Electron microscopy of dry peanut (Arachis hypogaea L.) seeds crushed for oil removal. Fixation and embedding of anhydrously prepared tissues

Summary Aqueous fixatives caused dry seed tissues to swell; mashed peanuts, crushed to remove oil, swelled even more. Use of anhydrous, organic solvents as vehicles for fixatives enabled maintenance of dimensional stability during fixation of dry seed tissues; even crushed seed tissue did not swell significantly when processed anhydrously. However, anhydrously processed specimens proved difficult to section. The difficulty was due to imperfect permeation of plastic into the seed tissues during embedding. An explanation of why anhydrously processed dry seed tissues are so difficult to embed in plastic is offered.     

Diagnosis of iron deficiency in groundnut,Arachis hypogaea L.

Summary Investigations into iron deficiency have been hindered by the lack of a satisfactory diagnostic tissue test, which in turn results from the total iron content of plant tissue commonly being an unreliable index of the iron status. Our measurements of chlorotic and normal leaves of field grown groundnut (Arachis hypogaea L.) showed that total iron was unsatisfactory as the measure of iron status of plant tissue. It was found that iron status was better assessed from an estimate of the ferrous iron content of fresh leaf materials obtained by extraction with o-phenanthroline. Extractable iron content increased with leaf age. Chlorotic buds or the first fully opened leaf always contained less than 6μg extractable-Fe/g fresh tissue. Approved for publication as ICRISAT Journal Article No. 307.     

Micropropagation in Peanut (Arachis hypogaea L.)

Multiple shoots in Arachis hypogaea L. could be induced from the de-embryonated cotyledons (DC), embryo-axes (EA) and mature whole seeds (MWS) in MS medium supplemented with different levels of benzylaminopurine (BAP). DC was the most suitable explant with 57.9 % induction and more than 40 shoots per explant in 31.6 % of cases. Though EA and MWS had high percent induction at or above 30 mg dm^–3 BAP, only 10 – 14 shoots per explant were observed. In DC, multiple shoots were confined to the proximal end and in EA they originated from the axillary bud region. Histological studies on DC confirmed the origin of shoots from the region of attachment with the embryo. Shoots could be rooted in MS medium containing 2 g dm^–3 charcoal and 200 mg dm^–3 casein hydrolysate. Sixty percent of the rooted plantlets could be established in the field.     

Phytohormones and light regulation of the growth habit in peanuts (Arachis hypogaea L.)

Diageotropic side branches in runner type peanuts assume anorthotropic position when grown in the dark but return to aplagiotropic postition when transferred back to light. The effectof light on the trailing habit of lateral branches depends onthe quality and intensity of the light taking place under blue+farred light, but not under blue alone. Light intensity below 28Kergs.cm^–2.sec^–1 changed the growth of the runner'slaterals from trailing to erect. Inhibitors of both GA and auxinactivity were higher in the laterals of runners than in thoseof the erects. Along with the change in the trailing habit bylow light intensity, a decrease in inhibitor level was observed.Gibberellin-like activity was smaller in both extracts and diffusatesof the growing tip of lateral branches than in the main axis.An inhibitor found only in lateral branches of runner type plantscould be detected in erect plants in the presence of auxin.The predominant factor controlling differences in the growthhabit of side branches of the erect and runner types is thepresence of an inhibitor; while, within each type, levels ofgibberellin seem to account for the different growth habit ofthe axis and laterals. (Received January 23, 1973; )     

Some Observations on Infection of Arachis hypogaea L. by Rhizobium

The infection process in Arachis hypogaea by rhizobia differsfrom that normally found in Trifolium spp. in that no infectionthreads are formed. The root hairs, which are long (up to 4mm), septate, and often with large basal cells, occur only atthe sites of emerging lateral roots. Infection occurs only wherethe root hairs have large basal cells. Rhizobia cause curlingand deformation of the root hairs (as in Trifolium spp.) butenter the root at the junction of the root hair and the epidermaland cortical cells. The bacteria are distributed intercellularlyvia the middle lamellae and enter the cortical cells throughthe structurally altered cell wall, often close to the hostcell nucleus. The root hairs and large basal cells become infectedin the same way. Within the cortical cells of the emerging lateralroot the rhizobia multiply rapidly and the invaded cells dividerepeatedly to form the nodule tissue. Bacteriod formation occursonly when the host cell ceases to divide.     

Utilization of wild relatives in genetic improvement of Arachis hypogaea L.

Summary The chromosome complements of 12 taxa in section Arachis were karyotypically and meiotically analysed. In taxa with 2n=20 the arm ratio of the respective pair of chromosomes was taken as an independent quantitative character and statistically analysed by Mahalanobis D². Two clusters were formed, one represented solely by A. batizocoi and the other consisting of the remaining 11 taxa. This grouping was confirmed by canonical analysis. In the larger group of species, A villosa and A. correntina were closely related karyotypically and on D² distance, while A. cardenasii forms a distinct subgroup. A. cardenasii lacks the short A chromosome recorded in other species of this group, and A. batizocoi is no longer the only species to have a pair of chromosomes with a secondary constriction. The taxa with 2n=40, A. monticola and A. hypogaea, are karyotypically very similar, though there is a difference in the number of chromosome pairs with a secondary constriction. On the basis of karyomorphological affinity, especially in relation to marker chromosomes, A. cardenasii is probably one of the ancestors of the tetraploid species studied.Approved as ICRISAT Journal Article No. 169 and released for publication     

Diallel analysis in groundnut (Arachis hypogaea L.)

Summary An 8 × 8 full diallel experiment based on 4 bunch plus 4 spreading types of groundnut (Arachis hypogaea L.) was conducted over three environments. For both number of pods and pod yield, additive, nonadditive and reciprocal cross effects were detected and these were also influenced by changes in environments. For number of pods additive genetic variance was predominant whereas it was approximately equal to non-additive genetic variance for pod yield. Graphical analysis revealed the presence of strong non-allelic interaction for number of pods whereas for pod yield absence of dominance and/or presence of non-allelic interaction was evident.Part of Ph.D. Thesis of the first author     

Absence of Root Hairs in Non-Nodulating Groundnut, Arachis hypogaea L.

Root hairs observed at the site of lateral root emergence innodulating groundnut cultivars were found to be absent in non-nodulatinggroundnut lines. In a segregating F₂-population of the crossNC 17 x PI 259747 a strong association was observed betweenthe presence of root hairs and nodulation, and the absence ofroot hairs and non-nodulation. Key words: Root hairs, Arachis hypogaea, Non-nodulation     

Utilisation of wild relatives in the genetic improvement of Arachis hypogaea L.

Summary Cross-compatibility of species in section Arachis Krap. et Greg. nom. nud., and chromosome pairing and pollen fertility in their interspecific F₁ hybrids were studied to further understand the phylogenetic relationships among these species. Except those with A. batizocoi Krap. et Greg. nom. nud., hybrids between diploid species have near normal bivalent frequency (9.1–9.8) and moderate to high pollen fertility (60–91%). Hybrids between A. batizocoi and other species have low bivalent frequency (5.2–6.9) and very low pollen fertility (3–7%). These results confirm the earlier separation of these species into two groups based on karyomorphology and Mahalanobis D² calculated on arm ratios. These studies also provide a picture of relative affinities between A. batizocoi, the lone member of one cluster, and the other species, and among the rest of the species. They also indicate that the basic chromosome complement in the two groups of species is the same. Chromosome pairing in triploid hybrids, (A. hypogaea L. X diploid wild species), suggests that A. batizocoi is the closest diploid relative of A. hypogaea. It is closer to A. hypogaea subspecies fastigiata Waldron than to A. hypogaea subspecies hypogaea Krap. et. Rig. Other diploid species of the section Arachis are equidistant from A. hypogaea, and have the same genome which has strong homology to one of the genomes of A. hypogaea. Based on the present results, the two tetraploid species, A. monticola Krap. et Rig. and A. hypogaea can be recognised as two forms of the same species. Breeding implications have been discussed in the light of chromosome behaviour observed in hybrids of A. hypogaea X diploid species, and on the presumptions that A. hypogaea has an AABB genomic constitution, and that among the diploid species, the B genome is present in A. batizocoi while the A genome is common to the other diploid species of section Arachis.Submitted as Journal Article No. 328 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Utilization of wild relatives in the genetic improvement of Arachis hypogaea L.

Summary Synthetic amphidiploids were established in 32 combinations involving 8 diploid wild species representing both A and B genomes of section Arachis. Bivalent and multivalent associations in the amphidiploids of 7 A genome species confirm that these species have identical genomes. Contrastingly, high bivalent frequencies in amphidiploids involving the A and B genome species suggest that A. batizocoi has a distinct B genome that is partially homologous to the other genome A represented in the rest of the species. Crossability, chromosome pairing and pollen and pod fertility in hybrids between A. hypogaea and amphidiploids have revealed that these amphidiploids can be used as a genetic bridge for the transfer of genes from the wild species into the cultivated groundnut.Submitted as Journal Article No. 530 by International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Partial decline of Arachis hypogaea L. photosynthesis triggered by drought stress

Photosynthetic capacity (PC) of three peanut cultivars (Arachis hypogaea L. cvs. 57-422, 73-30, and GC 8-35) decreased during drought stress (decline in relative water content from ca. 95 to 70 %) and recovered two days after rewatering. Mild water stress was not limiting for the total ribulose-1,5-bisphosphate carboxylase/oxygenase activity, since this enzyme activity increased under drought. Photosystem (PS) 2 and PS1 (the latter only in cv. GC 8-35) electron transport activities decreased under drought. The ratio of the variable to maximal chlorophyll fluorescence (Fv/Fm) decreased mainly in the cv. GC 8-35. All cultivars showed decreases in photochemical quenching (qP) and quantum yield of PS2 electron transport (Φe). Increase of basal fluorescence (F0) was observed in the cvs. 73-30 and GC 8-35, while the cv 57-422 showed a decrease. After rewatering a sharp increase was observed in the majority of the parameters. Thus under the present stress conditions, the cv GC 8-35 was the most affected for all the parameters under study. The cv. 57-422 showed a higher degree of tolerance being gradually affected in photosynthetic capacity (PC) in contrast to the two other cvs. which showed a sharp decrease in PC at the beginning of the drought cycle. This revised version was published online in September 2006 with corrections to the Cover Date.     

Genetic Diversity of Rhizobia Nodulating Arachis hypogaea L. in Central Argentinean Soils

The diversity of thirty-nine isolates from peanut plants growing at fourteen different sites in the Argentinean province of Córdoba was examined by rep-PCR, RFLP of PCR amplified 16S rRNA gene and complete sequencing of ribosomal genes. The genomic analysis of the peanut isolates indicated that each group encompasses heterogeneity among their members, having distinct rep fingerprints and 16S rRNA alleles. Complete sequencing of 16S rRNA demonstrated that native peanut rhizobia from Córdoba soils representative of the slow and fast growers are phylogenetically related to Bradyrhizobium japonicum and Bradyrhizobium sp. and Rhizobium giardinii and R. tropici species, respectively. The nodC gene sequence analysis showed phylogenetic similarity between fast grower peanut symbionts and Rhizobium tropici.     

光对不同叶龄花生叶片糖酵解代谢的影响

光对花生不同叶龄的磷酸丙糖、3-磷酸甘油醛脱氢酶、丙酮酸激酶和丙酮酸含量的影响不同。成长叶片光合速率大于暗呼吸,在光下,TP增高,细胞质G3PDh活性受抑制,PK活性和Pyr含量下降;DCMU处理则消除光的影响,TP下降,细胞质G3PDh和PK活性升高。花生成长叶在光下糖酵解(EMP)途径受抑制,抑制位点是G3PDh和PK。幼叶光合微弱,呼吸作用强,TP和Pyr及细胞质酶活均不受光、暗条件和DCMU处理影响,其EMP途径和在暗中同样速率运转。老叶光合和暗呼吸均较弱,TP和两种酶活不论在光和暗中均无差异,Pyr少,EMP途径运转也慢。     

Genetic relationships among three chlorophyll-deficient mutants in peanut,Arachis hypogaea L.

Summary The genetic relationships of three chlorophyll-deficient mutant peanuts, lutescens (lu), aureus (au), and virescent (v) were studied under field and greenhouse conditions. The F₁ plants from crosses between these mutants produced phenotypically normal green. In F₂, aureus X virescent segregated 675 normal green : 225 virescent : 45 aureus : 15 virescent aureus : 64 seedling lethal, and lutescens X virescent segregated 45 normal green : 15 virescent : 3 lutescens : 1 seedling lethal. (Lutescens peanuts were seedling lethal in the field.) As previously reported, the F₂ of aureus X lutescens gave 225 normal green : 15 aureus :15 lutescens : 1 seedling lethal. The three chlorophyll-deficient factors (au, lu, and v) show independent inheritance. The recessive combinations from the parental types between aureus and virescent and between aureus and lutescens would produce plants with a combination of their respective parental characteristics, but the recessive combination between lutescens and virescent was nearly albino. The v-au and lu-au seedlings have a longer life span than the v-lu seedling has. The genotypes for the three mutants are tentatively identified as lutescens VV Au₁Au₁Au₂Au₂lu₁lu₁lu₂lu₂L₁L₁L₂L₂, aureus VV au₁au₁ au₂au₂ Lu₁Lu₁ Lu₂Lu₂ L₁L₁ l₂l₂, and virescent vv Au₁Au₁ Au₂Au₂ lu₁lu₁ Lu₂Lu₂ l₁l₁ L₂L₂.     

Genetic variability of Brazilian Indian landraces of Arachis hypogaea L

The Kayabi Indians who inhabit the Xingu Indigenous Park, located in West Central Brazil, have grown and managed peanuts for a long time. A great number of landraces are being maintained by these tribes and some of this germplasm has morphological traits that exceed the variation described in the taxonomic literature. Here, we analyzed the genetic variability of these landraces using a set of microsatellite markers. The analysis showed that, in general, the indigenous samples grouped according to the villages where they were collected. The microsatellite markers used in the present study detected high levels of genetic variation. Similarity groups, genetically distant from each other, were formed, allowing a more efficient use of the existing genetic variability. The present study also showed that these materials can extend the genetic variability available for peanut-breeding programs. Additionally, the microsatellite markers revealed a large dissimilarity among germplasm accessions representing Arachis hypogaea varieties so far included in the same subspecies fastigiata (aequatoriana + peruviana vs fastigiata + vulgaris), a subject that deserves further investigation. Finally, the Xingu Indigenous Park proved to be an important center of diversity for peanut.     

Fractional changes in phenolic acids composition in root nodules of Arachis hypogaea L.

Phenolic acids are active antimicrobial compounds and root signaling molecules that play important roles in plant defense responses. They are generally present in plants as glycosides or esters. A range of soluble and bound phenolic acids were detected in roots and root nodules of Arachis hypogaea L., among which five were identified by high performance liquid chromatography (HPLC) coupled with UV–Vis diode array detector (DAD), viz., p-coumaric acid (p-com), p-hydroxybenzaldehyde (HBAld), p-hydroxybenzoic acid (HBA), caffeic acid (CA) and protocatechuic acid (PA). Para-coumaric acid was constitutively present in all fractions whereas HBA was present in the soluble form only in young nodules. CA and PA were mostly present in the wall bound fraction. The root nodules contain higher concentration of phenolic acids than non-nodulated roots and presence of peroxidase and polyphenol oxidase indicate the metabolism of phenolic acids in roots and root nodules. These results indicate that phenolic acids (p-com and CA) in bound-glycosidic or ester forms were major components in cell wall fortification which provide protection to the root nodule from pathogen attack.