Phylogenetic and recombination analysis of rice black-streaked dwarf virus segment 9 in China.

Rice black-streaked dwarf virus (RBSDV) is an economically important virus that causes maize rough dwarf disease and rice black-streaked dwarf disease in East Asia. To study RBSDV variation and recombination, we examined the segment 9 (S9) sequences of 49 RBSDV isolates from maize and rice in China. Three S9 recombinants were detected in Baoding, Jinan, and Jining, China. Phylogenetic analysis showed that Chinese RBSDV isolates could be classified into two groups based on their S9 sequences, regardless of host or geographical origin. Further analysis suggested that S9 has undergone negative and purifying selection.

[Analysis on breeding potential of eight synthetic populations to improve a Chinese maize hybrid Zhengdan 958].

Maize (Zea mays L.) populations are potential sources of favorable alleles absent in parental inbred lines to improve elite hybrids. The maize hybrid Zhengdan 958 has been hampered by the lack of favorable new alleles for improving yield and commodity quality. In the present study, 16 testcrosses made by using eight synthetic populations as the donors and the two parental lines of Zhengdan 958 as the receptors were evaluated in 2009 and 2010 at Shunyi, Beijing and Xinxiang, Henan Province for grain yield and test weight. Four genetic parameters were used to determine the breeding potential of eight synthetic populations as the donors to improve the target hybrid. Several synthetic populations were identified as the potential sources of favorable alleles absent in the target hybrid for each trait evaluated. The two most promising germplasms, WBMC-4 and Shanxi Syn3, had the potential for simultaneously improving grain yield and test weight of the target hybrid, which could be used to improve the parental lines Zheng 58 and Chang 7-2, respectively, and further broaden the germplasm base of Chinese heterotic groups PA and Sipingtou.

[Characterization and potential utilization of maize populations in America region].

Introgression of exotic maize (Zea mays L.) germplasm is an effective approach to broadening the genetic base of Chinese germplasm. America is the center of maize origin and germplasm diversity. By analyzing general combining ability effects and heterosis responses among maize populations from the U.S., International Maize and Wheat Improvement Center (CIMMYT), and Brazil studied by different authors, 24 elite maize populations from America region, including eight U.S. populations, eight CIMMYT populations, and eight Brazilian populations, were identified as having high potential in China. Based on adaptation improvement, we suggest to introgress BSSS(R)C10, BS10(FR)C14, BS13(S)C9, BSK(HI)C8 Syn 3, BR106, Pop44(C8), and Pop45(C3) into Chinese heterotic group A, and introgress BS11(FR)C14, BS16(S)C3 Syn 2, BS29(R)C3, BSCB1(R)C14, BR105, and Pop42(C4) into Chinese heterotic group B by forming semi-exotic populations or pools, respectively, in order to broaden the Chinese germplasm base.

[QTL mapping of plant height and ear position in maize (Zea mays L.)].

A molecular linkage map for the maize hybrid of cross between Ye478 and Dan340 was constructed by using 150 co-dominant SSR markers. The total map length was 1 478.7 cM with an average interval of 10.0 cM. Composite interval mapping was used to identify the plant height (PH) and ear position (EH) QTL at 5 environments based on the phenotypic data of 397 F2:3 families. Then 21 PH and 25 EH relevant QTL were identified. The mean contribution of 12.2% and 14.9% QTL for plant height was identified at the interval of umc2025 - umc1035 on chromosome 1 and umc1822 - bnlg1118 on chromosome 5, respectively. Meanwhile, the mean contribution of 10.2% and 22.8% to ear position were identified at the interval of phi029 - umc1102 on chromosome 3 and phi109188 - bnlg1118 on chromosome 5. The main QTL for PH and EH were both found at the regions of Bin5.05 - 5.07 on chromosome 5. The additive and partial dominant effects were the main genetic basis for plant height and ear position in maize. The effect of population size and environments on QTL mapping were analyzed.

[Comparative QTL mapping of resistance to sugarcane mosaic virus in maize based on bioinformatics].

The development of genomics and bioinformatics offers new tools for comparative gene mapping. In this paper, an integrated QTL map for Sugarcane mosaic virus (SCMV) resistance in maize was constructed by compiling a total of 81 QTL loci available with the Genetic Map IBM2 2005 Neighbors as reference. These 81 QTL loci were scattered on 7 chromosomes of maize, and most of them was clustered on chromosome 3 and 6. By using meta- analysis method, we identified one and two "consensus QTLs" on chromosomes 3 and 6, respectively. These three QTLs cover the genetic distances of 6.44 cM, 6.16 cM and 27.48 cM on the genetic map IBM2 2005 Neighbors, respectively. Four positional candidate resistant genes were identified within the "consensus QTL" on chromosome 3 via comparative genomics strategy. These results suggested that application of the combined meta-analysis within a species with sequence homologous comparison in a related model plant is an efficient approach to identify the major QTL and its candidate gene(s) for the target traits. The results of this study provided useful information for identifying and cloning of the major gene(s) conferring resistance to SCMV in maize.

[Construction of a SSR linkage map and mapping of quantitative trait loci (QTL) for leaf angle and leaf orientation with an elite maize hybrid].

Maize (Zea mays L.) breeders have begun selecting for more compact plants for higher density planting in order to increase yield per unit area. Leaf angle and leaf orientation are very important traits affecting maize plant type (compactness). In this study, a genetic linkage map containing 138 simple sequence repeat (SSR) markers was constructed based on a mapping population consisting of 500 F2 individuals from the cross between inbred lines Ye478 and Dan340. This SSR linkage map spans a total of 1 394.9 cM with an average interval of 10.1 cM. Quantitative trait loci (QTL) for leaf angle and leaf orientation were identified in 397 F2:3 families. Six QTL for leaf angle were detected that could explain 41.0% of the phenotypic variation; while, eight QTL were detected for leaf orientation that could explain 60.8% of the phenotypic varia-tion. Single QTL contribution to phenotypic variation ranged from 2.9% to 13.6%. Additive and partial dominance were the main genetic effects for leaf angle and leaf orientation; in addition, nine pairs of locus interactions were detected for the two traits, indicating that epistatic interactions at the two-loci level also play a measurable role in the genetic basis of the two traits.

Towards an expanded linkage map and exploration on co-dominant scoring of AFLPs in maize.

Simple sequence repeats (SSRs) and amplified fragment length polymorphisms (AFLPs) have become the most important markers for molecular mapping. Primarily based on restriction fragment length polymorphism (RFLP) markers, extensive linkage maps of maize had been developed. To construct a near-saturated genetic linkage map, an expanded maize genetic linkage map was constructed using a population of 234 F2 individuals derived from a cross of X178 and B73 base on an essential SSR framework map of maize. The level of polymorphisms and genetic properties of SSR and AFLP markers were characterized. A total of 249 markers consisting of 130 SSRs and 119 AFLPs have been landed on 10 chromosomes of maize. The 249-locus map spanned 1 659.3 centi-morgans (cM) and had a mean density of 6.66 cM. This mapping population and related information should connect further research involving analysis of quantitative trait loci, comparative genomics, and heterosis. Moreover, in many studies, AFLPs were analyzed on the basis of the presence or absence of a band on the electrophoresis gels. A new method based on double polymorphic bands of co-dominant scoring of AFLPs was explored according to the similarity of loci amplified from AFLP enzyme combination.

[Ecosystem services evaluation based on geographic information system and remote sensing technology: a review].

Ecosystem services evaluation is a hot topic in current ecosystem management, and has a close link with human beings welfare. This paper summarized the research progress on the evaluation of ecosystem services based on geographic information system (GIS) and remote sensing (RS) technology, which could be reduced to the following three characters, i. e., ecological economics theory is widely applied as a key method in quantifying ecosystem services, GIS and RS technology play a key role in multi-source data acquisition, spatiotemporal analysis, and integrated platform, and ecosystem mechanism model becomes a powerful tool for understanding the relationships between natural phenomena and human activities. Aiming at the present research status and its inadequacies, this paper put forward an "Assembly Line" framework, which was a distributed one with scalable characteristics, and discussed the future development trend of the integration research on ecosystem services evaluation based on GIS and RS technologies.