| According to NCⅡgenetic mating design, 72 temperate-tropical hybrids were made bycrossing between 8 southern inbred lines and 9 northern inbred lines. Then the photoperiod sensitivephenomenon characteristics, the heredity characteristics of traits related to Photoperiod Sensitivity, thecombining ability of traits related to Photoperiod Sensitivity among the lines and heterosis between twokinds inbred lines, were analyzed based on field experiments conducted on Beijing and Ya'an. Themain results were as follows:1. Temperate-tropical hybrids have 6 characteristics of photoperiod sensitive phenomenon:①These hybrids have strong level of photoperiod sensitivity as a whole. Following the length of lightshines becoming long, the growing period were prolonged, the male and female florescence wereinconsistent, ear height, plant height, leaf numbers, ear length, and bare length of corncob wereincreased, ear diameter and grain weight per plant were decreased. These hybrids presented betteradaptability in south China's short length Sunshine environment, but the adaptability was quite bad innorth China's long length Sunshine environment.②The extent of response to photoperiod sensitivitywere varied among traits. ASI＞days of tassel to pollen＞days to silk＞days to tassel among traits ofgrowing period; ear height＞leaf numbers＞plant height among traits of plant; bare length of corncob＞ear length＞ear diameter＞grain rate per ear among traits of ear; kernels per row＞grain weight perplant＞numbers of ear row＞100-kernel weight among traits of yield. Traits of growing period andplant have higher-level photoperiod sensitivity than traits of ear and yield.③The extent of response tophotoperiod sensitivity were varied among those hybrids, moreover, existing various of change typeamong different type traits, all traits of growing period and plant presented one direction changing type:"less sensitivity" to" positive strong sensitivity"; most traits of ear and yield presented double directionschanging type: "no-sensitivity" to "negative strong sensitivity" or "positive strong sensitivity".④Thereare 11 primary traits related to Photoperiod Sensitivity, such as ASI, days of tassel to pollen, days to silk,days to tassel, ear height, leaf numbers, plant height, bare length of corncob, ear length, kernels per row,and grain weight per plant.⑤There are photoperiod sensitive inbred lines and photoperiod no-sensitiveinbred lines not only among southern inbred lines but also among northern inbred lines, the photoperiodsensitivity of inbred line is mostly depended on the germplasm type in it, and not depended on thelocation of selection.⑥The type and extent of hybrids' photoperiod sensitivity were dependent on theirparental lines' photoperiod sensitivity characters which were related to the germplasm.2. The temperate-tropical hybrids have 3 primary heredity characters among the traits related tophotoperiod sensitivity:①The genetic models of most traits related to photoperiod sensitivity match upto additive-dominance model, few of them match up to additive-dominance-epistasis model, and the traits match up to the latter model become fewer in the environment of longer Sunshine length.②Theponderance of genetic effects is different among the traits that all belonged to addition-dominancemodel, most of them have main additive gene effect, very few have main dominance gene effect as willas grain weight per plant.③While the length of light shines changing to long, the number ofdominance genes decreased in most traits, and the number of epistasis genes decreased or disappearedin some traits. The degree of average dominance has reduced, and the predominant position for additivegene effect was more distinct. This confirmed that we should pay more attention to use the additivegene effect when we improving and utilizing tropical maize germplasm.3. GCA (General Combining Ability, GCA)is more important than SCA (Special CombiningAbility, SCA)to the traits related to photoperiod sensitivity no matter the temperate-tropical hybridsgrow in the long or short length of light shines, and while the length of light shines changing to long, thesignificance of GCA swelled more, and the significance of SCA fell some, the narrow-sense heritabilityenlarged. The change of the length of light shines could conduce GCA and SCA been instable. Northerninbred lines, such as HuangZao4 and JinHuang44 with strong earliness, 478 and Zheng58 with dwarfstaff, can be apt to cross fine temperate-tropical hybrids. Three Southern inbred lines, YA8201, 18599,YA3729 and three northern inbred lines, 178, 7922 and Zheng58 have higher relative effect value ofgrain weight per plant GCA.4. The better ways to breed commercial temperate-tropical maize hybrids in China ought to usecomplex heterotic patterns. The well proportion of tropical maize germplasm in the temperate-tropicalhybrids must be according to the degree of the tropical maize germplasm's photoperiod sensitivity andbreeding purpose. There is no limit of the proportion when the tropical maize germplasm has less or notphotoperiod sensitivity. While the tropical maize germplasm has strong photoperiod sensitivity, thetemperate-tropical hybrid with 25～50% tropical maize germplasm is better to adapt southern cornregion in China, about 25% tropical maize germplasm is better to adapt northern corn region in China.
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