Date March 1, 1993

Title of Project Leaf Yellowing in Easter Lilies: Causes and Solutions

Institution where work is being conducted Clemson University and Purdue University

Amount of Endowment Grant$ 12, 000
Covering Period 1/93 to 12/93

Anticipated Date of Project Completion/Final Report December 1995 or December 1996

Individual(s) Conducting Project:

(List Project Leader First)

Dr. William B. Miller, Proiect Leader - Title Associate Professor

Telephone Number 803-656-0898

Dr. P. Allen Hammer - Title Professor

Dr. Nihal C. Rajapakse - Research Associate

Mr. James H. Blake - Title Extension Associate

Leaf Yellowing in Easter Lilies: Causes and Solutions

William B. Miller, P. Allen Hammer, Nihal C. Rajapakse, James H. Blake

Clemson University and Purdue University

Progress Report to the American Floral Endowment, 3/1/93

A. Project Objectives:

1 . Define and systematically study cultural practices that influence leaf yellowing (both

gradual and catastrophic) in Easter lily.

2. Evaluate potential remedial practices, including anti-senescence chemical treatments.

3. Develop cultural and/or other production guidelines, disseminated through trade

literature and other sources, for the industry.

B & C. Summary and Results of Work Completed to Date:

We are presently growing 400 6-inch pots of ‘Nellie White’ and 200 6-inch pots of ‘Ace’

Easter lilies in glass greenhouses in West Lafayette, Indiana. Half the plants are growing

at a positive DIF of 70′F day/60′F night temperature and half the plants are growing at a

negative DIF of 58′F/67′F night temperature. Night temperatures are applied from 5 pm

until 8 am. The average daily temperatures are the same between the two houses. These

plants will be used for studying the effect of DIF on postharvest longevity and

biochemical differences. At Clemson, we have about 300 ‘Nellie White’ and 100 ‘Ace’

plants growing. We have just reached visible bud at both research locations. Several

experiments have been initiated, and are outlined below. Because of the nature of the

crop and its timing, we have no direct results as yet from this first crop, but experiments

in progress are outlined below. Mr. Anil Ranwala, a Ph.D. candidate at Clemson, is

assisting in the research.

In South Carolina, we have collected many samples from commercial plants

showing gradual lower leaf yellowing, and will be analyzing them for carbohydrate and

nitrogen later this spring and summer. We hope to learn whether gradual leaf yellowing

is associated with nitrogen deficiency and/or “carbohydrate stress” in lower leaves.

Another hypothesis is that catastrophic leaf yellowing in cold-stored lilies is

dependent on postharvest light and/or temperature. Cold-stored plants will be held after

storage at 7O’F with or without “interior” lighting. Onset of leaf yellowing will be

followed over time, and leaves sampled for chlorophyll loss.

To test the hypothesis that negative DIF, or high forcing temperatures, increase

the incidence of post-harvest leaf yellowing, plants are being grown at Purdue +10 or -11′F

DIF to give equal 24-hour temperature averages. Tissue will be collected at Purdue for

carbohydrate and nitrogen analysis at Clemson. Further, plants will be shipped to

Clemson for post harvest evaluation. At Clemson, other plants will be transferred to a 70′F

NT greenhouse for the last 4 weeks of forcing to simulate a late crop being forced

under higher temperature. Carbohydrate samples, and post harvest quality will be

evaluated.

Finally, ‘Nellie White’ plants are being grown with reduced fungicide applications

and/or high irrigation rates at Clemson. Leaf yellowing will be noted.

D. Future Plans Covered by the Endowment Grant:

We will be analyzing tissue samples from this project throughout the summer. We will

have results of several experiments ready for the September 1 progress report.

E. Anticipated Benefits for Floral Industry:

While Easter lilies are among the most valuable crops on a square foot basis in U. S.

floriculture, they suffer from two potentially serious leaf-yellowing disorders: 1) a

gradual yellowing of basal leaves during forcing, and 2) “catastrophic yellowing” which

mainly occurs during post-production shipping and marketing. This disorder strikes

quickly, causing a normal looking plant to turn almost entirely yellow within a few days

after cold storage. We are evaluating the cultural factors (growth regulators, nutrition,

fungicide application, high temperature forcing, shipping, and cold storage) which are

involved in these disorders. Our research is of great value to the industry for maintaining

profitability of the crop. If successful, it would allow confident handling and shipping of

this crop and reduce economic loss in the industry.

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