PHYSIOLOGICAL EFFECTS OF HEAT STRESS ON LIMA BEAN (Phaseolus lunatus) AND DEVELOPMENT OF HEAT TOLERANCE SCREENING TECHNIQUES

Authors

E. G. Ernest, University of DelawareFollow
R. J. Wisser, University of Delaware
G. C. Johnson, University of Delaware

Date of this Version

3-2017

Citation

ANNUAL REPORT OF THE BEAN IMPROVEMENT COOPERATIVE, No. 60, March 2017. Published by USDA.

Comments

U.S. government work.

Abstract

INTRODUCTION Heat stress reduces yields of May and early June-planted lima beans (Phaseolus lunatus) on the Delmarva Peninsula. High temperatures during flowering reduce or delay pod set and can result in later harvest, lower yield and split sets. We are working to develop heat tolerant baby and Fordhook type lima bean cultivars that are adapted to the Mid-Atlantic Region. Both field and greenhouse screening methods have been used to test inbred lines for heat stress response, but greenhouse screening has been particularly useful in determining the physiological effects of heat stress.

METHODS Eight lima bean inbred lines were grown in two climate controlled chambers inside of the greenhouse under hot and cool night temperature regimes. Experiments were arranged in a randomized complete block design with 5 replications. Target night temperatures were 27 °C in the hot chamber and 18 °C in the cool chamber. For experiment 1, target daytime temperatures were 32-35 °C in the hot chamber and 27-30 °C in the cool chamber. For experiment 2 target daytime temperatures for both chambers were 32-35 °C. Newly opened flowers were collected from plants grown under hot and cool night conditions. The style, with pollen adhering to it, was removed from the flower, stained with acetocarmine, then viewed and photographed under 40x magnification. We later counted stained pollen grains visible in the photograph. We harvested pods from the plants at maturity and noted the number pods, number of seeds per pod, total number of seeds and total weight of seeds for each plant.