Little has been done with respect to breeding for salt-tolerant cowpea (Vigna unguiculata) cultivars despite of salt stress being a growing threat to cowpea production. Seedling stage is one the most susceptible stages to salt stress in cowpea. Establishing a streamlined methodology for rapidly screening a large number of genotypes will significantly contribute toward enhancing cowpea breeding for salt tolerance. Therefore, the objective of this study was to establish and validate a simple approach for salt tolerance evaluation in cowpea seedlings. A total of 30 genotypes including two controls (PI582468, a salt-tolerant genotype, and PI255774, a salt-sensitive genotype) were greenhouse-grown under 0 mm and 200 mm NaCl. A total of 14 above-ground traits were evaluated. Results revealed: (1) significant differences were observed in average number of dead plants per pot, leaf injury scores, relative salt tolerance (RST) for chlorophyll, plant height, and leaf and stem biomass among the 30 genotypes; (2) all PI255774 plants were completely dead, whereas those of PI582438 were fully green after 2 weeks of salt stress, which validated this methodology; (3) RST for chlorophyll content was highly correlated with number of dead plants and leaf injury scores; (4) RST for leaf biomass was moderately correlated with number of dead plants and leaf injury scores; and (5) RST in plant height was poorly correlated with number of dead plants and leaf injury scores Therefore, less number of dead plants per pot, high chlorophyll content, and less leaf injury scores were good criteria for salt tolerance evaluation in cowpea. This study provided a simple methodology and suggested straightforward criteria to evaluate salt tolerance at seedling stage in cowpea.
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Waltram Ravelombola, Jun Qin, Yuejin Weng, Beiquan Mou and Ainong Shi
Wei-Ling Chen and Hsueh-Shih Lin
Kimberly Moore, Charles Wajsbrot, Cristina Burgart and Luci Fisher
Because salts in irrigation water decrease plant growth, we wanted to develop a quick and easy method for evaluating salt tolerance that could be used in the greenhouse. Using plastic containers with lids, sea salt, and rooted cuttings, we monitored changes in plant quality, growth, and leaf water potential as electrical conductivity (EC) and sodium (Na) levels increased. In the first of two experiments, we compared sea hibiscus (Hibiscus tilliaceus) leaf water potential and plant quality in solutions with an EC of 0, 2.1, 4.2, 6.1, or 8.2 dS·m−1 (0, 240, 420, 610, or 1010 mg·L−1 Na). After 14 days, sea hibiscus quality in solutions with an EC of 6.1 or 8.2 dS·m−1 was less than plants in solutions of 0, 2.1, or 4.2 dS·m−1. There was no difference in quality among plants in 0, 2.1, or 4.2 dS·m−1 solutions. To test this method, in Expt. 2, we compared coleus (Coleus ×hybridus), copperleaf (Acalypha wilkesiana), ficus (Ficus benjamina), jasmine (Jasminium multiflorum), and plumbago (Plumbago auriculata) plant quality and growth in solutions with an EC of 0, 1.3, 2.1, 4.2, 5.6, or 6.1 dS·m−1 (0, 170, 240, 420, 520, or 610 mg·L−1 Na). Coleus quality declined at an EC greater than 1.3 dS·m−1, whereas jasmine and plumbago quality declined at an EC greater than 2.1 dS·m−1 Copperleaf and ficus declined at an EC greater than 4.2 dS·m−1. Plant response did vary with low to medium salt-tolerant plants tolerating at an EC up to 1.3 and 170 mg·L−1 Na, whereas plants with a greater salt tolerance tolerated at EC and Na values up to 4.2 dS·m−1 and 420 mg·m−1 Na, respectively. The use of this method benefits growers by determining upper EC and Na limits when faced with poor-quality water resulting from saltwater intrusion or when using reclaimed wastewater with greater EC and Na levels.
Noa K. Lincoln, Theodore Radovich, Kahealani Acosta, Eli Isele and Alyssa Cho
Breadfruit (Artocarpus altilis) cultivation is gaining momentum throughout the tropics due to its high yield and nutritious fruit. One impediment to expanding production of breadfruit is the lack of agronomic research related to production management. We examined foliar nutrient concentrations of different leaf positions and leaf parts to assess within- and between-tree variance to inform an effective sampling protocol. We further validated the sampling protocol on 595 trees at 87 sites that were assessed for yield and productivity. Foliar nutrients differed significantly by categories of productivity. For the first time, breadfruit-specific standards of foliar nutrient concentrations are presented for consideration. In conclusion, we recommend that foliar sampling use petioles harvested from leaves in the third position from the branch tip using sun-exposed leaves in the midcanopy of each tree.
Fekadu Fufa Dinssa, Peter Hanson, Dolores R. Ledesma, Ruth Minja, Omary Mbwambo, Mansuet Severine Tilya and Tsvetelina Stoilova
Amaranth (Amaranthus sp.) is an important leafy vegetable in Africa where most farmers grow unimproved landraces. Information about amaranth genetic diversity and its adaptation to different environments will help breeders develop improved commercial varieties that meet market requirements. The objectives of this study were to investigate the performances of amaranth entries for vegetable yield across locations and seasons, assess the relative contributions of genetic vs. environmental sources of variation to yield, and cluster locations into mega-environments (MEs) to suggest future test sites. Twenty-six diverse entries were evaluated for vegetable yields in replicated trials at five locations in wet-cool and hot-dry seasons in Tanzania. Season explained the highest proportion (52.1%) of the total sum of squares followed by entries (24.9%) and locations (23.0%). Mean yield across the hot-dry season trials (27.7 t·ha−1) was 47.3% greater than the mean yield across wet-cool season trials (18.8 t·ha−1). Differences among entries in vegetable yield were higher in the hot-dry season than in the wet-cool season, indicating that gain from selection is likely to be greater in the hot-dry season. Most entries performed well in either wet-cool or hot-dry season but a few entries were adapted to both seasons. Two MEs were identified, one characterized by lower altitudes, higher temperatures, and less fertile soils, and a second ME associated with higher altitudes, lower temperatures, and more fertile soils. Each ME may serve as an initial selection site for their respective target environment. Targeting a specific season may give a better chance of finding high-yielding varieties.
Xun Chen, Nai-xin Liu, Li-juan Fan, Yu Du and Ling Wang
Qiang Zhang, Wenting Dai, Hui Yang, Wenting Jia, Xuefei Ning and Jixin Li
In this study, newly harvested ‘New Queen’ melons were treated with calcium chloride (CaCl2) and 1-methylcyclopropene (1-MCP) alone or in combination before storage. The results show that respiration rate, ethylene release, activity, and gene expression of pectinases such as polygalacturonase (PG), pectin methylesterase (PME), and pectate lyase (PL) in ‘New Queen’ melons decreased dramatically when treated with 2% CaCl2 and/or 1 μL·L–1 1-MCP. In addition, climacteric behavior and flesh hardness reduction were inhibited. It was also discovered that softer melon flesh was more conducive to the growth and reproduction of decay-causing microorganisms, according to their growth curves in melons that were different in flesh hardness, suggesting inhibiting fruit softening can slow down the growth of microorganisms in fruit flesh and thus reduce fruit decay rate. The combined use of CaCl2 and 1-MCP was more effective in suppressing respiration rate, ethylene release, and protopectin hydrolysis, which could greatly delay the softening, reduce the decay rate, and extend the shelf life of ‘New Queen’ melons.
Ebrahiem M. Babiker, Stephen J. Stringer, Hamidou F. Sakhanokho, Barbara J. Smith and James J. Polashock
Species of Botryosphaeria and Neofusicoccum are major pathogens of blueberry worldwide. Accurate identification of these species is essential for developing effective management practices. A multigene sequencing strategy was used to distinguish between six isolates of stem blight pathogens collected from two different regions of the United States. The temperature growth study revealed that the optimal temperature for growth of five of the tested isolates ranged from 25 to 30 °C, although no significant difference was detected for the growth of Neofusicoccum spp. isolate SD16-86 at 20, 25, 30, and 35 °C. In vitro fungicide assays showed four fungicides, cyprodinil + fludioxonil, propiconazole, pyraclostrobin + boscalid, and azoxystrobin, were effective against the tested isolates with isolate SD16-86 being less sensitive compared with the other isolates. In a detached stem assay, none of 39 blueberry accessions displayed immunity or a high level of resistance to the two tested isolates, and no significant difference in lesion length was detected among the seven tested Vaccinium species inoculated with the two isolates.