| The fact that potato (Solanum tuberosum L.) has a narrow genetic base and inherits in tetrasomic manner hinders the progress in new potato development. Inercultivar crosses usually lead to new cultivars released with some kinship each other. Tetrasomic inheritance makes the segregation of progenies more complicated and makes it hard to study the inheritance behavior of the traits of interest. These base the potato breeding efforts on experience, not sciences in some potato breeding programs. Monohaploid is a sound tool which can be explored for genetic study and breeding efforts. However, the frequency at which monohaploids are produced is still low, and therefore its use is limited in genetics and breeding of potato. In this research, selection for anther culture capability was first made on 60 Solanum phureja-S. stenotomum(PHU-STN) hybrid clones, which were derived from 12 cycles of recurrent selection for long day adaptation, and 13 clones were found to be competent for anther culture. Of these, 4 clones, BD10-7, BD29-1, BD40-2 and BD46-7, were chosen for the study of the factors affecting anther culture, including pretreatment, hormone, carbon source and medium additive. The main results are as follows:(1) The color and size of anther can be used as criteria for judging the microspore developmental stage. Even though differences existed in genotypes, green-yellow anther, flower bud in 7 mm and anther in 3 mm were indicators that most of the microspores were in the mononuclear stage.(2) Obvious difference was found for anther culture capability in the 60 diploid clones plated. Thirteen clones showed positive response to anther culture, of which BD46-1, BD60-3, BD72-9 had a callus induction rate of up to 3.33%, followed by BD40-2 and BD12-7, being 2.22% and 1.67%, respectively.(3) Anther pretreatments of the clone BD29-1 with low temperature, heat shock, mannitol, and centrifuge were compared in various treatments, and the pretreatment of anther with mannitol for 48 h or centrifuge at 6000 r/min for 30 min was found to be effective for decreasing the brown percentage of anther plated and increasing the percentage of callus formation.(4) Addition of 0.1 mg/L 2,4-D in a 2,4-D gradient experiment to the callus induction medium MS+0.5 mg/L NAA+0.5 mg/L KT had the best result for callus formation. Of eight different hormone combinations, MS+1.0 mg/L2,4-D + 0.1 mg/L 6-BA+60 g/L sucrose +7 g/L agar was most effective for callus formation or embryogenesis.(5) Addition of 30 g/L or 80 g/L maltose, instead of 60 g/L sucrose, to medium gave higher percentage of callus formation.(6) Addition of 5% potato extract, or 50 mg/L AgNO3, or 1m mol/L Silver Thiosulfate (STS) to the callus inducing medium produced more callus than the control did, of which 1 mmol/L STS gave the best result.(7) Four of the thirteen clones in anther culture produced regenerated plantlets, and two produced deformed plantlets. By counting the chloroplast number of guard cell of leaves of the regenerated plantlets, two of the twelve plantlets tested proved to be monohaploids.In this research, monohaploid was produced for the first time from diploid PHU-STN hybrids. The knowledge about the factors influencing anther culture of diploid potatoes could help design suitable medium and set environmental conditions for monohaploid production, which may be used extensively in genetic study and practical breeding. |
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