Yiping Zou, Qingguang Li, Donglin Zhang, Youwang Liang, Mingzhuo Hao, and Yujie Yang
David G. Tork, Neil O. Anderson, Donald L. Wyse, and Kevin J. Betts
The genus Linum L. contains ≈200 primarily blue-flowered species, including several ornamentals, yet no reports exist regarding the cut flower potential of this genus. The objective of this study was to evaluate the cut flower potential of perennial flax cultivars (L. perenne L. ‘Blue Flax’ and ‘Sapphire’; Expt. 1, 2018) and accessions (L. austriacum L., L. lewisii Pursh., and L. perenne; Expt. 2, 2019), and record traits that will enable breeding and selection for improved cut flower performance. The mean vase life across both cultivars in Expt. 1 was 9.2 days. In Expt. 2, L. perenne had the longest average vase life (9.3 days), followed by L. austriacum (9.1 days) and L. lewisii (8.3 days). The floral preservative (Floralife 300) significantly increased vase life by an average of 1.7 days in Expt. 1, and 1.6 days in Expt. 2, and resulted in a significantly greater number of flowers (≈2x) in both experiments. Significant variation was observed among genotypes for most traits, including vase life (6.2 to 11.3 days) and number of flowers (1.3 to 10.5), highlighting the opportunities for improving the potential of cut flower perennial flax through breeding.
Shing-Shan Tsai and Yao-Chien Alex Chang
In the commercial production of phalaenopsis orchids, the cultivation time after deflasking is used to describe the plant age and maturity. Carbon-to-nitrogen (C/N) ratio is often used as an indicator of plant growth and flowering potential. High C/N ratios are considered to promote reproductive growth, and low C/N ratios are associated with the early vegetative growth or even inhibiting flowering. This study investigated how plant age and maturity affected flowering ability and flower quality of phalaenopsis and their relationship to C/N ratio. The plant materials of various ages were the purple, small-flowered Phalaenopsis Sogo Lotte ‘F2510’ and white, large-flowered P. Sogo Yukidian ‘V3’, which were 2 to 7 months and 10 to 20 months after deflasking, respectively. Plants were placed under 25/20 °C for 4 months to force flowering and investigate the flowering-related parameters. The leaf C/N ratio of both varieties increased in general with the increase of plant age. The spiking (flower-stalk emergence) rate of P. Sogo Lotte ‘F2510’ 2 months after deflasking was only 42%, which indicates that these plants were not completely out of their juvenile phase, whereas that of those 3 to 7 months after deflasking was 100%, indicating that plants had acquired full flowering ability. No linear correlation was found between the C/N ratio and days to spiking, to first visible bud, to first flower open, and to 90% flower opening in the white, large-flowered P. Sogo Yukidian ‘V3’. However, there was a positive correlation between the C/N ratio and inflorescence length, flower-stalk diameter, first flower diameter, and flower count. Thus, the C/N ratio is feasible to be used as an indicator for assessing the flowering quality in phalaenopsis.
Ed Stover, Stephen Mayo, Randall Driggers, and Robert C. Adair Jr.
The U.S. Department of Agriculture citrus scion breeding program is urgently working on developing huanglongbing (HLB; pathogen Candidatus Liberibacter asiaticus)-tolerant cultivars with excellent fruit quality and productivity when HLB-affected. The slow process of assessing new citrus hybrids is a major impediment to delivery of these much-needed cultivars. We generate thousands of hybrids each year, germinate the seedlings, grow them for 2 years in the greenhouse, plant them at high density in a field where the disease HLB is abundant, grow them for 5 to 10 years, and make selections based on tree performance and fruit quality of these HLB-affected trees. Based on promising reports of accelerated citrus growth when grown in a metallized reflective mulch (MRM) system, we tested the hypothesis that the MRM system may accelerate growth and selection of new hybrid seedlings compared with conventional soil culture (CSC). In the MRM system, tree rows are covered with a layer of metallized plastic film and drip irrigation is installed beneath the plastic. In 2 years of analysis, tree canopy volume was significantly greater with MRM in 2020 (27% greater than CSC) but not in 2021, and MRM tree height was greater in 2021 (7% greater than CSC). Mortality was significantly greater with MRM in both 2020 and 2021(in 2021: 32% vs. 17% under CSC), and MRM trees had more chlorotic leaves. Because of staff limitations, plant debris and soil were not routinely cleared from MRM, thus diminishing any benefit from the reflective surface. Better maintenance might have resulted in more sustained evidence of MRM growth benefits. With the current resource availability, the MRM system does not appear to accelerate the assessment of hybrid seedling trees.
Jianlin Wei, Shutian Li, Ping He, Xinpeng Xu, Deshui Tan, Yan Li, Guosheng Li, Yuesheng Guo, and Rongzong Cui
Accurate estimation of the nutrient requirements of Chinese onion is essential to increase its nutrient utilization efficiency and yield. In this study, the yield and nutrient uptake data were collected from major Chinese onion growing regions during 2001 to 2018, and the relationship between Chinese onion yield and nutrient uptake was evaluated using the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model. The QUEFTS model predicted the linear-parabolic platform curve of the balanced nutrient uptake of Chinese onion and estimated the demand of nitrogen (N), phosphorus (P), and potassium (K) for the potential target yields ranging from 40 t/ha to 120 t/ha. The nutrients required for the target yield increased linearly before reaching 60% to 70% of the potential yield. Nutrient requirements for producing 1 t of Chinese onion were 1.91 kg N–0.28 kg P–1.71 kg K. The corresponding nutrient internal efficiency (IE, yield per unit nutrient uptake) was 524.6 kg/kg, 3585.7 kg/kg, and 584.3 kg/kg for N, P and K, respectively. Subsequently, a nutrition decision-making software, Nutrient Expert (NE), for the Chinese onion was developed based on the improved QUEFTS model. Field verification studies for NE fertilizer recommendation were conducted in multiple Chinese onion growing plots for 2 consecutive years. Results showed that the QUEFTS model can be used to accurately estimate the nutrient requirements for Chinese onion within a defined range of target yield.
Thomas E. Marler and Gil N. Cruz
Knowledge about the position of tree roots is needed to understand tree biology and inform management decisions. Cycad species produce pachycaul stems and are not represented in the published studies on the relationships between aboveground tree traits and root system spread. We measured the radius of root egress from 6-year-old Cycas edentata de Laub., Cycas micronesica K.D. Hill, and Cycas nitida K.D. Hill & A. Lindstrom plants in an ex situ cycad germplasm collection into an 8-m-wide buffer zone in which no trees were growing. We then determined the relationships of root system radius to aboveground plant traits. The root system radius extended 5.2 to 7.5 m from the base of the stems, and was 3.5 times the plant height, 32 to 36 times the stem diameter, and 3.6 to 4.2 times the radius of the canopy dripline. Values for root radius in relation to plant height and canopy radius exceeded published data for leptocaul tree species, but values for stem diameter were less than these data. These findings on the location of cycad roots provide adaptive management cycad knowledge to inform horticulture decisions such as avoidance of roots during soil disturbance and placement of fertilizers and systemic pesticides.
Justin Scheiner, Larry Stein, John R. Clark, James N. Moore, Margaret Worthington, and James Kamas
Yaxin Zhao, Xuetao Ma, Haiying Li, Yuxin Chen, Sijie Wang, Juan Zhou, and Yan Ao
Achala N. KC, Ann L. Rasmussen, and Joseph B. DeShields
Sprayable formulation of 1-methylcyclopropene (1-MCP) was tested as a preharvest application on European pears to determine the best timing and rate of 1-MCP application for maintaining fruit firmness and quality of trees during harvest and in storage after harvest. Two rates of 1-MCP, 0.06 and 0.13 g⋅L−1 active ingredient (a.i.) (minimum and maximum rates, respectively), were sprayed 1 week and 2 weeks before commercial harvest on two cultivars, Bosc and Comice, in 2017 and 2018. After 2 months in cold storage (0 ± 1 °C), differences in fruit firmness of both cultivars were observed among treatments. For ‘Bosc’, fruit treated with both rates 1 week before harvest were 50% firmer than nontreated control fruit. For ‘Comice’, fruit treated with the maximum rate both 2 weeks and 1 week before commercial harvest were 46% and 31% firmer than nontreated control fruit, respectively. However, after 4 months in storage, no differences in fruit firmness of both ‘Bosc’ and ‘Comice’ were observed among treatments. The sprayable 1-MCP application applied 2 weeks before commercial harvest also affected the fruit firmness on trees. The maximum rate of 1-MCP treatment consistently maintained the fruit firmness by 5.0 N compared with fruit treated with the minimum rate and nontreated controls. This effect was significant until 1 week after commercial harvest for both cultivars and until 2 weeks after commercial harvest for ‘Bosc’. The poststorage fruit firmness and overall eating quality of ‘Bosc’ were unaffected by the maximum rate of 1-MCP application as well as the extended harvest time. However, for ‘Comice’, the overall eating quality was negatively impacted by 1-MCP treatments. This study suggests that the maximum rate (0.13 g⋅L−1 a.i.) of 1-MCP application 2 weeks before commercial harvest maintains the fruit firmness of ‘Bosc’ for at least 2 weeks more and offers an extended harvest window for better preharvest management. Furthermore, this treatment improves the physiological fruit quality such as senescence scald during the poststorage period without significantly affecting the poststorage ripening of ‘Bosc’ after 4 months of storage.
Camila M.L. Alves, Hsueh-Yuan Chang, Cindy B.S. Tong, Charlie L. Rohwer, Loren Avalos, and Zata M. Vickers
Shading has been used to produce high-quality lettuce (Lactuca sativa) in locations where production conditions are not optimal for this cool-season crop. To learn what additional benefits shading provides if heat-tolerant cultivars are used and to understand the effects of shading on growth, sensory quality, chemical content, and transcriptome profile on heat-tolerant lettuce, we grew two romaine lettuce cultivars with and without shading using 50% black shadecloth in 2018 and 2019. Shading reduced plant leaf temperatures, lettuce head fresh weights, glucose and total sugars content, and sweetness, but not bitterness, whereas it increased lettuce chlorophyll b content compared with unshaded controls. Transcriptome analyses identified genes predominantly involved in chlorophyll biosynthesis, photosynthesis, and carbohydrate metabolism as upregulated in unshaded controls compared with shaded treatments. For the tested cultivars, which were bred to withstand high growing temperatures, it may be preferable to grow them under unshaded conditions to avoid increased infrastructure costs and obtain lettuce deemed sweeter than if shaded.