| Maize chilling damage cause a huge production loss in Northeast China and some provinces alpine mountains and also was a disasters for many countries and regions. Chilling stress has become a major factor limiting production of maize in Northeast abiotic stress. It is a most cost-effective way to breed and select chilling maize germplasm. It is important to identify chilling tolerance for germplasm and conduct genetic research. Moreover, it has practical significance to select chilling tolerance germplasm and conduct quantitative trait loci (QTL) mapping for chilling tolerance. In our study,36maize inbred lines were measured by germinate at low temperatures, budding survival rate, seedling morphological traits and physiological indicators to establish chilling tolerance indicator system. Based on the chilling tolerance indicator system,276maize inbred lines from Plant Resources Research Center of Heilongjiang boreal were evaluated by chilling tolerance indicator such as germination, budding and seedling. Chilling-resistant inbred Diangull and chilling intolerance inbred T935were constructed a Double haploid (DH) population for QTL mapping of chilling tolerance traits from germination to seedling. We also analyzed the data from P1, P2and DH population by a major gene polygene joint segregation analysis model to find the genetic architecture. The obeject of our study were to:(1) establish maize chilling tolerance identification systems and quantitative indicators;(2) select chilling tolerance germplasm;(3) reveal the genetic architecture of chilling tolerance;(4) QTL mapping for chilling tolerance;(5) find closely linkage markers for chilling tolerance which was benefit for maker assisted selection (MAS) to select chilling tolerance maize inbred lines. The mainly results were as follows:1. It showed significant positive correlation (R=0.620) between relative germination rate of seed germination and field relatively germination at10℃and25℃temperature. This indicator can be used maize germination identification chilling tolerance because there was significant difference among tested inbred lines. The standard deviation and coefficient of variation was largest among different inbred lines at2℃under6days, which can distinguish genetic differences for maize chilling tolerance. So this stress conditions can be used for chilling tolerance germplasm screening. It is feasible that the survival rate when maize leaf stage at3℃low temperature under5days as indicate for chilling tolerance. The maize chilling tolerance closely related with that total dry weight of seedlings, seedling dry weight, root dry weight, MDA, chlorophyll, conductivity, SOD, CAT and other eight indicators. The average value of membership function of these indicators can comprehensively evaluate maize seedling chilling tolerance. Meanwhile, the choice of these traits can provide theoretical basis on morphological and physiological level for breeders to develop strong chilling-resistant maize varieties 2. Fifty inbred lines showed strong chilling tolerance at germination stage such as PFM32, Ji4112, ZYM237. EY20. ZYM264, DiangullA, Kenzi167-1. Six inbred lines showed strong chilling resistance at budding stage such as T123, HR10, HB14, KLM17. ZYM249, ZYM264. Nine inbred lines showed strong seedling chilling tolerance such as PFM32, ZYM249, HR10, Ji818, Long53, H050, Yiniu, Zha917, Binzi901. The inbred lines such as PFM32, ZYM264, DiangullA, ZYM249, KLM17, T123, Ji63, HR10showed strong chilling tolerance at three different periods which can be used for maize breeding for chilling resistance. At low temperatures, Russian inbred lines showed largest average relative germination rate, budding survival and seedling survival rate among different regions of inbred lines, significantly higher than China and France inbred lines. The proportion of first class inbred lines among all inbred lines for Russian inbred lines was highest, significantly higher than China and France inbred lines. Russian inbred lines have more chilling tolerance genes in maize germplasm and it is effective way to develop strong chilling-resistant germplasm in Russian.3. The genetic for maize chilling tolerance genes involved in major and multiple genes whose major gene heritability is high, and there are multiple genetic modification. The trait on germination based on germination rate controlled by2genes based on additive-epistatic major genes plus multi-gene models. The heritability for major gene was91.57%and polygene was7.86%. The trait on budding survival rate controlled by3genes based on additive-epistatic major genes plus multi-gene models. The heritability for major gene was95.48%and polygene was4.46%. The trait on seedling survival rate controlled by2genes based on additive-epistatic major genes plus multi-gene models. The heritability for major gene was86.50%and polygene was12.91%. Therefore, to improve chilling tolerance in maize research, we should also pay attention to the accumulation of multiple genes in spite of utilization of major gene.4. Eighteen QTL were detected for maize chilling tolerance from germination to seedling distrubited among chromosome1,2,3,4,5,6,9,10, which explaining3.16%to15.71%phenotypic variance. The number of QTL controlling germination, budding and seedling chilling tolerance were5,7and6respectively. The phenotypic variance for QTL on chromosome6was over10%and this QTL was detected in these three periods, which may be a hotspot for early growth of maize resistant to chilling related traits. Among all the QTLs, the QTL on chromosome6between markers bnlg1641and bnlgl422was related to chilling tolerance during budding and seedling. However other QTL explained for chilling tolerance only a single period. So the genetic mechanisms may be different for different periods of chilling tolerance. |
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