Experiments were conducted to assess the impact of crown architecture on light availability beneath the trees, flowering, fruiting, yield and quality of jamun (Syzygium cumini [L.] Skeels). Trees were maintained as control, palmette and open centre crown. Impact was evaluated for three consecutive years, i.e. 2017–2019. Diffuse light beneath the trees ranged from 69.7 ± 2.22 to 45.9 ± 1.45%, whereas direct light varied from 30.4 ± 0.97 to 54.1 ± 1.78%. At flowering and fruit development stage (June), photosynthesis rate (A) in control trees was 12.5 ± 0.43 μmol CO2/m2/s; however, at fruit maturity and dormancy (August), it was only 9.5 ± 0.35 μmol CO2/m2/s. Similarly, in palmette and open centre trees, photosynthesis rate at flowering and fruit development stage was 13.5 ± 0.46 and 15.7 ± 0.54 μmol CO2/m2/s, respectively; whereas at fruit maturity and dormancy, photosynthesis rate dropped to 10.5 ± 0.39 and 11.7 ± 0.43 μmol CO2/m2/s, respectively. Substantial variation in stomatal conductance (gs), vapour pressure deficit (VPD) and transpiration rate (E) was also found. Days to start flowering ranged from 92 ± 0.33 to 98 ± 0.33. Similarly, days to end flowering varied from 99 ± 0.07 to 107 ± 0.36, days to fruit set 132 ± 0.33 to 139 ± 0.33 and days to fruit maturity 176 ± 0.48 to 184 ± 0.63. Significant variation in fruit length, fruit width and fruit weight was also found. Total soluble solids in fruit pulp varied from 9.0 ± 0.15 to 12.2 ± 0.149°Brix and fruit yield 62.3 ± 1.5 to 86.7 ± 1.33 kg per tree. Noteworthy variation in fruit quality traits was also recorded. This study illustrates that crown architecture has considerable impact on gas exchange parameters, flowering, fruiting, yield and quality of jamun.

Fifty morphological characteristics, fruit production over 3 years (from 1999 to 2002) and the amplified fragment length polymorphism (AFLP) technique were used to analyse a set of 48 guava (Psidium guajava L.) accessions cultivated in Mexico, in order to characterize their genetic relationships. Germplasm was collected from the Calvillo-Cañones region and planted in Huanusco, Mexico. The study included two P. cattleianum (Sabine) and two P. friedrichsthalianum (Berg-Niedenzu) accessions from Costa Rica as outgroups. Principal component analysis (PCA) explained less than 30% of total variation and 14 characteristics from trees (1), leaves (2) and fruits (11) were the most informative. PCA analysis separated the germplasm into three major groups of accessions based on fruit size and weight, stem diameter and leaf size. Significant differences in fruit yield were detected among accessions and years, where P. guajava produced 36 kg/year/tree of fresh fruit while P. cattleianum and P. friedrichsthalianum showed fruit yield lower than 7 kg/year/tree. The fruit yield broad sense heritability was 0.25. The AFLP analysis produced two clusters of Psidium accessions, the first included P. cattleianum and P. friedrichsthalianum, and the second P. guajava accessions. This is the first report about the use of AFLP marker methodology for the genetic characterization of Mexican native guava germplasm and the results based on phenotypic and productive characteristics suggest that germplasm was selected from open pollinated trees.