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Open access

Roxana Myers, Andrea Kawabata, Alyssa Cho and Stuart T. Nakamoto

Kona coffee root-knot nematodes (Meloidogyne konaensis) cause severe declines in ‘Kona Typica’ arabica coffee (Coffea arabica) trees in Hawaii. Defoliation and destruction of the root system result in significant yield losses and can kill the host. Grafting with other coffee (Coffea) species that exhibit tolerance to kona coffee root-knot nematodes is a viable solution for mitigating damage in the field. An infested field was established in 2006 with ‘Kona Typica’ scions grafted on seven accessions of promising rootstock and nongrafted ‘Kona Typica’ as the control. Four grafted trees of each accession were planted per plot with four repetitions. Yield data were assessed for the 2016–17, 2017–18, and 2018–19 seasons. Three liberica coffee (Coffea liberica) accessions [‘Arnoldiana’ (‘Arnoldiana’ 1 and ‘Arnoldiana’ 2), ‘Dewevrei’, and ‘Fukunaga’ 1], demonstrated higher yields of coffee cherry compared with nongrafted ‘Kona Typica’ in the 2016–17 season. In the 2017–18 and 2018–19 seasons, five accessions of liberica and ‘Nemaya’ robusta coffee (Coffea canephora) exhibited higher cherry yields than ‘Kona Typica’. Plant vigor was greater in trees grafted on ‘Arnoldiana’ and ‘Fukunaga’ compared with other accessions and nongrafted ‘Kona Typica’, with taller trees, higher vertical branches, thicker trunk circumferences, and overall better health. After 13 years in the field, nongrafted ‘Kona Typica’ showed the highest mortality, with 81% of trees lost. Liberica rootstocks performed consistently well in the presence of kona coffee root-knot nematodes, with the healthiest trees, highest yields, and least mortality of the coffee species evaluated.

Open access

Wenjing Guan, Dean Haseman and Dennis Nowaskie

Grafting technology is increasingly being accepted in the United States, particularly for tomato (Solanum lycopersicum) production under protected structures. There is a great potential to expand this technology to other high tunnel crops. Using grafting technology in cucumber (Cucumis sativus) production is widely adopted in Asia to enhance cucumbers’ tolerance to low temperatures. But this technique is rarely used in the United States mainly because of the lack of information on the performance of the grafted plants under local production systems. Figleaf gourd (Cucurbita ficifolia), Cucurbita moschata, and squash interspecific hybrid (Cucurbita maxima × C. moschata) are the most used cucumber rootstocks worldwide. But their comparative performance was largely unknown for cucumber production in high tunnels in the Midwest United States. This study was therefore designed to compare the major types of cucumber rootstocks with the goal of identifying a rootstock with the maximized benefits for high tunnel cucumber production in the area. Nongrafted ‘Socrates’ and ‘Socrates’ grafted with Cucurbita moschata, squash interspecific hybrid, and figleaf gourd rootstocks were evaluated in high tunnels from March to June or July in 2016–19 at the Southwest Purdue Agricultural Center in Vincennes, IN. Transplant establishment, vine growth, and yield in early- and main-crop seasons were investigated. Grafted plants regardless of rootstocks ensured transplant survival even when the soil temperatures were dropped below 10 °C. Suboptimal soil conditions were encountered in the first month after transplanting. Grafted cucumbers with squash interspecific hybrid rootstock significantly increased vine growth from March to April and increased early-season yields (yield before 15 May) by 1.8 to 18.2 times compared with the early-season yields of the nongrafted cucumbers. The benefits provided by using grafting technology dismissed around middle May. Only squash interspecific hybrid rootstock improved cucumber yields in the entire production seasons. Cucumbers grafted with figleaf gourd rootstock had the lowest yield and the least plant growth after mid-May, indicating figleaf gourd rootstock may not be suitable for cucumber production under the current production system. Overall, squash interspecific hybrid was the most promising rootstock for early-season high tunnel cucumber production in the Midwest United States.

Open access

Andrés Mayorga-Gómez, Savithri U. Nambeesan, Timothy Coolong and Juan Carlos Díaz-Pérez

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.

Open access

Jacob H. Shreckhise, James S. Owen Jr., Matthew J. Eick, Alexander X. Niemiera, James E. Altland and Brian E. Jackson

Soilless substrates are routinely amended with dolomite and sulfate-based micronutrients to improve fertility, but the effect of these amendments on phosphorous (P) in substrate pore-water during containerized crop production is poorly understood. The objectives of this research were as follows: compare the effects of dolomite and sulfate-based micronutrient amendments on total P (TP), total dissolved P (TDP), orthophosphate P (OP), and particulate P (PP; TP − TDP) concentrations in pour-through extracts; to model saturated solid phases in substrate pore-water using Visual MINTEQ; and to assess the effects of dolomite and micronutrient amendments on growth and subsequent P uptake efficiency (PUE) of Lagerstroemia L. ‘Natchez’ (crape myrtle) potted in pine bark. Containerized crape myrtle were grown in a greenhouse for 93 days in a 100% pine bark substrate containing a polymer-coated 19N–2.6P–10.8K controlled-release fertilizer (CRF) and one of four substrate amendment treatments: no dolomite or micronutrients (control), 2.97 kg·m−3 dolomite (FL); 0.89 kg·m−3 micronutrients (FM); or both dolomite and micronutrients (FLM). Pour-through extracts were collected approximately weekly and fractioned to measure pore-water TP, TDP, and OP and to calculate PP. Particulate P concentrations in pour-through extracts were generally unaffected by amendments. Relative to the control, amending pine bark with FLM reduced water-extractable OP, TDP, and TP concentrations by ≈56%, had no effect on P uptake efficiency, and resulted in 34% higher total dry weight (TDW) of crape myrtle. The FM substrate had effects similar to those of FLM on plant TDW and PUE, and FM reduced pore-water OP, TDP, and TP concentrations by 32% to 36% compared with the control. Crape myrtle grown in FL had 28% lower TDW but pour-through OP, TDP, and TP concentrations were similar to those of the control. Chemical conditions in FLM were favorable for precipitation of manganese hydrogen phosphate (MnHPO4), which may have contributed to lower water-extractable P concentrations in this treatment. This research suggests that amending pine bark substrate with dolomite and a sulfate-based micronutrient fertilizer should be considered a best management practice for nursery crop production.

Open access

Qinglu Ying, Yun Kong and Youbin Zheng

To facilitate machine harvest for labor savings, the height of microgreens needs to reach ≈5 cm. Recent studies indicate that monochromatic blue light (B) can promote stem elongation similar to far-red light (FR). To examine whether nighttime B treatments can promote plant elongation without compromising yield and quality, mustard (Brassica juncea) and arugula (Eruca sativa) microgreens were grown under different light-emitting diode (LED) lighting regimes in a growth chamber. The 16-hour daytime lighting comprised 20% B and 80% red light (R), and had a total photosynthetic photon flux density (PPFD) of 300 µmol·m–2·s–1 at canopy level. During the 8-hour nighttime, the plants were exposed to the following treatments: 1) dark (D) as one control; 2) 4 hours of B at 40 µmol·m–2·s–1 followed by 4 hours of darkness (40B-D); 3) 4 hours of darkness followed by 4 hours of B at 40 µmol·m–2·s–1 (D-40B); 4) 8 hours of B at 20 µmol·m–2·s–1 (20B); 5) 8 hours of B + FR, and each of them at 20 µmol·m–2·s–1 (20B20FR); and 6) 8 hours of FR at 20 µmol·m–2·s–1 (20FR) as another control. The plants were harvested after 11 days of treatment. Nighttime B treatments (40B-D, D-40B, and 20B), compared with D, increased plant height by 34% and 18% for mustard and arugula, respectively, with no difference among the three B treatments. The combination of B and FR (20B20FR), compared with B alone, further increased plant height by 6% and 15% for mustard and arugula, respectively, and showed a similar promotion effect as 20FR. Plant height did not meet the machine harvest requirement for both species with the D treatment, but did so for mustard with the nighttime B treatments and for arugula with the 20B20FR treatment. There was no difference in biomass among all treatments except that 20B, compared with D, increased the fresh weight (FW) of arugula by 12%, showing a similar promotion effect as 20FR. Despite a greater promotion effect on elongation than B alone, 20FR reduced the leaf index compared with D. However, B alone or the 20B20FR treatment increased leaf thickness compared with D, and increased chlorophyll content index (CCI), leaf index, dry matter content, and leaf thickness to varying degree with species, compared with 20FR. Overall, nighttime B alone, or its combination with FR, promoted microgreen elongation without compromising yield and quality.

Open access

Job Teixeira de Oliveira, Rubens Alves de Oliveira, Fernando França da Cunha, Isabela da Silva Ribeiro, Lucas Allan Almeida Oliveira and Paulo Eduardo Teodoro

The objective of this work was to investigate the direct and indirect relationships of morphological variables on garlic bulb yield. The primary components of garlic bulb yield, including clove mass, number of cloves per bulb, and bulb diameter and bulb length, are the variables that affect garlic bulb yield directly. Leaf length and growth of a secondary bulb had a negative correlation to garlic bulb yield. Growth of a secondary bulb also had a negative correlation with the number of cloves per bulb and root dry mass. Irrigation with the deficit, applied at the stage of bulb formation, had a positive correlation with garlic yield and a slightly negative correlation with total plant mass, bulb length, and secondary bulb growth.

Open access

Nan Tang, Xiuting Ju, Yafan Hu, Rulong Jia and Daocheng Tang

Scale propagation is a cost-effective and time-saving reproduction method for lily bulb production. The effects of different incubation temperatures and plant growth regulators on the scale propagation of Lilium davidii var. unicolor were investigated. The results showed that temperature influences the scale rot incidence rate, speed of scale differentiation and bulblet formation, as well as the size of bulblets. The optimum temperature for scale propagation of L. davidii var. unicolor was 30 °C. Scales incubated at 30 °C showed a lower rot incidence and faster differentiation and produced larger bulblets. The application of gibberellic acid (GA3), 1-naphthaleneacetic acid (NAA), and 6-benzylaminopurine (6-BA) had no significant influence on the differentiation rate of scales. GA3 application reduced the incidence rate of scale rot. However, treatment with 50 mg/L NAA and 2 mg/L 6-BA significantly increased the rot incidence rate in the second week of propagation. Both treatments with 100 mg/L NAA and 100 mg/L GA3 produced a higher number of bulblets than their controls after 6 weeks of incubation. GA3 at 100 and 150 mg/L increased the diameter of bulblets, resulting in more large bulblets (grade 1) and fewer small bulblets (grade 3). 6-BA did not facilitate propagation by scaling.

Open access

Youping Sun, Liqin Li, Yuxiang Wang and Xin Dai

Spirea (Spiraea sp.) plants are popular landscape plants in Utah and the Intermountain West United States. Spiraea betulifolia, S. japonica, S. media, S. nipponica, and S. thunbergii were evaluated for salinity tolerance in a greenhouse experiment. Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution at an EC of 3.0 or 6.0 dS·m−1 for 8 weeks. At the end of the experiment, all spirea plants survived and retained good visual quality, with average visual scores greater than 4 (0 = dead, 5 = excellent) when irrigated with saline solution at an EC of 3.0 dS·m−1, with the exception of S. thunbergii, which showed slight foliar salt damage and an average visual score of 3.8. When irrigated with saline solution at an EC of 6.0 dS·m−1, all S. thunbergii plants died, S. media exhibited severe foliar salt damage and an average visual score of 1.5, and S. betulifolia, S. japonica, and S. nipponica displayed slight-to-moderate foliar salt damage and average visual scores greater than 3. Regardless of spirea species, shoot dry weight decreased by 20% and 48% when irrigated with saline solution at ECs of 3.0 and 6.0 dS·m−1, respectively, compared with the control. Saline solution at an EC of 3.0 dS·m−1 did not affect net photosynthesis (Pn) of all spirea species except S. nipponica, but saline solution at an EC of 6.0 dS·m−1 decreased the Pn of all species by 36% to 60%. There were 37, 7, 36, 21, and 104 times more sodium (Na+) concentrations in leaf and 29, 28, 28, 13, and 69 times more chloride (Cl) concentrations in leaf than in the control when S. betulifolia, S. japonica, S. media, S. nipponica, and S. thunbergii were irrigated with saline solution at an EC of 6.0 dS·m−1. Correlation analyses indicated that foliar salt damage and reduced plant growth and photosynthesis were induced mainly by Cl ions accumulated in the spirea leaves. S. thunbergii was the most sensitive species; it had high mortality and low visual quality at both salinity levels. Spiraea japonica, S. nipponica, and S. betulifolia were relatively more tolerant and had good visual quality at elevated salinity compared with S. media and S. thunbergii. These research results are valuable for growers and landscape professionals during plant selection for nursery production using low-quality water and landscapes in salt-prone areas.

Open access

Jehanzeb Khan, Yubin Yang, Qiang Fu, Weiqiang Shao, Jianke Wang, Li Shen, Yan Huai, Guy Kateta Malangisha, Abid Ali, Ahmed Mahmoud, Yi Lin, Yongyuan Ren, Jinghua Yang, Zhongyuan Hu and Mingfang Zhang

Watermelon (Citrullus lanatus) is an important horticultural crop that is sensitive to heavy metals such as lead (Pb) in polluted water or soil. However, there are no available data regarding Pb tolerance phenotyping in watermelon. Watermelon seedlings were exposed to various Pb doses (0, 20, 40, 60, 80 µm·L–1 Pb) for 14 days, after which 20 µm Pb was identified as the optimal treatment for lead tolerance analysis in watermelon because it caused significant symptoms (leaf chlorosis, stubby and yellow roots) but little damage to seedlings. Subsequently, the Pb responses were analyzed in eight watermelon varieties (V1–V8), and membership function analysis was used to determine a single Pb tolerance index. Of the eight watermelon varieties, V4 and V7 were ranked the most Pb tolerant; V1, V2, V5, and V6 were moderately Pb tolerant; and V3 and V8 were the most Pb-sensitive varieties. Compared with most Pb-sensitive varieties (V3 and V8), the most Pb-tolerant varieties (V4 and V7) maintained high antioxidant activity, and had lower malondialdehyde (MDA) and total soluble protein (TSP) contents. In addition, carotenoid and chlorophyll (both a and b) contents were stimulated and inhibited, respectively, in leaves of high-Pb translocation varieties (V4 and V8). Principal component analysis (PCA) revealed relative root length as an indicator of Pb tolerance because it correlated significantly with shoot growth. These results provide useful insight into the mechanism of Pb tolerance in cucurbit crops, as well as information regarding the breeding of watermelon with enhanced tolerance to this heavy metal (Pb).

Open access

Zhanao Deng, Sandra B. Wilson, Xiaobao Ying, Chunxian Chen, Rosanna Freyre, Victor Zayas and David M. Czarnecki II