Pisum sativum wild-type and mutant stipules and those induced by an auxin transport inhibitor demonstrate the entire diversity of laminated stipules observed in angiosperms

About a quarter of angiosperm species are stipulate. They produce stipule pairs at stem nodes in association with leaves. Stipule morphology is treated as a species-specific characteristic. Many species bear stipules as laminated organs in a variety of configurations, including laterally free large foliaceous, small, or wholly leaf-like stipules, and as fused intrapetiolar, opposite, ochreate or interpetiolar stipules. In Pisum sativum, the wild-type and stipule-reduced and cochleata mutants are known to form free large, small, and leaf-like stipules, respectively. Auxin controls initiation and development of plant organs and perturbations in its availability and distribution in the meristems, caused by auxin transport inhibitor(s) (ATIs), lead to aberrations in leaf development. The effect(s) of ATI(s) on stipule development are unexplored. To study the effect of the ATI 1-N-naphthylphthalamic acid (NPA) on stipule morphogenesis, P. sativum explants were grown in vitro in presence of a sublethal concentration of NPA. The NPA-treated shoots produced fused stipules of all the different types described in angiosperms. The observations indicate that (a) the gene sets for stipule differentiation may be common in angiosperms and (b) the interspecies stipule architectural differences are due to mutations, affecting gene expression or activity that got selected in the course of evolution.     

A GENETIC SYNDROME AFFECTING LEAF DEVELOPMENT IN PISUM

A recessive foliage mutant of Pisum, designated ‘sinuate leaf’ (sil), was found to have two distinct forms of expression, depending on the background genotype. In an af/af background—wherein leaflets are converted to tendrils—sil/sil plants had adventitious tendrils arising from clefts in the distal portion of the stipule. These adventitious tendrils were morphologically modified, just as were the true tendrils on the same plant, by different allelic combinations at the tl locus. In the standard Af background, sil/sil plants had neither incised stipules nor adventitious tendrils, although they did have undulated and somewhat distorted leaflets and stipules. Because mutant expression was variable in an Af background, classification of segregating populations was uncertain. This uncertainty was removed by taking advantange of pleiotropic effects exerted by sil in the presence of one of the wax mutants, wlo, wb, or wsp. Homozygous wlo plants ordinarily have uniformly waxy stipule surfaces, but when the plants were also homozygous for sil the stipule tips were waxless. Conversely, wb/wb and wsp/wsp plants ordinarily have uniformly waxless stipules, but when wb/wb or wsp/wsp plants were also homozygous recessive for sil the stipule tips were waxy. However, sil had no observable effects of any kind on the stipule tips of plants with stipules reduced in size by the action of st/st. By their individual and combined effects, the foliage mutants used in this study revealed developmental relationships among leaf parts not otherwise evident in non-mutant plants.     

Genetics of resistance to cotton leaf curl disease in Gossypium hirsutum L. under field conditions

One hundred and forty two cotton germplasm lines were screened for cotton leaf curl virus symptoms in field evaluations during 2003, 2004, and 2005. Fifty cross combinations involving 30 of these lines classified resistant or susceptible were used for inheritance study of the disease. All the F(1) plants of crosses involving resistant x resistant, resistant x susceptible, and susceptible x resistant parents were resistant, indicating dominant expression of the disease resistance and there were no maternal or cytoplasmic effects detected from reciprocal hybridization. In 22 crosses, 4 types of segregation patterns were obtained in the F(2) generations. A good fit for 15 (resistant):1 (susceptible), 13 (resistant):3 (susceptible), 9 (resistant):7 (susceptible) ratios indicated digenic control of the trait with duplicate dominant, dominant inhibitory, and duplicate recessive epistasis, respectively. Three-gene control with triplicate dominant epistasis was obtained in one of the crosses. This segregation pattern, however, needs further confirmation due to smaller population size. The absence of complementary gene action was obtained in 1 susceptible x susceptible and 27 resistant x resistant crosses as their F(1)s were susceptible and resistant, respectively, and F(2) generation lacked segregation.     

Genetics of rough seed coat texture in cowpea

Seed coat texture is an important trait in determining the acceptability of cowpea varieties in different regions. A rough seed coat is preferred in western and central Africa, since it permits easy removal of the seed coat which is essential for indigenous food preparations. On the other hand, a smooth seed coat is preferred in eastern and southern Africa as well as in parts of South America where cowpea is consumed as boiled beans without removing the seed coats. This study was undertaken to elucidate the inheritance of seed coat texture so that cowpea breeders may adopt appropriate breeding strategy to develop cowpea varieties with preferred seed types for different regions. The F1 plants between smooth- and rough-seeded parents as well as between rough- and rough-seeded parents produced smooth seeds, indicating a complementary gene action and dominance for smooth seed coat. The F2 plants from the smooth x rough cross segregated into a 3 smooth:1 rough seed coat ratio, but the F2 plants from rough x rough crosses segregated into a 9 smooth:7 rough seed coat ratio. The F1 plants from backcross to the smooth parent were all smooth, while the F1 plants from backcross to rough parent segregated in a 1 smooth:1 rough seed coat ratio. However, both the backcross populations in rough x rough crosses segregated into 1 smooth:1 rough seed coat ratio. These results indicate that two pairs of independent recessive genes confer rough seed coat texture in cowpea and the presence of at least one dominant gene at each of the two loci results into smooth seed coat. The gene symbols rt1rt1 and rt2rt2 are being assigned for rough seed coat texture in cowpea.     

Inheritance of differences in organ trichome formation in Arabidopsis thaliana (L.) Heynh. plants

It was determined that, according to the character "hairiness of rosette leaves", gl1-1 allele in homozygote state suppresses action of dis2-1 allele (dis2-1 < gl1-1), therefore F2 segregation is identified in a typical for recessive epistasis ratio of 9:3:4. Inheritance of differences in hairiness of stem leaves corresponds to the Mendel scheme of segregation (9:3:3:1), which is typical for dihybrids. Hairiness is absent on stems of triple recessive for dis2-1, er-1, gl1-1 plants, and segregation in F2 is observed in the ratio of 9:3:4.     

Inheritance of apospory in bahiagrass,Paspalum notatum

Previous studies on the inheritance of aposporous apomixis in bahiagrass showed a wide range of segregation ratios in crosses involving sexual and aposporous apomictic plants. The F1 progenies were classified through a visual progeny test carried out on few F2 plants. The number of sexual F1s highly exceeded the apomictics leading to the conclusion that apomixis was controlled by a few recessive genes. The present study examines the inheritance of apospory in bahiagrass. A sexual plant was self-pollinated and crossed with an aposporous apomictic plant as pollen donor. Backcross and F2 progenies were obtained in several combinations. All self-pollinated sexual plants or sexual x sexual crosses produced progenies free of apospory. All crosses involving a sexual and an apomictic plant produced approximately three times more apospory-free plants than plants with apospory. Bahiagrass is of autotetraploid origin and hence is expected to display tetrasomic inheritance. The most widely accepted genetic model for inheritance of apospory in tropical grasses is a single dominant gene with tetrasomic inheritance. In the present experiments none of the apospory-free F1s segregated for the apospory trait indicating that it is most likely a dominant character. However, the observed results fit better a modified model: tetrasomic inheritance of a single dominant gene with pleiotropic effect and incomplete penetrance. The excess of apospory-free plants in the F1 progeny could be ascribed to some distortion in the segregation pattern due to a pleiotropic lethal effect of the dominant A allele with incomplete penetrance. Alternatively, partial lethality of factors linked to aposporous gene may account for segregation distortion against apospory.     

Inheritance of flower color and spininess in safflower (Carthamus tinctorius L.)

Safflower (Carthamus tinctorius L.) flowers are used for coloring and flavoring food and also as fresh-cut and dried flowers. The most important characteristics which contribute to the ornamental value of safflower are flower color and spinelessness. The objective of this study was to determine the inheritance mode and the number of genes controlling spininess and flower color in some Iranian genotypes of safflower. The results indicated that the existence of spines on the leaves and bracts of safflower is controlled by a single dominant gene in which the spiny phenotype was completely dominant to spineless. In some crosses, flower color was controlled by two epistatic loci each with two alleles, resulting in a ratio of 13:3 in the segregating F2 population for plants with orange and yellow flowers. Also, other mechanisms of genetic control, such as duplicate dominance and duplicate recessive types of epistasis, were observed for flower color in other crosses that led to ratios of 7:9 and 15:1 for plants with orange and yellow flowers, respectively. The results suggest that for ornamental use or in the food dying industry, genotypes with orange or yellow flowers and without spines on the leaves and bracts can be produced.     

Studies in Brazilian Passifloraceae III. A new species of Passiflora

A new species ofPassiflora from Minas Gerais, Brazil, is described and namedP. saccoi. This species belongs to subgenusPassiflora seriesLobatae harms because of its lobed leaves, foliaceous, semi-ovate to semi-oblong stipules that are attached on one side above base and, hence, often appear sub-reniform, and foliaceous, verticillate bracts borne near the apex of the peduncle.     

New allele of the COCHLEATA gene in pea Pisum sativum L

Analysis with the polymerase chain reaction showed that the Khlorofill-4 pea Pisum sativum chlorophyll-deficient mutant with reduced stipules has an altered structure of the COCHLEATA (COCH) gene, carrying a new mutant COCH allele. The phenotype of the mutant was described in comparison with another form having reduced stipules (stipules reduced) and the control. Leaves of the coch mutant are smaller and have other proportions than in the control; stipules are absent from leaves of the first nodes and are narrow, bandlike, or spoonlike at later ontogenetic stages. It was concluded that the cell number in the stipule epidermis is reduced in the st and coch mutants compared to the wild type.     

Mechanisms that control knox gene expression in the Arabidopsis shoot

Knotted1-like homeobox (knox) genes are expressed in specific patterns within shoot meristems and play an important role in meristem maintenance. Misexpression of the knox genes, KNAT1 or KNAT2, in Arabidopsis produces a variety of phenotypes, including lobed leaves and ectopic stipules and meristems in the sinus, the region between lobes. We sought to determine the mechanisms that control knox gene expression in the shoot by examining recessive mutants that share phenotypic characteristics with 35S::KNAT1 plants. Double mutants of serrate (se) with either asymmetric1 (as1) or asymmetric2 (as2) showed lobed leaves, ectopic stipules in the sinuses and defects in the timely elongation of sepals, petals and stamens, similar to 35S::KNAT1 plants. Ectopic stipules and in rare cases, ectopic meristems, were detected in the sinuses on plants that were mutant for pickle and either as1 or as2. KNAT1 and KNAT2 were misexpressed in the leaves and flowers of single as1 and as2 mutants and in the sinuses of leaves of the different double mutants, but not in se or pickle single mutants. These results suggest that AS1 and AS2 promote leaf differentiation through repression of knox expression in leaves, and that SE and PKL globally restrict the competence to respond to genes that promote morphogenesis.     

EARLY LEAF ONTOGENY AND THE SHOOT APEX OF COLOPHOSPERMUM MOPANE (LEGUMINOSAE)

Shoot tips of Colophospermum mopane (Kirk ex Benth.) Kirk ex Léonard produce leaves which at maturity are bifoliate and devoid of stipules. Investigation of their early ontogeny, however, shows that these leaves begin as trifoliate structures partially enclosed by their stipules. The latter are fused along their mid regions, forming a tongue-like “connector.” The lower chamber of this stipule pair harbors the apical meristem while the upper compartment enfolds the two lateral leaflets. The terminal leaflet, histologically resembling the stipules, also fulfills a similar function by covering the top portion of its sister leaflets. Anatomically, the shoot apex displays a pendulum symmetry, with rather steep elevation of that internode portion which subtends the newly formed primordium. Some comparisons with the shoot apex of Hymenaea are drawn.     

STIPULES IN SOME MEMBERS OF THE VITACEAE: RELATING PROCESSES OF DEVELOPMENT TO THE MATURE STRUCTURE

The development of stipules especially their spatial and temporal pattern of initiation in relation to the leaf was investigated in Vitis riparia Michx., cv. Concord, Parthenocissus tricuspidata (Sieb. & Zucc.) Planch., Cissus oblonga (Benth.) Planch., Cissus hypoglauca (F.v.M.) A. Gray, and Cissus rhombifolia Vahl. Early initiation is characterized by the occurrence of a single primordium with a wide insertion on the flank of the shoot apex. Distinguishing between stipule primordia and the leaf primordium is impossible at this early stage. Distinct primordia can only be seen in later stages of development. At maturity, the stipules occupy free lateral positions. Developmental processes such as timing of initiation and zonal growth seem to play an important role in early development. In five of the six taxa examined in this study, the early initiation of stipules, their close association with the leaf and also their faster relative rate of growth during early development appear to give them a characteristic protective function. In contrast, C. rhombifolia stipules are initiated later than the leaf and seem to develop at a slower rate than the leaf proper. Consequently, they never enclose their associated leaf but instead cover the next youngest leaf. Many different criteria are used to distinguish the broad category of stipules, and therefore many interpretations have been made depending on the type of approach that is used. This study attempts to look at stipules in terms of developmental processes and demonstrates a more accommodating leaf/stipule concept which provides a clearer comprehension of the nature of the stipule.     

Inheritance of time to flowering in chickpea in a short-season temperate environment

Time to flowering is central in determining the adaptation and productivity of chickpea in short-season temperate environments. We studied the genetic control of this trait in three crosses, 272-2 x CDC Anna, 298T-9 x CDC Anna, and 298T-9 x CDC Frontier. From each cross, 180 F2 plants and parents were evaluated for time to flowering under greenhouse conditions. In summer 2004, multiple generations including P1, F1, P2, F2, and F2:3 (also called MG5) were evaluated for time to flowering under field conditions. The data on time to flowering in the F(2) populations were continuous in distribution but deviated from normal distribution. The F2:3 families derived from this showed a bimodal distribution for time to flowering, a typical case of major-gene inheritance model with duplicate recessive epistasis. A joint segregation analysis of MG5 also revealed that time to flowering in chickpea was controlled by two major genes along with other polygenes. Late flowering was dominant over early flowering for both major genes with digenic interaction between them, mainly an additive x additive type. This information can be used to formulate the most efficient breeding strategy for improvement of time to flowering in chickpea in short-season temperate environments.     

Linkage of a RAPD marker with powdery mildew resistance

The aim of this study was to investigate the inheritance of powdery mildew disease and to tag it with a DNA marker to utilize for the marker-assisted selection (MAS) breeding program. The powdery mildew resistant genotype Fallon(er) and susceptible genotype 11760-3ER were selected from 177 genotypes by heavy infestation of germplasm with Erysiphe pisi through artificial inoculation. The F1 plants of the cross Fallon/11760-3 indicated the dominance of the susceptible allele, while F2 plants segregated in 3 : 1 ratio (susceptible : resistant) that fit for goodness of fitness by chi2 (P > 0.07), indicating monogenic recessive inheritance for powdery mildew resistance in Pisum sativum. A novel RAPD marker OPB18 (5'-CCACAGCAGT-3') was linked to the er-1 gene with 83% probability with a LOD score of 4.13, and was located at a distance of 11.2 cM from the er-1 gene.     

水稻Dwarf1移码突变的新突变体鉴定

从一批水稻品种"中花11"组织培养苗里分离到一个矮化突变株"C6PS",它的T2代群体株高呈现3:1分离。利用该群体矮化单株与"珍汕97"、"牡丹江8"构建2个F2群体F2(CZ)、F2(CM),两个群体中高株与矮株均呈现3:1分离,证明该性状变异为单基因控制。"C6PS"表现型与已经报道的Dwarf1隐性突变体"d1"相似,以D1附近标记RM430检测F2(CZ)群体基因型,结果显示群体表型与RM430基因型呈极显著相关(P=0.0001),将该基因初步定位于Dwarf1附近。对"C6PS"及"中花11"进行D1序列分析显示,突变株中D1基因在其第九个外显子与第九个内含子的剪接位点上发生6个碱基的缺失,根据缺失两侧序列设计C6PS-D1L/R标记,在T2代群体该标记与表型呈现共分离,表明"C6PS"是一种新的Dwarf1突变体。cDNA测序显示突变体d1基因转录产物发生26个碱基的缺失,导致移码产生终止突变,从而无法翻译出有功能的Gα蛋白,因此,它是一个Gα功能缺失突变体。叶倾斜度检测显示"C6PS"对油菜素内酯响应比野生型"中花11"弱。     

Chromosomal localisation of a recessive gene tp controlling the pleiotropic character topiary in Solanum

Summary Seven out of twelve possible types of primary trisomies of dihaploid S. tuberosum were crossed as females with a disomic recessive mutant for topiary (tp tp) identified in S. infundibuliforme. All primary trisomics used proved to be homozygous dominant. Trisomic plants from the seven F1's were crossed with a disomic heterozygous F1 plant (supposed genotype Tp tp). In the half sib progeny of each trisomic type the mutant plants could be easily identified by the presence of typical lateral shoots, particularly at the cotyledonary nodes. The observed segregation ratios for normal to mutant were tested against the expected non-critical ratio 3 1 and against various critical ratios. It is concluded that the gene tp is located on chromosome 3 of the potato.     

New allele of the <Emphasis Type="Italic">COCHLEATA</Emphasis> gene in pea <Emphasis Type="Italic">Pisum sativum</Emphasis> L.

Analysis with the polymerase chain reaction showed that the Khlorofill-4 pea Pisum sativum chlorophyll-deficient mutant with reduced stipules has an altered structure of the COCHLEATA (COCH) gene, carrying a new mutant COCH allele. The phenotype of the mutant was described in comparison with another form having reduced stipules (stipules reduced) and the control. Leaves of the coch mutant are smaller and have other proportions than in the control; stipules are absent from leaves of the first nodes and are narrow, bandlike, or spoonlike at later ontogenetic stages. It was concluded that the cell number in the stipule epidermis is reduced in the st and coch mutants compared to the wild type.     

STRUCTURAL CHANGES IN POPULUS DELTOIDES TERMINAL BUDS AND IN THE VASCULAR TRANSITION ZONE OF THE STEMS DURING DORMANCY INDUCTION

Morphological and anatomical changes in shoots of vigorously growing cottonwood plants (Populus deltoides Bartr.) were studied during dormancy induction in 8-hr short days (SD) and in control plants grown in 18-hr long days (LD). Pronounced structural changes occurred in terminal buds after 4 wk and full dormancy was achieved in 7 wk of SD. Leaf expansion ceased after 5 wk of SD as foliage leaves matured to the terminal bud base at leaf plastochron index 0 (LPI 0). Within the bud, total leaf length (lamina + petiole) decreased and stipule length increased progressively each week; thus, the ratio total leaf length/stipule length decreased rapidly, especially at the position of incipient bud-scale leaves LPI - 1 and LPI - 2. These bud-scale leaves were fully developed by wk 6 and were derived from enlarged stipules and aborted laminae. The full complement of primordia within the bud at the start of SD eventually matured as foliage leaves and the first bud-scale leaf (LPI - 1) was initiated immediately following transfer to SD. Acropetal advance of the primary-secondary vascular transition zone (TZ) was associated with leaf maturation. However, it did not advance throughout the entire vascular cylinder as in LD, but only in those leaf traces serving mature leaves beneath the terminal bud. In both LD and SD treatments the same linear relationship was maintained between LPI of the TZ and LPI of the most recently matured leaf; both parameters simultaneously increased in LD and decreased in SD. Thus, the relationship between leaf maturation and advance of the TZ was maintained irrespective of environment.     

Paragonimus ohirai: genetic control of tetrazolium oxidase isozymes

The Japanese lung fluke, Paragonimus ohirai, has three electrophoretic variants: F, FS, and S of tetrazolium oxidase (EC 1.15.1.1). Variant flukes were crossed in the laboratory. In both crosses, S X S and F X F, parental phenotypes appeared in all respective F1 progeny. In a cross of F X S, all F1 individuals derived from each parent showed the same phenotype (FS) indicating a heterozygote. On the other hand, from the cross of FS X S, 13 of FS and 11 S were observed from a parent (FS) while 2 FS and 1 S were recovered in three clones from the other parent (S). In the case of a cross between FS X F, a parent (F) produced 9 FS and 18 F clones in the offspring, numbers not significantly different from the expected values of Mendelian inheritance at the 0.01 level. The breeding data indicate that the tetrazolium oxidase isozymes of P. ohirai are controlled by two alleles, ToF and ToS, at a single locus.