Causes of Gastrodia elata trait degeneration and control methods

Degeneration of Gastrodia elata traits usually manifests as a decline in the yield of arrow gastrodia, with the individuals becoming smaller and slender; the yields of rice gastrodia and white gastrodia drop substantially, the tubers turn ginger-yellow or light brown, stress resistance is poor, and the original yield and traits cannot be fully expressed. The causes are generally as follows:

1. Multiple generations of asexual propagation. Degeneration generally begins to appear after 5 to 6 generations of asexual propagation, but the speed of degeneration differs when cultivated on different soils; degeneration is slower when cultivated on granite soil, followed by yellow-brown earth sandy soil parent material, and the acidic soil formed by the weathering of shale or limestone.

2. Continuous cropping. Under normal circumstances, the yield is high in the first year and low in the second year, and after 3 to 4 years the yield declines rapidly.

3. Degeneration of Armillaria mellea. It first manifests as reduced adaptability and stress resistance, with slow growth of the rhizomorphs; then the rhizomorphs become inelastic and fragile, and even turn into empty shells. As the number of subculturing generations continues to increase, Armillaria mellea forms thick, long, numerous and branched brown-black rhizomorph networks on the inoculated wood.

4. Dense deep-layer cultivation. This method causes a lack of oxygen during the growth of Gastrodia elata, leading to a decline in vitality.

5. Diseases. Old seed gastrodia, old inoculated wood and old planting pits are the most susceptible to disease; in mild cases growth is poor, and in severe cases there is a total loss of harvest.

6. High temperature. It induces and accelerates disease onset, causing poor growth of Gastrodia elata; the most obvious sign is that the head of the arrow gastrodia takes on a "bottleneck" shape, with increased numbers of rice gastrodia and small white gastrodia, and increased numbers of rotted gastrodia.

Control methods: (1) Use wild species and introduced species from other regions, especially introducing from higher terrain to lower terrain. (2) Screen and cultivate high-quality Armillaria mellea strains, purify and expand them, compare lines, rejuvenate and propagate them, cultivate high-quality inoculated wood, and use high-quality loose culture material as filler and mulch. (3) Change the cultivation site, choose acidic sandy loam, and avoid continuous cropping. (4) Adopt sexual propagation techniques. Alternate sexual propagation with asexual propagation; corms from sexual propagation are planted for only 4 to 5 generations. (5) Apply hybrid varieties. (6) Strictly prevent and control diseases.