A greater understanding of the epidemiology of flower bud rot caused by Pseudomonas syringae pv. actinidiae (Psa) in New Zealand green-fleshed kiwifruit cultivars is required to develop successful disease-management strategies. This study sought evidence as to whether the source of Psa bacteria that causes flower bud infection is internal or external to the flower buds as they emerge in spring. Psa was detected using qPCR in asymptomatic flower buds of two green-fleshed cultivars during spring 2016 and 2017, between bud emergence and immediately before flower opening. Bacterial isolations were made from surface sterilised and non-sterilised buds. Asymptomatic and symptomatic buds were dissected and isolations made from each of the dissected flower parts over time. Significantly more Psa was detected from non-sterilised flower buds during the early stages of bud development compared with later stages. Bud dissections showed that Psa colonisation began in the outer flower parts and moved inwards and this coincided with the development of bud rot symptoms. This study supports a hypothesis that bud rot arises when buds are externally contaminated by Psa early in their development and subsequent infection moves into the inner parts of developing flowers, destroying tissue and causing bud death. Effective control must aim to prevent initial Psa contamination.
The bacterial pathogen Pseudomonas syringae pv. actinidiae biovar 3 (Psa) causes significant economic losses in the kiwifruit industry. This pathogen can overwinter in kiwifruit without the plant showing visible symptoms. Molecular tools, developed to detect this pathogen from cultures, had not previously been tested at an orchard level on dormant winter vines. This epidemiological study aimed to detect and quantify the inoculum present on established vines over winter, targeting the areas of the scion on the pergola. The experiment was conducted on female and male vines of four cultivars: Actinidia chinensis var. chinensis 'Zesy002' (commonly called Gold3), A. chinensis var. chinensis 'Zesy003' (Gold9), A. chinensis var. deliciosa 'Hayward' , and A. chinensis var. chinensis x A. chinensis var. deliciosa 'Zesh004' (Green14). Psa biovar 3 was detected on the vines of all four cultivars, with quantification of the inoculum load (cfu/ml) estimated. Inoculum in all four cultivars increased from winter to spring and inoculum was distributed unevenly around the cankers. This research indicates Psa can be present in asymptomatic tissue, suggesting management of the vines for Psa needs to occur over the winter.Liotryphon caudatus was introduced into New Zealand to control codling moth (CM; Cydia pomonella) in the early 1900s. As part of ongoing research into the biological control of CM, a laboratory colony of L. caudatus was established from field-collected adults, reared on diapausing CM larvae. The longevity and fecundity of laboratory-reared L. caudatus adults were measured at 23±1°C and 16 h photoperiod. Longevity in a non-host environment was measured by holding a newly emerged female and a male in a container with water and food. Survival of 18 pairs was monitored daily. The food and water in the containers were refreshed regularly. The fecundity and the longevity of females were measured by providing five diapausing CM larvae to each of nine mated females (age 7-10 days) in a similar container with food and water. The CM larvae were replaced every 48 hours until the females were dead. In the non-host environment, the mean longevity of a female and a male was 52.8±3.1 and 40.5±1.5 days respectively. In the host environment, the mean longevity of a reproducing female was 81.2±6.5 days, with a mean fecundity of 150.8±24.1 eggs. These findings will facilitate ongoing investigations of the interactions between L. caudatus and Mastrus ridens, a recently released gregarious ectoparasitoid of codling moth, in apple-growing areas where L. caudatus has already established.
Pseudomonas syringae pv. actinidiae biovar 3 (Psa) causes kiwifruit bacterial canker and also bud rot, which destroys developing flower buds and can become a severe problem, particularly in green-fleshed cultivars. The effects of weather and inoculum factors on bud-rot development were investigated. Experiments were conducted on two green kiwifruit cultivars: Actinidia chinensis var. deliciosa 'Hayward' and A. chinensis var. chinensis × A. chinensis var. deliciosa 'Zesh004' (known as Green14), at four sites for two consecutive years. Temperature and rainfall were recorded from bud burst to flowering and bud-rot incidence was monitored from approximately two weeks after flower bud appearance until flowering. Correlations between weather parameters and final bud-rot incidence, and between initial bud-rot and final bud-rot incidence were investigated. There was no significant association between temperature and final bud-rot incidence, but total rainfall and number of days of rain were positively correlated with final bud-rot incidence. Initial bud-rot incidence showed the strongest correlation with final bud-rot incidence and appeared to be the main factor that contributed to bud-rot. Neofabraea actinidiae can occasionally cause post-harvest rot in kiwifruit. Quantitative polymerase chain reaction (qPCR) analysis represents a feasible and accurate option for identifying and quantifying this rot but is limited because qPCR results do not differentiate live and dead conidia. Propidium monoazide (PMA) is a photoreactive dye that penetrates into the damaged cell-wall membranes of dead conidia binding to the DNA and thus suppressing its amplification by qPCR. A commercial kit containing PMA was trialled for differentiating between live and dead N. actinidiae conidia. The most suitable conditions were 1 μM PMA with 10 min light emitting diode (LED) exposure, and could clearly distinguish high concentrations of live from similar concentrations of dead conidia when tested separately and as a mixture. Low concentrations of live N. actinidiae conidia could be distinguished from dead ones when tested separately, but not as a mixture. Additional work is needed to optimise the effectiveness of the PMA binding and apply this concept in the orchard.
Bud rot caused by Pseudomonas syringae pv. actinidiae biovar 3 (Psa) is a severe issue for the kiwifruit industry in New Zealand, particularly within green-fleshed cultivars. Successful management of this disease requires a detailed understanding of the disease cycle, such as identifying when and where Psa is present in/on winter- and flower-buds, the timing of bud-rot initiation, incidence and progression, and any varietal/seasonal/environmental differences. Relevant data is being collected on two green-fleshed cultivars: Actinidia chinensis var. deliciosa ‘Hayward’ and A. chinensis var. chinensis x A. chinensis var. deliciosa ‘Zesh004’ (commonly known as Green14), at four sites where bud rot had been noticed previously. Winter buds are sampled fortnightly and flower buds are sampled weekly from each site. Results from the first year, 2016, indicate that bud-rot incidence was higher in ‘Hayward’ than in Green14. Psa was detected in dormant and sprouted winter buds but its presence was inconsistent. Psa was detected in all parts of dissected ower buds, with the highest incidence in sepals, then in stalks, and gradually lower detection rates in petals, anthers and ovaries respectively.
Pseudomonas syringae pv. actinidiae biovar 3 (Psa) causes kiwifruit bacterial canker and also bud rot, which destroys developing flower buds and can become a severe problem, particularly in green-fleshed cultivars. The effects of weather and inoculum factors on bud-rot development were investigated. Experiments were conducted on two green kiwifruit cultivars: Actinidia chinensis var. deliciosa ‘Hayward’ and A. chinensis var. chinensis × A. chinensis var. deliciosa ‘Zesh004’ (known as Green14), at four sites for two consecutive years. Temperature and rainfall were recorded from bud burst to flowering and bud-rot incidence was monitored from approximately two weeks after flower bud appearance until flowering. Correlations between weather parameters and final bud-rot incidence, and between initial bud-rot and final bud-rot incidence were investigated. There was no significant association between temperature and final bud-rot incidence, but total rainfall and number of days of rain were positively correlated with final bud-rot incidence. Initial bud-rot incidence showed the strongest correlation with final bud-rot incidence and appeared to be the main factor that contributed to bud-rot.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.