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1.
The rates of sap flow and xylem vessel features were studied in two-year-old nongrafted and grafted avocado (Persea americana Mill.) trees. Daily sap flow rates were measured with heat and balance stem gauges in clonal Duke 7 (D7) and Toro Canyon (TC) trees and ‘Hass’ clonal scions grafted onto clonal D7 (H/D7) and TC (H/TC) rootstocks. Vessel features as size, number and total vessel area were determined histologically in the stem of the scion and rootstock and the roots of the grafted trees. Significant differences in the sap flow rate were found among the rootstocks, where D7 had a 29% higher sap flow rate than did TC (grafted and nongrafted trees). There were no differences among xylem vessel features in the stems of any of the varieties. However in the roots, D7 had wider and fewer vessels then TC do. Also, D7 had a 19% higher total vessel area than TC. These results suggest that the differences in water consumption of ‘Hass’ on different rootstocks may be associated with differences in the efficiency of the roots to absorb water across conductive tissue which may be linked to differences in the area of xylem vessels in the root.  相似文献   
2.
Role of endogenous flavonoids in resistance mechanism of Vigna to aphids   总被引：1，自引：0，他引：1  
Cultivated and wild species of the genus Vigna were screened for their flavonoid content. Flavonoid HPLC analyses clearly showed that cultivated lines of cowpea (Vigna unguiculata L. Walp.) are very similar from a qualitative point of view, always showing three flavonoid aglycons: quercetin, kaempferol, and isorhamnetin. In addition, a positive relationship between resistance/susceptibility characteristics against aphids and flavonoid glycoside content of cowpea lines was found. The resistant lines showed a flavonoid content higher than that of susceptible ones. In vitro bioassays proved that, among endogenous flavonoids, quercetin and isorhamnetin possess a good inhibitory aphid reproduction rate. Flavonoid HPLC analyses of wild Vigna species supported evidence for the existence of different flavonoid chemotypes in some species of section Vigna. There are kaempferol chemotypes, kaempferol being the main aglycon detected, quercetin chemotypes, containing quercetin glycosides only, and two isorhamnetin chemotypes. When the resistance characteristics to aphids in different chemotypes of the same species were tested, it became evident that quercetin or isorhamnetin chemotypes showed a higher level of resistance compared to kaempferol chemotypes in the same species, thus demonstrating a direct involvement of quercetin or isorhamnetin in the resistance mechanism. These results can provide useful information for further studies on gene expression of resistance factors.  相似文献   
3.
ABSTRACT

The effect of salinity (1.5, 3.0, 4.5, or 6.0 dS m? 1) on ion concentrations [magnesium (Mg), calcium (Ca), potassium (K), sodium (Na), and chloride (Cl)] of one-year-old ‘Hass’ avocado (Persea americana Mill.) trees on one of three rootstocks [‘Duke 7’ (D7), ‘Toro Canyon’ (TC), or ‘Thomas’ (TH)] was investigated. Concentrations of Mg decreased in roots, stems, and older leaves with increasing substrate salinity. Salinity had no effect on Ca concentration of the trees. Potassium concentrations decreased in roots of all trees and stems of trees on TH. Potassium concentrations either remained unchanged or increased at salinity levels of 3.0 dS m? 1 and above in leaves and buds of all trees. Sodium increased in roots and woody organs in trees on all rootstocks. Leaf Na concentrations increased with salinity in trees on D7 and TH, but not TC. Chloride increased in all organs of all trees with increasing salinity, but to the greatest extent in trees on TH and to the least extent in trees on TC. At high substrate salinity concentrations, leaves of trees on TH rootstock had the highest leaf concentrations of Na and Cl, and the highest Na:K ratios. Sodium and chloride concentrations were correlated with necrosis in older leaves of TH, but less so in leaves of trees on TC or D7. Based on percent necrosis in older leaves with increased salinity, trees on TH performed poorest, whereas trees on TC exhibited the greatest salt tolerance. Leaf necrosis was consistently observed at Cl concentrations of 4 mg g? 1 or more, and at Na:K ratios of 0.01 or more in older leaves. Chloride concentration and Na:K ratio in older leaves appears to be a useful marker for salinity tolerance screening in avocado rootstocks. The relative tolerance of the various rootstocks appeared to be due primarily to their ability to exclude Na and Cl from the leaves.  相似文献   
4.
The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80–100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries.  相似文献   
5.
Mandarins are very prone to losing flavor quality during storage and, as a result, often have a short shelf life. To better understand the basis of this flavor loss, two mandarin varieties (‘W. Murcott’ and ‘Owari’) were stored for 0, 3 and 6 weeks at either 0 °C, 4 °C, or 8 °C plus 1 week at 20 °C, and then evaluated for sensory attributes as well as quality parameters and aroma volatile profile. The experiment was conducted multiple times for each variety over two seasons, using three separate grower lots per experiment. Flavor quality was reduced in ‘Owari’ following 4 weeks of storage as off-flavor increased, while for ‘W. Murcott’ the hedonic score decreased after the fruit were stored for 7 weeks. Sensory panelists also noted a decline in tartness during storage for both varieties that was associated with an increase in the ratio of soluble solids concentration (SSC) to titratable acidity (TA). Large increases in alcohols and esters occurred during storage in both varieties, a number of which were present in concentrations in excess of their odor threshold values and are likely contributing to the loss in flavor quality. Thirteen aroma volatiles, consisting mainly of terpenes and aldehydes, declined during storage by up to 73% in ‘Owari’, only one of which significantly changed in ‘W. Murcott’. Although many of these volatiles had aromas characteristic of citrus, their involvement in flavor loss during storage is unclear. ‘W. Murcott’ stored at 8 °C had slightly superior flavor to fruit stored at either 0 °C or 4 °C, and the better flavor was associated with higher SSC/TA and lesser tartness. Aroma volatiles did not play a role in the temperature effect on flavor as there were no significant differences in volatile concentrations among the three temperatures. There was no effect of storage temperature on the flavor of ‘Owari’.  相似文献   
6.
Facing current climate challenges and drastically reduced chemical options for plant protection, the exploitation of RNA interference (RNAi) as an agricultural biotechnology tool has unveiled possible new solutions to the global problems of agricultural losses caused by pests and other biotic and abiotic stresses. While the use of RNAi as a tool in agriculture is still limited to a few transgenic crops, and only adopted in restricted parts of the world, scientists and industry are already seeking innovations in leveraging and exploiting the potential of RNAi in the form of RNA‐based biocontrol compounds for external applications. Here, we highlight the expanding research and development pipeline, commercial landscape and regulatory environment surrounding the pursuit of RNA‐based biocontrol compounds with improved environmental profiles. The commitments of well‐established agrochemical companies to invest in research endeavours and the role of start‐up companies are crucial for the successful development of practical applications for these compounds. Additionally, the availability of standardized guidelines to tackle regulatory ambiguities surrounding RNA‐based biocontrol compounds will help to facilitate the entire commercialization process. Finally, communication to create awareness and public acceptance will be key to the deployment of these compounds. © 2019 Society of Chemical Industry  相似文献   
7.
Journal of Pest Science - Just over 20 years since the RNA interference (RNAi) mechanism was unraveled in the nematode Caenorhabditis elegans, the first RNAi-based pest control applications are...  相似文献   
8.
Journal of Pest Science - A correction to this paper has been published: https://doi.org/10.1007/s10340-021-01393-0  相似文献   
9.
Summary

Growth, yield, and leaf nutrient concentrations were measured in ‘Hass’ avocado (Persea americana Mill.) trees grown on one of ten clonally-propagated rootstocks (‘Borchard’, ‘D9’, ‘Duke 7’, G1033, G755A, G755B, G755C, ‘Thomas’, ‘Topa Topa’, or ‘Toro Canyon’) over a 10-year period in southern California. After 10 years, trees on ‘Borchard’ were larger than trees on all other rootstocks. Trees on all rootstocks displayed an alternate-bearing pattern, typical of avocado. Alternate-bearing was most pronounced in trees grafted onto ‘Topa Topa’ and ‘Toro Canyon’. Rootstocks in the G755 series had the lowest alternate-bearing index, but also had the lowest yields.Trees on ‘Duke 7’ and ‘Borchard’ had the highest cumulative yields, and trees on G755A, G755B, and G755C had the lowest yields. Differences in yield were due to differences in the number of fruit per tree, not individual fruit weight. When yield was evaluated in terms of canopy efficiency (kg fruit m–3), no rootstock outperformed ‘Duke 7’, the industry standard rootstock. Leaf concentrations of all nutrients examined (N, P, K, Ca, Mg, S, Zn, Cl, Mn, B, Fe, and Cu) were within, or close to the recommended ranges. P, Ca, and S were higher, and Fe was lower in high-yielding years in all rootstocks.  相似文献   
10.
A number of volatile compounds that contribute to orange flavor were quantified following high-temperature forced-air (HTFA) treatment of the fruit to determine if a relationship exists between the flavor loss that is observed following HTFA treatment and the volatile composition of the juice. Following different durations of HTFA treatment, fruit were stored for a period of 4 weeks and juiced and the juice subjected to headspace analysis using either a Tenax/Carbotrap column or a solid-phase microextraction device for trapping of the volatiles. alpha-Pinene, beta-myrcene, and limonene were reduced in amount by 60%, 58%, and 34%, respectively, over the course of the 5-h HTFA treatment. The influence of heat on the amount of decanal was less clear, although in one of the two fruit lots there was little change. The amount of ethanol was reduced by 70% after the initial hour of HTFA treatment and then steadily increased to exceed the initial amount during the remaining 4 h of the treatment. Taste evaluations of the fruit showed a reduction of flavor quality following 4 h or more of treatment. Percent acidity and soluble solids, two other very important determinants of flavor, were nearly unchanged by treatment. Alterations in the volatile constituents of oranges by HTFA treatment may be an important reason behind the negative impact of this treatment on flavor quality.  相似文献   
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