amplified using arbitrary primers to generate 138 polymorphic and reproducible random amplification of polymorphic DNA (RAPD) markers. Nei’s and Shannon’s diversity indices for C. chinense (0.28 and 0.419, respectively) were higher in South America compared with Central America or the Caribbean, corresponding to its putative center of diversity. The study showed the existence of three phylogenetic clusters within C. chinense. The largest cluster consisted of accessions from the Upper Amazon region, the Guianas including Venezuela, and the Lesser Antilles of the Caribbean. The other major cluster was represented by accessions principally from the Lower Amazon region. Another distinct but small cluster consisted of samples solely from the Greater Antilles of the Caribbean. The discovery of the three phylogenetic clusters within C. chinense may have potential for exploiting heterosis in breeding. The implications of the findings to the understanding of the phylogenetic origin and distribution of C. chinense are discussed.
Marissa Moses and Pathmanathan Umaharan
Winston Elibox and Pathmanathan Umaharan
Sixteen morphophysiological parameters of horticultural importance were investigated in 82 anthurium accessions grown in the Caribbean. The spathe colors included red, pink, white, green, orange, purple, coral, and brown and obake types with red, pink, and white spathe colors accounting for 63.4% of the accessions. There was wider variation in spadix color combinations than spathe color. There was wide variation for the cut flower and leaf parameters evaluated with productivity and peduncle length having the smallest and largest range, respectively. The frequency distributions were skewed to the right for spathe length, spathe width, spathe size, spadix length, spadix diameter, leaf width, leaf size, and productivity and was normal for leaf length, spadix angle, peduncle length, petiole length, and spathe showiness. Accessions with wider leaves had longer leaves and longer petioles; those with longer spathes had wider spathes; and those with longer peduncles had correspondingly longer petioles. Peduncle length also showed moderate, weak correlations with other leaf measurements and spathe parameters, respectively. Spadix diameter showed moderate correlations with leaf parameters. Spathe showiness showed moderate, weak correlations with spathe measurements and productivity, respectively. Principal component analysis of the 13 quantitative parameters showed that the first three principal components explained 75% of the variation in the accessions. Leaf length, leaf width, leaf size, petiole length, peduncle length, and spadix diameter; spathe length, spathe width, spathe size, and spathe showiness; and productivity loaded on the first, second, and third component, respectively. Hence, one leaf and one spathe size parameter, spathe showiness, petiole length, peduncle length, spadix length, spadix angle, spadix diameter, and productivity as well as spathe, spadix, peduncle, and petiole colors can be used as descriptors for anthurium. Based on these results and market information, an Anthurium ideotype adapted to the humid tropics is described.
Winston Elibox and Pathmanathan Umaharan
Anthurium andraeanum Hort. is an important tropical ornamental crop regarded as second only to orchids in its commercial importance. The genetic basis for productivity in anthurium was studied using parent–offspring regression analysis. Sixteen parental genotypes (4 years old) and 14 biparental progeny families (60 plants each, 4 years old) derived from the parents were used in the study. Yield expressed as number of cut flowers per plant per year (CFPY) was significant both between parental genotypes (P < 0.001) and between progeny families (P < 0.05). Mean CFPY of the parent genotypes was normally distributed and ranged from 4.8 in ‘Local Mina Red’ to 9.8 in ‘Kalapana’ with a mean of 7.5. CFPY in Year 1 was strongly correlated to that in Year 2 (Pearson’s r = 0.96; Spearman’s r = 0.93) and the broad sense heritability (H2) was high (87.6%) under controlled shadehouse conditions. CFPY in the progeny families varied from four to 14 with progeny means ranging from 5.7 in ‘Honduras/Local Mina Red’ to 7.2 in ‘Mirjam/Kalapana’. Progeny of seven and 10 crosses possessed mean CFPY greater than that of the more productive parent and the midparent values, respectively. The frequency distribution for productivity of the 840 progeny plants was skewed to the right with a modal class of six to seven. The correlation coefficient between progeny CFPY and midparent CFPY was large and significant (r = 0.90, P < 0.001). The regression of mean progeny CFPY on mean midparental CFPY was strong (y = 0.51x + 2.56; R 2 = 0.81) with an estimated narrow sense heritability (h2) of 51.0%. A breeding strategy for improving per plant productivity based on the results is discussed.
Winston Elibox and Pathmanathan Umaharan
The inheritance of spathe color in anthurium (Anthurium andraeanum Hort.) was studied in 77 crosses involving 59 parental genotypes. The progeny segregation into “colored : white” did not fit the genetic model proposed by , but fit a duplicate recessive epistasis model involving genes O and R, in which either O or R or both in the recessive form would result in white-spathed progeny. The progeny segregation into red or orange group was in agreement with the model and is determined by the status of the M gene. The dosage effect of particularly the R gene accounted for the differentiation of reds from pinks and oranges from corals. Putative roles for the three genes (M, O, and R) in the flavonoid biosynthetic pathway are postulated.
Winston Elibox and Pathmanathan Umaharan
The vase life of 26 anthurium (Anthurium andraeanum Hort.) cultivars was evaluated in three separate trials. In the first trial, the influence of 12 morphophysiological characteristics of the cut flower on vase life was investigated. Of these, only spathe color and abaxial stomatal density were able to accurately predict vase life. A vase life prediction equation based on abaxial stomatal density, green/not green and white/not white was able to explain the cultivar variation in vase life in two separate trials conducted over two seasons. The equation was further validated using a different set of anthurium cultivars. Although vase life varied over seasons, the relative ranking of cultivars was similar as indicated by joint regression analysis. Changes in vase life over season were mediated through changes in stomatal density. Time to spadix necrosis was the only senescence indicator that occurred in all cultivars and was highly correlated to vase life determined by a complex criterion in all trials. Time to spadix necrosis is therefore suggested as a simplified criterion for vase life assessment. The possible mechanism for vase life deterioration and an approach to improving vase life in anthurium is discussed.
David Gopaulchan, Adrian M. Lennon, and Pathmanathan Umaharan
Anthurium (Anthurium andraeanum) is a tropical ornamental valued for its colorful spathe (modified bract) that subtends the inflorescence. The present genetic model for spathe color inheritance in anthurium does not account for differences among the red- and pink-spathed cultivars or for differences in the shades of pink among pink cultivars. To identify the mechanisms responsible for the variation in color and intensity, five genetically defined pink-spathed cultivars, with respect to the O, R, and M loci, with varying shade intensities, along with a genetically defined red-spathed cultivar (control), were analyzed at the mRNA, protein, chemical, and phenotypic levels at different spathe development stages. Spathe color values were recorded based on CIE L*a*b* system. Intensity of color (L*, which represents lightness) correlated with the anthocyanin content, with L* showing a strong negative relationship with anthocyanin abundance. Additionally, the red spathe accumulated anthocyanin throughout the spathe developmental stages, whereas the pinks either produced anthocyanin at early stages of development, which decreased as the spathe matured or showed a marked delay in anthocyanin accumulation. The level of anthocyanin closely mirrored flavonoid 3′-hydroxylase (F3′H) expression but did not correspond with the expression of any of the other genes assayed, chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS). It was found that earlier the expression and higher the rate of expression of F3′H during spathe development, the greater the accumulation of anthocyanin in the spathe. Differences in the a* color space parameter among cultivars also suggests that qualitative differences in color could be mediated through F3′H. Other ancillary mechanisms that down regulate F3H, ANS, and DFR expression levels, evident in some pink cultivars, are discussed.
Winston Elibox, Charles P. Meynard, and Pathmanathan Umaharan
Thirty four pepper accessions (Capsicum chinense Jacq.) from the Caribbean were evaluated under controlled environmental conditions viz. darkness, 21.8 °C, and 90% relative humidity (RH) to determine the genetic variation and morphophysiological changes associated with loss of shelf life. The experiment was arranged in a randomized complete block design with three replications and 10 fruits per replication. The following parameters were recorded over a period of 20 days: fruit weight, shrivelling score, and proportion of fruits showing incipient pedicel necrosis, up to 20% pedicel necrosis, total pedicel/calyx necrosis (but with no pericarp necrosis), incipient pericarp necrosis. Water loss overtime, water loss slope and intercept, and days to incipient pedicel necrosis, 20% pedicel necrosis, total pedicel/calyx necrosis, and incipient pericarp necrosis were derived from the data. There were significant differences (P < 0.05) among accessions with respect to all parameters measured. Deterioration under storage initiated as incipient necrosis of the pedicel tip, which proceeded along the entire pedicel and calyx and subsequently into the pericarp. Shelf life varied from 6.6 to 16.9 days based on days to 20% pedicel necrosis and up to 19.5 days based on days to incipient pericarp necrosis. Shelf life based on days to 20% pedicel necrosis, total pedicel/calyx necrosis, and incipient pericarp necrosis were highly autocorrelated (r = 0.94 to 0.99, P < 0.01) and paralleled water loss from fruits. Pepper accessions with heavier fresh fruit weights had lower water loss rates and longer shelf lives than those with lighter fruits. Days to 20% pedicel necrosis and incipient pericarp necrosis were the best measures of shelf life as they best predicted marketability and usability of fruits as early as 8 days after harvest (DAH) (R 2 = 0.94) and 9 DAH (R 2 = 0.82), respectively, thus reducing the time of shelf life studies by half. Based on days to 20% pedicel necrosis, five accessions with shelf lives over 15 days were identified.
Sarah M. Bharath, Christian Cilas, and Pathmanathan Umaharan
Aromatic hot peppers (Capsicum chinense Jacq.) are an important agricultural commodity for many small-scale farmers in the Caribbean because it is a commercially viable crop and one that is integral to the cuisines of the region. The large variation in fruit shape, size, color, pungency, and aroma of this species facilitates a diverse range of uses. Using 264 accessions from a Caribbean germplasm collection (representing primarily the Caribbean Basin, Central and South America), this study investigated 1) morphological variation in 13 fruit descriptors of agro-economic importance; and 2) morphological groups based on geographic origin. All 13 fruit descriptors showed significant variation. Fruit color [immature (six states) and mature (12 states)] was the most diverse qualitative fruit trait. Among the quantitative traits, fruit weight and fruit width showed the highest broad-sense heritability (0.81), and fruit weight was highly correlated with fruit width and placenta size. Cluster analysis revealed four main clusters, which did not show a clear separation of accessions based on major geographic regions, but there was a highly significant association (P < 0.0001) between geographic subgroups and the clusters to which they were assigned. Most accessions of the Northern Caribbean (particularly the Bahamas and Puerto Rico) separated quite distinctly from most accessions of the Southern Caribbean and clustered with most accessions of Central and South America. Accessions of the Southern Caribbean (Lesser Antilles, Trinidad & Tobago) were substantially more similar to each other than they were to most accessions of Central and South America, thereby suggesting genetic differences between accessions of the Southern Caribbean islands and the mainland populations. Collectively, the results show that this germplasm collection contains useful accessions with desired fruit quality traits and a level of genetic variation that can be used to encourage its active conservation and use for further evaluation trials and crop improvement as well as guide ongoing complementary germplasm introductions to augment the collection’s diversity.
Fazeeda N. Hosein, Adrian M. Lennon, and Pathmanathan Umaharan
Gene function studies in anthurium (Anthurium andraeanum) have been hindered by the low efficiency of stable transformation, the long regeneration time required as well as the genotype-dependent nature of Agrobacterium (Agrobacterium tumemaciens)-mediated transformation protocols. Agrobacterium-mediated transient expression assays can serve as an attractive alternative for investigating gene function once such assays are optimized. The effects of host factors (genotype, explant type, and developmental maturity of explants), Agrobacterium factors (strain, growth phase, and its concentration), media conditions (infiltration medium used, acetosyringone concentration, type of surfactant, and its concentration), and other experimental factors (infiltration time, cocultivation time, and vacuum infiltration) were investigated on the efficiency of Agrobacterium transient transformation, with replications, using transient expression of β-glucuronidase as an indicator. Although the efficiency of transient transformation was initially found to be highly host genotype-dependent, the genotypic differences in transient transformation efficiency diminished as the protocol was optimized. Agrobacterium strain GV3101 grown to an optical density at 600 nM (OD600) of 1.5 and resuspended to a final OD600 of 0.8 in infiltration medium [0.5% glucose, 10 mm 2-(N-morpholino) ethanesulfonic acid] supplemented with 100 μM acetosyringone and 0.05% of a non-ionic surfactant (S240), for an infiltration period of 16 hours and a cocultivation timeframe of 2 days yielded transient transformation efficiencies as high as 100%.
Darin A. Sukha, Pathmanathan Umaharan, and David R. Butler
The flavor attributes of cacao (Theobroma cacao) is becoming an important consideration in trade specifically for fine or flavor cocoa. In this market segment, flavor along with other physical attributes, not only contributes to the quality of a cocoa lot but also the price premium obtained. Past studies have shown evidence of pollen parent effects on yield, bean size, and pod characteristics, but its effect on flavor attributes is not clearly understood. An incomplete diallel mating design involving five cacao cultivars [West African Amelonado (WAA), Imperial College Selection (ICS) 1, Iquitos Mixed Calabacillo (IMC) 67, and two Trinidad Selected Hybrids (TSH) coded as CCL 200 and CCL 201] with widely differing flavor attributes were used to investigate the magnitude of female and male parent effects on key intrinsic flavor attributes. The seeds derived from pods arising from these pollinations were fermented, dried, and made into cocoa liquor according to standardized methods. Flavor evaluations were carried out by a trained sensory panel for nine flavor attributes with five repetitions and hidden flavor reference controls. The study was conducted over two cocoa crop years. The results failed to detect dominant xenia effects for important ancillary flavor attributes (i.e., cocoa flavor, acidity, fruitiness, and floral flavors), but showed significant female parent effects for cocoa and floral flavors. Small but inconsistent male parent effects were seen for astringency. Lack of xenia effect for the major flavor attributes implies that the flavor quality of cocoa beans is determined principally by the genotype of the female parent.