What causes red drupes?

Red drupe in Prime-Ark 45. Likely due to excessive rain, These drupes never turned black.

Usually all the drupelets on a ripe blackberry fruit are uniformly black. Sometimes the fruit can have drupes that are white, tan or red. White and tan drupelets have been discussed before (https://teamrubus.blogspot.com/search?q=white+drupelet). 

The focus of this post is to discuss the occurrence of red drupes in blackberry fruit. This reddening can occur after and before fruit is harvested.  There are several known causes of red drupes and some conditions that are speculation. No matter what the cause, excessive amounts of red drupes can result in rejection of fruit in wholesale markets.

After harvest

Reversion. This is the most common cause of red drupes.

Symptoms. Drupes are black at harvest and turn red after harvest.

What is known. Research conducted by Max Edgley from the University of Tasmania looked at several factors including nitrogen rates, physical damage during harvest and transportation to the cooler, air temperatures during harvest, slow or fast cooling of fruit after harvest.  

Key Findings from the University of Tasmania study:

• Physical damage (bruising, impact and fruit compression) during harvest and shipping is the main cause of red drupelet disorder
• High nitrogen fertigation during harvest can significantly increase the amount of fruit with red drupelet disorder post-harvest
• Fruit core temperatures exceeding 23C (73F) at harvest significantly increase the amount of red drupelet post-harvest
• Harvest times, techniques, and shipping conditions can be manipulated to reduce incidence of red drupelet disorder
• A step-cooling process reducing the rate of cooling post-harvest has been effective in reducing incidence of the disorder
• They also found that early season fruit is more prone to this disorder. 

https://www.utas.edu.au/tia/research/research-projects/projects/red-drupelets-on-blackberries2

https://www.utas.edu.au/__data/assets/pdf_file/0015/1110435/Blackberry-red-drupelet-fact-sheet-2017.pdf 

Addedum from Alejandra Salgado (PhD U Ark):  a weak cell wall can also cause reversion. 

See also blog post on red drupe reversion here: https://teamrubus.blogspot.com/search?q=white+drupelet


Before harvest

Redberry mite. (Redberry disease).

Symptoms. Fruit that are infected with Redberry mites have drupes never turn black. Red drupes are hard.

What is known. The mites inject a toxin into the base of the drupelets and as a result, the drupelets fail to develop normally.  Redberry mites are uncommon in the eastern United States. If you suspect they are the cause of red drupelets, samples should be submitted to your local plant disease and insect clinic for diagnosis.

Here is more information from:

Utah State University.

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2944&context=extension_curall
University of California

http://ipm.ucanr.edu/PMG/r71400111.html 

Excessive rain.

Symptoms. Red drupes are soft and never turn black.

What is known. There have been reports of significant red drupelet in parts of NC this year in fruit that are otherwise ripe and ready to harvest. Many, but not all of the fields have tunnels over them. The cultivar Prime-Ark 45 is seeing most of this disorder this season on the floricane crop. We cannot confirm that the rain is causing the red drupes, it is just our best guess at this time as the above (reversion and redberry mite) have been ruled out.

Viruses?

Red drupes have not been identified as symptoms associated with viruses to the best of our knowledge. 


Authors: Gina Fernandez, Hannah Burrack and Penny Perkins-Veazie and in consultation with multiple experts around the world. 

Managing (?) older plantings of raspberries and blackberries

In our raspberry trials in the NC mountains, where raspberries are adapted and are capable of producing good crops, we have seen productivity decline after the 5th year of fruit production. While in the peidmont areas, we see a dramatic decline in the 2nd year of fruit production of raspberries (they are not adapted to the region). Blackberries on the other hand, tend to be more adapted and will live longer in most regions of the state. However, how long they will last is not known. In North Carolina and other states in the Southern US a recent rise in acreage of blackberries occurred in the past few years and as these plantings age, we need to monitor them to determine how long they will be productive both in terms of fruit and profits.

In the southern US, heat, drought, insects, diseases, if not controlled can take their toll on the productivity of a blackberry and raspberry field. Likewise, plant and soil health needs to be monitored in order to provide a plant with optimal nutrition.  Because this is a fairly new industry, we don't have long term experiences with the crop, however, below are a list of things to think about and address as needed as your plantings age.

Observation of annual growth. Growers should keep good records of individual fields and compare productivity from year-to-year. In addition to yield records, the plants health can be monitored by looking number of canes/plant, cane diameter,  and number of fruiting laterals. You do not need to count each of these, but a picture taken at the same spot in the field each year could help you identify any issues.

Diseases and insects. There is a long list of diseases that can negatively impact  blackberry or raspberry plant health.  In fields that are lightly managed, I most often see cane blight and viruses, and borers negatively impact productivity. 

Weeds. Perennial weeds harder to control over time and annual weeds will compete with crop. Both will impact productivity if left unchecked.

Fertility. There is no known long term research for caneberry fertility in the southern US. However, routine soil and plant tissue samples will help you determine needs and adjustments. Tissue samples should be taken each year and sent for evaluation. In NC, samples should be taken after fruit harvested from the plants. Leaves from the 3-5th node of the primocane plant should be taken and sent to NCDA and they will make recommendations for the following season. Keep your records so you can see if there are trends in your fields. Below are the recommended levels of macro and micronutrients.

Yield and prifitabilty. Good yield records for each field should be taken every year. A simple comparison each year will be your most useful indicator of planting productivity over time. Based on a budget developed at NC State University, when a grower is getting $14/flat, a 10% reduction in yield, their returns fall from $6036 to $4359/acre (see blue font below). You can get a copy of this budget and play with the inputs (any boxes that are blue can be edited).  http://ncsu.edu/enterprises/blackberries-raspberries/management/blackberry-raspberry-budgets-pricing/

Estimated Returns per Acre for Commercial Blackberry Production
for Varying Yields and Wholesale Prices per Flat.  Total yield 19,000lbs/acre, 80% marketable, so net of 15,200 marketable lbs/acre.
	Wholesale Market ($/flat)	Marketable Flats per Acre
		1,621	2,027	2,533	3,040	3,648
	$8.96	($8,173)	($7,533)	($6,732)	($5,932)	($4,971)
	$11.20	($4,542)	($2,993)	($1,058)	$878	$3,200
	$14.00	($2)	$2,682	$6,036	$9,390	$13,415
	$16.80	$4,538	$8,356	$13,129	$17,902	$23,629
	$20.16	$9,986	$15,166	$21,641	$28,116	$35,887

Estimated Returns per Acre for Commercial Blackberry Production
for Varying Yields and Wholesale Prices per Flat. Total yield is 17,100 lbs/acre, 80% marketable yield, so net of $13,600 lbs/acre.
	Wholesale Market ($/flat)	Marketable Flats per Acre¹
		1,459	1,824	2,280	2,736	3,283
	$8.96	($8,429)	($7,853)	($7,133)	($6,412)	($5,548)
	$11.20	($5,161)	($3,767)	($2,025)	($283)	$1,807
	$14.00	($1,075)	$1,340	$4,359	$7,377	$11,000
	$16.80	$3,011	$6,447	$10,743	$15,038	$20,193
	$20.16	$7,914	$12,576	$18,403	$24,231	$31,224

Hot days ahead

Temperatures are predicted to soar into the 100's in NC in the next few days. Raspberries and even their more heat tolerant cousins blackberries will be stressed.  The most important thing you can do at this time is to make sure your plants are well watered. This will help reduce the stress to the plant and enable your berries to continue to ripen and get plump.

Raspberry roots are usually in the top 10" of soil, while blackberries roots can be much deeper. However, the majority of the water is taken up by the roots in the top 6" of soil. Water stress before or during harvest can seriously reduce productivity. Water is the most critical factor for optimal fruit growth and primocane development, a berry is afterall more than 90% water! A shortage of water will limit fruit size and also the number and diameter of primocanes for next years crop.

White (grey or tan) drupelets

In the last few days I have had several calls and emails from growers concerned about white drupelets. Here are a few points that I have gleaned from experience and other articles (see links at the end of the post).

• It is thought that this condition is caused by UV radiation and appears when there has been an sudden increase in temperatures.
• Rainfall appears to make the problem worse, with sunlight on wet berries plus high temperatures. (We have had quite a bit rain in parts of NC lately).
• This was thought to be a result of stinkbug damage many years ago. BUT not now.
• Apache shows more of this problem than any other variety, but white drupelets have been seen on most of the Arkansas varieties. 
• Tolerance for white drupelet varies to some extent by grower. Growers that ship berries have no tolerance, while pick-your-own growers can tolerate a few white drupelets (see last point, educate your clientele).
• White drupelet disorder is usually a problem early in the season and then disappears.
• The berries are still edible, they make delicious pies, juice, ice cream...

For more information see

http://plantpathology.uark.edu/Number_15-2010.pdf

and

http://www.raspberryblackberry.com/Webdocs/nabga08-06news.pdf

Rotating Cross Arm Trellis

RCA trellis with young untrained canes at Piedmont Research Station, 2011.

At our Piedmont Research Station, in Salisbury NC, we (Gina Fernandez and Penny Perkins-Veazie) have started evaluating the Rotating Cross Arm Trellis system. This project is in cooperation with Dr. Fumi Takeda, USDA-ARS. Dr. Takeda has been working on this system for many years and is helping us train and manage the canes on this trellis.

This year we are determining if row orientation will impact blackberry fruit quality. Row are orientated N-S and E-W. The set in the foreground is running  E-W while the second set of trellises in the background of this image runs N-S. We will be collecting yield data and post harvest attributes. We think that this type of trellis may improve fruit quality and yield.

This trellis system also has potential to enable growers to cover the plants in the winter or during spring frosts like the one we had this year. The trellis arms rotate, so the canes can be layed down and row covers could be placed over the trellis to protect the plants, similar to what is done in strawberries. Here is a picture of a field with the RCA in Ohio in the summer and winter.

The trellis was donated by Trellis Growing Systems (http://trellisgrowingsystems.com/).

Can raspberries be picked pink for fresh markets?

By Penelope Perkins-Veazie, Plants for Human Health Institute, North Carolina State University and Gina Fernandez, Department of Horticultural Science NC State University

Raspberries are the most perishable of the temperate fruit crops. If you set them on your kitchen counter, you can watch the mold grow within 24 hours. This fruit’s delicate nature is due to its fragile structure, where drupelets are connected together by only a few trichomes (fruit hairs), no cuticle is present, and gray mold (Botrytis cinerea) can set up spores during bloom and produce fuzzy gray fruit as the berries are ripening.

While raspberry fruit mostly produce ethylene from the fruit calyx (the part of the fruit that remains on the plant), there is a small amount of ethylene, the fruit ripening hormone, present in many varieties. This actually can pose an advantage for fruit growers producing raspberries in the warmer parts of the season. Fruit at the pink or even pink-yellow stage will often detach from the calyx with minimal tugging.

We initiated a small test in 2010 to investigate the ability of raspberries to attain full ripeness if harvested unripe. These fruit were harvested in August and September from plants grown in high tunnels at the Upper Mountain Research Station, Laurel Springs, NC. Temperatures within the tunnels were above 85°F for approximately four hours per day. Unripe and ripe raspberries were picked at weekly intervals for the tests, over a three-week period, and one to two clamshells per cultivar and ripeness were used for the study. 

Raspberries were picked into halfpint clamshells and transported at 5°C in refrigerated ice chests (Kooltron) to Kannapolis, and held at 39 °F for six days. Subsamples were removed at day 0 to check firmness, color, sugars, and acidity. Subjective ratings were taken after storage by checking each berry for softness, leak, and mold. The overall color of the fruit within the clamshell was determined subjectively as 0 (light red) to 3 (dark purple red). Percent saleable fruit was determined by using the relationship of color to percent (where rating of 0 was 100% saleable to 3 was 0% saleable).

Surprisingly, even fruit picked considerably unripe (yellow-pink) achieved full color, soluble solids content, acidity, and flavor (tasted at random) after six days storage (Table 1). The biggest disadvantage of picking unripe berries was a depression in berry size of 4% to 20%, depending on variety and relative ripeness at harvest. What was clear from ratings was that fruit picked pink was much firmer and less leaky than berries picked at the normal commercial fresh market ripe stage (Table 2). The amount of moldy berries was slight (less than 10%), due to a rigorous fungicide spray program and the protective effect of the tunnels from moisture and wind.

We hoped that berries varieties known to turn dark red after storage, such as Joan J, would be less fully red if picked pink prior to storage. In fact, we found that color could not be slowed enough, with fruit reaching full color as soon as 2 days at 39° F after harvest. Figure 1 illustrates the change in color of ‘Culivar’ in ripe and unripe berries at 0, 5 and 10 days after harvest.

Flavonoids are compounds are compounds  that are associated with health benefits, and higher levels in fruit are good. Flavonoids in raspberry include the anthocyanins that give raspberries much of their red color, along with other colorless phenolic compounds. In raspberries picked before full ripeness, flavonoid content was decreased by 5-15% after storage. The slight loss in flavonoids in the less ripe fruit was madeup in the better appearance and firmness of the raspberries.

Harvesting raspberries at the pink stage is possible. We did not observe significant problems with composition and flavor, and early picking improves the number of marketable fruit. However, harvesting less ripe fruit is likely dependent on air temperature (detaching raspberries is difficult in cool weather), and will require more attention and training of pickers during harvest than pulling off fully ripe berries. Although we did not determine optimal temperatures for picking unripe berries in this study, the ability of raspberries to fully color up and soften may depend greatly on having a production environment where temperatures are at 75° F for at least four hours.

Table 1.  Comparison of raspberry fruit harvested unripe (pink) or ripe (red)
before and after storage at 4C, averaged for Joan J, Nantahala, Caroline
Variant	Days	Unripe	Ripe	Mean
Total phenolics	0	2858	2866	2862
(mg/kg gallic acid equivalents)	6	3090	3144	3117*
Total anthocyanin	0	508	530	519
(mg/kg cyan-3-glucoside equivalents)	6	510	589	550*
FRAP (Ferric reducing antioxidant potential)	0	28.6	26.8	27.7
(umol/g trolox equivalents)	6	28.5	28.8	28.6
Soluble solids content (%)	0	11.2	10.9	11.1
	6	11.9	11.7	11.8
Titratable acidity (%)	0	1.23	1.26	1.24
	6	1.05*	1.19*	1.12*
Means separated within column and days 0,6 using student's t-test, P<5%.

Table 2.  Comparison of raspberries picked unripe (pink) or ripe (red) after storage at 4C for 6 days
	%Leaky berries		%Soft		%Saleable	color
Variety	Unripe	Ripe	Unripe	Ripe	Unripe	Ripe
Autumn Britten	1a	42b	48ab	93a	43b	7b
Caroline	8a	19a	61a	86ab	47b	33ab
Nantahala	2a	37b	38b	75b	67a	47a
Mean	3a	33*	49	82*	52	29*
Means separated within column among cultivars, by letter (P<5%) using REGWQ.

The original version of this article (including photos) appears in Autumn 2011 issue of "The Bramble."  To access this article, you must be a member of the North American Raspberry and Blackberry Association. To become a member to: http://www.raspberryblackberry.com/index.cfm and click on Membership in the left purple panel. 

New Publication

Dr. Ramón Molina-Bravo, was a PhD student that worked with myself and Dr. Bryon Sosinski at NCSU. Dr. Molina-Bravo just published an article that details a study that he conducted as part of his research. In a nutshell, he was able to identify several plants in a population of seedlings that had higher chlorophyll fluorescence, a trait that is associated with heat tolerance. We are using those individuals in our breeding program to see if they will survive the heat in additional locations and we will be using them in crosses in the near future.  Congrats Ramon! Here is a link to that article. doi:10.1016/j.scienta.2011.07.022

Heat stress in raspberries, part 2

So, many of you are probably thinking "Why would anyone try to grow raspberries in a hot, humid environment like North Carolina?" Well, you are not the only one that has had that thought. There are several points that I want to make in regard to this idea.

First, North Carolina has multiple environments. The three primary regions are the Coastal Plain, Piedmont and the Mountains.  So, within the state we have a range of elevations from sea level to over 3000 ft (ca 1000 m). This allows us to grow our plants in a wide range of environments.  In the summer, all regions are hot, some are just not as hot, with high temperatures only in the 80's. However, this range of climates allows some growers to produce fruit earlier in the season and some can go later in the season. We are not trying to produce raspberries in the coastal plain in mid July. That is just too hot for this delicate fruit.

Second, in warm conditions, fruit set is often a problem. However, in our screening process, we find that some of our test plants that are able to survive the heat and have flowers that can produce fruit.  And it is this last group that we choose to select and propagate for further observations. 

Third, even if a raspberry variety can survive in the hotter areas, we find that fruit size improves when we move it to our more moderate locations (see example of fruit size above). The two pictures are fruit from the same selection planted in two different places. The hotter location is SH (the Sandhills) and Sal (Salisbury) is only 90 miles away. 

Lastly, we are finding, thanks to Dr. Penny Perkins-Veazie, that even though some of the newer varieties look good at harvest, once we pick them they go downhill rapidly. Amazingly, the test plants from our program always seem to do better. 

The role of the environment on the performance of a variety is huge. In fact plant breeders spend alot of time evaluating GXE (Genotype X Environment) interactions. We know that the environmental influence on raspberry performance is significant and that our hot and humid climate enables us to screen in an environment that is not ideal for most raspberry varieties. But we are trying and think we are making good progress.

Heat stress in raspberries, part 1

Severe leaf cupping

Moderate leaf cupping

Today in North Carolina, the temperatures are expected to reach 99F (37C). This type of heat is extremely stressful for raspberry plants and very often they will not live for more than a year or two under these conditions. However, we have found that by screening plants in this type of environment, we are able to find some plants that are somewhat tolerant of heat.

Above are pictures of 2 plants in a seedling population taken on the same day last week when it was hot like it is today. The plants are from the same parents, and are in fact, adjacent to one in another in the field at the Sandhills Research Station in Jackson Springs, NC.  The leaves on the first plant are cupped upward, a classic sign of heat stress, while the second plant has leaves that are only moderately cupped. Most of the plants in this population had severely cupped leaves. But a few did not and those are the ones that we will keep, and test in future trials.

Award Winning Student!

Christine Bradish, a MS candidate just returned from the Berry Health Symposium #berryhealth. She won 1st place in the poster competition.  Christine is working with Drs. Penny Perkins, Wei Jei and myself and is in the final stages of her MS degree at NC State University.


Christine looked for flavonoids in red raspberry that are known to be good for you.  She used metabolite-profiling to qualify, quantify, and compare major flavonoid compounds in primocane-fruiting red raspberry cultivars grown at three locations with varying elevation and average temperatures in North Carolina. 


She found:
 •There was significant qualitative and quantitative differences in the metabolite profiles, due to variation in cultivar, location, and environmental factors. (=not all raspberries are the same in terms of health benefits)

•Plants exposed to longer durations of heat stress (over 85°F) had higher total phenolics measurements and antioxidant capacity due to greater production of flavonoid secondary metabolites. (=stress may increase the good compounds in berries)

Implications: 

•Utilization of metabolite profiles, such as the ones in this study, could help breeding programs identify key metabolites contributing to antioxidant properties, and define the genotype-by-environment interactions on them. 

•This technology may be useful for the development of nutritionally enhanced varieties, and further tailoring for functional foods.

The link to the proceedings is below. Her abstract is on page 61.
http://www.berryhealth.org/Information/2011_preproceedings_sm.pdf