Assessment of genetic diversity and population structure among a collection of Korean Perilla germplasms based on SSR markers
GENES & GENOMICS
Authors: Oh, Jun Seok; Sa, Kyu Jin; Hyun, Yoon; Cho, Gyu-Taek; Lee, Ju Kyong
Background Information on the genetic variation of genetic resource collections is very important for both the conservation and utilization of crop germplasms in genebanks. Var. frutescens of Perilla crop is extensively cultivated in South Korea as both an oil crop and a vegetable crop. Objectives We used SSR markers to evaluate the genetic diversity, genetic relationships, and population structure of 155 accessions of var. frutescens that have been selected as genetic resources for the development of leaf vegetable cultivars and preserved in the RDA-Genebank collection from South Korea. Methods A total of 155 accessions of var. frutescens of Perilla crop collected in South Korea were obtained from the RDA-Genebank of the Republic of Korea. We selected 20 SSR markers representing the polymorphism of and adequately amplifying all the Perilla accessions. Results The average GD and PIC values were 0.642 and 0.592, respectively, with ranges of 0.244-0.935 and 0.232- 0.931. The genetic variability in the southern region of South Korea was higher than that in the central region. The clustering patterns were not clearly distinguished between the accessions of var. frutescens from the central and southern regions of South Korea. Conclusion These results regarding the genetic diversity and population structure of the 155 accessions of var. frutescens of South Korea provide useful information for understanding the genetic variability of this crop and selecting and managing core germplasm sets in the RDA-Genebank of the Republic of Korea.
Transient response of drain current following biasing stress in GaN HEMTs on SiC substrates with a field plate
JAPANESE JOURNAL OF APPLIED PHYSICS
Authors: Ma, Qiang; Yoshida, Tomoyo; Ando, Yuji; Wakejima, Akio
This paper investigates the current collapse and transient response of a drain current (I-d) following the transition to an off-state in GaN high-electron-mobility transistors (HEMTs) on SiC substrates. Within a short time (similar to 10(-3) s.) after anI(d)transition, significant current collapse and delayed recovery are observed in GaN HEMTs with a long gate-to-drain distance (L-gd). Moreover, at least two time constants (tau(1)and tau(2)) are found to exist in HEMTs with anL(gd)of over 4.0 mu m. As theL(gd)becomes longer, the activation energy required for electron emission is increased from 0.46 to 0.65 eV, which causes the time constant (tau(2)) to rise. Furthermore, the period of the off-state affects the time constants of GaN HEMTs without a field plate (FP). An extension of the off-state leads to an increase in the activation energy of the de-trapping process, and tau(1)and tau(2)are increased from 13 to 21 ms and from 150 to 350 ms, respectively.