Drying half the root-zone of potted avocado (<i>Persea americana</i>Mill., cv. Hass) trees avoids the symptoms of water deficit that occur under complete root-zone drying

Neuhaus, A.; Turner, D. W.; Colmer, Timothy D.; Kuo, John; Eastham, Judy

doi:10.1080/14620316.2007.11512291

Cited by 13 publications

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“…'Dusa' rootstock response to either R. necatrix infection or water stress treatments displayed water potential and g s values that dropped below -1.0 MPa and 0.05 mol m -2 s -1 , respectively, suggesting an oxidative burst in photosynthetic tissues [75,76]. This agrees with the higher NPQ and qN values [77,78] and with a potential vulnerability to cavitation that could limit water flow from roots towards the upperparts of the trees, especially in severe-WS [79,80]. In the R. necatrix/avocado interaction, this limitation of water flow is consistent with the profuse invasion of root vascular system during pathogen root colonization [70,81].…”

Section: Discussionsupporting

confidence: 71%

Mild water stress-induced priming enhance tolerance to Rosellinia necatrix in susceptible avocado rootstocks

Martínez-Ferri

Moreno-Ortega

Berg

et al. 2019

Preprint

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Background: White root rot (WRR) disease caused by Rosellinia necatrix is one of the most important threats affecting avocado orchards in temperate regions. The eradication of WRR is a difficult task and environmentally friendly control methods are needed to lessen its impact. Priming plants with a stressor (biotic or abiotic) can be a strategy to enhance plant defense/tolerance against future stress episodes but, despite the known underlying common mechanisms, few studies use abiotic-priming for improving tolerance to forthcoming biotic-stress and vice versa (‘ cross-factor priming’ ). To assess whether cross-factor priming can be a potential method for enhancing avocado tolerance to WRR disease, ‘Dusa’ avocado rootstocks, susceptible to R. necatrix , were subjected to two levels of water stress (mild-WS and severe-WS) and, after drought-recovery, inoculated with R. necatrix . Physiological response and expression of plant defense related genes after drought-priming as well as the disease progression were evaluated. Results: Water-stressed avocado plants showed lower water potential and stomatal limitations of photosynthesis compared to control plants. In addition, NPQ and q N values increased, indicating the activation of energy dissipating mechanisms closely related to the relief of oxidative stress. This response was proportional to the severity of the water stress and was accompanied by the deregulation of pathogen defense-related genes in the roots. After re-watering, leaf photosynthesis and plant water status recovered rapidly in both treatments, but roots of mild-WS primed plants showed a higher number of overexpressed genes related with plant defense than severe-WS primed plants. Disease progression after inoculating primed plants with R. necatrix was significantly delayed in mild-WS primed plants. Conclusions: These findings demonstrate that mild-WS can induce a primed state in the WRR susceptible avocado rootstock ‘Dusa’ and reveal that ‘ cross-factor priming’ with water stress (abiotic stressor) is effective for increasing avocado tolerance against R. necatrix (biotic stressor), underpinning that plant responses against biotic and abiotic stress rely on common mechanisms. Potential applications of these results may involve an enhancement of WRR tolerance of current avocado groves and optimization of water use via low frequency deficit irrigation strategies.

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Section: Discussionsupporting

confidence: 71%

Mild water stress-induced priming enhance tolerance to Rosellinia necatrix in susceptible avocado rootstocks

Martínez-Ferri

Moreno-Ortega

Berg

et al. 2019

Preprint

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“…Restrictions to water flow in the leaf petiole were caused by embolisms/cavitation. In well-watered trees, or those subjected to drought on only one side of the trunk, no tyloses were found in the xylem vessels (Turner et al, 2001;Neuhaus et al 2007).…”

Section: Xylem Vesselsmentioning

confidence: 99%

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF AVOCADO (Persea americana Mill.): A REVIEW

Carr

2013

Ex. Agric.

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The results of research on the water relations and irrigation need of avocado are collated and reviewed in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information is given on the centre of origin (Mexico and Central America) and the three distinct ecological areas where avocados are grown commercially: (1) Cool, semi-arid climates with winter-dominant rainfall (e.g. Southern California, Chile, Israel); (2) Humid, subtropical climates with summer-dominant rainfall (e.g. eastern Australia, Mexico, South Africa); and (3) Tropical or semi-tropical climates also with summerdominant rainfall (e.g. Brazil, Florida and Indonesia). Most of the research reported has been done in Australia, California, Israel and South Africa. There are three ecological races that are given varietal status within the species: Persea americana var. drymifolia (Mexican race), P. americana var. guatemalensis (Guatemalan race) and P. americana var. americana (Antillean, West Indian or Lowland race). Interracial crossing has taken place. This paper summarises the effects of water deficits on the development processes of the crop and then reviews plant-water relations, crop water requirements, water productivity and irrigation systems. Shoot growth in mature trees is synchronised into flushes. Flower initiation occurs in the autumn, with flowering in late winter and spring. Flowers form on the ends of the branches. A large heavily flowering tree may have over a million flowers, but only produce 200-300 fruits. Fruit load adjustment occurs by shedding during the first three to four weeks after fruit set and again in early summer. Water deficits during critical stages of fruit ontogeny have been linked to fruit disorders such as ring-neck. Reproductive growth is very resistant to water stress (compared with vegetative growth). Avocado is conventionally considered to be shallow rooted, although roots extend to depths greater than 1.5 m. The majority of feeder roots are found in the top 0.60 m of soil and root extension can continue throughout the year. Leaves develop a waxy cuticle on both surfaces, which is interrupted by stomata on the abaxial surface (350-510 mm −2 ), many of which are blocked by wax. Stomata are also present on the sepals and petals at low densities (and on young fruit). During flowering, the canopy surface area available for water loss is considerably increased. Stomatal closure is an early indicator of water stress, which together with associated changes in leaf anatomy, restricts CO 2 diffusion. There have only been a few attempts to measure the actual water use of avocado trees. In Mediterranean-type climates, peak rates of water use (in summer) appear to be between 3 and 5 mm d −1 . For mature trees, the crop coefficient (K c ) is usually within the range 0.4-0.6. The best estimate of water productivity is between 1 and 2 kg fruit m −3 . Soil flooding and the resultant reduction in oxygen level can damage roots even in the absence of root rot. Avocado is particularly sensiti...

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“…We selected Persea americana, a species in which partial leaf death during drought is well described (Neuhaus et al, 2007), to test whether leaf embolism drives partial leaf area mortality and whether heterogeneous leaf mortality is associated with a large variation in embolism resistance between individual leaves. We exposed P. americana plants to a controlled drought until incipient signs of leaf mortality were observed, after which plants were rewatered and allowed to fully rehydrate.…”

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confidence: 99%

Xylem Embolism Resistance Determines Leaf Mortality during Drought in Persea americana

2019

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The driver of leaf mortality during drought stress is a critical unknown. We used the commercially important tree Persea americana, in which there is a large variation in the degree of drought-induced leaf death across the canopy, to test whether embolism formation in the xylem during drought drives this leaf mortality. A large range in the number of embolized vessels in the petioles of leaves was observed across the canopy of plants that had experienced drought. Despite considerable variation between leaves, the amount of embolized vessels in the xylem of the petiole strongly correlated with area of drought-induced tissue death in individual leaves. Consistent with this finding was a large interleaf variability in xylem resistance to embolism, with a 1.45 MPa variation in the water potential at which 50% of the xylem in the leaf midrib embolized across leaves. Our results implicate xylem embolism as a driver of leaf mortality during drought. Moreover, we propose that heterogeneity in drought-induced leaf mortality across a canopy is caused by high interleaf variability in xylem resistance to embolism, which may act as a buffer against complete canopy death during prolonged drought in P. americana.

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Drying half the root-zone of potted avocado (Persea americanaMill., cv. Hass) trees avoids the symptoms of water deficit that occur under complete root-zone drying

Cited by 13 publications

References 0 publications

Mild water stress-induced priming enhance tolerance to Rosellinia necatrix in susceptible avocado rootstocks

Mild water stress-induced priming enhance tolerance to Rosellinia necatrix in susceptible avocado rootstocks

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF AVOCADO (Persea americana Mill.): A REVIEW

Xylem Embolism Resistance Determines Leaf Mortality during Drought in Persea americana

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