A new plum breeding program has kicked off in Murcia, Spain to answer the needs of the Japanese plum industry, focusing on ways to supply new early ripening varieties between May and June.

Dr. David Ruiz of CEBAS - CSIC, one of the entities involved in the program, highlighted the program's importance during the International Symposium on Plums and Sweet Cherries at Fruit Attraction, held last week in Madrid.

"Spain is a major world plum producer with around 200,000 tons (MT) per year. It is the second major fruit behind the peach in Spain, surpassing the production of other fruit such as apricots and cherries," he told the audience.

He explained that Extremadura, Murcia and Andalusia were the main producing areas in Spain.

"In Extremadura, production is now close to 80,000MTper year and in the region of Murcia and Andalusia, it is around 40,000MT per year. This data gives an idea of ​​the socioeconomic importance of this crop in Spain," he said.

However, in recent years there has been a decrease in the area cultivated for plums, which went from 21,000 hectares in 2005 to 18,500 in 2009.

Ruiz explained Japanese plum growing in Spain had a number of problems and deficiencies, including reduced use of early ripening varieties and the fact many of the varieties introduced in recent years have shown adaptation problems to the cultivation conditions, as well as having high royalties.

This is compounded by the frequent floral self-incompatibility in virtually all varieties of Japanese plum, which means the fruit needs adequate pollination, he said.

"There are very few varieties that have been studied and confirmed as self-compatible," he added.

"There are many cases where you have pollinators on farms but not the percentages required to produce adequate pollination and, moreover, we should also have bees for pollination to occur."

The expert said another problem facing the Japanese plum in the poor quality of the fruit, which affects their marketing and, therefore, profitability.

Along with this is the Sharka virus, which affects the majority of Japanese plum varieties and causes, in many instances, loss of commercial value.

"So far, there is no known source of resistance in the Japanese plum to this disease, so it is a major problem and one that we should try to address as soon as possible," he said, adding that the Japanese plum is an excellent host to aphids which transmit the virus, making the fruit a diffuser of the disease to other species.

"Given the economic importance and all these deficiency problems in growing the species, it is paradoxical that the existence of breeding programs for this species is very scarce," he said.

He explained that on an international level there are some programs in South Africa and the United States.

Program Objectives

Among the objectives of the program is the development of new varieties with an early maturing period (May and June).

"We think that is our principle niche for production, profitability and marketing for Japanese plums. We have virtually no competition in the European market, in international markets at the time. It is also a time when supply is scarce varietal and so we think obtaining those early varieties has great potential."

Work is also being done on floral self-compatibility and on improving productivity and fruit quality to have a product with good color combinations and pulp.

The expert noted that, within possible means, they will also attempt to introduce Sharka virus resistance in the species.

"As there are no known sources of resistance to Sharka virus in Japanese plums, we have been forced to try to introduce this resistance through interspecific crosses with other species such as the apricot or European plum, where there are some varieties with genotypes resistant to the virus," he said.

In the same way, since the beginning of the program, they have raised four action lines. One is the creation of a collection of potentially usable varities as parental varieties.

"The existence of Japanese plum collections is scarce. Collections do exist but fundamentally, they are collections of European plums, and we think it is appropriate to seek a collection of interesting varieties."

"Another interesting line of action is to evaluate key aspects of commercial varieties," he said.

While the program is new and results still low, Ruiz said that the main priorities of the program have progressed satisfactorily.

"We are very motivated and encouraged that things are going reasonably well."

They will also study in depth the need for winter cold to make the plant come out of lethargy and they are evaluating the flowering date and maturity in growing conditions.

Information

The program has the support of produce enterprises in the Murcia region. It was conceived and is being developed in coordination between fruit breeding group CEBAS-CSIC and fruit-growing group IMIDA of Murcia, with the support of the Murcia Office of Agriculture and Water.

Both research groups have extensive experience in breeding stone fruit.

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