Yung-chang Lai
Associate Researcher , Department of Agronomy 
Chia-Yi Agricultural Experiment Station
Taiwan Agricultural Research Institute
Phone:886-5-2771341
Fax:  886-5-2773630
Email: davidlai@dns.caes.gov.tw
Education
Ph. D. (2003) in Department of Agronomy, National Chung Shing University.
M. S. (1988) in Department of Agronomy, National Chung Shing University.
Area of Research Interest
Breeding of sweet potato 
Publication
Journal paper
1.Lai, Y. C., B. H. Lee and  F. C. Liu. 1996. Effects Climatic Factors on the Storage 
      Root Yield of Sweet Potato. Chiness J. Agromet.3(3):169-173.
    The effects of climatic factors on the storage root yield of spring and fall were 
studied in Chiayi Agricultural Station and Chiayi Weather Service office. Results 
indicated that the storage root yield of fall was significantly higher than spring during
growth periods, As for the climatic factors, such as air temperature, and precipitation
on spring were higher that fall, that would promote the yield of  vine. The daily
temperature range of fall was higher rhat spring during growth periods, that would 
enlarge the storage root of sweet porato. The storge yield was higher on fall that on 
spring.
2.Lai, Y. C., C. H. Liao and Y. S. Chen. 1996. Effects of Different Planting Dates on
   the Storage Root Yield of Spring and Summer Crop Sweet Potato in Jin-Shan Area.
  Jour. Agric. Res. China. 45(1):26-34.
    The effects of different planting dates on the Storage root yield of spring and 
summer season sweet potato in Jin-Shan was studied in 1992. Results indicated that 
the storage root yield of sweet potato increased markedly during growth period and
 reached the maximun at 120 days after planting, Day-night temperature diffentiate is 
the mostimportant climatic factor to affect the enlargement of storage root of sweet potato.
3. Li, L., C. H Liao and Y. C. Lai 1996.  The Efficiency of Seedings Selection in the
    Early Generations of Sweet Potato(Ipomoea batatas L.)  J. Agri. Asso. of chinu new
    series 173:2-16.
    The purposes of this study were to investigate(1)the effects of seed shape and size on
 the performance some morphological and yield traits of true-seed seedings and plants from
 vine cuttings of the seedings, (2) the correlations of some qualitative and 
quantitative traits between the plants from vine cccuttings of the seedings and their 
respective clonal generations, and(3)the effects of environmental factors on the selection
 efficency of some important traits from the early and late generations of clones. The materials
 included seedings from seeds of varying shape and size obtained from a randomly
 intermating sweet potato population, and the seedings and their respective clonal 
generations in multi-locational trials conducted in the falland winter crop seasons at 
Chiayi Agricultural Experiment Station and other regions in Taiwan from 1985 to 1995. 
Experimental results indicated that significant variation for most traits(the only exception 
was dry matter content of storage root)of seedings from different seed categories. Larger
 seeds tended to result superior growth vigor, stem diameter and primary root weight at 
seeding stage, and superior average storage root weight per plant.These results indicated 
that the selection of large and optimally matured seeds, in combination with other criteria, 
would be beneficial in a sweet potato breeding program. In general, larger seeds resulted in 
high correlations be tween primary root weight and stem diameter and primary root diameter 
at seeding stage. The correlation coefficients between 23 sweet potato seedings  and their 
respective first clonal generations ranged from 0.155 to 0.348**for storage root yield, and from
 0.112 to 0.825 for protein content of the storage roots. The relative low variable r values 
indicated that a modeeeeerate intensity of selection combined with other criteria would be 
effective for selecting high yield and protein content of storage roots in the early generations
. For dry matter content and flesh color of storage roots, a highly sigrificant correlation existed
 between the seedings and their respective first clonal generation. It is therefore suggested that
 efficient selection of these two traits could be achieved at the seedlings or in the first clonal 
generation . The correlations were significantly positive between the first and thesecond clonal 
generations for yield, flesh color, and dry matter and crude protein contents of storage roots. 
The r values were generally higher than those obtained in the seedlings and their respective first
 clonal generations. Thus, a strict selection of these traits in the first clonal generation would be
 more efficient than in the seedlings.Among different locations within the same region, the 
variance components of genotyp×location interaction were generally small and the correlation
 coeffcients were highly significant positive for yield, flesh color, and dry matter and protein 
contents of storage roots. For experiments conducted in. the same location, the genotype×year 
interaction was not significant but the correlations were highly significant for yield and dry matter,
 protein, reducing sugar, and starch contents of storage roots. These results indicated that it might 
not be necessary to select the traits in the first clonal generation over differents were low. It was 
therefore recommended to conduct the advanced trial over different regions for selecting the 
quantitative traits.