The Reproductive Development, Anther Dehiscence and Pollen Viability of Yard-long Bean
Date Issued
2011
Date
2011
Author(s)
Wu, Pei-Jhen
Abstract
Yard-long bean (Vigna unguiculata ssp.sesquipedalis (L.) Verdc.) thrives in warm weather with good tolerance to drought and to moisture. It has a wide range of soil adaptation and is an important summer vegetable in Taiwan. However, the crop succumbs to seed borne viral diseases and abrupt environmental changes often result in reduced pod yield and quality. Being a self-pollinated legume, yard-long bean usually has low seed set upon manual crossing. There is few report on the reproductive biology of the yard-long bean and it is essential to know the flowering and the pollen behavior of the plant in order to ensure the success in commercial production and the seed set in breeding work. Four yard-long bean cultivars, including two viny (cvs. ‘Green-pod Kaohsiung’ and ‘Milady’) and two dwarf types (cvs. ‘Bush’ and ‘K.Y. Bush’) were grown in the open field of experimental farm and the phytotron with day and night temperature regimes of 30/25 oC and 25/20 oC at National Taiwan University. It took 22.6 and 21.6 days after sowing for cvs. ‘Green-pod Kaohsiung’ and ‘Milady’, respectively to start vining under 25/20 oC. Plants grown in the field and 30/25 oC of phytotrons were earlier to vine and to develop reproductive structures than plants under 25/20 oC, however, the node position of the first flower bud remained same in three environments, i.e. node 8.3 - 8.7 for ‘Green-pod Kaohsiung’ and node 3.0 - 3.7 for the other three varieties. All plants were grown in 25/20 oC till visible inflorescence shown and then they were either moved to 30/25 oC or kept at 25/20 oC. Flower buds due to bloom or open the next day were collected at 7:00 pm and thereafter at 4-hr intervals to examine the timing of anther dehiscence. The results showed that flowers of yard-long beans completed the anther dehiscence at 0:00 am of the day of anthesis. Pollen viability was tested by three staining methods. Both Alexander and TTC (2,3,5-triphenyl tetrazolium chloride) methods gave higher staining rate than FDA (fluorescein diacetate) test which showed less than 30% of staining. TTC staining results may indicate the temporal change in pollen viability, the staining rate was 96.98% from pollens collected at 8 pm of the day before anthesis and it decreased to 53.29% at 4:00 pm of day of anthesis. The pod set rates were 70% and 15% for cvs. ‘Green-pod Kaohsiung’ and ‘Bush’, respectively from pollinated buds due to bloom the next day under temperature of 25/20 oC. To make a hybridization cross, both emasculation and pollination can be carried out for yard-long bean in the afternoon of day before anthesis. All pollens failed to germinate in vitro on B&K or other modified culture medium tested. Sucrose as high as 50% was needed to prevent pollen from burst, supplements such as polyethylene glycol, bovine serum albumin, GA and crushed yard-long bean stigma were added with no success. Other modification included pH and formulations, no pollen germinated in excess of its diameter. Yard-long bean pollen is difficult species to germinate in vitro.
Subjects
2,3,5-triphenyl tetrazolium chloride
fluorescein diacetate
aniline blue
Type
thesis
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