Investigation on Male Sterility in Zea mays Study on Male-Sterility in Zea mays Ⅷ. RFLP Analysis of mtDNA of YⅡ-1 Type Maize Male-Sterile Cytoplasm A Study on cms-WA Cytoplasmic Susceptibility of Rice to Pyricularia oryzae and Xanthomonas campestris pv.oryzae