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This study was conducted in a newly established (2-year-old) almond orchard to investigate the effects of five different mulching materials (woven and nonwoven fabric, black and white polyethylene, almond shell) and flame treatments applied at two different frequencies (FL20 and FL30) on weed control and almond growth compared with those of conventional herbicide (glyphosate) application and weedy control. Thus, this study included nine different treatments. The impacts of these treatments on weed density and coverage were periodically monitored. Additionally, the biomass of the weeds was measured at the end of the season to evaluate the effects of the treatments. Because the almond orchard was not yet in the economic fruit-bearing stage, the effects of the treatments were examined in terms of parameters that characterize almond growth, such as plant height, trunk diameter, shoot length, and shoot thickness. The chlorophyll content and water potential values of the trees were also determined. The results of this two-season study indicated that synthetic mulches provided the best outcomes in terms of weed control and almond growth. No weed emergence was observed throughout the season in any of the synthetic mulch treatments. Although almond shells used as organic mulch were highly effective for blocking sunlight, they failed to prevent the growth of some vigorously growing perennials such as Cynodon dactylon and Sorghum halepense that emerged from gaps. Flame treatments demonstrated rapid and effective results; however, they were less successful against the aforementioned monocot perennial weeds and required frequent repetition because of the lack of residual effects. Glyphosate, an herbicide that is commonly used in conventional orcharding, was applied five times throughout the experiment and proved effective weed management compared with that of the weedy control. However, considering the increasing herbicide resistance, environmental and health issues, and growing interest in organic almond cultivation, synthetic mulch applications have emerged as good options. Despite the initially higher establishment costs, synthetic mulches effectively controlled weeds and reduced water stress, thereby promoting almond tree growth.

Open Access

The aim of this study was to establish a regeneration system of watermelon. Watermelon W1 was selected as the experimental material using seedling shoots as a receptor. The effects of different concentrations of 6-Benzylaminopurine (6-BA) on the shoot-tip of watermelon seedlings were studied. Number of shoots at the stem tip were counted every other day until the new buds reached 2 cm. The new stem tip was cut, and the effect of different concentrations of Murashige and Skoog (MS) medium on the number of regenerated roots and root length of shoots were studied. The results showed that the differentiation rate was highest when the 6-BA concentration was 0.7 mg/mL to 0.8 mg/mL. The optimum concentration for root regeneration was 1/8 MS. At this concentration, the number rooted was the highest, and root length was also promoted.

Open Access

Pyroxasulfone is a very long chain fatty acid (VLCFA) inhibitor (group 15) with potential for preemergence weed control in orchard crops and would be beneficial for reducing selection pressure for resistance to more commonly used herbicides, such as glyphosate. Pyroxasulfone is registered and widely used in corn and soybeans in the United States as a solo product and in several premix formulations. However, there is limited published information on the performance and safety of pyroxasulfone in tree nut orchard systems. To assess the potential fit for pyroxasulfone in this crop sector, a series of crop safety and weed control efficacy experiments were carried out in key California orchard crops and in fallow fields with common orchard weeds. The non-crop studies were conducted near Davis, CA, to evaluate winter annual weed control with pyroxasulfone in comparison with pendimethalin and indaziflam. In addition, an irrigation incorporation experiment was conducted in summer to evaluate the effects of incorporation timing on pyroxasulfone, pendimethalin, and indaziflam efficacy as a measure of relative stability. Orchard weed control experiments were conducted in spring in an almond orchard near Arbuckle, CA, and a walnut orchard near Davis, CA. The orchard experiments included pyroxasulfone, pendimethalin, and indaziflam in various rate combinations with glufosinate. To evaluate crop safety, 2-year experiments were conducted to evaluate repeated applications of above-label rates of pyroxasulfone at 1199 g·ha−1 and S-metolachlor at 14,010 g·ha−1 on 1- to 2-year-old almond, pistachio, and walnut trees near Davis. Pyroxasulfone performed similarly to commercial standards with up to 95% control of broadleaf and grass weeds with pyroxasulfone and indaziflam providing 96% to 100% control of annual bluegrass, and pyroxasulfone (293 g·ha−1) being the only herbicide to suppress (>70%) common lambsquarters at 60 days after treatment (DAT). Other weeds controlled by pyroxasulfone include swinecress, redroot pigweed, yellow nutsedge, and Italian ryegrass. No differences were found among treatments in the incorporation timing study indicating adequate stability on the soil surface under summer conditions. Crop injury was not observed in the established orchards or the young orchard studies and there were no treatment effects on tree trunk diameter of almond, pistachio, and walnut in the 2-year crop safety experiments. These results indicate a potential for pyroxasulfone in California tree nut orchard systems that would be an additional site of action and beneficial for management of herbicide-resistant weeds in these crops.

Open Access

Intercropping of ornamental flowering plants like Lycoris radiata Herb. and Cuphea hookeriana Walp. with tea trees can enhance the visibility and esthetic appeal of tea gardens. However, there has been limited research of the impact of intercropping ornamental flowering plants with tea trees on the soil in tea gardens. During this study, our objective was to analyze the effects of intercropping systems on tea garden soil by examining the physicochemical properties of rhizosphere soil samples from tea gardens intercropped with L. radiata and C. hookeriana. We also performed rhizosphere microbial metagenomic sequencing to assess the microbial community structure. The results revealed significant improvements in soil physicochemical indicators, particularly pH. Although intercropping systems had minor impacts on bacterial diversity and abundance, they had more pronounced effects on the community structure of microorganisms at the phylum and genus levels. Furthermore, an analysis of microbial functions using Functional Annotation of Prokaryotic Taxa (FAPROTAX) revealed enrichment of carbon and nitrogen cycling pathways in the tea garden soil. Our findings indicated that intercropping practices have the potential to enhance the visual appeal of tea gardens while improving soil fertility and modulating the microbial community structure. These results contribute to our understanding of intercropping strategies and the implications of intercropping for tea tree growth and ecosystem functioning.

Open Access

Most of the tomato (Solanum lycopersicum) varieties currently used in organic farming were bred for conventional farming, often characterized by high-input use. These varieties do not perform as well in low-input organic systems, generating the need to develop varieties that are adapted to organic management systems. This project focused on improving flavor, disease resistance, and yield, all identified as key traits by organic tomato farmers in the Upper Midwest, USA. Ten advanced tomato breeding lines and two check varieties were developed and evaluated for 16 traits in organic high tunnel systems in 2020 and 2021. The line CSDE-F6.47 averaged 6.32 kg/plant and obtained high flavor intensity and overall flavor scores (3.78 and 3.69 out of 5, respectively). The line JBDE-F5.31 was another outstanding line, with a yield of 5.18 kg/plant, with good flavor intensity (3.32) and overall flavor (2.92) scores. Broad-sense heritability of marketable weight per plant was high (0.91), and the genetic variance was also high, which shows the opportunity to continue to increase the marketable weight in lines with excellent flavor. A significant positive correlation was found between overall flavor and °Brix (0.56), and titratable acidity (0.70), indicating that both measurements can be good predictors of overall flavor. The most promising lines will be further evaluated on-farm to evaluate their potential as releasable varieties.

Open Access

Improving the productivity of sweet pepper (Capsicum annuum) is essential to meeting the increasing global demand. This can be partially accomplished by investigating and determining high-yield traits, thereby enabling the selection or breeding of high-yield plants. Therefore, this study aimed to determine the high-yield traits of sweet pepper by analyzing its yield components. We analyzed yield components of commercially available cultivars (red and yellow) that were hydroponically grown in a greenhouse (e.g., total fruit fresh weight, fruit dry weight, fruit dry matter content, total dry matter production, and light-use efficiency) using Pearson’s correlation coefficient (r). Our results showed the following: the total fruit fresh weight was positively and negatively correlated with the fruit dry weight (r = 0.83; P < 0.001) and fruit dry matter content (r = –0.70; P < 0.001), respectively; the fruit dry weight was positively correlated with the total dry matter production (r = 0.50; P < 0.01), and the total dry matter production was positively correlated with the light-use efficiency (r = 0.93; P < 0.001); and the cultivars with the high total fruit fresh weight were characterized by the notably low fruit dry matter content and high light-use efficiency (e.g., ‘Gialte’). In conclusion, high-yielding sweet peppers are characterized by a low fruit dry matter content and high light-use efficiency.

Open Access

Macrophomina phaseolina, the causal agent of charcoal rot, is one of the most destructive soil-borne pathogens that affect the global strawberry industry. Resistant cultivars are critical for ensuring the profitability of strawberry production without the protection historically provided by methyl bromide. Previously, three loci, namely, FaRMp1, FaRMp2, and FaRMp3, associated with quantitative resistance to Macrophomina phaseolina have been identified and validated across diverse populations and environments. Among those, the locus with the largest effect, FaRMp3, was initially detected in crosses with an exotic Fragaria ×ananassa selection. We introgressed the favorable FaRMp3 allele into elite germplasm in the University of Florida strawberry breeding program already segregating for FaRMp1 and FaRMp2 and confirmed its phenotypic effects across various genetic backgrounds. Subsequently, we developed a high-throughput genotyping assay to facilitate the transfer and selection of FaRMp3 in breeding populations via marker-assisted selection. Given that three quantitative trait loci (QTL) contribute to partial resistance to Macrophomina phaseolina, stacking them within a single genotype presents a potential strategy for enhancing resistance. We screened 564 individuals that segregate for favorable alleles at all three QTL to assess their effects singly and in combination across multiple genetic backgrounds and production seasons. Inoculated field trials revealed that the three QTL cumulatively enhanced resistance levels, and that two-way QTL combinations including FaRMp3 provide increased protection against the pathogen. Pyramiding all three loci achieved the strongest resistance and could provide substantial economic value to the strawberry industry.

Open Access