水稻稻瘟病诱导抗病性的研究进展

综述了近年来水稻稻瘟病诱导抗病性研究的主要进展，介绍了生物因子和非生物因子诱导水稻对稻瘟病的局部和系统抗性，分析了可能的抗性机制，并指出了目前诱导抗性中存在的问题和其未来发展前景。     

Global impact of mutation-derived varieties

During the past seventy years, worldwide more than 2250 varieties have been released that have been derived either as direct mutants or from their progenies. Induction of mutations with radiation has been the most frequently used method for directly developed mutant varieties. The prime strategy in mutation-based breeding has been to upgrade the well-adapted plant varieties by altering one or two major traits, which limit their productivity or enhance their quality value. In this paper, the global impact of mutation-derived varieties on food production and quality enhancement is presented. In addition, the economic contribution of the selected mutant varieties of rice, barley, cotton, groundnut, pulses, sunflower, rapeseed and Japanese pear is discussed. In several mutation-derived varieties, the changed traits have resulted in synergistic effect on increasing the yield and quality of the crop, improving agronomic inputs, crop rotation, and consumer acceptance. In contrast to the currently protected plant varieties or germplasm and increasing restrictions on their use, the induced mutants have been freely available for plant breeding. Many mutants have made transnational impact on increasing yield and quality of several seed-propagated crops. Induced mutations will continue to have an increasing role in creating crop varieties with traits such as modified oil, protein and starch quality, enhanced uptake of specific metals, deeper rooting system, and resistance to drought, diseases and salinity as a major component of the environmentally sustainable agriculture. Future research on induced mutations would also be important in the functional genomics of many food crops. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of 'Anahuac' wheat mutant lines for aluminum tolerance

Seeds from the aluminum sensitive cultivar ‘Anahuac’ were treated by gamma-ray radiation. Twenty eight selected Al⁺³ tolerant mutants were compared to the original Anahuac and the tolerant wheat cultivars IAC-24 and IAC-60 from 1994 to 1996 in acid (Capão Bonito) and limed (Monte Alegre do Sul and Tatui) soil field trials. Grain yield and agronomic characteristics were analyzed. Twenty six mutant lines yielded higher than the sensitive Anahuac cultivar in the acid soils of Capão Bonito. Under limed soil conditions, the mutants had a similar yield to the original sensitive cultivar. The majority of the mutants were similar in yield to the tolerant cultivars IAC-24 and IAC-60 under both conditions. Some of the mutants showed altered agronomic characteristics but even in these cases this will not limit its utilization. The results indicated that tolerant lines with good characteristics may be obtained from a susceptible cultivar by mutation induction, thus allowing cropping in conditions where Al⁺³ is a limiting factor.     

Selection of Semidwarf, Early Maturing and Blast Resistant Mutants after Mutagenic Seed Treatment in Two Locally Adapted Indian Rice Cultivars

The objective of this study was to induce semidwarf, early maturing and blast resistant mutants in two adapted Indian rice cultivars. Seeds of the rice cultivars ‘Madhu Malti’ and ‘Phul Patas 72’ were treated with gamma rays and ethyl methane sulfonate (EMS) as well as a combination of gamma rays and EMS. A total of 96 dwarf (< 75 cm) and semidwarf (< 100 cm) and 104 early flowering/maturing M₂ plants were identified among the 18,060 M₂ plants observed. Sixty-eight blast resistant M₂ plants were also identified. The true mutant status of these plants has yet to be determined in progeny tests. The induction of desired mutant types in locally adapted cultivars could prove to be superior over their introduction from non-adapted foreign materials via backcrossing in that the important agronomic characteristics of adaptation to the local environment are retained in the mutants.     

Effectiveness of Ethrel as a Male Gametocide in Pearl Millet and its Influence on Ergot

In field and greenhouse experiments Ethrel (2-chloroethyl phosphonic acid) was tested for its male garnetocidal effects on pearl millet (Pennisetum americanum) and its subsequent effects on ergot development. Application of Ethrel at 2000 ppm at late boot or early protogyny was the most effective for inducing male sterility in the hybrid, EJ 104. Female fertility in a male sterile line, however, was not affected by Ethrel treatment. Ethrel at 2030 ppm applied at ihe late boot stage resulted1 in partial paniele exsertion, and reduced plant height anc. panide length. In vitro Ethrel (2000 ppm) completely inhibned pollen germination but did not affect germination of conidia of Claviceps fusiformis, the causal agent of ergot of pearl millet. Ergot resistance or susceptibility in pearl millet lines was not affected., probably because Ethrel could not induce complete male sterility.     

EMS Induction of Early Flowering Mutants in Spring Rape (Brassica napus)

Studies were undertaken to induce early flowering mutants by ethyl methanesulphonate (EMS) treatments of Brassica napus seeds. EMS treatments for 12 h of a highly inbred B. napus line TBS had adverse effects on M¹ plant development and fertility only when concentrations were greater than 1%. However, an EMS concentration of 1.5% did not reduce M₁ plant fertility to an extent which significantly reduced production of M₂ seeds. Genetic changes induced by EMS treatment and affecting flowering time were of three main types: (1) Changes within a polygenic system reflected by increased variation in flowering time among M₂ families. As the increase in variation was due primarily to a higher frequency of later flowering plants, these polygenic changes would be of little value in developing better-adapted cultivars. (2) Induction of a recessive mutation at a major gene locus which caused M₃ plants homozygous for the mutant gene to flower at least 20 days earlier than the parental line TB8. (3) Induction of a dominant mutation at a major gene locus which affects flowering time by causing a substantial reduction in vernalization requirement. M₂ plants carrying the mutant gene flowered as early as 59 days before the parental line. These major gene mutations could be rapidly exploited in the development of agronomically superior cultivars for short-season, lower rainfall environments in Western Australia.     

Increase of genetic variation in some lettuce cultivars by induction of mutations: A technical note

Summary Colchicine treatments of 13 lettuce cultivars for production of polyploid lettuce also resulted in rapid growing diploid mutants.     

Induced mutations in winged bean (Psophocarpus tetragonolobus L. DC) with low tannin content

Four mutants of winged bean (Psophocarpus tetragonolobus (L.) DC) with altered tannin content were selected among the M₃ seeds present on M₂ plants following mutagenic treatment of seeds of cvs UPS 122 and Kade 6/16 using gamma radiation from a Co⁶⁰ gamma source. These mutants were selected from the most chimeric parts of the M₁ plant, which had earlier been identified to be the first mature pods on the M₁ plant and the earliest formed M₂ seeds in the M₁ pods. The indirect selection of tannin mutants was based on searching for seed coat colour changes in M₃ seeds. Cv UPS 122 yielded the mutants 3/1-10-12 and X22 from 1958 and 1883 M₂ plants respectively. Cv Kade 6/16 yielded the mutants 3/9-0-12 and 3/4-10-7 from 1442 and 1011 M₂ plants respectively. One of the mutants, 3/4-10-7, which was the only desirable one, had a level of tannin of about 25% of the wild type cv. Kade 6/16. The other three mutants had similar or increased tannin levels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences in partial resistance of barley to powdery mildew (Erysiphe graminis DC F.SP. hordei Marchal) after chemomutagenesis. II. Reaction of mutants to pathotypes

Summary Seedlings of 45 barley mutants with partial resistance in the field and their parental cultivars Asse, Bomi, and Vada were exposed to six local and two foreign races of powdery mildew, in climatically controlled cabinets. Infectability, pustule size, infection grade, and infection type were estimated. No mutant did demonstrate strong race-specific reactions although some race-specific interactions of moderate grade could be detected. The results of infection of mutants with single races confirmed the quantitative character of their change in resistance determined in the earlier field assessments. The 20 investigated mutants with increased resistance expressed a lower level of disease with each of the used races. Out of the 10 mutants with higher susceptibility in the field, 4 mutants again exhibited higher degrees of infection over all the different races, while the remaining 6 mutants were not distinguishable from the original cultivar under the given growing conditions. Out of the tested 14 developmentally resistant mutants, only the 5 genotypes with different seedling reaction could be analyzed for race-specificity in this study. In all the above cases as the result of one gene mutation, quantitative shifts in level of infection were recorded over all the 8 races.Qualitative estimates of infection type were supported by data on the frequency of chlorotic or necrotic lesions and green islands on the infected leaves. But quantitative methods of assessment, e.g. infection frequency and pustule size, were more effective in studying partial resistance of the mutants. Infection grade, estimated visually 14 days after inoculation, was in agreement with the quantitative parameters accurately measured 7 days after inoculation. Therefore, its careful use can be recommended to speed the screening by narrowing down the materials. Differences in virulence level of the races were observed and their influence on race-specificity studies was discussed.     

Effects of seed irradiation on yield and quality of essential oil in palmarosa (Cymbopogon martinii Stapf.)

Summary Dry seeds of palmarosa (Cymbopogon martinii Stapf) var. motia were subjected to 12 doses of gamma rays ranging from 5 kr to 100 kr to find out the effects of gamma irradiation on growth parameters, herbage yield and yield and quality of essential oil. Several biological parameters such as seedling growth, pollen fertility, mitotic chromosome behaviour, productive tillers/plant, leaf area index, leaf/stem ratio (by fresh weight) and total herbage yield/ /plant together with yield and quality of oil have been studied in the first (M₁) generation. Marked stimulatory effects of gamma radiation in 10 kr and 15 kr doses have been compared with the control for herbage yield, oil percentage and total alcohols (free geranyl and geranyl acetate).The two yield contributing traits, herbage yield/plant and leaf area index were remarkably increased in 15 kr, which indicates that in palmarosa the 15 kr dose is more effective than the higher doses in producing microlevel mutations. The yield and quality of oil at 10 kr and 15 kr doses were enhanced significantly. The results on high yield and quality of oil as induced by gamma-irradiation were discussed from the point of view that a gene may have been altered by mutagen treatment to produce a metabolic block between geraniol and geranyl acetate on the biosynthetic pathway or that modifier genes controlling the expression of a key precursor molecule may have been further modified to give rise to a geraniol rich chemotype in palmarosa.