中国农业科学Issue(14)：2697-2704,8.DOI:10.3864/j.issn.0578-1752.2015.14.002
西南地区玉米地方品种B染色体多态性分析
B Chromosome Polymorphisms in Maize (Zea mays L.) Landrace Populations from Southwest China
摘要
Abstract
Objective] The objective of this study is to analyze B chromosome polymorphisms in maize landrace populations from Southwest China, to evaluate their genetic diversity at cellular level and provide evidence for the introduction path of maize in China.[Method] Thirty maize landrace populations from Sichuan Province, Chongqing city, Yunan Province, and Guizhou Province in southwestern China were used. Fifty individuals per landrace population were sampled, and ten cells from a single plant were scored for the presence of Bs under a microscope. A total of 15 000 cells (30 × 50 × 10) in the mitotic metaphase were analyzed. Ten slides, from ten individuals per landrace population, were C-banded using conventional Giemsa staining with modifications.[Result] Besides 10 pairs of standard chromosomes, the landrace populations contain a metacentric B chromosome (BM) morphologically similar to the first chromosome of the karyotype, a subtelocentric B (BST) identical in size to BM, and a spot-shape microchromosome (BS) without centromere. Seven maize landrace populations from Sichuan possessed three forms of Bs. In the populations of maize landraces from Chongqing both BM and BST forms were found, whereas BST and BS were identified in the populations of maize landraces from Yunnan. Nine populations from Guizhou were the only one (BST) where BM and BS were exclusive. The mean length of BM, BST, and BS was 2.82 µm, 2.78 µm, and 0.9 µm, respectively. In comparison with the metacentric pair of the standard karyotype, measurements conducted on the cells with Bs estimated a relative length of 34%-52% for the BM, 32%-58% for BST, and 13%-18% for the BS, and relative lengths for BM, BST, and BS were on the average 43%, 45%, and 15%, respectively. The mean arm ratios for BM, BST, and BS were 1.19, 1.98, and 1.00, respectively. Of the eighteen populations with B chromosomes, seven, five, four, and two populations originated geographically from Sichuan, Chongqing, Yunnan, and Guizhou, respectively. Eighteen of the thirty populations sampled exhibited numerical polymorphisms and a total of 487 Bs were identified in 421 individuals. The frequency of B chromosomes per individual varied from 0 to 90% with an average of 29.6%. The populations from Sichuan possess a higher frequency of B chromosomes in both population and individual levels. The highest number of B chromosomes in a cell was 2 with the predominant dose being 0. The mean frequency of B chromosomes for the 0B, 1B, and 2B cell were 97.04%, 2.81%, and 0.15%, respectively. BST is the predominant form accounting for 67% of the Bs in the populations, followed in turn by BM and BS corresponding to 19% and 14%, respectively. It might be hypothesized that BST represented an ancestor B chromosome in maize, whereas the BST and BS were variants of the BM, implying that the evoluation of BM and BS have occurred in a smaller time and space scale. The Giemsa staining exhibited that the BM and BST forms, easily distinguished from A chromosomes, shared some homologous DNA sequences and were both heterochromatic as well as GC-rich. The mean C-band number varied from 11.0 to 20.6 in the 0B cell, 10.8 to 19.4 in the 1B cell, and 10.5 to 18.6 in the 2B cell, indicating a negative correlation between B chromosomes and C-bands in the A chromosome set.[Conclusion] Cytological observations revealed that maize landrace populations from southwest China had a higher level of genetic diversity. For the B chromosome in them, there existed morphological and numerical polymorphisms. Sichuan is the geographical centre of maize landraces in this region based on geographical distributions of the B chromosome. This supported the theory on a maize introduction path in China.关键词
玉米/B染色体/多态性/西南地区Key words
maize/the B chromosome/polymorphisms/southwest China引用本文复制引用
姚启伦,陈发波,刘红芳,方平,赵彩芳..西南地区玉米地方品种B染色体多态性分析[J].中国农业科学,2015,(14):2697-2704,8.基金项目
国家自然科学基金项目（31371633）、重庆市教委科研项目 （）
