Deciphering structural and temporal interplays during the architectural development of mango trees.

Plant architecture is commonly defined by the adjacency of organs within the structure and their properties. Few studies consider the effect of endogenous temporal factors, namely phenological factors, on the establishment of plant architecture. This study hypothesized that, in addition to the effect of environmental factors, the observed plant architecture results from both endogenous structural and temporal components, and their interplays. Mango tree, which is characterized by strong phenological asynchronisms within and between trees and by repeated vegetative and reproductive flushes during a growing cycle, was chosen as a plant model. During two consecutive growing cycles, this study described vegetative and reproductive development of 20 trees submitted to the same environmental conditions. Four mango cultivars were considered to assess possible cultivar-specific patterns. Integrative vegetative and reproductive development models incorporating generalized linear models as components were built. These models described the occurrence, intensity, and timing of vegetative and reproductive development at the growth unit scale. This study showed significant interplays between structural and temporal components of plant architectural development at two temporal scales. Within a growing cycle, earliness of bud burst was highly and positively related to earliness of vegetative development and flowering. Between growing cycles, flowering growth units delayed vegetative development compared to growth units that did not flower. These interplays explained how vegetative and reproductive phenological asynchronisms within and between trees were generated and maintained. It is suggested that causation networks involving structural and temporal components may give rise to contrasted tree architectures.

Differential effects of low and high temperature stress on pollen germination and tube length of mango (Mangifera indica L.) genotypes.

Mango flowering is highly sensitive to temperature changes. In this research, the maximum values of pollen germination rate (PGR), pollen tube length (PTL) and their cardinal temperatures (Tmin, Topt and Tmax) were estimated by using quadratic equation and modified bilinear model under the conditions of 14-36 °C. The pollen germination rate in four mango varieties ranged from 29.1% ('Apple mango') to 35.5% ('Renong No. 1'); the length of pollen tube ranged from 51.2 µm ('Deshehari') to 56.6 µm ('Jinhuang'). The cardinal temperatures ranges (Tmin, Topt and Tmax) of pollen germination were 20.3-22.8 °C, 26.7-30.6 °C and 30.4-34.3 °C, respectively; similarly, cardinal temperatures (Tmin, Topt and Tmax) of pollen tube growth were 20.3-21.2 °C, 27.9-32.1 °C and 30.2-34.4 °C respectively. Of those, 'Renong No. 1' could maintain relatively high pollen germination rate even at 30 °C, however, 'Deshehari' had the narrowest adaptive temperature range. These results were further confirmed by changes of superoxide dismutase, catalase activity and malondialdehyde content. These results showed that mango flowering was highly sensitive to temperature changes and there were significant differences in pollen germination rate and pollen tube length among different varieties. Current research results were of great significance for the introduction of new mango varieties in different ecological regions, the cultivation and management of mango at the flowering stage and the breeding of new mango varieties.

Low cuticle deposition rate in 'Apple' mango increases elastic strain, weakens the cuticle and increases russet.

Russeting compromises appearance and downgrades the market value of many fruitcrops, including of the mango cv. 'Apple'. The objective was to identify the mechanistic basis of 'Apple' mango's high susceptibility to russeting. We focused on fruit growth, cuticle deposition, stress/strain relaxation analysis and the mechanical properties of the cuticle. The non-susceptible mango cv. 'Tommy Atkins' served for comparison. Compared with 'Tommy Atkins', fruit of 'Apple' had a lower mass, a smaller surface area and a lower growth rate. There were little differences between the epidermal and hypodermal cells of 'Apple' and 'Tommy Atkins' including cell size, cell orientation and cell number. Lenticel density decreased during development, being lower in 'Apple' than in 'Tommy Atkins'. The mean lenticel area increased during development but was consistently greater in 'Apple' than in 'Tommy Atkins'. The deposition rate of the cuticular membrane was initially rapid but later slowed till it matched the area expansion rate, thereafter mass per unit area was effectively constant. The cuticle of 'Apple' is thinner than that of 'Tommy Atkins'. Cumulative strain increased sigmoidally with fruit growth. Strains released stepwise on excision and isolation (εexc+iso), and on wax extraction (εextr) were higher in 'Apple' than in 'Tommy Atkins'. Membrane stiffness increased during development being consistently lower in 'Apple' than in 'Tommy Atkins'. Membrane fracture force (Fmax) was low and constant in developing 'Apple' but increased in 'Tommy Atkin'. Membrane strain at fracture (εmax) decreased linearly during development but was lower in 'Apple' than in 'Tommy Atkins'. Frequency of membrane failure associated with lenticels increased during development and was consistently higher in 'Apple' than in 'Tommy Atkins'. The lower rate of cuticular deposition, the higher strain releases on excision, isolation and wax extraction and the weaker cuticle account for the high russet susceptibility of 'Apple' mango.

Molecular docking studies and anti-enzymatic activities of Thai mango seed kernel extract against snake venoms.

The ethanolic extract from seed kernels of Thai mango (MSKE) (Mangifera indica L. cv. 'Fahlun') (Anacardiaceae) and its major phenolic principle (pentagalloyl glucopyranose) exhibited dose-dependent inhibitory effects on enzymatic activities of phospholipase A(2) (PLA(2)), hyaluronidase and L-amino acid oxidase (LAAO) of Calloselasma rhodostoma (CR) and Naja naja kaouthia (NK)venoms by in vitro tests. The anti-hemorrhagic and anti-dermonecrotic activities of MSKE against both venoms were clearly supported by in vivo tests. Molecular docking studies indicated that the phenolic molecules of the MSKE could selectively bind to the active sites or their proximity, or modify conserved residues that are critical for the catalysis of PLA(2), and selectively bind to the LAAO binding pocket of both CR and NK venoms and thereby inhibit their enzymatic activities. The results imply a potential use of MSKE against snake venoms.

Hydraulic and mechanical stem properties affect leaf-stem allometry in mango cultivars.

Leaf size-stem size allometric relationships are important features of biomass allocation in plants and are affected by biological functions linking the two organs. They have been studied at specific and supraspecific levels, but not at the infraspecific level. It was hypothesized that allometric relationships link leaf size and stem size at the cultivar level, and are cultivar-specific in relation to distinctive functional stem traits: hydraulic conductivity and mechanical strength. Allometric relationships between leaf size and stem size were established for 3 yr, using the standardized major axis method, on current-year branches, composed of one to 16 growth units, for four mango (Mangifera indica) cultivars characterized by contrasting growth habits. The hydraulic and mechanical stem properties of these cultivars were also measured. The slopes of the relationships were similar among cultivars, but not the y-intercepts. Different y-intercepts in the stem mass vs branch cross-sectional area relationship and in the leaf mass vs stem mass relationship were related to mechanical and to hydraulic stem properties, respectively. These results showed that leaf-stem allometry in mango cultivars was shaped by hydraulic and mechanical stem properties, supporting a functional interpretation of the relationship between leaf and stem dimensions.

Effect of Resin Ducts and Sap Content on Infestation and Development of Immature Stages of Anastrepha obliqua and Anastrepha ludens (Diptera: Tephritidae) in Four Mango (Sapindales: Anacardiaceae) Cultivars.

We determined the influence of resin ducts, sap content, and fruit physicochemical features of four mango cultivars (Criollo, Manila, Ataulfo, and Tommy Atkins) on their susceptibility to the attack of the two most pestiferous fruit fly species infesting mangoes in Mexico: Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart). We performed three studies: 1) analysis of resin ducts in mango fruit exocarp to determine the density and area occupied by resin ducts in each mango cultivar, 2) assessment of mango physicochemical features including fruit sap content, and 3) a forced infestation trial under field conditions using enclosed fruit-bearing branches to expose mangoes to gravid A. ludens or A. obliqua females. Infestation rates, development time from egg to prepupae and pupae, pupal weight, and percent of adult emergence, were assessed. 'Ataulfo' and 'Tommy Atkins' cultivars exhibited the highest resin duct density and sap content, the lowest infestation rate, and had a negative effect on immature development and pupal weight. In sharp contrast, 'Manila' and 'Criollo' cultivars, with the lowest resin duct density and sap content, were highly susceptible to A. ludens and A. obliqua attack. We conclude that sap content and the number, size, and distribution of resin ducts as well as firmness in mango fruit exocarp are all involved in the resistance of mango to A. ludens and A. obliqua attack.

Analysis of diversity among six populations of Colombian mango (Mangifera indica L. cvar. Hilacha) using RAPDs markers

Currently in Colombia, there are only records of morph-agronomic characterizations of Mangifera indica cvar. Hilacha; molecular studies on this mango variety have not been carried out. The aim of this work was to identify the genetic diversity of six populations of mango Hilacha by RAPDs markers, as a fundamental base for breeding programs, conservation and selection of promissory materials for the fruit industry at the national level. From 60 primers evaluated in the populations, five primers were selected and were launched in the six populations. Polymorphic bands of RAPDs were transformed into binary matrices, which were then processed with NTSYS-PC, POPGENE and TFPGA softwares. The overall genetic diversity, H T = 0.468 +/- 0.0016, is very similar to the average subpopulation genetic diversity, H S = 0.4431 +/- 0.0024, which revealed a small genetic differentiation among the mango Hilacha populations studied (G ST = 0.0532). This means that each population contained in average 95 percent of the total genetic diversity found in the global population analyzed. Considerable gene flow between populations (Nm = 9) was found. Finally, we recommend studying the genetic diversity of mango Hilacha populations with other molecular markers to complement the information obtained and to find similarities or differences with the results presented herein.