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101.
Pyramiding of Xa7 and Xa21 for the improvement of disease resistance to bacterial blight in hybrid rice 总被引:3,自引:0,他引:3
‘Minghui 63’ is a restorer line widely used in hybrid rice production in China for the last two decades. This line and its derived hybrids, including ‘Shanyou 63’, are susceptible to bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo). To improve the bacterial blight resistance of hybrid rice, two resistance genes Xa21 and Xa7, have been introgressed into ‘Minghui 63’ by marker‐assisted selection and conventional backcrossing, respectively. The single resistance gene‐introgressed lines, Minghui 63 (Xa21) and Minghui 63 (Xa7) had higher levels of resistance to bacterial blight than their derived hybrids, Shanyou 63 (Xa21) or Shanyou 63 (Xa7). Both Xa21 and Xa7 showed incomplete dominance in the heterozygous background of rice hybrids by infection with GX325 and KS‐1‐21. The improved restorer lines, with the homozygous genotypes, Xa21Xa21 or Xa7Xa7, were more resistant than their hybrids with the heterozygous genotypes Xa21xa21 or Xa7xa7. To further enhance the bacterial blight resistance of ‘Minghui 63’ and its hybrids, Xa21 and Xa7 were pyramided into the same background using molecular marker‐aided selection. The restorer lines developed with the resistance genes Xa21 and Xa7, and their derived hybrids were evaluated for resistance after inoculation with 10 isolates of pathogens from China, Japan and the Philippines, and showed a higher level of resistance to BB than the restorer lines and derived hybrids having only one of the resistance genes. The pyramided double resistance lines and their derived hybrids have the same high level of resistance to BB. These results clearly indicate that pyramiding of dominant genes is a useful approach for improving BB resistance in hybrid rice. 相似文献
102.
103.
Inter-relationships among cane yield and commercial cane sugar and their component traits in autumn plant crop of sugarcane 总被引:1,自引:0,他引:1
Seventeen diverse clones of sugarcane (Saccharum spp.) (7 early, 6 mid season and 4 late) were planted in October 1991 and
1992 in flooded (FE) and non flooded (NFE) environments for evaluation of cane yield, commercial cane sugar (CCS), internode
length, internode number, stalk length, stalk thickness (circumference), stalk number, sugar recovery, and stalk weight. Cane
yield showed significant positive phenotypic correlation coefficient (PCC) with stalk number in FE (P ≤ 0.05) and NFE (P ≤
0.01). Stalk length had a significant positive PCC with stalk weight in both environments, and with internode length in FE
(P ≤ 0.05). Commercial cane sugar also expressed significant positive PCC with cane yield in both environments (P ≤ 0.01),
but with stalk number only in NFE (P ≤ 0.05). Genotypic correlation coefficients were generally in the same direction as PCC
but higher in magnitude. In both environments, stalk number and stalk weight had relatively high positive direct effects on
cane yield. However, flooding tended to enhance the direct effect of stalk weight and diminish the direct effect of stalk
number on cane yield. Only cane yield and sugar recovery had high direct effects on CCS. Selection for improvement of cane
yield can be based on stalk number and stalk weight in both environments. High yielding clones can be further screened for
more sugar recovery to improve CCS.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
104.
Breeding wheat and rye for resistance to Fusarium diseases 总被引:6,自引:1,他引:6
T. Miedaner 《Plant Breeding》1997,116(3):201-220
Fusarium culmorum and F. graminearum Groups 1 and 2 cause seedling blight, crown rot, foot rot and head blight in wheat and rye that may affect grain yield and quality for baking and feeding. This review starts with an analysis of Fusarium populations with regard to their genetic variation for aggressiveness, mycotoxin production, and isolate-by-host genotype interaction. To assess resistance in the different host growth stages, quantitative inoculation and disease assessment techniques are necessary. Based on estimated population parameters, breeding strategies are reviewed to improve Fusarium resistance in wheat and rye. Epidemiological and toxicological aspects of Fusarium resistance that are important for resistance breeding are discussed. F. culmorum and F. graminearum display large genetic variation for aggressiveness in isolate collections and in naturally occurring populations. The production of mycotoxins, especially deoxynivalenol and its derivatives, is a common trait in these populations. Significant isolate-by-host genotype interactions were not found across environments in wheat and rye. Artificial infections in the field are indispensable for improving Fusarium crown rot, foot rot and head blight resistance in wheat and rye. For a reliable disease assessment of large populations, disease severity ratings were found to be the most convenient. The differentiation of host resistance is greatly influenced by an array of nongenetic factors (macro-environment, microclimate, host growth stage, host organ) that show significant interactions with host genotype. Selection for environmentally stable resistance has to be performed in several environments under a maximum array of different infection levels. Selection in early growth stages or on one plant organ does not in most cases allow prediction of resistance in adult-plant stages or another plant organ. Significant genetic variation for resistance exists for all Fusarium-incited diseases in breeding populations of wheat and rye. The patho-systems studied displayed a prevalence of additive gene action with no consistent specific combining ability effects and thus rapid progress can be expected from recurrent selection. In wheat, intensive testing of parental genotypes allows good prediction of the mean head blight resistance after crossing. Subsequent selection during selfing generations enables the use of transgression towards resistance. In hybrid breeding of winter rye, the close correlation between foot rot resistance of inbred lines and their GCA effects implies that selection based on the lines per se should be highly effective. This is not valid for F. culmorum head blight of winter rye caused by a greater susceptibility of the inbred lines compared to their crosses. For both foot rot and head blight resistance, a high correlation between the resistance to F. graminearum and F. culmorum was found in wheat and rye. Mycotoxin accumulation occurs to a great extent in naturally and artificially infected plant stands. The correlation between resistance traits and mycotoxin contents are medium and highly dependent on the environment. Further experiments are needed to clarify whether greater resistance will lead to a correlated reduction of the mycotoxin content of the grains under natural infection. 相似文献
105.
Eleven progenies, ten bi-parental and one selfed, of tetraploid potato were assessed for phenotypic segregation ratios of
resistance to susceptible individuals against two isolates of P. infestans, one avirulent to all 11 known potato R genes (avirulent
pathotype) and one virulent to eight R genes (virulent pathotype). Assuming Mendelian inheritance of independent R genes,
the numbers of individuals segregating for resistance to both races could not be explained sufficiently for all progenies.
However, the assumed presence of dominant, specific suppressors of the R gene function that were elicited by specific isolates
of the fungus and that segregated in the host independently from R genes explained all frequencies of resistant and susceptible
individuals in each of the progenies studied.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
106.
The inheritance of the reaction of maize (Zea mays L.) to anthracnose leaf blight caused by Colletotrichum graminicola was studied in eight generations derived from a cross between a hypersensitively resistant inbred. LB–58, and a susceptible inbred, A632. The generations consisted of the two parents, F1, F2 backcrosses and the backcrosses-selfed, Chisquare analysis of the data for individual locations as well as across locations indicated that resistance at both the seedling and mature plant stages of development is conditioned by a single dominant gene, designated CgL. A study of the reactions of LB-58 in several hybrid combinations indicated that resistance was expressed in ail cast-s even though the expression of CgL gene was modified somewhat in different hybrid combinations. 相似文献
107.
Gummy stem blight resistance of cucumbers (Cucumis sativus L.) 总被引:1,自引:0,他引:1
Summary A start was made with breeding for resistance to gummy stem blight in cucumber. A method has been development for screening plants in a young stage. Using this method a distinct level of resistance was found in plants of Leningradsky, Wjarnikovsky,a P.I. entry from Birma, Rheinische Vorgebirge and a P.I.entry from Turkey. Lines developed from this material show a higher level of resistance than Dutch slicing and pickling cucumber varieties. 相似文献
108.
ZHANG Rong-Yue WANG Xiao-Yan YANG Kun SHAN Hong-Li CANG Xiao-Yan LI Jie WANG Chang-Mi YIN Jiong LUO Zhi-Ming LI Wen-Feng HUANG Ying-Kun 《作物学报》1962,47(2):376-382
The aim of this study was to assess brown rust resistance of new sugarcane varieties bred in China and main cultivated varieties in sugarcane planting area, and screen the elite new brown rust resistant varieties for popularization and application in production. In total, 60 new varieties in the national regional test of new sugarcane varieties were tested in Kaiyuan and Lincang, and 34 main cultivated varieties were studied in Lincang, Puer, and Yuxi, Yunnan province, and Yizhou, Guangxi province, China, where the incidence of brown rust was particularly high. The resistance of these sugarcane varieties to brown rust was investigated under natural inoculation and molecular marker-assisted identification was used to detect the brown rust resistance gene Bru1. The results of field survey showed that 66 (70.21%) of the 94 new and main cultivated varieties were highly resistant to moderately resistant, and 28 (29.79%) were susceptible to highly susceptible. Molecular detection indicated that Bru1 gene was found among 54 (57.45%) of the 94 new and main cultivated varieties. Some main cultivated varieties that were currently planted across large areas such as Guitang 29, Guitang 44, Dezhe 03-83, Liucheng 03-1137, Yuetang 60, and Guitang 46 were highly susceptible to brown rust, and 31 new varieties such as Yuegan 48, Funong 09-2201, Guitang 08-120, Liucheng 09-15, Zhongzhe 1, Yunzhe 08-1609, Yunrui 10-187, and Zhongtang 1201 were resistant. Therefore, in the sugarcane planting areas with high incidence of brown rust and wet and rainy climates, more effort should be eliminated the main susceptible varieties and promoted the application of new resistant varieties. This will help to achieve a reasonable distribution of varieties, fundamentally control the outbreak of disease in sugarcane planting areas, and provide security for the high-quality development of sugarcane industry in China in the future. 相似文献
109.
Quantitative trait loci for resistance to Fusarium head blight in recombinant inbred wheat lines from the cross Huapei 57-2 / Patterson 总被引:3,自引:0,他引:3
Fusarium head blight (FHB), primarily caused by Fusarium graminearum in North America, often results in significant losses in yield and grain quality of wheat (Triticum aestivum L.). Evaluation of FHB resistance is laborious and can be affected by environmental conditions. The development of DNA markers
associated with FHB quantitative trait loci (QTL) and their use in breeding programs could greatly enhance selection. The
objective of this study was to identify the location and effect of QTLs for FHB resistance using simple sequence repeat (SSR)
markers. A population of wheat recombinant inbred lines derived from the cross ‘Huapei57-2’/‘Patterson’ was characterized
for type II resistance in one field experiment and two tests under controlled conditions in the greenhouse. Bulked segregant
analysis followed by QTL mapping was used to identify the major segregating QTLs. Results indicate that ‘Huapei 57-2’ may
have the same resistance allele as ‘Sumai3’ at a QTL located on the short arm of chromosome 3B. Other QTLs of lower effect
size were identified on the long arm of 3Band on chromosomes 3A and 5B. Our findings along with results from other studies
demonstrate that the effect of the QTL on3BS is large and consistent across a wide range of genetic backgrounds and environments.
Pyramiding this QTL with other FHB QTLs using marker-assisted selection should be effective in improving FHB resistance in
a wheat breeding program.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
110.
Molecular diversity in Indian sugarcane cultivars as revealed by randomly amplified DNA polymorphisms 总被引:5,自引:0,他引:5
Genetic diversity in 28 prominent Indian sugarcane varieties cultivated under a wide range of agroclimatic conditions, was
studied using 25 RAPD markers. The mean genetic distance among the 28 varieties was only 29.31%, implying that a large part
of the genome is similar among the varieties. This probably arises from the lack of parental diversity, with few clones which
are themselves related, contributing to the parentage of these varieties. The parentage of the varieties did not contribute
significantly to the clustering pattern. Varieties belonging to the same parentage were grouped under different clusters while
varieties from different parentages were grouped under the same cluster. The tropical and subtropical identities of the varieties
also did not contribute to the clustering pattern as individual clusters included varieties from both tropics and subtropics.
This shows that genetically similar varieties are present in both the regions. Among the varieties, Co 7717 was found to be
totally
distinct and divergent from rest of the varieties. The study reveals the limited genetic base of the current Indian commercial
varieties and the need to diversify the genetic base by using new sources from the germplasm.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献