Location: Vegetable Crops Research
Project Number: 5090-21220-007-031-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Sep 15, 2022
End Date: Sep 14, 2024
Objective:
OBJECTIVE 1: Characterizing the fungal population
OBJECTIVE 2: Evaluating the environmental contributors to fruit rot expression
OBJECTIVE 3: Developing system to deploy genetic resources for optimized fruit rot management
OBJECTIVE 4: Developing integrated models to predict fruit rot incidence
Approach:
In this proposed project, we will use a variety of techniques, including physiological, molecular, and biochemical, to investigate the heat stress and relative humidity responses in cranberry and their effect on fruit rot incidence. The critical temperatures that cause physiological breakdown in cranberry fruit, resulting in fruit rot damage, will be investigated using three cultivars with various levels of fruit rot resistance. We will examine the effect of three different levels of heat stress on four distinct stages of fruit development at temperatures of 35oC, 40oC, and 45oC. Experiments with and without fruit rot fungal inoculum will be conducted at the Cranberry Research Station in Wisconsin. Forced convection devices equipped with a data heater 120V, a fan, a data logger, and an insulated duct line will be used to create heat stress. The temperature of the fruit will be determined by implanting a thermocouple beneath the fruit's skin, inflicting just little harm to a few epidermal cells. Temperature and relative humidity of the ambient air will also be determined above and below the canopy using a temperature humidity probe.
The influence of relative humidity will be investigated by utilizing a humidifier and dehumidifier to impose three degrees of relative humidity in ARS growth chambers: low (40 percent), medium (60 percent), and high (80 percent). At temperatures of 35oC and 40oC, the three levels of RH will be determined at pea size, green fruit stage, blush stage, and full red color. Experiments will be conducted with and without a fungal inoculum for fruit rot. Temperature and relative humidity of the ambient air and canopy level will be measured using a temperature humidity probe.
Fruits will be sampled weekly until harvest following heat stress and relative humidity treatments. The fruit's heat damage symptoms will be visually examined during heat stress treatment and ranked on a scale of one to five, with one indicating no damage and five indicating severe damage. Additionally, we will examine the cuticle and wax structure of the fruit, as well as the anthocyanin concentration, in both heat and relative humidity trials. The incidence of fruit rot will be assessed using a multiplex approach in inoculated and uninoculated plots with and without heat and RH. Following each heat treatment, samples of the fruits will be taken to extract DNA. The presence of fruit rot fungus will be determined through polymerase chain reaction (PCR) using a fungal-specific primer. Anthocyanins, chlorophyll, reactive oxygen species, and quinic acid will all be quantified. This will enable us to identify the major environmental parameters influencing the incidence of fruit rot in cranberries. This study will discover cranberry cultivars that are resistant to heat and fruit rot and will assist in the development of cultivars with higher fruit rot tolerance using molecular breeding. Finally, we will collaborate with the cranberry industry and growers to convey knowledge about how to improve cranberry fruit rot resistance.
