Sensitivity to Drought Stress of Three Soybean Cultivars During Different Growth Stages

Three soybean ( Glycine max L.) culivars, Lee-74, Wright , and Ra 401 , were subjected to 100 % (control), 75 %, and 50 % of field capacity during vegetative (VI), flowering (R2), and pod-filling (R4) stages in greenhouse and field studies. Stress applied at R2 significantly reduced the yield in the greenhouse, while in the field, the maximum reduction was observed when the plants were subjected to stress at R4. Stress during VI reduced the yield components less than stress applied during R2 or R4 stages in both studies. The pod number and seed weight were the yield components most affected by drought stress, and the number of seeds per pod the least affected. Yield stress index was significantly correlated with the yield and its components. The reproductive stage was clearly more sensitive to drought than the vegetative stage. The cultivar Lee 74 had the highest yield and the second highest yield stress index whereas the cultivar Ra 401 had the lowest yield.     

Additive gene action for resistance to Puccinia striiformis F.SP. Tritici in Triticum dicoccoides

Summary Seven single-plant selections of wild emmer, with temperature-sensitive minor-effect genes for stripe rust resistance, were intercrossed in eight combinations. The resulting progenies were studied for a possible additive gene action.The transgressive segregation towards resistance in F₂ observed in all the combinations indicates that additive gene action for resistance indeed occurs in wild emmer. The common occurrence of this phenomenon in random combinations suggests further that several minor-effect genes are involved.Following selection of the most resistant plants in F₂, a marked shift towards resistance was noted in F₃, which demonstrates a positive response to selection. In some instances, additive resistance selected for (in F₂) at the high temperature-profile was expressed (in F₃) also at the low temperature-profile. This kind of resistance, when utilized in breeding programmes, promises therefore to be effective over a range of temperatures.     

A melon genotype with superior competence for regeneration and transformation

Transformation efficiency of melon is low and is still regarded as a challenge. In this paper, the regeneration and transformation response of ‘BU‐21/3′, a newly characterized melon breeding line, is described. The line seems to be superior in this regard to previously evaluated genotypes. Agrobacterium‐mediated delivery of the GUS or GFP reporter genes into cotyledon explants was used to evaluate efficiency of transient and stable transformation. Good transient expression was observed, and stable transformation frequencies of 0.4‐1.5 transgenic shoots per explant were obtained. Transgenic plantlets were transferred to a contained greenhouse as early as 8‐10 weeks after transformation. Transgenic plants are fertile and exhibit a true‐to‐type phenotype. The ‘BU‐21/3’ line may become a useful tool for the facilitation of transgenic breeding in melon.     

RFLP mapping of QTLs for photoperiod response in tropical sorghum

Genetic control of flowering time in sorghum was investigated using a recombinant inbred lines population derived from a cross between IS 2807, a slightly photoperiod sensitive tropical caudatum landrace, and IS 7680,a highly photoperiod sensitive tropical guinea landrace. Progenies were sown with their parents at six different dates between 1995 and 1997 in Burkina Faso. Direct field measures and synthetic measures derived from the implementation of a model were used to characterize the photoperiod response. Emphasis was put to identify the most relevant traits to account for Basic Vegetative Phase (BVP) and photoperiod sensitivity sensus stricto. One QTL was detected on Linkage Group (LG) F for the traits related to BVP. Two QTLs were detected on LGs C and H for the traits related to the photoperiod sensitivity sensus stricto. This gives credit to at least partially independent genetic determinisms for those two components of photoperiod response. Evidences for possible orthology of the QTLs detected here with other QTLs and major genes involved in flowering time of sorghum and rice are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of variation and interrelationships in potato germplasm

Summary As the exploitation of economic characters in potato is reaching a plateau, use of exotic germplasm offers an ideal opportunity for further improvement. Fifty-five accessions from eleven countries were studied under long and short day conditions. Wide variation was noticed for a number of phenological, morphological and tuber characters. Analysis of variation and correlations has demonstrated possibilities for using this diverse germplasm in various potato improvement programs.Abbreviations APC - Andean Primitive Cultivars - AUDPC - Area Under Disease Progress Curve - CCBL - Commerical Cultivars and Breeding Lines - LD - Long Days - SD - Short Days     

Linkage relationships of genes for leaf morphology and double flowering in Matthiola incana

Summary The inheritance and linkage relationships of a leaf morphology gene of Matthiola incana were investigated. The allele for sinuate leaf shape, c, was found to be recessive to the allele for normal entire leaf, C. The c allele was tightly linked to the recessive allele for double flowering, s. The recombination frequency between the two loci was close to zero. The mode of inheritance of the C gene was in accordance with the hypothesis that a pollen lethal gene is responsible for the constant 1:1 segregation ratio of double-flowered (= male sterile) to single-flowered (= fertile) plants in most M. incana breeding lines. The sinuate leaf allele seemed to reduce the frequency and delay the flowering of double-flowered plants. The importance of the C gene as a double flowering marker in the cultivation and the breeding of M. incana is discussed.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1128-E, 1993 series.     

Effectiveness of Twenty-Four Barley Resistance Genes Against Powdery Mildew (Erysiphe graminis DC f. sp. hordei Em. Marchal) in Spain

Twenty-four near-isogenic barley lines, with a cv.‘Pallas’ background, carrying different mildew resistance genes were subjected in 1987, 1989 and 1990 to natural infection by the pathogen at several different and contrasting Spanish sites in order to study its virulence. The virulence genes proved to be geographically grouped into three regions: western (Valladolid), southern (Sevilla) and northern and northeastern (Navarra, Lleida and Girona). The mildew population of Lleida was more variable when compared with Navarra and Valladolid. Overall, the most effective resistance genes were: Ml-a13 + Ml-(Ru3), mlo and Ml-(1402).     

Genes for Resistance to Yellow Rust in Seedlings of Wheat Cultivars from Pakistan Tested with British Isolates of Puccinia striiformis

Seedlings of 26 wheat caltivars from Pakistan were tested with 18 British races of P. striiformis. It is postulated that the race-specific genes Yr6, Yr7, Yr9 and perhaps Yr2 were present among the cultivars, and that there was other resistance not controlled by these genes.     

Resistance to the gall mite and American gooseberry mildew in black currants in relation to season of leafing out

Summary In black currant (Ribes nigrum) backcross progenies segregating for resistance to the gall mite, Cecidophyopsis ribis Westw. (gene Ce from Ribes grossularia L.), and to American gooseberry mildew, Sphaerotheca mors-uvae (Schw.) Berk. (gene Sph ₃from R. glutinosum), significant differences in season of leafing out occurred between the resistant and susceptible classes. The data are consistent with the hypothesis that two additive genes, Lf ₁and Lf ₂, controlled season of leafing out and that Ce and Sph ₃ were linked with Lf ₁.     

A stability analysis of time to flowering as a screen for responsiveness to temperature and photoperiod in cowpea (Vigna unguiculata)

Summary Twenty-one genotypes of cowpea (Vigna unguiculata), comprising landraces and varieties, were grown in 22 photothermal environments in Nigeria and Niger, West Africa, and a stability analysis of days from sowing to flowering (f) was carried out. Cowpeas are rarely insensitive to photoperiod; they are typically quantitative shortday plants wherein f is delayed when photoperiod (P) is longer than the critical photoperiod (P _c ). Therefore, in order to quantify genotypic variation in temperature sensitivity, genotype f was regressed against the mean trial f in circumstances where P c (i.e. approximately 13 hd^-1) and mean temperature (T) was between 19° and 28° C. Correspondingly, in order to assess genotypic variation in photoperiod sensitivity, trials where T was near optimal (25°–28° C) but where P ranged from 10–14.5 hd^-1 were used. These stability analyses detected no significant differences (P>0.05) between genotypes 9n temperature sensitivity but revealed significant differences (P<0.001) in photoperiod sensitivity. Regression coefficients from the stability analysis were strongly correlated (r=0.94, 19df) with a photoperiod sensitivity constant, c, determined from a photothermal flowering model. A stability analysis of f from field trials can therefore identify and quantify genotypic variation in response to temperature and photoperiod in cowpea.Abbreviations f days from sowing to flowering - P mean photoperiod - P _c critical photoperiod - P _ce ceiling photoperiod - T mean temperature - T _b base temperature - T _o optimum temperature - SDP short-day plant