Agronomy2015, 5(4), 555-568; doi:10.3390/agronomy5040555 (registering DOI) - published 27 November 2015 Show/Hide Abstract
Abstract: Tobacco blue mold, caused by the obligately biotrophic oomycete pathogen Peronospora tabacina D.B. Adam, is a major foliar disease that results in significant losses in tobacco-growing areas. Natural resistance to P. tabacina has not been identified in any variety of common tobacco. Complete resistance, conferred by RBM1, was found in N.debneyi and was transferred into cultivated tobacco by crossing. In the present study, we characterized the RBM1-mediated resistance to blue mold in tobacco and show that the hypersensitive response (HR) plays an important role in the host defense reactions. Genetic mapping indicated that the disease resistance gene locus resides on chromosome 7. The genetic markers linked to this gene and the genetic map we generated will not only benefit tobacco breeders for variety improvement but will also facilitate the positional cloning of RBM1 for biologists.
Abstract: Although iodine is not essential for plants, they take it up readily and, in foodchains, are significant sources of iodine for organisms with an essential requirement for it. During several nuclear accidents radioiodine has been an important component of releases of radioactivity and has caused serious contamination of foodchains. Differences in iodine uptake by different plant taxa are, therefore, important to nutritional and radioecological studies. Using techniques we have developed for a range of other elements, we analyzed inter-taxa differences in radioiodine uptake by 103 plant species and between varieties of two species, and analyzed them using a recent, phylogenetically-informed, taxonomy. The results show that there are significant differences in uptake above and below the species level. There are significant differences between Monocots and Eudicots in iodine uptake, and, in particular, hierarchical ANOVA revealed significant differences between Genera within Families. These analyses of the taxonomic origin of differences in plant uptake of iodine can help the prediction of crop contamination with radioiodine and the management of stable iodine in crops for nutritional purposes.
Abstract: Greenhouse and field experiments showed that conidia of the fungal pathogen, Phoma commelinicola, exhibited bioherbicidalactivity against spreading dayflower (Commelina diffusa) seedlings when applied at concentrations of 106 to 109 conidia·mL−1. Greenhouse tests determined an optimal temperature for conidial germination of 25 °C–30 °C, and that sporulation occurred on several solid growth media. A dew period of ≥ 12 h was required to achieve 60% control of cotyledonary-first leaf growth stage seedlings when applications of 108 conidia·mL−1 were applied. Maximal control (80%) required longer dew periods (21 h) and 90% plant dry weight reduction occurred at this dew period duration. More efficacious control occurred on younger plants (cotyledonary-first leaf growth stage) than older, larger plants. Mortality and dry weight reduction values in field experiments were ~70% and >80%, respectively, when cotyledonary-third leaf growth stage seedlings were sprayed with 108 or 109 conidia·mL−1. These results indicate that this fungus has potential as a biological control agent for controlling this problematic weed that is tolerant to the herbicide glyphosate.
Abstract: Wheat is an important cereal crop worldwide that often suffers from moisture deficits at the reproductive stage. Polyethylene glycol (PEG)-treated hydroponic conditions create negative osmotic potential which is compared with moisture deficit stress. An experiment was conducted in a growth chamber to study the effects of PEG on root hair morphology and associated traits of wheat varieties. Plants of 13 wheat varieties were grown hydroponically and three different doses of PEG 6000 (w/v): 0% (control), 0.3% and 0.6% (less than −1 bar) were imposed on 60 days after sowing for 20 days’ duration. A low PEG concentration was imposed to observe how initial low moisture stress might affect root hair development. PEG-treated hydroponic culture significantly decreased root hair diameter and length. Estimated surface area reduction of root hairs at the main axes of wheat plants was around nine times at the 0.6% PEG level compared to the control plants. Decrease in root hair diameter and length under PEG-induced culture decreased “potential” root surface area per unit length of main root axis. A negative association between panicle traits, length and dry weight and the main axis length of young roots indicated competition for carbon during their development. Data provides insight into how a low PEG level might alter root hair development.
Abstract: This two-year study compared nine northwest Washington dry bean (Phaseolus vulgaris L.) heirloom (H) varieties with 11 standard (S) commercial varieties in matching market classes using organic, non-irrigated production practices. Heirloom and standard varieties differed in days to harvest (DTH) (110 DTH and 113 DTH, respectively), while both days to harvest (113 DTH and 110 DTH) and yield (2268 kg∙ha−1 and 1625 kg∙ha−1) were greater in 2013 than in 2014. Varieties with the shortest DTH both years were “Bale” (H), “Coco” (H), “Decker” (H), “Ireland Creek Annie” (H and S), “Kring” (H) and “Rockwell” (H). Varieties that had the highest yield both years were “Eclipse” (S), “Lariat” (S) and “Youngquist Brown” (H). Only “Eclipse” (S) had the shortest cooking time both years, while “Rockwell” (H), “Silver Cloud” (S) and “Soldier” (S) had short cooking times in 2013, and “Orca” (S) and “Youngquist Brown” (H) had short cooking time in 2014. Varieties with the highest protein content both years were “Calypso” (S), “Coco” (S) and “Silver Cloud” (S). Further research should investigate yield of early maturing standard varieties, with a focus on color-patterned beans that are attractive for local markets.
Abstract: This study was undertaken with the objective of evaluating micro-dosing of mineral fertilizer combined with seed priming in sorghum, groundnut, sesame, and cowpea. On-station and on-farm trials were conducted for two consecutive seasons (2009/2010 and 2010/2011) at Al-Tukma village (12°00′57.60′′ N and 29°46′12.15′′ E) in South Kordofan State, 15 km southeast of Dilling city. Heavy cracking clay soil is the dominant soil type in the region with low fertility. The experiments for each crop consisted of two priming levels (primed seeds vs. non-primed) and four micro-doses of NPK mineral fertilizer (0, 0.3, 0.6 and 0.9 g per planting pocket or hole). On-farm trials in 15 fields consisted of control, seed priming, and seed priming + micro fertilizer (0.3 g/planting hole). Data collected included plant vigor, stand count, plant height, grain and straw yield, seed weight, and other relevant agronomic traits. This study shows that it is possible to increase productivity of sorghum, sesame, groundnut, and cowpea in the semi-arid cracking clay of South Kordofan State at a low cost and with a moderate risk for farmers through seed priming and micro-dosing of fertilizers. Seed priming combined with micro-dosing NPK mineral fertilizer of 0.9 g was the best treatment for plant establishment, seedling vigor, grain yield, and hay yield in sorghum and groundnut, whereas the combination of seed priming and 0.3 g micro-doing of fertilizer was the best in sesame. Seed priming and micro-dosing of fertilizer of 0.6 g was the best combination for cowpea. On-farm trial results indicated that priming alone and priming combined with fertilizer application significantly increased the yields of sorghum, groundnut, and cowpea over the control (P = 0.01). Of the crops tested, groundnut responded most favorably to micro-dosing and seed priming, with a value to cost ratio (VCR) of 26.6, while the highest VCR for sorghum, sesame, and cowpea was 12.5, 8.0 and 4.4, respectively. For the best productivity and profitability, we recommend using seed priming in combination with the micro-dosing of 0.9 g/hole of 15:15:15 NPK fertilizer for sorghum and groundnut, of 0.3 g/hole for sesame, and of 0.6 g/hole for cowpea grown in the semiarid South Kordofan State of Sudan.