Katri Himanen

Thermal and hyperspectral imaging for Norway spruce (Picea abies) seeds screening

Hyperspectral and thermal lifetime imaging were used to assess spruce seed quality.Viable, empty and infested seeds were resolved with high accuracy with both methods.400-1000nm data was not as informative as 1000-2500nm and thermal decay data.Classification of 93% accuracy was obtained using three wavelengths in SWIR range.The results suggest that high-throughput spruce seed quality testing is possible. The quality of seeds used in agriculture and forestry is tightly linked to the plant productivity. Thus, the development of high-throughput nondestructive methods to classify the seeds is of prime interest. Visible and near infrared (VNIR, 400-1000nm range) and short-wave infrared (SWIR, 1000-2500nm range) hyperspectral imaging techniques were compared to an infrared lifetime imaging technique to evaluate Norway spruce (Picea abies (L.) Karst.) seed quality. Hyperspectral image and thermal data from 1606 seeds were used to identify viable seeds, empty seeds and seeds infested by Megastigmus sp. larvae. The spectra of seeds obtained from hyperspectral imaging, especially in SWIR range and the thermal signal decay of seeds following an exposure to a short light pulse were characteristic of the seed status. Classification of the seeds to three classes was performed with a Support Vector Machine (nu-SVM) and sparse logistic regression based feature selection. Leave-One-Out classification resulted to 99% accuracy using either thermal or spectral measurements compared to radiography classification. In spectral imaging case, all important features were located in the SWIR range. Furthermore, the classification results showed that accurate (93.8%) seed sorting can be achieved with a simpler method based on information from only three hyperspectral bands at 1310nm, 1710nm and 1985nm locations, suggesting a possibility to build an inexpensive screening device. The results indicate that combined classification methods with hyperspectral imaging technique and infrared lifetime imaging technique constitute practically high performance fast and non-destructive techniques for high-throughput seed screening.

Soaking effects on seed germination and fungal infection in Picea abies

Abstract The effect of soaking on germination and occurrence of fungal infections on Norway spruce (Picea abies (L.) Karst.) seeds and germinants was studied in three commercial seed lots. Treatments in which seeds were soaked in water for 24 h or in which the water was changed during the soak did not have an effect on the species diversity or on the abundance of the fungi isolated from the seeds. Different fungi were found in different seed lots. Most of those isolated are saprophytic or weakly pathogenic, but pathogens such as Sirococcus conigenus (D.C.) P.F. Cannon & Minter and Trichothecium roseum (Pers.) Link were also isolated. Soaking increased germination energy but had no effect on final germination percentage. The number of mouldy seeds and germinants with disease symptoms was different among seed lots when seeds were germinated on water agar. When germinated in low humified Sphagnum peat, no differences in the emergence of disease symptoms were observed among seed lots. The frequency of disease was lower in peat than in water agar. Soaking had no effect on disease emergence in germination trials on either water agar or in Sphagnum peat.