The use of ethephon to promote uniform harvest drop of mature macadamia nuts in south-east Queensland

Trials were carried out in 1982-83 on cultivars Keauhou, Kakea and Own Choice. Ethephon at 200 mg/litre + Plus 50 wetting agent at 0.25 ml/litre led to >90% of the nuts dropping within 14 days with Keauhou and Kakea. The response by Own Choice was more variable. Increasing the wetting agent concentration to 0.5 mg/litre enhanced ethephon effectiveness. Applying 200 mg/litre ethephon to Keauhou and Kakea to achieve a single harvest is considered economic. With Own Choice, inexpensive additives which significantly increase the effectiveness of ethephon are required before its use can be recommended. Leaf drop was not excessive with any of the treatments used

Nitrogen and environmental factors influencing macadamia quality

Applications of nitrogen fertiliser in macadamia orchards remain high, despite indications that optimum yields and quality are obtained at a lower rate. This 6-year study examined the effect on quality of 230, 690 and 1150 g nitrogen/tree . year, applied in April (floral initiation), in April and June (inflorescence development), in April, June and November (rapid nut growth and premature nut drop), in April, June, November and January (nut maturation/oil accumulation) or monthly. Higher rates of nitrogen increased kernel recovery by 1% in 5 years out of 6. In 1 year only, 4 or more split applications of the medium and high rates of nitrogen increased kernel recovery by up to 1.6%. These increases were insufficient to compensate for depressed yields (17% lower) at high nitrogen. In good years, when yields were above average, kernel recovery tended to be high and in years with poor yields, kernel recovery tended to be low except when nuts were small. Moderate summer—early autumn rainfall of about 100 mm/month was associated with high kernel recovery whereas very heavy rainfall (>200 mm/month) during this period was detrimental. The percentage of first grade kernels was influenced most by season but was negatively correlated with the rate of nitrogen. Impurities, including immature, deformed, mouldy and insect-damaged kernels, were lowest at low rates of nitrogen and highest during wet harvest seasons. Time of nitrogen application had no significant effect on yield, kernel recovery, the percentage of first-grade kernels or impurities. For sustained high yield and quality, 355 g nitrogen, or 0.8 kg urea/tree.year, applied in April—June is indicated. Agronomic and economic advantages of reducing rates of nitrogen applied to macadamia orchards are enhanced by increasingly important environmental considerations. Multiple regression analyses indicated that the rate, strategy and timing of nitrogen application, rainfall, temperature, flushing and litterfall were correlated with kernel recovery and first-grade kernels but more work is needed to elucidate the significance of these factors

SARS-CoV-2-specific nasal IgA wanes 9 months after hospitalisation with COVID-19 and is not induced by subsequent vaccination

BACKGROUND: Most studies of immunity to SARS-CoV-2 focus on circulating antibody, giving limited insights into mucosal defences that prevent viral replication and onward transmission. We studied nasal and plasma antibody responses one year after hospitalisation for COVID-19, including a period when SARS-CoV-2 vaccination was introduced. METHODS: In this follow up study, plasma and nasosorption samples were prospectively collected from 446 adults hospitalised for COVID-19 between February 2020 and March 2021 via the ISARIC4C and PHOSP-COVID consortia. IgA and IgG responses to NP and S of ancestral SARS-CoV-2, Delta and Omicron (BA.1) variants were measured by electrochemiluminescence and compared with plasma neutralisation data. FINDINGS: Strong and consistent nasal anti-NP and anti-S IgA responses were demonstrated, which remained elevated for nine months (p < 0.0001). Nasal and plasma anti-S IgG remained elevated for at least 12 months (p < 0.0001) with plasma neutralising titres that were raised against all variants compared to controls (p < 0.0001). Of 323 with complete data, 307 were vaccinated between 6 and 12 months; coinciding with rises in nasal and plasma IgA and IgG anti-S titres for all SARS-CoV-2 variants, although the change in nasal IgA was minimal (1.46-fold change after 10 months, p = 0.011) and the median remained below the positive threshold determined by pre-pandemic controls. Samples 12 months after admission showed no association between nasal IgA and plasma IgG anti-S responses (R = 0.05, p = 0.18), indicating that nasal IgA responses are distinct from those in plasma and minimally boosted by vaccination. INTERPRETATION: The decline in nasal IgA responses 9 months after infection and minimal impact of subsequent vaccination may explain the lack of long-lasting nasal defence against reinfection and the limited effects of vaccination on transmission. These findings highlight the need to develop vaccines that enhance nasal immunity. FUNDING: This study has been supported by ISARIC4C and PHOSP-COVID consortia. ISARIC4C is supported by grants from the National Institute for Health and Care Research and the Medical Research Council. Liverpool Experimental Cancer Medicine Centre provided infrastructure support for this research. The PHOSP-COVD study is jointly funded by UK Research and Innovation and National Institute of Health and Care Research. The funders were not involved in the study design, interpretation of data or the writing of this manuscript

Large-scale phenotyping of patients with long COVID post-hospitalization reveals mechanistic subtypes of disease

One in ten severe acute respiratory syndrome coronavirus 2 infections result in prolonged symptoms termed long coronavirus disease (COVID), yet disease phenotypes and mechanisms are poorly understood1. Here we profiled 368 plasma proteins in 657 participants ≥3 months following hospitalization. Of these, 426 had at least one long COVID symptom and 233 had fully recovered. Elevated markers of myeloid inflammation and complement activation were associated with long COVID. IL-1R2, MATN2 and COLEC12 were associated with cardiorespiratory symptoms, fatigue and anxiety/depression; MATN2, CSF3 and C1QA were elevated in gastrointestinal symptoms and C1QA was elevated in cognitive impairment. Additional markers of alterations in nerve tissue repair (SPON-1 and NFASC) were elevated in those with cognitive impairment and SCG3, suggestive of brain–gut axis disturbance, was elevated in gastrointestinal symptoms. Severe acute respiratory syndrome coronavirus 2-specific immunoglobulin G (IgG) was persistently elevated in some individuals with long COVID, but virus was not detected in sputum. Analysis of inflammatory markers in nasal fluids showed no association with symptoms. Our study aimed to understand inflammatory processes that underlie long COVID and was not designed for biomarker discovery. Our findings suggest that specific inflammatory pathways related to tissue damage are implicated in subtypes of long COVID, which might be targeted in future therapeutic trials

Effects of temperature on premature nut drop in macadamia

Five-year-old Macadamia integrifolia (cultivars Keauhou, Keaau and Kau) trees in pots were grown in a controlled environment for 10 weeks after nut set. High temperatures of (a) 30 and 35 deg C, compared with (b) 20 and 25 deg , induced a larger number of nuts to drop early. After the initial nut drop period, temperature maintained at, or returned to 25 deg , resulted in little additional nut drop. When temperatures at (b) were increased to 25 and 30 deg , respectively, further nut drop occurred. When the temperature was increased from 30 to 35 deg , the rate of drop was intermediate between treatments (a) and (b). It is suggested that 30 deg might be critical in promoting unacceptable levels of nut drop. By avoiding extreme day temperatures, the proportion of the potential crop which is lost through premature nut drop may be reduced

Macadamia yield and quality responses to phosphorus

Phosphorus fertiliser was applied to mature macadamia trees on 3 plantations with relatively low soil P in south-eastern Queensland at rates of 0, 10, 20, 40, 80, 160, and 320 kg P/ha at El Briale and Como Park and 0, 15, 30, 60, 120, 240, and 480 kg P/ha at Haylock. High rates of P were being applied to macadamias throughout the Australian industry and this study was designed to provide a basis for determining optimum application rates and critical soil P levels. Soil P was 33–199.5, 38.1–267.0, and 62.3–253.0 mg/kg at El Briale, Como Park, and Haylock, respectively. A tentative critical soil P concentration of 84–88 mg/kg was indicated, based on relative yields at El Briale and Haylock. Yield responsiveness to applied P was greatest at Haylock on a heavy soil that may have adsorbed P more readily, and had a higher P buffer capacity, than the lighter soils at the other sites. Leaf P was unresponsive to applied P, and hence soil P in this study. This is of concern since leaf P is used extensively to guide nutrition management. Further work is required to clarify relationships between leaf and soil P concentrations

Leaf nitrogen as a guide for fertilising macadamia

Despite the lack of evidence for a critical level of leaf nitrogen in macadamia, fertiliser management has been largely based on tentative standards for high yielding trees. Trees on a lower plane of nitrogen nutrition, however, produced higher yields of good quality nuts. This study was therefore carried out to establish the relationship between yield and nitrogen status of trees. Three rates of nitrogen fertiliser (0.5, 1.5 and 2.5 kg urea/tree . year; 230, 690 and 1150 g nitrogen respectively) were applied to macadamia trees in 1 of 5 application strategies: 1 application in April (floral initiation); 2 applications, one in April and one in June (inflorescence development); 3 applications, April, June and November (rapid nut growth and premature nut drop); 4 applications, April, June, November and January (oil accumulation); and 12 monthly split applications. Multiple applications were all equal in size. The association between high yields and low nitrogen status was confirmed. In some, but not all, years, yield was negatively correlated with leaf nitrogen, accounting for 47 and 59% of the variation in yield of commercially acceptable nuts (>19 mm diameter) in 1991 and 1993, respectively. It is therefore recommended that the standard for leaf nitrogen in macadamia be lowered from 1.4–1.5 to 1.3% under Australian conditions. These results raise concerns at the current trend for leaf nitrogen to be as high as 1.8%. It would be prudent to cease nitrogen applications on at least a small experimental block until leaf nitrogen declined to 1.3% and then maintain this level for at least 3 years and monitor yields

Macadamia responses to mild water stress at different phenological stages

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental. Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield

Macadamia responses to mild water stress at different phenological stages

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental. Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield