View
0
Download
0
Category
Preview:
Citation preview
HEAT AND LIGHT STRESS/SUNBURN
Schrader, L.
schrader@wsu.edu
Professor Emeritus, Washington State University, Wenatchee, WA
KEYWORDS Apple; skin disorders; sunburn necrosis; sunburn browning; photo-oxidative sunburn; fruit surface temperature (FST); Fuji stain; lenticel marking; sunburn scald in Granny Smith; water core in Honeycrisp ABSTRACT Several fruit skin disorders are induced by heat and/or light stress in apples (Malus x domestica Borkh.). Some disorders appear on fruit prior to harvest, whereas others do not appear until after harvest and cold storage. Fruit do not utilize much light energy, so excess light energy is converted to heat injury. On a hot day, the fruit surface temperature (FST) of the sun-exposed side of apple can be 20 to 30 °F above air temperature. Sunburn is usually the major cause of cullage. It appears before harvest and its incidence often provides an early signal that other disorders will appear later. Three types of apple sunburn have been characterized (Figure 1). One type (sunburn
necrosis) is caused by heat alone. A high FST of ~126 °F results in thermal death followed by necrosis. A second type (sunburn browning) occurs with high FST (115 to 120 °F) and damaging UV-B radiation. A third type (photooxidative sunburn) appears to be caused by visible light alone and occurs on green peel (non-acclimated to light) that is suddenly exposed to full sunlight so that photobleaching occurs first, followed by necrosis. This third type results from photooxidative damage and can occur at much lower FST and without UV-B radiation. Another disorder that results from heat and light
Necrosis Browning Type 3
Figure 1: Three types of fruit skin disorders induced by heat and/or light stress
stress is lenticel marking. Its incidence increases in fruit that have more severe sunburn. Fuji stain is a skin disorder that appears only after a period of cold storage. This stain disorder appears primarily in sunburned fruit, and its incidence rises sharply as the severity of sunburn increases. We have evidence that UV-B radiation is involved; incidence of stain is higher in orchards with excess Nitrogen. Another disorder that is enhanced by heat stress is bitter pit (especially in Jonagold). Although Calcium deficiency is reported to cause bitter pit, we observed increased bitter pit in Jonagold apples that were exposed to high temperatures and water stress as they neared maturity. Color of the peel did not develop normally, but had a blotchy appearance. High temperatures near maturity also increased water core in ‘Honeycrisp’. This physiological disorder is associated with internal moisture stress, and high temperatures cause premature conversion of starch to sugar and pronounced leakage from cells into intercellular spaces. Sunburn scald in ‘Granny Smith’ develops during cold storage on the sun-exposed side of fruit that showed sunburn browning earlier in the season. If sunburn browning is prevented, the skin disorders listed above seldom appear. This suggests that management practices are needed to reduce absorption of UV-B radiation and to keep FST below critical temperatures at which sunburn browning occurs. Such practices include overhead evaporative cooling; sunscreen such as RAYNOX; sun blockers such as Eclipse or Surround WP; and photo-selective netting.
DR. LARRY SCHRADER
PROFESSOR EMERITUS
WSU TREE FRUIT RESEARCH &
EXTENSION CENTER
WENATCHEE, WA USA
HEAT AND LIGHT STRESS/SUNBURN
WSU FRUIT SCHOOL, WENATCHEE, WA
NOVEMBER 18, 2015
Schrader-2015©
MANY DISORDERS IN APPLES ARE
INDUCED BY HEAT AND/OR LIGHT
STRESS.
SOME DISORDERS WILL APPEAR
BEFORE HARVEST AND OTHERS APPEAR
LATER IN COLD STORAGE
DEFINE STRESS ENVIRONMENT
INTRODUCTION
Schrader-2015©
1. MAX. AIR TEMP OF 95 TO 109 ºF
2. HIGH SOLAR RADIATION—PFD >2200 µmol
m-2 s-1
3. RELATIVE HUMIDITY OF <20%
4. LITTLE OR NO WIND
RESULT OF THIS ENVIRONMENT:
HIGH FRUIT SURFACE TEMPERATURE
(FST) THAT INDUCES SEVERAL FRUIT
SKIN DISORDERSSCHRADER-2015©
IF SOLAR (LIGHT) ENERGY IS NOT USED,
THE EXCESS ENERGY IS CONVERTED TO
HEAT ENERGY.
LEAVES USE LIGHT ENERGY FOR
PHOTOSYNTHESIS ETC., AND CAN
DISSIPATE EXCESS ENERGY THROUGH
TRANSPIRATION. LEAF TEMPERATURE =
AIR TEMPERATURE
WHY DOES FRUIT SURFACE
TEMPERATURE (FST) INCREASE IN THIS
STRESS ENVIRONMENT?
SCHRADER-2015©
FRUIT, HOWEVER, USE LITTLE ENERGY
FOR PHOTOSYNTHESIS, AND POSSESS
LITTLE ABILITY FOR DISSIPATING EXCESS
ENERGY.
THUS, HEAT ENERGY ACCRUES AND
INCREASES FST TO TEMPERATURE AT
WHICH A SKIN DISORDER IS INDUCED.
SCHRADER-2015©
SCHRADER-2015©
25
30
35
40
45
50
55Te
mp
era
ture
(oC
)
No EC FST Air T
104 °F
95 °F
122 °F
113 °F
SCHRADER-2015©
APPLE SKIN DISORDERS
SEVERAL SKIN DISORDERS CAUSED BY
LIGHT AND/OR HEAT STRESS
SOME DISORDERS APPEAR BEFORE
HARVEST & SOME APPEAR LATER
1. SUNBURN
2. LENTICEL MARKING
APPEAR BEFORE HARVEST:
SCHRADER-2015©
3. ‘HONEYCRISP’
WATERCORE
4. ‘JONAGOLD’
BITTER PIT
DISORDERS
ENHANCED BY
HEAT STRESS
SCHRADER-2015©
5. ‘FUJI’ STAIN 6. “SUNBURN SCALD”
OF ‘GRANNY SMITH’
DISORDERS APPEAR AFTER COLD STORAGE
SCHRADER-2015©
SUNBURN USUALLY #1 SOURCE OF
CULLAGE—OFTEN AT LEAST 10% OF
CROP LOST WITHOUT PROTECTANTS
APPLES IN WASHINGTON STATE VALUED
AT $2 BILLION (U.S.); SO 10% LOSS COSTS
GROWERS ~$200 MILLION/YEAR
CONFUSION EXISTS ABOUT
TYPES AND CAUSES OF
SUNBURN IN FRUITS—MANY
HAVE USED DETACHED
FRUITS TO STUDY SUNBURN
SCHRADER-2015©
SUNBURN AS INDICATOR
SUNBURN DAMAGE CAN SERVE AS
INDICATOR THAT OTHER HEAT AND LIGHT-
INDUCED DISORDERS WILL APPEAR
Schrader-2015©
1. SUNBURN NECROSIS
WE IDENTIFIED AND CHARACTERIZED THREE
TYPES OF SUNBURN & THEIR CAUSES:
2. SUNBURN BROWNING
3. PHOTOOXIDATIVE SUNBURN
SCHRADER-2015©
WHAT CAUSES SUNBURN NECROSIS?
SUNBURN NECROSIS OCCURS WHEN FRUIT
SURFACE TEMPERATURE (FST) REACHES
~126 ºF ± 2 ºF FOR ONLY 10 MIN UNDER WASH-
INGTON STATE ENVIRONMENTS.
THERMAL DEATH OCCURS;
CELL MEMBRANES BECOME
LEAKY; & NECROSIS APPEARS.
SCHRADER-2015©
SUNBURN BROWNING
SUNLIGHT REQUIRED.
BLOCKING DAMAGING UV-B
SUNBURN BROWNING OCCURS AT FST OF 115
TO 120 ºF (VARIETY-DEPENDENT) IN WASH.
STATE ENVIRONMENTS. UV-B RADIATION ALSO
INVOLVED. PINK LADY MOST TOLERANT;
CAMEO AND HONEYCRISP MOST SUSCEPTIBLE
RADIATION & REDUCING FRUIT SURFACE
TEMP. (FST) DECREASES SUNBURN.
SO TWO CAUSAL FACTORS: HIGH FST;
DAMAGING UV-B RAYSSCHRADER-2015©
Sb-0 Sb-1 Sb-2 Sb-3 Sb-4 Sb-5
NONE NECROSIS
1Schrader and McFerson System
SIX CLASSES OF SUNBURN1
SCHRADER-2015©
PHOTOOXIDATIVE SUNBURN
• OCCURS ON “NON-ACCLIMATED” APPLES
SUDDENLY EXPOSED TO FULL SUNLIGHT
• INITIAL DAMAGE—BLEACHING OR WHITENING OF
APPLE SURFACE (PEEL) APPEARS WITHIN 24 HR
OF EXPOSURE TO FULL SUNLIGHT.
• BLEACHED AREA TURNS BROWN
WITH CONTINUED EXPOSURE TO
SUNLIGHT; CELLS BECOME LEAKY
• TEMPERATURE- INDEPENDENT
• VISIBLE LIGHT—CAUSES PHOTOOXIDATIVE
DAMAGE (FREE RADICALS etc.)
SCHRADER-2015©
THREE TYPES OF SUNBURN:
NECROSIS, BROWNING, & PHOTO-
OXIDATIVE
SCHRADER-2015©
HEAT ONLY HEAT + LIGHT LIGHT ONLY
DOES SUNBURN BROWNING AFFECT
INTERNAL FRUIT QUALITY, OR IS SUNBURN
“SKIN-DEEP?”
CONDUCTED A SYSTEMATIC STUDY OF
FRUIT QUALITY IN ‘GALA’ (also FUJI,
GRANNIES, GOLDEN DELICIOUS, &
JONAGOLD) WITH DIFFERENT GRADES OF
SUNBURN BROWNING (Sb-0 TO Sb-4)
SCHRADER-2015©
EFFECT OF SUNBURN BROWNING
ON FRUIT QUALITY OF APPLES
1. FLESH FIRMNESS
2. SOLUBLE SOLIDS CONCENTRATION (SSC)
3. TITRATABLE ACIDITY (TA)
4. RATIO OF SSC TO TA
SCHRADER-2015©
Schrader-2015©
Schrader et al. 2009. J. Amer. Soc. Hort. Sci. 134:148-155
CONCLUSIONS—FRUIT QUALITY
1. AS SEVERITY OF SUNBURN INCREASED:
A. FLESH FIRMNESS INCREASED
B. SOLUBLE SOLIDS INCREASED
C. TITRATABLE ACIDITY DECREASED
D. RATIO OF SSC TO TA INCREASED!!
2. EXTENDED STORAGE—TA DECREASED
RAPIDLY; RATIO OF SSC:TA ROSE MARKEDLY
SCHRADER-2015©
SCHRADER-2015©
CONCLUSIONS—FRUIT QUALITY
3. AS SUNBURN SEVERITY INCREASED, STARCH
DECREASED ON SHADE & SHOULDER SIDE
4. SUNBURN IS MORE THAN SKIN DEEP—
AFFECTS THE CORTEX TOO
HOW CAN SUNBURN BROWNING BE
REDUCED?
1. WHAT ABOUT FST?
EVAPORATIVE COOLING (EC) IS MOST
EFFECTIVE WAY TO DECREASE FST, BUT
INSTALLATION IS EXPENSIVE & WATER USE IS
HIGH. PROVIDES NO UV PROTECTION.
2. WHAT ABOUT UV RADIATION?
BLOCK ONLY PART OF DAMAGING UV RAYS,
AS UV-B IS REQUIRED FOR “RED COLOR”
PIGMENT (i.e. ANTHOCYANIN) DEVELOPMENT
SCHRADER-2015©
TOOLS FOR SUPPRESSING SUNBURN
1) APPLY A SUNSCREEN (i.e. RAYNOX®)
2) APPLY A SUNBLOCKER (PARTICLE FILM)—
SURROUND WP, ECLIPSE; PURSHADE
3) ACTIVATE EVAPORATIVE COOLING (EC)
5) PHOTO-SELECTIVE NETTING & BAGGING
6) GOOD HORTICULTURAL PRACTICES—
PROPER PRUNING, THINNING, IRRIGATION ETC.
Schrader-2015©
4) BMP: COMBINE RAYNOX® AND EC
A HAPPY ‘FUJI’ APPLE—RAYNOX® + EC
SCHRADER-2015©
THANKS FOR YOUR
ATTENTION
QUESTIONS?
Schrader-2015©
Schrader et al. 2009. J. Amer. Soc. Hort. Sci. 134:148-155
Schrader-2015©
Schrader et al. 2009. J. Amer. Soc. Hort. Sci. 134:148-155
Schrader-2015©
Schrader et al. 2009. J. Amer. Soc. Hort. Sci. 134:148-155
Schrader-2015©
Schrader et al. 2009. J. Amer. Soc. Hort. Sci. 134:148-155
Recommended