Physiological Effects of Winter Rape (Brassica napus var. oleifera) Prehardening to Frost. I. Frost Resistance and Photosynthesis during Cold Acclimation

The objective of the research was to define the changes in photosynthetic activity induced by prehardening and to determine their involvement in frost tolerance of winter rape.
Prehardening of winter rape, consisting of keeping the plants at + 12°C during the light periods from sprouting until the beginning of the 1st stage of cold hardening, contributed to increasing its effectiveness. After 42 days of hardening at + 2°C the resistance of the prehardened plants equalled that attained by winter rape in the most favourable seasons of vegetation in the field. Prehardening stimulated the efficiency of photosynthesis at chill temperatures (+ 2–5°C). Differences in photosynthetic efficiency, like those in frost resistance, increase with successive weeks of hardening. They also concern the leaves already developed at the hardening temperature. A prehardened photosynthetic apparatus is less susceptible to the progress of photoinactivation taking place when the seedlings are kept at + 2°C. It also demonstrated greater activity even during the first hour of hardening or in the newly expanding leaves, and also at higher temperatures, most probably because of the more efficient progress of the dark, processes. The described changes in the functioning of the photosynthetic apparatus induced by prehardening were thus qualitatively very similar to those observed during long-term growth at + 5°C. already described in the literature.     

Phenotypic polymorphism of six enzymes in the grasspea (Lathyrus sativus L.)

Summary The phenotype variation in six enzymes, 6-phosphogluconate dehydrogenase (6-PGD), malate dehydrogenase (MDH), peroxidase (PRX), isocitrate dehydrogenase (IDH), galactose dehydrogenase (GD) and glutamate oxaloacetate transaminase (GOT), was investigated using horizontal starch gel electrophoresis in 52 accessions of the grasspea, Lathyrus sativus. Phenotypic polymorphism was observed for all six enzymes. High phenotypic polymorphism (Pj) was observed for PRX and 6-PGD, while there was little polymorphism for GOT, with only two accessions showing variation. There was no correlation between phenotypic polymorphism and region of origin, or groupings of accessions made on the basis of flower colour. Tentative genetic interpretations of banding patterns are given for five of the enzyme systems. The level of apparent heterozygosity was higher than expected in this predominantly autogamous species. The level of variation in the grasspea is discussed in terms of its potential for exploitation through plant breeding.     

Relationship between Prehardening, Photosynthetic Activity at Cold Acclimation Temperatures and Frost Tolerance in Winter Rape (Brassica napus var. oleifera). The Consequences for the Reliability of Frost Resistance Estimation under Controlled Conditions

The effect of prehardening (early stage of growth at moderate low temperatures (+12°C) during the day) on the reliability of frost resistance estimation in a controlled environment has been studied on three winter oilseed rape cultivars differing markedly in their field survival rate (Leo, Górczański and Idol). It has been also examined the relationship between the photosynthetic activity during the first stage of cold acclimation and the level of frost resistance observed in investigated cultivars. Presented results demonstrated that prehardening, which increases to a significant degree the effectiveness of the cold acclimation process, also increases the differences in cold hardiness between cultivars, and limits the magnitude of experimental errors made during frost resistance estimation under controlled conditions. In all studied cultivars, prehardening increases significantly the photosynthetic activity during cold acclimation. On the other hand, both in the prehardened and in the non-prehardened plants, no relation has been found between either gas exchange rates or chlorophyll 'a' fluorescence characteristics at low temperatures and cultivar ability for acclimation. Neither the existing differences in photosynthetic activity, nor the degree of photosynthetic apparatus acclimation to cold, which occurs during prehardening, are the factors responsible for the frost resistance variation observed between studied cultivars.     

Involvement of Chromosomes 5A and 5D in Cold-Induced Abscisic Acid Accumulation in and Frost Tolerance of Wheat Calli

The relationship between frost tolerance and abscisic acid (ABA) accumulation was studied in callus cultures of three wheat cultivars differing in the level of frost-tolerance, and of the 5A and 5D chromosome substitution lines from the frost-tolerant variety ‘Cheyenne’ into frost-sensitive ‘Chinese Spring’. Following cold hardening, the increase in ABA level in the calli of the two frost tolerant cultivars was significantly higher than in those of the frost-susceptible cultivar. Similarly, in 5A and 5D substitution lines, significantly higher ABA levels were detected than in the recipient ‘Chinese Spring’. One week-long ABA treatment at 26 °C induced a significantly higher level of frost tolerance than that achieved by cold hardening, irrespective of the frost sensitivity of the examined genotypes.     

低温胁迫下不同乌菜光合及荧光特性的变化及耐寒性评价

为寻求有效的方法来鉴定乌菜的耐寒性,本研究以6个乌菜材料为研究对象.对6个材料分别进行梯度降温(昼/夜)处理:18 ℃/12℃、12 ℃/6 ℃、6 ℃/0℃,每个阶段温度处理3 d,共9 d;之后测定6份材料经梯度降温胁迫后的光合和荧光特性,以及几种生理生化指标变化和相关性,同时用隶属函数法对供试材料的耐寒性进行综合...     

Assessment of Cold and Heat Tolerance of Winter-grown Canola (Brassica napus L.) Cultivars by Pollen-based Parameters

Winter‐grown canola (Brassica napus L.) production is limited mostly by frost and winter kill in the southern canola‐growing regions of the United States. Tolerance to cold and heat were assessed by studying percentage of pollen viability (PV), in vitro pollen germination (PG) and pollen tube length (PTL) for 12 field‐grown cultivars. Freshly collected pollen from all cultivars were incubated on artificial solid growth media at a constant temperature ranging from 10 to 35 °C at 5 °C interval for 30 h to determine PG and PTL. A modified bilinear model best described the temperature response functions of PG and PTL. Canola cultivars showed significant variability (P < 0.001) for PV (61.3 % to 89.7 %), PG (29.0 % to 48.2 %) and PTL (463 to 931 μm). The average cardinal temperatures, T_min, T_opt and T_max, for PG and PTL were 6.4, 24.3 and 33.7 °C, respectively. Principal component analysis revealed that maximum PG, PTL, T_min and T_opt of both PG and PTL were the most important factors in determining cold tolerance, whereas T_max of PG and PTL, and maximum PG and PTL were more responsible in separating the cultivars for heat tolerance. The canola cultivar, KS3077, was the most cold tolerant with the lowest T_min and the widest temperature adaptability range, and the cultivar Kadore was the most heat tolerant with the highest T_max for the PG. The identified cold‐ and heat‐tolerant cultivars may be useful in canola‐breeding programmes to develop cultivars suitable for a niche environment.     

Chlorophyll Fluorescence‐Based Studies of Frost Damage and the Tolerance for Cold‐Induced Photoinhibition in Freezing Tolerance Analysis of Triticale (×Triticosecale Wittmack)

Freezing tolerance of 60 breeding lines of winter hexaploid triticale (×Triticosecale Wittmack) was studied in the field‐laboratory experiment. The experiment was repeated over three winters. The survey was also carried out in plants grown and cold‐acclimated in the laboratory. In both the experiments, plant survival analysis and chlorophyll fluorescence‐based studies on energy flows in photosystem II (PSII) (JIP‐test) after freezing of detached leaves were performed. In the laboratory experiment, the temperature of 50 % electrolyte leakage from leaves and the resistance against cold‐induced photoinhibition were additionally investigated. In the case of plants’ cold‐acclimated in the field, determination of the freezing tolerance of PSII gave similar results as the determination of freezing tolerance of whole plants. Both traits were strongly affected by genotype–environmental interactions, but these effects were less visible for PSII characteristics. In the laboratory experiments, a strong correlation between freezing tolerance and the tolerance for cold‐induced photoinhibition of photosynthesis was observed. The possibility of the use of chlorophyll fluorescence‐based techniques for the determination of freezing tolerance in triticale is discussed.     

Genetic control of low temperature tolerance in germination of the common bean (Phaseolus vulgaris L.)

Summary Cultivars tolerant to low temperature during the germination and emergence stages and carriers of the grain quality standards demanded by consumers are needed to increase the success of irrigated common bean in Southern Minas Gerais State. To study the genetic mechanisms controlling these traits and assess the possibility of generating the desirable materials, a diallel cross involving ten cultivars including introductions and pure lines from the breeding program of ESAL was carried out. Speed of germination of the F₂ generation from the crosses was assessed under laboratory conditions at 12°C. The diallel analysis was carried out using Griffing's method IV (1956) and predictions of the cross potential were made by the methodology developed by Jinks & Pooni (1986). The results indicated that the parents differed in germination speed at low temperatures with Small White, A-488 and Rio Vermelho being the most tolerant and Carioca, ESAL 591 the most sensitive. No effect of the reciprocal crosses was observed either for germination percentage or germination speed. The parents A-488, Small White and Rio Vermelho showed the greatest general combining ability. Additive genetic effects predominated for both traits. Our results suggest that cold tolerance can be bred successfully into commercially acceptable cultivars.     

Identification of pearl millet [Pennisetum glaucum (L.) R. Br.] lines tolerant to soil salinity

Crop tolerance to salinity is of high importance due to the extent and the constant increase in salt-affected areas in arid and semi-arid regions. Pearl millet (Pennistum glaucum), generally considered as fairly tolerant to salinity, could be an alternative crop option for salt affected areas. To explore the genotypic variability of vegetative-stage salinity tolerance, 100 pearl millet lines from ICRISAT breeding programs were first screened in a pot culture containing Alfisol with 250 mM NaCl solution as basal application. Subsequently, 31 lines including many parents of commercial hybrids, selected from the first trial were re-tested for confirmation of the initial salinity responses. Substantial variation for salinity tolerance was found on the basis of shoot biomass ratio (shoot biomass under salinity/ non-saline control) and 22 lines with a wide range of tolerance varying from highly tolerant to sensitive entries were identified. The performance of the genotypes was largely consistent across experiments. In a separate seed germination and seedling growth study, the seed germination was found to be adversely affected (more than 70% decrease) in more than half of the genotypes with 250 mM concentration of NaCl. The root growth ratio (root growth under salinity/control) as well as shoot growth ratio was measured at 6 DAS and this did not reflect the whole plant performance at 39 DAS. In general, the whole plant salinity tolerance was associated with reduced shoot N content, increased K⁺ and Na⁺ contents. The K⁺/Na⁺ and Ca⁺⁺/Na⁺ ratios were also positively related to the tolerance but not as closely as the Na⁺ content. Therefore, it is concluded that a large scope exists for improving salt tolerance in pearl millet and that shoot Na⁺ concentration could be considered as a potential non-destructive selection criterion for vegetative-stage screening. The usefulness of this criterion for salinity response with respect to grain and stover yield remains to be investigated.     

Testing for Tolerance to Aphids in Indian Mustard, Brassica juncea (L.) Czern and Coss.

Brassica juncea plants were screened for aphid tolerance using three methods. Seven and 14 days old seedlings grown in wooden trays in a glasshouse were kept between infector trays with heavy aphid infestation. There were no surviving plants in the susceptible genotypes 50 days after sowing but survival rates ranging between 80 and 90 % were observed for selection 44. The progenies of the surviving plants were tested under natural infestation in the field. Plants were scored for leaves without aphids 40 days after sowing, healthy plants at harvest and seed yield in g/m² For most of these lines, the aphids’ survival, life span and fecundity (nymphs produced per adult) were recorded after introducing five newly-born nymphs on excised fifth leaves cultured in petri dishes. Selections showing greater tolerance to aphids than the check cultivars were identified in the progenies of a cross RLM-514 × T-6342. It was concluded that the excised leaf method can provide a reliable measure of the lines’ reaction to aphids.     

The Introduction of Transgenes to Control Blackheart in Pineapple (Ananas Comosus L.) cv. Smooth Cayenne by Microprojectile Bombardment

Summary A transformation technique for the introduction of transgenes to control blackheart by particle bombardment has been developed for pineapple cv. Smooth Cayenne. Leaf callus cultures capable of high frequency organogenesis with a short regeneration time were used as explant material. Gus and gfp reporter genes were used to observe and determine transient and stable expression. The ppo gene, isolated from pineapple, was introduced to control blackheart. Co-transformation occurred with constructs containing the nptII gene conferring geneticin resistance. We have recovered 15 independent transgenic gus and gfp lines each from 8 separate experiments and 22 ppo lines from 11 experiments. Gus, gfp, ppo and nptII positive plants have been regenerated, which have been shown by Southern blot analysis to be stable transgenics containing multiple copies of the introduced genes. These results show that biolistic gene delivery in pineapple can be successfully achieved at an acceptable efficiency of 0.21–1.5% for genetic improvement of ’Smooth Cayenne’, the industry standard throughout the world.     

Identification of segregation-distortion-neutral alleles to improve pollen fertility of indica-japonica hybrids in rice (Oryza sativa L.)

The genetics of resistance to Ascochyta blight (Ascochyta fabae f. sp. fabae) was studied in two populations of faba bean (Vicia faba). Plants of a resistant population, ILB 752, and a susceptible one, NEB 463, were screened for their reaction to the pathogen and the results were quantified on a scale of 0–5. Crosses were made between plants both within and between accessions and the F₁ and F₂ generations assessed in a field trial 21 and 45 days after inoculation. Disease scores were greater at 45 days than at 21 days and they were not significantly affected by the presence of susceptible spreader rows in part of the trial. ILB 752 carried a major dominant gene conferring resistance while NEB 463 carried the recessive allele for susceptibility. Furthermore, a minority of plants of NEB 463 appeared to carry at least one pair of complementary recessive genes, also conferring resistance. Most of the plants of ILB 752 were homozygous for the dominant resistance gene and a few were heterozygous. Reciprocal crosses behaved identically, indicating the absence of maternal effects in the expression of Ascochyta blight resistance in faba beans. The results show that it is important to confirm the level of heterozygosity for the resistance genes in this partially outbreeding species before crossing is commenced. The major dominant gene for resistance, identified in ILB 752, has clear potential for use in breeding for Ascochyta blight resistance. The minor genes identified in NEB 463 also show the potential for accumulating resistance through mass selection. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detection of QTLs for salt tolerance in Asian barley (Hordeum vulgare L.) by association analysis with SNP markers

Two hundred ninety-six Asian barley (Hordeum vulgare L.) accessions were assessed to detect QTLs underlying salt tolerance by association analysis using a 384 single nucleotide polymorphism (SNP) marker system. The experiment was laid out at the seedling stage in a hydroponic solution under control and 250 mM NaCl solution with three replications of four plants each. Salt tolerance was assessed by leaf injury score (LIS) and salt tolerance indices (STIs) of the number of leaves (NL), shoot length (SL), root length (RL), shoot dry weight (SDW) and root dry weight (RDW). LIS was scored from 1 to 5 according to the severity of necrosis and chlorosis observed on leaves. There was a wide variation in salt tolerance among Asian barley accessions. LIS and STI (SDW) were the most suitable traits for screening salt tolerance. Association was estimated between markers and traits to detect QTLs for LIS and STI (SDW). Seven significant QTLs were located on chromosomes 1H (2 QTLs), 2H (2 QTLs), 3H (1 QTL), 4H (1 QTL) and 5H (1 QTL). Five QTLs were associated with LIS and 2 QTLs with STI (SDW). Two QTLs associated with LIS were newly identified on chromosomes 3H and 4H.     

黄淮海地区大豆耐旱根系性状的遗传分析

从83份黄淮海地区代表性材料中按根系类型选取28份,在苗期以株高、叶龄、根干质量和茎叶干质量隶属函数的平均值为指标进行2年耐旱性重复鉴定,从中筛选出晋豆14强耐旱型材料。比根干质量、比总根长、比根体积与耐旱隶属函数值均呈极显著正相关,可作为耐旱性的根系性状指标。利用科丰1号×南农1138-2衍生的RIL群体为材料,对耐旱相关根系性状采用主基因 多基因混合遗传模型分离分析法进行遗传分析。结果表明,该两亲本间比根干质量、比总根长、比根体积的遗传均为两对主基因加多基因模型,后两者主基因间有连锁(重组率4.30%,1.93%);主基因遗传率为62.26%~91.81%,多基因遗传率为2.99%~24.75%;耐旱相关根系性状各主要由1对主基因控制,另1对效应较小,三性状的改良均着重在主基因加性效应。     

Evaluation of a collection of faba bean (Vicia faba L.) genotypes originating from the Maghreb for resistance to chocolate spot (Botrytis fabae) by assessment in the field and laboratory

Screening of 136 faba bean lines forresistance to chocolate spot caused by thefungus Botrytis fabae was conductedin field conditions with artificialinoculation. Detached leaves of thesegenotypes were also assessed for diseaseseverity after inoculation under controlledconditions with a B. fabaesuspension. The BPL710 and Aguadulcegenotypes were inserted as resistant andsusceptible checks, respectively. Diseasesymptoms were scored visually in bothexperiments. Diameter of lesions andproduction of spores were measured in thedetached leaf assay. The disease scoreindex and diameter of lesions were used tocalculate the area under the diseaseprogress curve (AUDPC) to measure thedisease progress. Significant differenceswere detected among genotypes for reactionto the disease in the field. However, nocomplete resistance was observed. Forhighly susceptible and highly resistantgenotypes, the laboratory assay generallyled to the same result as the field test,nevertheless, for more intermediate levelsthe agreement was weak. On detached leaves,diameter of lesions was significantlycorrelated to the AUDPC of disease scores(r = 0.89) and moderately correlated tosporulation (r = 0.52). The correlationbetween field AUDPC and detached leaf AUDPCof disease scores was low (r = 0.26). A lowcorrelation was also observed between fieldAUDPC and lesion size (r = 0.30) andbetween field AUDPC and sporulation (r =0.32). Among the 136 genotypes evaluated inthis study, nine were convincingly andhighly resistant in both tests. FRYM167 andFRYA58 genotypes were the most resistantwith low AUDPC of disease scores, low AUDPCof lesion diameter and low sporeproduction. These genotypes obviously havepartial resistance.     

Maize Smut Induced by Ustilago maydis (D. C.) Corda – Reaction of Maize Hybrids and Lines to Smut Disease

A field experiment was carried out during the growing seasons 1982, 1983 and 1984 to evaluate the reaction of different maize hybrids and lines to smut disease and to give further informations on the effect of environmental factors on smut incidence.
The kernels of 17 different maize hybrids and 17 inbred line were planted in the field and the stand was maintained constant of 30 plants per row during the respective years. Each plant was subjected to an artificial infection by dropping 2 ml of U. maydis -spore suspension into the leaf whorl at 6–8 leaf stage. Field observations, concerning the number, the size and location of smut galls were recorded for each individual plant whenever the symptoms appeared. The reaction of maize genotypes was evaluated on a new classified system and the differential response was correlated with the changes ol meteorological data.
The results indicated that hybrids: Circe LG9, E1, Kaceplns, Limac-LG11 and RA 94A x RA 320 as well as lines: F2, L1, L2, L8, RA 94A, RA 320, W33 and W401 were highly resistant; while the hybrids E2, F7 x EP1.J and Giga as well as lines: EP1J, F115, L5 and L6 were highly susceptible. The reaction of these genotypes exhibited an identical behaviour during the 3 years. The remaining genotypes were unstable and showed differential response to degree of infection and location of smut galls. The increase of smut infection in 1982 relative to that recorded in 1984, under the same wet weather conditions, was attributed to the increase of air temperature and sunshine duration. Under dry weather condition, as in 1983, increasing temperature and sunshine duration had little effect on smut incidence.     

The inheritance of the cold induction response with respect to floral initiation in white clover (Trifolium repens L.)

Summary The inheritance of the cold induction response in the UK cultivar of white clover Menna, was assessed in controlled environments.Only 50% of the population flowered without prior cold induction. The cold period increased the number of stolons which became reproductive.All families from the crosses between induction and non-induction requiring genotypes produced progeny lacking a cold requirement for flowering.Heritability estimates for the number of flowers per plant, reproductive buds per stolon and stolon number were high.The necessity of eliminating the cold induction requirement in potentially valuable white clover cultivars in relation to seed production at lower latitudes is discussed.     

Characterization of morphological variation and cold resistance in interspecific somatic hybrids between potato (Solanum tuberosum L.) and S. brevidens Phil.

Summary Somatic hybrids between Solanum tuberosum L. cv. Gracia (2n=4x=48) and Solanum brevidens Phil. (2n=2x=24) were produced via fusion of mesophyll protoplasts. Selection of the protoplast derived putative hybrid calli was based on their vigorous growth. Additive isozyme patterns and chromosome numbers as well as the expression of parental morphological characters have proved the hybrid origin of the selected regenerants. Extensive chromosome loss during the regeneration process resulted in aneuploid hybrids with high frequency. Genomic instability could not be detected in these plants during the period of vegetative propagation. Regenerants from hybrid tissues exhibited wide morphological variation especially in tuber formation. The detailed morphological analysis based on the use of multivariate method (principal component analysis, PCA) enabled to identify morphological groups among the hybrid clones. The positioning of hybrid clones in the PCA space could not be correlated with chromosome numbers. The genomic ratio represented by the tetraploid and diploid parents influenced the morphology of somatic hybrid population according to the applied analytical system. Two selected hybrid clones have exhibited an intermediate degree of frost tolerance compared to the parents, based on the recovery of plants from lower buds after freezing of potted plants.     

春甘蓝抽薹的生理与相关基因转录分析

本研究以高代自交获得的4份具有不同抽薹时间且遗传稳定的春甘蓝品系为材料,在观察其园艺学性状的基础上,分析了抽薹性状与可溶性蛋白和可溶性糖含量之间的关系,结果显示,耐抽薹春甘蓝品系的可溶性蛋白和可溶性糖含量低于不耐抽薹的,抽薹前春甘蓝的可溶性蛋白和可溶性糖含量也均低于抽薹后的.进一步的转录分析结果表明,5个与植物抽薹开花...     

Diallel analysis of partial resistance to powdery mildew caused by Erysiphe graminis f. sp. hordei in spring barley (Hordeum vulgare L.)

Summary Six spring barley genotypes with growth stage dependent expression of partial resistance to powdery mildew were crossed following a half diallel scheme. Data for percentage infected leaf area at different growth stages from the F1 and F2 generation and the F2 offspring were analyzed. The absence of a contrast between parents and offspring indicated that dominance effects were not important at the young growth stages. Diallel analysis showed that general combining ability effects (GCA) were important at all growth stages. Although significant, specific combining ability effects were of minor importance. The cross between the most resistant parents with the largest, negative GCA resulted in the most resistant progeny.