The high level of wide-compatibility of variety ‘Dular’ has a complex genetic basis

Wide-compatibility varieties (WCVs) are a special class of rice germplasm that is able to produce fertile hybrids when crossed to both indica and japonica rice varieties. WCVs may differ greatly in their spectrum and level of compatibility. The objective of this study was to determine the genetic basis of wide-compatibility conferred by ‘Dular’, a landrace variety from India that has demonstrated a high level of wide-compatibility in previous studies with a broad range of indica and japonica varieties. A three-way cross (‘Balilla/Dular//Nanjing 11’) was made and the resulting F₁ population evaluated in the field for spikelet fertility. A total of 235 plants from this population was assayed individually for restriction fragment length polymorphisms (RFLPs) at 159 marker loci covering the entire rice genome at regular intervals. Quantitative trait locus (QTL) analysis identified 5 loci, located on chromosomes 1, 3, 5, 6 and 8, as having significant effects on hybrid fertility, which jointly explained 55.5% of the fertility variation in this population. The QTL on chromosome 5 ( f5) showed the largest effect on hybrid fertility, followed by those on chromosomes 6 ( f6), 3 ( f3) and 1 ( f1), with the one on chromosome 8 ( f8) having the smallest effect. Genotypes each composed of an allele from ‘Dular’ and an allele from ‘Nanjing 11’ at four ( f3, f5, f6 and f8) of the five QTLs contributed to the increase of fertility in the population. In contrast, the genotype composed of alleles from ‘Balilla’ and ‘Nanjing 11’ at the fifth locus ( f1) was in the direction of increasing fertility. Analysis of variance using marker genotypes at the five QTLs as the groups detected two interactions involving four of the five loci, a 2-locus interaction between f5 and f8 and a 3-locus interaction among f3, f5 and f6. The level of hybrid fertility is the result of complex interactions among these loci. The implication of the present findings in the utilization of the wide-compatibility of ‘Dular’ in rice breeding programs is also discussed. Received: 21 October 1997 / Accepted: 30 December 1997     

Sample size for collecting seeds in germplasm conservation: the case of the Lima bean (Phaseolus lunatus L.)

 The design of optimum sampling strategies integrating criteria of efficiency relevant to multilocus models and many target populations has been investigated with respect to the number of plants and the number of seeds per plant to be sampled for a Lima bean (Phaseolus lunatus L.) gene pool. This study, using five populations and six polymorphic enzyme loci, shows that the number of plants rather than the number of seeds collected per plant primarily determines the success of seed sampling, suggesting that plant number plays an essential part in maintaining the allelic multiplicity of predominantly selfing species like Lima bean. According to the results, it appears that among Lima bean populations an efficient sampling procedure is achieved by collecting 1–4 seeds from 200 to 300 plants. These sample sizes will retain 8–10 alleles, regardless of their frequencies. When we consider polymorphism at the 5% level, it is expected that sampling 10–80 plants will collect combinations of 4–8 alleles. Based on data from genetic and demographic studies, we suggest an efficient sampling scheme for Lima bean germplasm at both population and geographical levels. Received: 10 March 1998 / Accepted: 1 April 1998     

Dissection of a major QTL for photoperiod sensitivity in rice: its association with a gene expressed in an age-dependent manner

 A proposed major quantitative trait locus (QTL) for photoperiod sensitivity on chromosome 6 in rice was examined by introducing a chromosomal segment from a sensitive line into an insensitive one. The crossing experiments showed that a range of variation in heading date occurred in the later generations and that the region might contain at least a major gene and two additional recessive genes controlling photoperiod sensitivity. Gene mapping experiments showed that the major gene was Se-1 and that a recessive gene (tentatively named se-pat) was loosely linked to it. The responses to photoperiods were examined among the different genotypes under natural and controlled conditions. The two genes acted additively on the degree of photoperiod sensitivity. However, se-pat plants showed a response to photoperiods that differed from that of the other sensitive lines; a short-day treatment at the seedling stage delayed heading in the former plants, suggesting that the manner of its expression was age-dependent. A recessive gene similar to se-pat seemed to be widely distributed in wild and cultivated rice, suggesting that the gene complex in the region plays a significant role in response to photoperiod. Received: 8 October 1997 / Accepted: 1 April 1998     

Phenolics and the activities of phenylalanine ammonia-lyase, phenol-β-glucosyltransferase and β-glucosidase in cucumber roots as affected by phenolic allelochemicals

Seven-day-old seedlings of cucumber (Cucumis sativus L.) cv. Wisconsin were treated with 0.1 mM solutions of cinnamic acid (ferulic and p-coumaric acids) and benzoic acid (p-hydroxybenzoic and vanillic acids) derivatives as stressors. The content of free and glucosylated soluble phenols and the activity of phenylalanine ammonia-lyase (E.C.4.3.1.5), phenol-β-glucosyltransferase (E.C.2.4.1.35.), and β-glucosidase (E.C.3.2.1.21.) in seedling roots as well as their length and fresh weight were examined. Changes in glucosylated phenolic content and phenol-β-glucosyltranspherase activity were observed under the influence of all phenolics applied. Treatment with ferulic and p-coumaric acids stimulated the increase of phenylalanine ammonia-lyase and β-glucosidase activity and slightly inhibited cucumber root growth.     

Effects of VA mycorrhizal colonization on photosynthesis and biomass production of Trifolium repens L.

The influence of vesicular–arbuscular mycorrhizal (M) colonization on biomass production and photosynthesis of Trifolium repens L. was investigated in two experiments in which the foliar nitrogen and phosphorus contents of non-mycorrhizal (NM) plants were manipulated to be no lower than that of M plants. Throughout both experiments there was a stimulation in the rate of CO₂ assimilation of the youngest, fully expanded leaf of M compared with NM plants. In addition, M plants exhibited a higher specific leaf area compared with NM plants, a response that maximized the area available for CO₂ assimilation per unit of carbon (C) invested. Despite the increased rate of photosynthesis in M plants there was no evidence that the additional C gained was converted to biomass production of M plants. It is suggested that this additional C gained by colonized plants was allocated to the mycorrhizal fungus and that it is the fungus, by acting as a sink for assimilates, that facilitated the stimulation in the rate of photosynthesis of the plant partner.     

Relative importance of osmotic-stress and ion-specific effects on ABA-mediated inhibition of leaf expansion growth in Phaseolus vulgaris

The osmotic and ion-specific components of salt-induced inhibition of leaf expansion growth were investigated in beans grown from 12 h to several days in either NaCl-containing solution cultures, an isosmotic concentrated macronutrient solution, or a vermiculite–compost mixture with low Na⁺ but high Cl^– availability. Inhibition of leaf expansion and leaf ABA increase was more intense in the NaCl than in the isosmotic macronutrient treatment. Root Na⁺ was highly correlated to inhibition of leaf expansion and leaf or xylem sap ABA. When Na⁺ was sequestered in soil, salinized plants showed no reduction in leaf expansion or ABA increase, regardless of the presence of high leaf Cl^– concentrations. Stomatal conductance exhibited an exponential relationship with the reciprocal value of xylem sap ABA. Our results indicate that an ion-specific effect caused by Na⁺ in roots may account for an ABA-mediated reponse of both stomatal closure and leaf expansion inhibition.     

不同地区小菜蛾种群羧酸酯酶的毒理学性质研究

在1995～1997年对湖北武汉、河北张家口地区小菜蛾Plutella xylostella(L.)种群的抗药性进行了研究。结果表明对阿维菌素的抗性和台湾敏感种群相比,武汉种群抗性为4.3倍,张家口种群抗性为1.8倍;对马拉硫磷的抗性武汉和张家口种群分别为2.2和2.9倍;对氟铃脲的抗性分别为3.2和0.5倍;对溴氰菊酯的抗性分别为2.4和1.7倍。对羧酸酯酶(Care)的研究结果表明,三个种群幼虫CarE对a-乙酸萘酯或β-乙酸萘酯(a或β-NA)水解活性差异显著,但成虫Care活性没有明显差异。武汉和张家口种群幼虫CarE对a-NA和β-NA的亲和力没有明显差异,但是武汉种群幼虫Care对底物的亲和力高于张家口种群。敏感品系Care对a—NA的亲和力明显高于对β-NA,相差约3倍。不同类型的抑制剂对小菜蛾幼虫CarE的抑制能力不同。增效磷和对氧磷对敏感品系CarE水解a-NA具有明显的抑制作用,分别比对武汉种群Care的抑制作用大4.577倍(SVl)和2.576倍(对氧磷)。     

小菜蛾对定虫隆的抗性生化机制初探

以定虫隆汰选的抗性指数为23.78倍抗性种群(CH-R),并以上海田间种群(SH-R,对定虫隆的抗性指数为9.16倍)作为参比种群,研究小菜蛾Plutella xylostlla(L.)对定虫隆的抗性机制,结果表明：CH—R种群多功能氧化酶O-脱甲基活力比相对敏感种群(SZ-S)提高1倍,而SH-R种群多功能氧化酶O-脱甲基活力虽有所提高,但与SZ-S种群相比差异并不显著;CH-R和SH-R种群羧酸酯酶比活力均明显高于Sz-S种群,分别为SZ-S种群的4.61和2.18倍,且CH-R种群的Km仅为SZ-S种群的1/20;酸性磷酸酯酶和碱性磷酸酯酶比活力种群间无明显差异;CH-R种群的几丁质酶活力降低48%,酚氧化酶活力降低60%。说明小菜蛾对定虫隆的抗性机制具有多因子性,多功能氧化酶解毒代谢能力的提高可能是主导抗性机制之一,羧酸酯酶、几丁质酶和酚氧化酶也参与了小菜蛾对定虫隆的抗性。     

A molecular systematic study ofCathaya, a relic genus of thePinaceae in China

The systematic position ofCathaya, a relic genus of thePinaceae, was discussed based on therbcL gene sequence. The sequence data were analysed with PAUP and MEGA programs. The great genetic distance value betweenCathaya and any other genus of thePinaceae showed thatCathaya was a distinct and isolated genus. The most parsimonious Fitch tree and neighbor-joining tree showed thatCathaya was distantly related to the clade comprisingAbies, Keteleeria, Pseudolarix andTsuga, and a sister group relationship betweenCathaya andPinus was weakly supported.Pseudotsuga is closely related toLarix. In theAbies-Keteleeria-Pseudolarix-Tsuga clade,Abies has a close relationship toKeteleeria whilePseudolarix is relatively closely related toTsuga.     

Plant regeneration through organogenesis from callus induced from mature zygotic embryos of loblolly pine

Mature zygotic embryos from three seed sources of loblolly pine were cultured on callus induction medium containing 10 mg l^–1 α-naphthaleneacetic acid, 4 mg l^–1 benzyladenine (BA), 400 mg l^–1 casein hydrolysate, and 400 mg l^–1 glutamine for 6 weeks. Light-yellow, loose, glossy, globular callus was formed, and the highest frequency was 35.7%. The highest differentiation frequency of callus on adventitious bud induction medium was 62.1%. After culture of calli with adventitious buds on elongation medium for 6 weeks, adventitious shoots more than 1.0 cm in height were selected for rooting. On rooting medium supplemented with 0.1 mg l^–1 indole-3-butyric acid, 1 mg l^–1 BA, and 0.5 mg l^–1 gibberellic acid, the highest rooting frequency of adventitious shoots was 46% in a culture period of 6 weeks. Established plants survived following transfer to soil at a frequency of 71%. Received: 14 May 1997 / Revision received: 25 September 1997 / Accepted: 11 October 1997