Bell peppers (Capsicum annuum L.) are ranked eighth in value for vegetable production in the United States (USDA-NASS, 2019). Due to the high value of bell peppers, disorders such as blossom-end rot (BER) can cause significant losses in yield by up to 35% for growers. BER is the symptom of a calcium (Ca2+) deficiency that may occur during periods of cell expansion when the supply of Ca2+ may be lower than demand. In this study, we determined the temporal patterns of the fruit Ca2+concentration ([Ca2+]) and accumulation in three separate studies under field and greenhouse conditions. In the three experiments, [Ca2+] during fruit development showed varied patterns: it remained constant, decreased transiently during the cell expansion phase, or displayed a more gradual sustained decrease. However, in the three experiments, fruit Ca2+ accumulation increased during development as fruit size increased. In two experiments, the distal part of the fruit had lower [Ca2+] than the proximal end. However, there was no correlation between [Ca2+] in various fruit sections with BER incidence. Seeds and placental tissue had increased [Ca2+] and several other macro- and micronutrients; this spatial distribution of Ca2+ coupled with subcellular Ca2+ distribution should be explored in future studies. The temporal pattern of Ca2+ accumulation in this study suggests that fruit Ca2+ uptake continues throughout fruit development. Therefore, Ca2+ application during bloom and early fruit development may prevent or minimize Ca2+ deficiency disorders in bell pepper.
Andrés Mayorga-Gómez, Savithri U. Nambeesan, Timothy Coolong and Juan Carlos Díaz-Pérez
Juan Carlos Díaz-Pérez, Kelly St. John, Mohammad Yamin Kabir, J. Alberto Alvarado-Chávez, Ania M. Cutiño-Jiménez, Jesús Bautista, Gunawati Gunawan and Savithri U. Nambeesan
Colored shade nets may affect plant growth and fruit yield of horticultural crops. The understanding of how colored shade nets influence plants, however, is far from complete. The objective of this study was to determine the effects of colored shade nets on bell pepper fruit yield, postharvest transpiration, color, chemical composition, and antioxidant capacity. The experiment was conducted in Tifton, GA, during the spring of 2015 and 2016. The experimental design was a randomized complete block with four replications and five colored shade net treatments (black, red, silver, and white nets, and an unshaded control). The nets were placed on the top of wooden rectangular structures (15 m wide × 6 m long × 5 m high), leaving the sides of the structures uncovered. Results showed that in both 2015 and 2016, marketable and total fruit number, yield, and individual fruit weight were reduced under the unshaded treatment. There were inconsistent differences in marketable and total fruit number, yield, and individual fruit weight among colored shade nets. Postharvest fruit transpiration and skin permeance were also reduced in unshaded conditions, and no differences were found among colored shade nets. Fruit color L* and b* values were highest, and a* value was lowest in unshaded conditions. Fruit soluble solids, total phenols, flavonoids, and antioxidant capacity [Cupric Reducing Antioxidant Capacity (CUPRAC) and Trolox Equivalent Antioxidant Capacity (TEAC)] responded differently among colored shade nets in the 2 years. Total phenols, flavonoids, and TEAC, however, were among the highest in unshaded conditions. In conclusion, results of the present study support previous findings that shade nets increase fruit yield and quality in bell pepper compared with fruit produced in unshaded conditions. Nevertheless, there were no consistent differences in fruit total and marketable yield and postharvest fruit transpiration and chemical composition of fruit produced under colored shade nets.