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The inheritance of capsaicinoid content was studied in five Capsicum pubescens Ruiz & Pav. genotypes using diallel analysis. General combining ability and specific combining ability effects were significant for all capsaicinoids studied, indicating additive and nonadditive gene actions are present. The association of high capsaicinoid contents with high positive general combining ability of the parents also indicates the predominance of additive gene action in capsaicinoid inheritance. Because of the predominant additive gene effect, recurrent selection would be a good breeding method to increase capsaicinoid level in the population studied. Heterosis was observed in hybrids for some of the capsaicinoids, suggesting that F1 hybrids could also be used to increase capsaicinoid content.

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Iris yellow spot virus (IYSV) causes a foliar disease in onion (Allium cepa L.) that results in a reduction in bulb size. Currently, no IYSV-tolerant or -resistant cultivar exists and a genetic source for tolerance or resistance has not been identified. Because other disease control methods are limited, host plant resistance offers the best hope to combat this disease. In this study, 13 winter-sown onion entries were screened for iris yellow spot (IYS) symptoms during the 2007 and 2008 cropping seasons. Twenty plants from each plot were observed and rated weekly during the growing seasons for straw-colored, necrotic lesions, typical of IYSV infection. Collected plant samples were assayed for IYSV by enzyme-linked immunosorbent assay (ELISA) and reverse-transcription polymerase chain reaction (RT-PCR). Visual rating was done using a scale of 1 to 9 with 1 representing no symptomatic tissue and 9 representing more than 50% tissue damage. Two different plant sampling methods were used in disease rating to determine their effect on mean severity and to correlate disease severity with absorbance values. Of the entries tested, plants of NMSU 05-33-1 exhibited a delay in symptom expression and lower IYSV levels relative to plants of other entries. Plants of ‘Denali’ and ‘Gelma’ appeared to be more susceptible to IYSV than plants of other entries. Plant selection within the plot over time did not influence disease rating values. When the same plants were rated and sampled for IYSV using ELISA, there was a strong, positive correlation between rating and absorbance values.

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Five legumes [hairy vetch (Vicia villosa Roth.), barrel medic (Medicago truncatula Gaerth.), alfalfa (Medicago sativa L.), black lentil (Lens culinaris Medik.), and red clover (Trifolium pratense L.)] were interseeded into sweet corn (Zea mays L.) at last cultivation when sweet corn was at about the V9 (early) or blister (late) stage. The effect of legume interseeding on sweet corn yield, and late-season dry-matter and N yields of aboveground portions of the legumes was determined. Sweet corn yield was not affected by legume interseeding. In 1993, legume dry-matter yields were 1420 kg·ha–1 interseeded early and 852 kg·ha–1 interseeded late. Nitrogen yields were 49 kg·ha–1 interseeded early and 33 kg·ha–1 interseeded late. In 1994, dry-matter yields were 2760 kg·ha–1 interseeded early and 1600 kg·ha–1 interseeded late. Nitrogen yields were 83 kg·ha–1 interseeded early and 50 kg·ha–1 interseeded late. In 1993, barrel medic was the highest-yielding legume with dry matter at 2420 kg·ha–1 and N at 72 kg·ha–1 interseeded early, while red clover yielded the lowest with dry matter at 340 kg·ha–1 and N at 12 kg·ha–1 interseeded late. In 1994, dry-matter and N yields ranged from 4500 and 131 kg·ha–1, respectively, for early interseeded barrel medic to 594 kg·ha–1 and 16 kg·ha–1, respectively, for late interseeded red clover.

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Three legumes [hairy vetch (Vicia villosa Roth.), barrel medic (Medicago truncatula Gaerth.), and black lentil (Lens culinaris Medik.)] were interseeded into `New Mexico 6-4' chile pepper (Capsicum annuum L.) when plants were 20–30 cm tall (3 Aug., “early” interseeding) or when plants were 30–40 cm tall (16–17 Aug., “late” interseeding) in 1993 and 1994. Our objectives were to determine the effect of legume interseeding on cumulative chile yield, and late-season dry-matter and nitrogen yields of aboveground portions of the legumes. Legumes were harvested on 8 Nov. 1993 and 15 Nov. 1994. Chile yield was not significantly affected by legume interseeding. In 1993, legumes accumulated 57% more dry matter and 55% more N when interseeded 3 Aug. vs. 16 Aug. In 1994, legumes accumulated 91% more dry matter and 86% more N when interseeded 3 Aug. vs. 17 Aug. Aboveground dry-matter yields in 1993 ranged from 1350 kg·ha–1 for black lentil interseeded late to 3370 kg·ha–1 for hairy vetch interseeded early. Nitrogen yields ranged from 52 kg·ha–1 for black lentil interseeded late to 136 kg·ha–1 for hairy vetch interseeded early. In 1994, hairy vetch was the highest yielding legume with dry matter at 1810 kg·ha–1 and N at 56 kg·ha–1 interseeded early, while black lentil yielded the lowest with dry matter at 504 kg·ha–1 and N at 17 kg·ha–1 interseeded late. In the spring following each interseeding year, we observed that hairy vetch had overwintered well, whereas barrel medic and black lentil had not, except when a few plants of barrel medic survived the winter of 1994–95. Results from this study indicate that legumes can be successfully interseeded into chile in the high-desert region of the southwestern United States without a significant decrease in chile yield.

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Identification of resistant or tolerant onion (Allium cepa L.) cultivars is crucial for the development of integrated management strategies for Iris yellow spot virus (IYSV). Exclusively vectored by onion thrips (Thrips tabaci), IYSV is a potentially devastating tospovirus of onion that has been confirmed to be present in 15 countries all over the world. In this study, 18 winter-sown onion entries were screened for IYSV symptom expression over two seasons. Over the growing season, straw-colored, necrotic lesions typical of IYSV infection were observed and rated for disease severity. Entries, NMSU 03-52-1, NMSU 04-41, NMSU 04-44-1, and ‘NuMex Jose Fernandez’, exhibited fewer symptoms than many other entries tested. ‘Caballero’, NMSU 04-57-1, NMSU 04-78-1, and ‘Cimarron’ exhibited more symptoms. Disease progression over time was rapid for entries exhibiting more symptoms and slow for entries exhibiting fewer symptoms. Enzyme-linked immunosorbent assay (ELISA) optical densities correlated poorly with the severity of disease symptoms. Trends in the disease progression over time emphasize the importance of rating IYSV symptoms late in the crop's development and to search for delayed disease progression rather than early symptom expression to determine IYSV susceptibility.

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Water saving, productivity, and quality of the chile pepper were evaluated under three irrigation treatments. Three drip irrigation treatments used were 1) control, where water was applied at the surface using two drip emitters; 2) partial root-zone drying vertically (PRDv), where subsurface irrigation was applied at 20 cm depth from soil surface; and 3) partial root-zone drying compartment (PRDc), where roots were divided into two compartments and irrigation was applied to one of the compartments on every alternate-day cycle for 15 days. Continuous measurements of soil water content were carried out during the growing seasons of 2013 and 2014, respectively. During both growing seasons, the stomatal conductance (g S) and net photosynthetic rates (Pn) were similar among all treatments including the control. In both PRD treatments, a higher rooting depth and root length density (RLD) than the control likely compensated for the water stress in dry soil zones by taking up more water from the water available parts of the root-soil system. In PRDc and PRDv treatments, 30% less water was applied than control without significant changes to plant stress expressed by stem water potential, plant height, capsaicinoid concentration, and yield. The increased irrigation water use efficiency (IWUE) demonstrated water saving potential of both PRD techniques for chile pepper production in water-limited arid environments.

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Biofumigation is a sustainable method of soil management in cash crop rotations that can increase soil organic matter (SOM), moderate soil pH, suppress weeds and soilborne pathogens through glucosinolates (GSL), and increase water infiltration. This 2-year (2011–13) field study evaluated four different Brassica crops for their biofumigant potential in a chile pepper rotation system in southern New Mexico. The four cultivars included: three mustards (Brassica juncea ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’) and one broccoli (Brassica oleracea var. botrytis ‘Arcadia’). As a result of concerns that these mustards could be hosts for nematodes, a greenhouse study was conducted in the second year to evaluate the biofumigant crops for their southern root-knot nematode (Meloidogyne incognita, RKN) host suitability and their seedling establishment in the presence of RKN. In Year 1 (2011), conditions were ideal, which resulted in high mustard biomass production and, consequently, significantly higher SOM and lower pH than the bare soil control plots. However, there were no chile pepper yield differences among treatments. Conditions were much less favorable in Year 2 and the resultant poor biomass production did not cause an increase in SOM as seen in Year 1. In the RKN greenhouse study, broccoli was the least susceptible biofumigant crop. After one nematode generation (683 cumulative heat units), RKN populations were less than half of the original inoculum level on the broccoli. However, RKN populations increased in the presence of ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’. Overall, broccoli produced lower biomass and lower GSL concentrations than the mustard treatments but may be a valuable crop for growers with nematode issues because RKN populations decreased in its presence. Based on high biomass production and high GSL concentration, ‘Caliente 199’ showed the most potential as a biofumigant crop for southern New Mexico.

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Bulb onion (Allium cepa L.) is an economically valuable vegetable crop in the United States. Onion production is threatened by onion thrips, which are the vector for Iris yellow spot virus, which is the causal agent of Iris yellow spot (IYS). New Mexico State University (NMSU) breeding lines 12-236, 12-238, 12-243, and 12-337 have exhibited fewer IYS disease symptoms in the field; however, little is known about the effects of the disease on the photosynthesis rate (Pn). We hypothesized that these NMSU breeding lines would have a higher Pn than IYS-susceptible cultivars Rumba and Stockton Early Yellow. To test this hypothesis, a field study was conducted for 3 years at NMSU, and Pn was measured five times throughout each season at 2-week intervals. During bulb development and maturation, which occurred at 10 and 12 weeks after transplanting, all NMSU breeding lines exhibited a higher Pn when compared with that of an IYS-susceptible cultivar. Pn was highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all cultivars. Additionally, a high Pn at 10 and 12 weeks after transplanting coincided with high bulb weight at harvest. NMSU breeding lines have increased Pn compared with that of IYS-susceptible cultivars and resulted in larger and more marketable bulbs. These results indicate that maintaining Pn may be related to reduced IYS symptom expression of onion.

Open Access

Phytophthora capsici is responsible for multiple disease syndromes of Capsicum annuum but the resistance mechanism is still unknown. Evaluating gene expression during foliar blight can be used to identify expression patterns associated with resistance in Capsicum species. This study reports a direct comparison of gene expression changes during the foliar blight syndrome using two different races of P. capsici on C. annuum host plants with resistant and susceptible phenotypes to those races. Four genes were evaluated for differential expression following leaf inoculation with P. capsici. RNA isolated from leaves at three time points was used to quantify gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Of four genes tested, two had differential expression in response to P. capsici at 72 hours postinoculation, a xyloglucan-specific endo-β-1,4-glucanase inhibitor protein (XEGIP2) in susceptible cultivar New Mexico Heritage 6-4 (NMH6-4), and a C. annuum cell wall protein (CWP) in resistant Criollo de Morelos 334 (CM334). Both genes had a 5-fold increase in transcription in leaves over the control. These results suggest that both genes are playing a role in disease resistance to foliar blight.

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During the past several years, watermelon trials have been performed in the state, but not as a coordinated effort. Extensive planning in 1997 led to the establishment of a statewide watermelon trial during the 1998 growing season. The trial was performed in five major production areas of the state including: The Winter Garden (Carrizo Springs); South Plains (Lubbock); East Texas (Overton); Cross Timbers (Stephenville); and the Lower Rio Grande Valley (Weslaco). Twenty seedless and 25 seeded hybrids were evaluated at each location. Drip irrigation with black plastic mulch on free-standing soil beds was used to grow entries in each area trial and yield data was recorded in a similar manner for each site. Results were reported in a statewide extension newsletter. Future plans include a continuation of the trial in the hope that multiple-year data will provide a basis for valid variety recommendations for watermelon producers in all areas of the state.

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