Tag: Michailides

Pistachio Cultivar Selection

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Goal – Identify new commercial cultivars with resistance to the most aggressive causal agents of Panicle blight of pistachio.

Activities
Evaluated resistance in all susceptible tissues (green tissues: panicles & fruit, woody tissues: stem) with the three most aggressive pathogens (Botryosphaeria dothidea, Neofusicoccum mediterraneum, and Lasiodiplodia citricola), either alone or in combination.  Inoculations were done on mature trees in an experimental orchard.

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Results & Outputs
To identify resistant germplasm, stem inoculations are required.  Inoculation of green tissues leads to blighted panicles and fruit. However, results were not different among cultivars and all three pathogen species colonized equally. In contrast, inoculation of stems lead to cankers of different lengths, depending on the cultivar and the pathogen.

Kerman, which makes up >90% of California pistachio acreage, showed an intermediate level of resistance, with cankers ranging from 5 to 20 cm. Even more resistant (i.e., with smaller cankers) were new cultivars Golden Hills, Lost Hills, and Randy. New cultivars Kalehghouchi, Joley, and Aria were most susceptible than Kerman. Among the pathogens, Lasiodiplodia citricola was the most aggressive species (i.e., caused the largest cankers) on all seven cultivars, including Kerman.

Significant Outcomes & Impacts
Several new cultivars – Golden Hills, Lost Hills – are more resistant than Kerman. The inoculation method we developed will be important for evaluating preventative fungicides, esp. given that even the most resistant cultivars still develop cankers.

Infection in Almonds

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Goals– To identify rates of wood-canker infections within almond orchards, determine management practices, identify the pathogens present in the orchard, and climate conditions conducive for sporulation in order to increase orchard 

Activities
Identification and surveying of infested orchards, isolation and identification of wood canker fungi, and spore trapping.

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Results & Outputs
Identified pruning wounds, growth cracks, and wood breakage serve as primary points of infection. Found that spore trapping of wood canker fungi is in association with rain events. Successfully extended these initial findings to almond growing clientele in CA.

Significant Outcomes & Impacts
Development of a preliminary model and management practices from field observations and spore trappings.

Almond Resistant Cultivar Selection

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Goal – Identify almond cultivars with resistance to the most aggressive causal agents of wood-canker diseases of almond: Band canker and Lower limb dieback.

Activities – Compared virulence of two Neofusicoccum species inoculated to the woody stems of potted almond plants.

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Results & Outputs
Peerless was the most resistant to both species of the pathogen. Carmel, Sonora, and Padre were among most susceptible, with some differences depending on the species. Susceptible cultivars had the highest mortality. Cankers were so severe in Sonora that 50% of the trees died after 10 months. This means that infections of young trees, esp. of susceptible cultivars, must be protected in young orchards.

Significant Outcomes & Impacts
Now that we know the causal agents, we must identify preventative practices.