Abstract Detail

Physiology

Tucker, Lauren [1], Bobich, Edward [2], Davis, Stephen [3], Mellano, Valerie [4], Ewers, Frank [5].

The effect of water stress on canker disease in Juglans californica.

The California black walnut (Juglans californica) is a threatened and endemic tree species that experienced unprecedented dieback during the historic 2012 to 2016 California drought, which appeared to be associated with canker disease. Following the dieback, the walnut trees were observed to be recovering by resprouting from their base, with cankers present on the drought resprouts. Juglans californica has been previously studied for its ability to resprout following wildfire, in which fire resprouts displayed enhanced water status compared to nearby adults. The purpose of this study was to determine if water stress affected the severity of canker disease for the walnut trees. The canker development of walnut trees was observed in field conditions at irrigated sites and non-irrigated sites for different growth forms, including coppice resprouts and adults present at irrigated sites and drought resprouts, adults, and resprouting adults present at non-irrigated sites. Canker development was observed by measuring canker number and length at an initial and final date in 2018, to determine canker initiation and elongation. Also, water potentials of the walnut trees were measured to determine water stress. It was hypothesized that walnut trees experiencing more negative water potentials would exhibit greater canker initiation and elongation. Therefore, it was hypothesized that walnut trees present at the irrigated sites would exhibit less canker initiation and elongation compared to the non-irrigated sites. Additionally, it was hypothesized that resprouts would have less canker initiation and elongation than adults due to the resprouts having an enhanced water status. Overall, walnut trees experiencing more negative water potentials were found to exhibit greater canker initiation and canker elongation. Trees at the irrigated sites had less canker initation and elongation than trees at the non-irrigated sites. The irrigated coppice resprouts overall exhibited low canker occurrence, with the coppice resprouts displaying less canker elongation than adults. In contrast, drought resprouts still appeared susceptible to canker disease, in which their canker development was similar to non-irrigated adults. This may emphasize the importance of water availability for walnut trees defending themselves from canker disease, or it may be related to the removal of upper branches in coppice resprouts, thus removing potential inoculum of the disease agent. Despite the presence of cankers, drought resprouts appeared green and healthy at the time of the study.

1 - California State Polytechnic University, Pomona, Biological Sciences, 3801 West Temple Ave, Pomona, CA, 91768, United States
2 - California State Polytechnic University, Pomona, Biological Sciences, 3801 West Temple Avenue, Pomona, CA, 91768, USA
3 - Pepperdine University, NATURAL SCIENCE DIV, 24255 Pacific Coast Highway, Malibu, CA, 90263, United States
4 - California State Polytechnic University, Pomona, Plant Sciences, 3801 West Temple Ave, Pomona, CA, 91768, United States
5 - California State Polytechnic University, Pomona, Department Of Biology, 3801 West Temple Avenue, Pomona, CA, 91768, United States

Keywords:
Juglans
Drought
canker disease
water stress
walnut
resprout.

Presentation Type: Oral Paper
Session: PHYS2, Physiology II
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 3:30 PM
Number: PHYS2003
Abstract ID:342
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation