摘要:

AbstractPotato viruses are prevalent worldwide and cause substantial economical losses in the potato crop (Solanum tuberosumL.). Therefore, various types of resistance to potato viruses identified in cultivated and wild potato species are used in potato breeding programs and are briefly reviewed in this paper. However, the current nomenclature of virus resistance specificities is confusing because it was adopted at an earlier time when several virus strain groups were believed to represent individual virus species and because it does not distinguish between strain‐specific and comprehensive resistance specificities. A consistent nomenclature is desirable to distinguish both currently known virus resistances and any novel virus resistances detected in the future. A descriptive and systematic nomenclature for resistance specificities is proposed which denotes (1) type of resistance (2) identity of virus (3) the virus strain group(s) against which the resistance is effective (4) the virus strain group(s) against which the resistance is not effective, and (5) the potato species in which the resistance is describe

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00952.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe restriction and amplification patterns of potato genomic DNA of eight different cultivars and breeding clones has been studied. The analysis was carried out by polyacrylamide high resolution gels, and subsequent blotting and hybridization to potato DNA probes, and by agarose gel electrophoresis of the amplification products obtained with a variety of random primers. Fingerprinting of the genotypes was possible using two enzyme‐probe combinations (Rsal‐GP35 andRsal‐CP6) and three random primers (OPA4, OPA19 and OPG12). Based on the same techniques, a number of plants from the cvs. Monalisa and Spunta originated from the sprouting ofin vitro‐induced tubers (vitrotubers) were analysed to test the reproducibility of RFLP and PCR patterns. No variations were found with RFLP analysis. Some different RAPD patterns were seen, showing putatively vitrotuber‐specific v

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00953.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe use of high nitrogen (N) inputs is becoming restricted in many countries due to environmental and economic considerations and reliable information is needed about parameters pertinent for breeding N‐use efficient triticales (xTriticosecaleWittmack). This study reports estimates of variances, heritabilities, correlations, and regression for 36 triticales, grown at three locations for 2 years with two N regimes (zero and normal N supply). Eleven traits were assessed. A 45% mean reduction in grain yield by low N input was mainly the result of a 25% lower number of tiller‐bearing spikes per m2 and 17% fewer kernels per spike, whereas 1000‐kernel weight was little affected. Genotype‐nitrogen interaction was of importance only in some environments and for certain traits. Heritability estimates at both N levels were similar and moderate to high. Correlations between N levels were high for nearly all traits. Regression analysis for grain yield revealed only few N‐efficient triticales with lower than unity slope together with a high grain yield. Based on the genetic parameters, it is concluded that a special low input breeding programme does not appear to be necessary in triticale. The breeder can select at either of the N levels with similar response. But he should include tests in low productivity environments at some early stages in the breeding process to avoid loss of genetic variation for N‐use

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00954.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractForty‐two winter wheat varieties and 193 F2and BC1F2seeds were screened forGlu‐D1dallele encoding the HMW glutenin subunits 5 + 10 using polymerase chain reaction (PCR). The segregating populations originated from crosses involving wheat parents with good and poor bread‐making quality. A clear PCR product of 450 bp, representing 1Dx5 of theGlu‐D1dallele was identified in 24 varieties and 111 hybrid seeds. Four differentGlu‐D1alleles: a (2 + 12), b (3 + 12), c (4 + 12) and d (5 + 10) were detected using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE). Only genotypes possessingGlu‐D1dgave a positive PCR signal, hexaploid triticale and 4 × wheat lackingGlu‐D1locus gave a negative signal. The efficiency of PCR selection for bread‐making quality in early generations using ha

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00955.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractSeven genotypes of winter durum wheat (Triticum durumDesf.) were cultured to establish an efficient method of callus formation and plant regeneration from mature embryo culture, and to compare the responses of immature and mature embryo cultures. Immature embryos were aseptically dissected from seeds and placed, with the scutellum upwards, in dishes containing Murashige and Skoog's (MS) mineral salts and 2mg 2,4‐ dichlorophenoxyacetic acid (2,4‐D) per litre. Calli and regenerated plants were maintained on 2,4‐D‐free medium. Mature embryos were moved slightly on the imbibed seeds. For callus formation, the seeds with moved embryos were placed, furrow downwards, in dishes containing 8 mg 2,4‐D per litre. The developed calli and regenerated plants were maintained on the MS medium. Plants regenerated from both embryo cultures were vernalized and grown to maturity in soil. Variability was observed among the wheat genotypes tested for various culture responses in both explant cultures. Callus induction rate and regeneration capacity of callus were independent of each other. Mature embryos have a low frequency of callus induction but a high regeneration capacity. Considering availability, rapidity and reliability, this form of mature embryo culture can be used as an alternative method for immature embry

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00956.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractQuantitative genetic theory was used to investigate selection differentials, expected and observed direct and correlated responses to simultaneous improvement of grain yield, kernel weight, and grain protein content in F3and F4populations of four spring wheat (Triticum aestivumL.) crosses. Selection in the F3generation based on the Smith‐Hazel index (SH) and yield was found to be superior to the other methods studied in identifying high‐yielding lines, but resulted in substantial decrease in grain protein level. Consequently, a 1.0% increase in protein from selection for protein depressed grain yield as much as 536 kg/ha below the population mean, reducing the expected yield gains per generation selection cycle by 250%. The weight‐free indices (EW), particularly the index involving only yield and kernel weight (EW3) and its linear approximation (EW4), and the desired gains indices were effective in improving protein content but were less efficient in selecting top‐yielding lines. Selection in the opposite direction using truncation of the lowest 10% of the population based on weight‐free‐index involving yield, kernel weight and protein (EW2) reduced all traits significantly compared with the mean of the unselected population indicating the effectiveness of the unweighted selection index. The observed genetic gains (Ra) from selection based on yield, the SH, EW3 and EW4 indices were slightly lower than the expected advances per cycle (R) in populations from crosses ‘Sinton’בGlenlea’ (C1), ‘Glenlea’בNB505’ (C2), and ‘A2P5’בNB320’ (C6) (Ra/R = 70 to 85%) but were higher in cross ‘NB505’בA2P5’ (C5) (Ra/R = 126 to 143%). It was concluded that weight‐free and the desired gains indices can be used to improve wheat grain yield and grain protein simultaneously in F3generation selection, as revealed by r

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00957.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractImproving rust resistance is one of the main goals in our breeding programme with perennial ryegrasses. We have studied the behaviour of our breeding material over several years in several locations under natural and artificial infection conditions. The narrow sense heritability of crown rust resistance is fairly high (0.46), providing scope for improving resistance, but this optimism is reduced by the negative correlation with yield. The most resistant material yielded 4% less than the most susceptible material. No decline in digestibility is expected when improving the disease resistance. The incidence of crown rust is very variable between years, locations and between spontaneous and artificial infections, creating constraints in selection.Observations for several years and at several locations appear to be the best way to improve rust resistance in perennial ryegrass.

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00958.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe rate of natural crosses occurring among the cultivatedBrassicaspeciesB. napus, B. rapa, andB. junceaand their two weedy relativesB. nigraandSinapis arvensiswas studied in co‐cultivation experiments under field conditions in Saskatchewan, Canada, with special reference to evaluation of the possibility of transgene escape from the cultivated to the weedy species. Natural crosses occurred amongB. napus, B. rapa, andB. juncea, indicating that hybridizations among these three species do occur under field conditions. On the other hand, no natural crosses occurred between the cultivated species andB. nigraorS. arvensis.It is concluded that the crosses between the cultivated and weedy species are practically impossible under field conditions in Saskatchewan, and that the escape of transgenes from transgenic cultivars ofB. napus, B. rapaandB. junceaintoB. nigraandS. arvensisis basically zero in this regio

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00959.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractEleven winter rapeseed inbred lines (I4) were characterized according to isozyme banding patterns from seven polymorphic enzyme systems. All lines could be qualitatively and quantitatively distinguished using two enzyme systems, shikimate dehydrogenase (SDH) and diaphorase (DIA). Genetic distances were calculated among lines and 15 selected two‐line hybrids were planted as experimental synthetics in field‐trials. Syn‐0 populations produced seed yields between 0.4% lower and 12.9% higher than the mean yields of the respective parental lines. Syn‐1 seed yields were 11–24.1% higher than the respective parental lines and the yield improvement was positively correlated with the genetic distance between the parental lines. This tendency suggests that genetic distances between cross components, calculated from isozyme polymorphism, can be used in prognosis of yield performance of synthetic rapeseed cultivars. Isozyme analysis was also applied to study fertilization behaviour in line mixtures, and differences among parental lines were observed with regard to the tendency for self‐pollination or out‐crossing. The partially very high outcrossing rate suggests the possible existence of a self‐incompa

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractSomatic hybrids ofSinapis alba+Brassica juncea(Sal Sal AABB) were synthesized by protoplast electrofusion. They were true genomic allopolyploids since they possessed 60 chromosomes, i.e. the sum ofS. alba(2n= 24) andB. juncea(2n= 36) chromosomes. Chromosome pairing was predominantly bivalent with the occasional occurrence of multivalents in the pollen mother cells at diakinesis and metaphase I. Hybrids were completely pollen‐sterile, but produced seeds on back‐crossing withB. junceaandB. campestris.A total of 37 BC1plants were raised from two somatic hybrids (JS‐1 and JS‐2) and 24 of these were analysed cytologically. The 22 plants originating from the pollinations of somatic hybrids withB. junceashowed a chromosome configuration of 18II+12I and had 42–86% pollen fertility. Two plants from the backcrosses of the somatic hybrid withB. campestrisformed 10II +20I, and had 0–4% fertile pollen. Total DNA analysis by probing with pTA71 carrying a full‐length 18S–25S rDNA fragment of the wheat nuclear genome revealed that the two somatic hybrids possessed all the characteristic bands of both the species, confirming their hybridity. Probing with the mitochondrialcoxIandatp9genes indicated mitochondrial genome recombination in the hybrids. Hybridization with chloroplast‐specificpsbDindicated that both the somatic hybrids possessed the cp genom

ISSN:0179-9541    

DOI:10.1111/j.1439-0523.1996.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY