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A. Gallais 《Euphytica》1988,39(2):95-104
Summary To discuss the utilisation of heterosis in plant breeding it is necessary to consider its genetic basis. In cross fertilized plants in which the phenomenon of heterosis is very important, such as maize, it appears that a great part can be explained by the mutation load. However in both autogamous or allogamous plants it is difficult to exclude a role of marginal overdominance which could justify hybrid variety production.To know in a relatively short time whether it will be better to develop lines or hybrids it is necessary to know the parameters (mean and variance) of the distribution of all varieties of a given type which can be derived from the breeding population. A numerical application allows the determination of the situations where the best single crosses will be better than the best lines. With some approximate values of the necessary parameters, the case of grain yield in maize and in wheat is briefly discussed.To develop lines or hybrids, a general strategy is given. Its main axis is population improvement which has to be adapted to the type of varieties to develop. It is shown that according to the situation the type of varieties to develop can change with time: single crosses can be more justified at the beginning and lines can be justified later if all heterosis were fixable. To develop hybrids the best scheme is reciprocal recurrent selection with half-sib or full-sib progenies followed by pedigree reciprocal selection initiated by full-sib progeny tests. With this strategy there is no problem of the prediction of hybrid performances. However it seems possible to develop some predictors of heterosis or of specific combining ability between two lines using some criteria of genetic distances. Preliminary results with distances computed from the behaviour of lines in a two-tester top cross design appears very stimulating.Communication given at the206th meeting of teh Genetical Society of Grain Britain 相似文献
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A backcrossing programme was carried out both to assess the stability of a cytoplasmic male‐sterility (CMS) source from Helianthus resinosus, designated RES1, and to incorporate it into inbred sunflower lines (HA89, RHA271, RHA801). All the progenies, grown in different environments, were completely male‐sterile. This suggests that the expression of this cytoplasm is stable. Female‐fertility of lines HA89, RHA271 and RHA801 carrying CMS RES1 were compared with those of the corresponding fertile inbred lines. There were no differences in the number of seeds per head. This indicates that female‐fertility is not affected by RES1 cytoplasm. Cytological studies showed that meiosis proceeds normally until the tetrad stage; consequently, the absence of pollen is caused by alterations that take place during postmeiotic stages. With the aim of identifying male‐fertility restorer genotypes, crosses were made between HA89 (CMS RES1) plants and different annual diploid and perennial hexaploid Helianthus species. All the diploid germplasm evaluated behaved as a CMS RES1 maintainer. However, the hexaploid species, H. resinosus, H. x laetiflorus, H. pauciflorus and H. tuberosus, restored pollen fertility in CMS RES1 plants. 相似文献
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Jing LI Peng XU Jia-wu ZHOU Feng-yi HU Xian-neng DENG Zhi-wei CHEN Da-yun TAO 《水稻科学》2011,18(2):110-115
Hybrid sterility between Oryza glaberrima and O. sativa seriously hampers the introgression of favorable genes from each other. In order to further understand this issue, identification and isolation of hybrid sterility QTLs as single Mendelian factors are an effective strategy. A genetic map was constructed using a BC1F1 population derived from a cross between an O. sativa japonica cultivar and an O. glaberrima accession. Four main-effect QTLs for pollen sterility were detected in the BC1F1. Five BC8F1 advanced backcross populations were developed via successive backcrosses based on phenotype and molecular selections. The BC8F1 populations showed bimodal distribution for pollen fertility and could be classified into semi-sterile and fertile types, fitting single Mendilian factor inheritance ratios. Three QTLs detected in the BC1F1 corresponding to qSS-3, qSS-6a and qSS-7 were mapped on chromosomes 6, 3 and 7, respectively, as single Mendilian factors. 相似文献
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使用激励手段提高农民的积极性,增加土地的利用率,从而提供产量以及粮食的总产量,实现粮食安全,保持18亿亩耕地红线。 相似文献
16.
168A是利用\"油研10号\"中的\"不育株(Y10A)\"与\"双低油菜品系H6(R31×中双4号)\"为材料,运用杂交改造的方法育成的甘蓝型油菜双低核不育两型系。该不育系品质好,芥酸含量0.4%,硫苷含量20.27μmol/g,含油量41.24%;育性稳定、恢复谱广,经济性状优良,易测配出黄籽型优质组合;繁殖、制种产量高,有利于产业化开发。 相似文献
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D L Barnes N F G Rethman C C De Witt G D Kotze 《African Journal of Range and Forage Science》2013,30(3):90-95
Abstract The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement. 相似文献