For several years, Applied Plant Research (PPO) has been working on a sporeless oyster mushroom. Research over the past year has produced 30 different prototypes of an HK35-based sporeless variety. In addition, 22 different prototypes have been developed of sporeless varieties based on the P24. In order to select the best from this huge range of prototypes, PPO set a number of trial cultivation runs (see MB1). These initial trails have now been completed.

For several years, Applied Plant Research (PPO) has been working on a sporeless oyster mushroom. Research over the past year has produced 30 different prototypes of an HK35-based sporeless variety. In addition, 22 different prototypes have been developed of sporeless varieties based on the P24. In order to select the best from this huge range of prototypes, PPO set a number of trial cultivation runs (see MB1). These initial trails have now been completed.

The strange appearance of the first sporeless variety, developed in the 1980s, meant it was unsaleable. The mushrooms were trumpet shaped and failed to grow erect. During the first trials, PPO devoted particular attention to the appearance of the mushrooms. However, appearance is not the only characteristic required to create a commercially successful variety. To make the right choice, the experience of the advisory commission for the project was drawn on. Two representatives from substrate companies, one representative from a spawn company and four growers form this commission. The commission assessed the various prototypes. The two best strains will shortly be grown on a larger scale on three farms. The experiences produced by these trials will ultimately determine if development of a commercial sporeless variety has progressed far enough.

Differences

The prototypes were grown on common straw substrate with three packages per log. Colonization of the substrate proceeded virtually identically with all the prototypes. However, there were clear differences in traits such as time of pinheading, yield and mushroom quality.

Compared to the HK35, the P24 is a variety that already starts producing quite quickly after blow down. The mushrooms are smaller and less fleshy than the HK35. The sporeless variety derived from the P24 had an entirely different appearance to the original P24. Normally all the oyster mushrooms grow vertically in a cluster. However, fruits from the sporeless P24 variety branched out randomly. As well as this, all the sporeless types derived from P24 produced mushrooms ranging in shape from umbrella-like to resembling trumpets, instead of the required shell form. Just five of the twenty sporeless derivations proved to be able to match the production speed of the original P24 variety. The yields of these sporeless varieties varied from 60 to 100 % of the production of the P24.

None of the tested sporeless P24-like types impressed the advisory commission enough to continue further trials for commercial suitability. As a note, the original variety P24 was not the favourite candidate of most members of the advisory commission in the first place. The PPO researchers also think the sporeless version of the P24 needs further development to make it commercially viable.

Candidates

HK35 is by far the most widely grown variety, which makes a sporeless version of this type a very interesting proposition. Although with most of the prototypes derived from the HK35 the fruit bodies grew in random positions, the advisory commission identified two potentially interesting candidates. With these varieties (referred to as variety 1 and 2) the growth pattern of the mushrooms was quite erect with an acceptable appearance. Production equalled that of the HK35. The time the flush appeared hardly differed with HK35 and variety 1. With variety 2 the first flush was a little slower in forming. However, it gave mushrooms with a more attractive colour.

PPO will shortly test variety 1 and 2 on three farms. These practical trials will demonstrate if a commercially acceptable variety has been developed. The researchers hope to be able to report on progress in December. These varieties already fully comply with one of the criteria: there's no trace of spores.

Sporeless variety interesting

A sporeless oyster mushroom offers multiple advantages. The most obvious one concerns labour conditions when harvesting and grading oyster mushrooms. Cultivating sporeless varieties is expected to be more energy efficient, as air can be recirculated without obstructing the filters. Practical experience will show the precise extent of these savings. Calculations indicate that a 40 % reduction in energy consumption should be possible. New to be built growing facilities - if cultivating sporeless varieties only- could use a smaller climate installation - which will save on construction costs.

It will be interesting to see the effect of sporelessness on long-term yields. At the moment oyster mushroom bags that are at the incubation stage are kept strictly separated from bags in production. The spores of oyster mushrooms are suspected of spreading diseases from one crop to another. This is supposed to explain why certain oyster mushroom growers have an excellent yield with a new variety, which rapidly declines after a few months until they start growing a different variety again.

If spores do prove to be the culprit, then it's logical that a sporeless variety will not produce such fluctuations.