No abstract

Hybrid sterility genes define species identities, setting reproductive barriers between distantly related Oryza relatives. They induce allelic-specific selective gametic abnormalities by killing pollens, embryo sacs, or both, and thus resulting in the male specific transmission ratio distortion (mTRD), female specific transmission ratio distortion (f TRD), and/or sex-independent transmission ratio distortion (siTRD) in hybrids. Although more than 50 hybrid sterility genes have been reported, comprehensive analysis on the distributional pattern of TRD systems in Oryza species is limited. In this review, we surveyed the TRD systems and the underlying possible mechanisms in these species. In rice, pollen killers which cause mTRD are often observed in higher frequency than egg killers and gamete eliminators, which are factors affecting f TRD and siTRD, respectively. Due to the rather massive population of pollen grains, their reduction in the number caused by hybrid sterility possesses a smaller selective disadvantage to the hybrid individuals, in contrast to female gamete abortion. The pattern of TRD distribution displays less abundancy in siTRD. It suggests that fixation of siTRD might require a certain time rather than single sex-specific factors. The presence of linked sterility factors worked for mTRD and f TRD, and strength of their linkage in chromosomal regions might determine the type of sterility and TRD. The study of TRD systems has a potential to reveal the relationships between selfish genes and their functions for reproductive isolation.

In this paper, we examined the solar module characteristics at standard test condition and different temperature and irradiance using LabVIEW software. For full utilization of photovoltaic(PV) system, it can be controlled by maximum power point tracking(MPPT) algorithm. The LabVIEW programing can easily implement perturb and observe (P&O) algorithm with various step sizes and their output characteristics. The results proved that the step size influence on the performance of the MPPT system. The bigger the step size, the less the tracking time but the more oscillation occurs in the steady state. Therefore, improved control system is required to solve that problem. The scheme that we devised can adjust the step size automatically to improve the MPPT speed and reduce the oscillation under steady state as well.