The study here aimed to investigate the effects of pre-winter ditching and freezing-thawing on soil microbial structure in different soil layers of old apple orchards. A total of 30 samples were obtained from 3 Nov. 2016 to 9 Mar. 2017. The relative abundance, alpha diversity, community structure of fungi, and the relationship between environmental factors and microbial community structure were analyzed, and the greenhouse experiments were used for further verification. Results showed that the number of actinomycete and total bacterial colonies decreased, whereas the number of fungi sustained decreased, resulting in a higher bacteria/fungi ratio. The percentage of Fusarium initially decreased, then later increased by 11.38%, 3.469%, 2.35%, 2.29%, and 3.09%. However, Fusarium levels were still 9% lower on 9 Mar. 2017 that on 3 Nov. 2016. Both the abundance and diversity of the community were higher in the upper soil than in the lower. The main environmental factor contributing to the percentage of Fusarium change was average temperature (AT), although highest temperature (HT) and water content (WC) also had an impact. The Malus hupehensis Rehd. seedlings growing in lower soil were more vigorous than that in upper soil. In sum, pre-winter ditching and freezing-thawing in old apple orchards can reduce the abundance percentage of harmful Fusarium and promote the growth of M. hupehensis Rehd. seedlings.
Haiyan Wang, Rong Zhang, Weitao Jiang, Yunfei Mao, Xuesen Chen, Xiang Shen, Chengmiao Yin, and Zhiquan Mao
Andrey Vega-Alfaro, Paul C. Bethke, and James Nienhuis
Production of Capsicum annuum peppers is often limited, especially in tropical environments, by susceptibility to soil pathogens including Ralstonia solanacearum. Grafting desirable cultivars onto selected rootstocks can increase adaptation to abiotic stress and is an alternative to pesticides for managing soilborne pathogens. Cultivars of two other pepper species, Capsicum baccatum and Capsicum chinense, are tolerant or resistant to an array of soilborne pathogens and have potential as rootstocks; however, knowledge of how interspecific grafting may affect scion fruit quality is lacking. Flowering time, yield, and fruit quality characteristics were evaluated in 2017 and 2020 for C. annuum cultivars Dulcitico, Nathalie (2017), Gypsy (2020), and California Wonder used as scions grafted onto Aji Rico (C. baccatum) and Primero Red (C. chinense) rootstocks, including self-grafted and nongrafted scion checks. In 2020, the rootstocks per se were evaluated. The two rootstocks (‘Aji Rico’ and ‘Primero Red’), three scions, and self- and nongrafted scions were evaluated using a factorial, replicated, completely randomized design in fields at the West Madison and Eagle Heights Agricultural Research Stations located in Madison, WI, in 2017 and 2020, respectively. Differences among the main effects for scion fruit quality characteristics were consistent with cultivar descriptions. No scion × rootstock interactions were observed. Rootstocks did not result in changes in total fruit number, yield, fruit shape (length-to-width ratio), or soluble solids of scion fruit compared with self- and nongrafted checks. The rootstock ‘Primero Red’ increased fruit weight and decreased time to flowering regardless of scion compared with self- and nongrafted checks. All scions were sweet (nonpungent) cultivars and both rootstocks were pungent cultivars. No capsaicinoids were detected in the fruit of sweet pepper scions grafted onto pungent pepper rootstocks. The results indicate that interspecific grafts involving ‘Aji Rico’ and ‘Primero Red’ will not have deleterious effects on fruit quality characteristics of sweet pepper scions.
Hongli Wei, Chao Gao, Jie Qiu, Li Long, Biao Wang, Lu Yang, and Yang Hu
This study aimed to investigate the flowering biological characteristics, floral organ characteristics, and pollen morphology of Camellia weiningensis Y.K. Li. These features of adult C. weiningensis plants were observed via light microscopy and scanning electron microscopy (SEM). Pollen viability and stigma receptivity were detected using 2,3,5-triphenyltetrazole chloride (TTC) staining and the benzidine–hydrogen peroxide reaction method. C. weiningensis is monoecious, with alternate leaves and glabrous branchlets. Its flowering period lasts 2 to 4 months, and the flowering time of individual plants lasts ≈50 days, with the peak flowering period from the end of February to the middle of March. It is a “centralized flowering” plant that attracts a large number of pollinators. Individual flowers are open for 12 to 13 days, mostly between 1230 and 1630 hr, and include four to six sepals, six to eight petals, ≈106 stamens, an outer ring of ≈24.6-mm-long stamens, an inner ring of ≈13.4-mm-long stamens, one pistil, and nine to 12 ovules. The flowers are light pink. The style is two- to three-lobed and 16.6 mm long, showing a curly “Y” shape. The contact surface of the style is covered with papillary cells and displays abundant secretory fluid and a full shape, facilitating pollen adhesion. The pollen is rhombohedral cone-shaped, and there are germ pores (tremoids). The groove of the germ pore is slender and extends to the two poles (nearly reaching the two poles). The pollen is spherical in equatorial view and trilobate in polar view. The pollen vitality was highest at the full flowering stage, and the stigma receptivity was greatest on days 2 to 3 of flowering. The best concentration of sucrose medium for pollen germination was 100 g/L. The number of pollen grains per anther was ≈2173, and the pollen-to-ovule ratio was 23,034:1. C. weiningensis is cross-pollinated. Seventy-two hours after cross-pollination, the pollen tube reached the base, and a small part entered the ovary. The time when the pollen tube reached the base after pollination was later than that in commonly grown Camellia oleifera. The results of this study might lay an important foundation for the flowering management, pollination time selection, and cross-breeding of C. weiningensis.
Brian J. Schutte, Abdur Rashid, Israel Marquez, Erik A. Lehnhoff, and Leslie L. Beck
Seaside petunia (Calibrachoa parviflora) is a mat-forming plant species that was recently reported in fall-seeded onion (Allium cepa) in the southwestern United States. To initiate development of herbicide recommendations for seaside petunia in onion, we conducted a study to determine seaside petunia susceptibility to commonly used herbicides for broadleaf weed control after onion emergence. Our study included herbicides applied at below-label rates, which provided insights on seaside petunia responses to reductions in the amount of herbicide available for plant absorption. For herbicides with preemergence activity, our growth chamber study indicated that soil applications of flumioxazin or oxyfluorfen (0.06 and 0.25 lb/acre, respectively) prevented seaside petunia seedling emergence when applied at 0.125×, 0.25×, 0.5×, and 1.0× the labeled rates for onion. Labeled rate treatments of dimethenamid-P (0.84 lb/acre) and S-metolachlor (0.64 lb/acre) inhibited seedling emergence similar to labeled rate treatments of flumioxazin and oxyfluorfen; however, below-label rate treatments of dimethenamid-P and S-metolachlor resulted in diminished control of seaside petunia compared with the labeled rate treatments. Following labeled rate applications of dimethyl tetrachloroterephthalate [DCPA (6 lb/acre)] and pendimethalin (0.71 lb/acre), more than 50% of seaside petunia seedlings emerged compared with the nontreated control. For herbicides with postemergence activity on weeds, our greenhouse study indicated that bromoxynil at 0.37 lb/acre, flumioxazin at 0.06 lb/acre, and oxyfluorfen at 0.25 lb/acre equally reduced growth of seaside petunia plants that were small at the time of spraying (stem length, 1–2 cm). Postemergence control of seaside petunia with oxyfluorfen and flumioxazin decreased as plant size at spraying increased; however, bromoxynil effects on seaside petunia remained high as stem length at spraying increased from 5 to 12 cm. Based on the results of this study, we conclude that promising herbicide programs for seaside petunia in onion include oxyfluorfen or flumioxazin for preemergence control and bromoxynil for postemergence control. These herbicides, alone and in combination, should be evaluated for seaside petunia control and onion phytotoxicity in future field trials.
Mingxia Wen, Peng Wang, Weiqin Gao, Shaohui Wu, and Bei Huang
Selenium (Se) fertilizer has a good effect on many field crops, but there are few reports on the application of Se fertilizer on citrus. We investigated the effects of 0 mg/L (CK, water treatment), 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L sodium selenite aqueous solutions on the growth, nutrition, and fruit quality of 15-year-old citrus unshiu (Citrus reticulata Blanco cv. Succosa). The results showed that a low concentration of Se fertilizer promoted the growth and development of the citrus plan, and a high concentration of Se fertilizer was found to slightly inhibit the growth and development of the plant. Among the different treatment groups, 150 mg/L selenium fertilizer showed have the best effect on these evaluated parameters. The results thus suggest that 150 mg/L of Se fertilizer promotes the formation of chlorophyll in the leaves of the test plant and increases the longitudinal and transverse diameter of the fruits and weight of single fruit, significantly enhancing the activity of antioxidant enzymes in the leaves, promoting the absorption of nutrients in the leaves, increasing the contents of total sugar and vitamin, and decreasing the acidity in the fruits and the pericarp thickness. It also promoted the accumulation of the total selenium content in the leaves and fruits and consequently improved the quality of the fruits. These results showed that appropriate concentration of Se treatment can improve the activity of antioxidant enzymes to enhance plant stress resistance, regulate the content of sugar and acid in fruits, and improve the quality of fruits.
Karen K. Schneck, Cheryl R. Boyer, and Chad T. Miller
Dahlia (Dahlia ×hybrida) is an important floriculture crop that has gained popularity in recent years. Greenhouse growers have recently reported a phenomenon known as “dahlia decline,” that can affect potted dahlias in greenhouse production. The crop exhibits graying foliage, root decline, and plant death, and the phenomenon has reportedly caused partial or total crop loss and has no known initiating factor. We hypothesized that plant exposure to supraoptimal root-zone temperatures (RZTs) during production may decrease dahlia root quality, especially above 40 °C and could initiate dahlia decline. Because there is a lack of understanding on how supraoptimal RZT may impact dahlia growth and development, experiments were conducted to evaluate the effects of supraoptimal RZTs on seven dahlia cultivars in Spring 2019 and 2020. Dahlias were grown for 4 to 5 weeks in the greenhouse and then root zones were exposed to ≈22 (control), 35, 40, 45, or 50 °C using a water bath. Root quality was rated before treatment and rated weekly after the hot water bath treatment, along with vegetative growth parameters for 4 weeks. In both years, significant decline in root ratings were observed. ‘XXL Veracruz’ and ‘XXL Sunset’ average root ratings decreased after a 45 and 50 °C treatments in year 2 and both cultivars demonstrated increased root rating averages by 3 weeks after treatment. Cultivars exhibited a significant increase in root rating in the final observations when compared with root ratings taken 1 week posttreatment even if the initial decline after treatment was not significant. Overall plant height was significantly impacted, resulting in shorter heights in both years for all cultivars as treatment temperatures increased to 50 °C in comparison with the control and 35 °C, and a few cultivars exhibited significantly shorter height at 40 and 45 °C. Ultimately, our research did not show typical plant responses that were consistent with reported dahlia decline, but we were better able to characterize dahlia response to supraoptimal RZT.
Lisa Wasko DeVetter, Suzette Galinato, Troy Kortus, and Jonathan Maberry
Floricane red raspberry (Rubus idaeus) produces biennial canes that are traditionally managed by annual selective removal of previously fruited floricanes and training of primocanes that will bear fruit in the next growing season. This process of pruning and training is labor intensive and costly, and growers would benefit from more economical methods of pruning and training. This 6-year project evaluated the economic viability of alternate-year (AY) production in a commercial floricane red raspberry field in northwest Washington and compared it to traditional, every-year (EY) production to assess whether the former could save costs. Despite savings from reduced chemicals, fertilizers, labor, general farm supplies, and other variable costs, the overall benefits of AY production were not enough to offset losses in revenue resulting from reduced yields under the conditions of this experiment in northwest Washington.
Yang Hu, Chao Gao, Quanen Deng, Jie Qiu, Hongli Wei, Lu Yang, Jiajun Xie, and Desheng Liao
Petalized anther abortion is an important characteristic of male sterility in plants. The male sterile plants (HB-21) evincing petalized anther abortion previously discovered in a clone population of the Camellia oleifera cultivar Huashuo by our research group were selected as the experimental material in this study. Using plant microscopy and anatomic methods and given the correspondence between external morphology and internal structure, we studied the anatomic characteristics of petalized anther abortion (with a fertile plant as the control group) in various stages, from flower bud differentiation to anther maturity, in hopes of providing a theoretical basis for research on and applications of male sterile C. oleifera plants, a new method for the selection of male sterile C. oleifera cultivars, and improvements in the yield and quality of C. oleifera. In this study, the development of anthers in C. oleifera was divided into 14 stages. Petalized anther abortion in male sterile plants was mainly initiated in the second stage (the stage of sporogenous cells). Either the petalized upper anther parts did not form pollen sacs, or the entire anthers did not form pollen sacs. The lower parts of some anthers could form deformed pollen sacs and develop, and these anthers could be roughly divided into two types: fully and partially petalized anthers. Abnormal callose and the premature degradation of the tapetum occurred in the pollen sacs formed by partially petalized anthers during the development process, resulting in the absence of inclusions in the pollen grains formed. Small quantities of mature pollen grains withered inward from the germinal furrows, exhibiting obvious abortion characteristics. The relative in vitro germination rate of the pollen produced by the partially petalized anthers of sterile plants was 11.20%, and the relative activity of triphenyltetrazolium chloride was 3.24%, while the fully petalized anthers did not generate pollen grains. Either the petalized anthers in male sterile plants did not produce pollen, or the vitality of the small amounts of pollen produced by sterile plants was very low compared with that of fertile plants. Such male sterile plants could be used to select correct clones and have good prospects for application in production.
Yasmina Chourak, El Hassan Belarbi, Evelynn Y. Martínez-Rivera, Tatiana Pagan Loeiro da Cunha-Chiamolera, Ana Araceli Peña-Fernández, José Luis Guil-Guerrero, and Miguel Urrestarazu
Saffron is one of the most appreciated, traditional, and expensive spices in the world. The objective of our study was to evaluate the effect of cooling the nutrient solution on the production, and organoleptic and commercial qualities of saffron grown in soilless culture. The nutrient solution was cooled to 4 to 5 °C whereas the control treatment was the fertigation supplied at ambient temperature. Corms were placed in a controlled cultivation chamber. The number of flowers per corms, and the weight and length of stigmas were measured. The amounts of safranal, crocin, and picrocrocin were analyzed spectrophotometrically according to the International Organization for Standardization [ISO/TS 3632-2 (2011) Normative]. Our results show that cooling of the nutritive solution increased flower production, the commercial phytochemical content, and organoleptic properties.
Alexandra Boini, Enrico Muzzi, Aude Tixier, Maciej Zwieniecki, Luigi Manfrini, and Luca Corelli Grappadelli
Photoselective nets were used to examine apple shoot physiology during dormancy and budbreak. Two trials were conducted: one in the field and one in controlled conditions. In the first, three colored nets (red, blue, and white, shading 20%) covered sections of single trees, leaving an empty portion as control, from December to April. The white net increased canopy air temperature compared with the blue one. Differences were found in carbohydrate seasonal patterns; however, it appeared that soil temperature had higher impacts on sugar movement in the trees. No differences were found in bud phenology. In the second trial, cuttings were placed in boxes constructed with the same-colored nets and monitored from the end of February to April. Results showed differences in phenology and carbohydrate translocation. The white box hastened bloom and its cuttings had higher amounts of carbohydrates at the end of the trial. On the contrary, the blue box delayed bloom while resources were still being consumed and its cuttings had the lowest amounts of reserves at the end of the trial. These results add new insights on apple physiology under different light spectra and commercial applications should not be excluded for improving crop management.