Peanut Leaflets Research Articles

Breeding of peanut variety Yuhua 4 by in vitro mutagenesis

The embryonic leaflets of peanut (Arachis hypogaea) variety Huayu 20 were used as explants and pingyangmycin as a mutagen to induce somatic embryos. Four weeks after the inoculation, the survived explants were transferred to somatic embryo germination medium containing screening reagent hydroxyproline, and finally 15 regenerated plants were obtained. Pedigree breeding method was used during the following selection breeding, and three lines with significantly increased yield and 23 lines with high oil content were obtained from these mutant offsprings. The line with both high yield and high oil content has passed peanut variety multi-location in Anhui province and was named "Yuhua 4". Its yield was 16.63% higher than that of the control variety Baisha 1016, ranking the first in all the testing varieties. Yuhua 4 showed the characteristics of early maturity, small pod and high oil content. The oil content of kernels was 56.10%, higher than that of original parent Huayu 20 with 49.50% oil content, tested by the Ministry of Agriculture of Oil and Products Quality Supervision, Inspection and Test Center (Wuhan), and the yield was 15% higher than that of Huayu 20. It was concluded that in vitro mutagenesis and target screening was an effective way on creating new germplasm and breeding new variety in peanut.

Estimating leaf area of warm‐season perennial legumes

AbstractRefining mathematical models may decrease labour and generate accurate estimates of leaf area in warm‐season perennial legumes. The aim of this study was to assess the use of mathematical models to determine the leaf area of four tropical forage legumes. Perennial legumes (Arachis pintoi, Stylosanthes spp., Calopogonium mucunoides and Neonotonia wightii) were collected, and an elliptical model and a corrected elliptical model were used to estimate leaf area. For comparison, linear models were also generated based on the leaflet area. The elliptical model was suitable for the initial forage peanut leaflets, while the corrected elliptical model proved suitable for estimating the area of the initial leaflets of all species as well as the terminal leaflets of forage peanut and stylo. The elliptical model could be used to estimate the area of both the initial and terminal leaflets only in stylo. Models were generated to estimate leaf area of all legumes requiring only the measurement of length and width from a single initial leaflet. In all of the studied legumes, the leaflet pairs were symmetrical, meaning the corrected elliptical model allows for the estimation of the leaflet area of each plant.

Interactions Between Frankliniella fusca and Pantoea ananatis in the Center Rot Epidemic of Onion (Allium cepa).

An Enterobacteriaceae bacterium, Pantoea ananatis (Serrano) Mergaert, is the causal agent of an economically important disease of onion, center rot. P. ananatis is transmitted by an onion-infesting thrips, Frankliniella fusca (Hinds). However, interactions between F. fusca and P. ananatis as well as transmission mechanisms largely remain uncharacterized. This study investigated P. ananatis acquisition by thrips and transstadial persistence. Furthermore, the effects of bacterial acquisition on thrips fitness were also evaluated. When thrips larvae and adults were provided with acquisition access periods (AAP) on peanut leaflets contaminated with the bacterium, an exponentially positive relationship was observed between AAP and P. ananatis acquisition (R(2) ≥ 0.77, P = 0.01). P. ananatis persisted in thrips through several life stages (larvae, pupae, and adult). Despite the bacterial persistence, no significant effects on thrips fitness parameters such as fecundity and development were observed. Immunofluorescence microscopy of adult thrips with P. ananatis-specific antibody after 48 h AAP on contaminated food revealed that the bacterium was localized only in the gut. These results suggested that the pathogen is not circulative and could be transmitted through feces. Mechanical inoculation of onion seedlings with fecal rinsates produced center rot symptoms, whereas inoculation with rinsates potentially containing salivary secretions did not. These results provide evidence for stercorarian transmission (transmission through feces) of P. ananatis by F. fusca.

Development of an Inoculation Method for Quantifying Fungicide Residues on Peanut Foliage

Abstract A bioassay was developed to evaluate residues of three foliar applied fungicides on peanut leaflets and stems obtained from the upper, middle, and lower canopy. Experiments were conducted to determine the effects of wounding and nutrient source on the development of Sclerotium rolfsii lesions. Results indicated that wounding was not required for infection on either tissue type, and that adequate lesion development was obtained when ¼ strength potato dextrose agar (PDA) was used as a nutrient source. Significant differences in lesion development were observed among canopy layers for leaflets and stems. Tissues collected from the upper canopy were more rapidly colonized by S. rolfsii than tissues from the middle or lower canopy. One-quarter strength PDA was used as a nutrient source to determine an appropriate sample size, and to evaluate the response of S. rolfsii to varying concentrations of azoxystrobin, flutolanil and tebuconazole on non-wounded tissues. Based on differences in the sample mean, standard deviation, and coefficient of variation, a total of 8 to 10 samples are required to obtain a reliable estimate. The application of fungicides significantly reduced the size of S. rolfsii lesions compared to the non-treated controls. Consistent results were obtained from the leaflet and stem assays, and lesion size decreased linearly with increasing log10+1 transformed fungicide concentration. The EC50 values from the leaflet and stem assays were 17.2, 9.5, and 18.1 mg/L, and 18.1, 8.3, and 13.5 mg a.i. /L for azoxystrobin, tebuconazole, and flutolanil, respectively. These results demonstrate an effective method to determine differences in the activity of foliar applied fungicides.

Analysis of Factors That Influence the Epidemiology of Sclerotinia minor on Peanut.

In North Carolina, sclerotia of Sclerotinia minor germinate myceliogenically to initiate infections on peanut. The effects of soil temperature and soil matric potential (ψM on germination and growth of S. minor have not been well characterized, and little is known about relative physiological resistance in different parts of the peanut plant. Laboratory tests examined the ability of the fungus to germinate, grow, and infect detached peanut leaflets at soil temperatures ranging from 18 to 30°C at ψM of -100, -10, and -7.2 kPa. In addition, detached pegs, leaves, main stems, and lateral branches from three peanut lines varying in field resistance were examined for resistance to infection by S. minor. Sclerotial germination was greatest at 30°C and ψM of -7.2 kPa. Final mycelial diameters decreased with decreasing ψM, whereas soil matric potential did not affect lesion development. Mycelial growth and leaflet lesion expansion were maximal at 18 or 22°C. Soil ψM did not affect leaflet infection and lesion expansion. Lesions were not observed on leaves incubated at temperatures of 29°C or above, but developed when temperatures were reduced to 18 or 22°C 2 days after inoculation. Pegs and leaflets were equally susceptible to infection and were more susceptible than either main stems or lateral branches. Results of this work, particularly the effects of temperature on S. minor, and knowledge of peanut part susceptibility has application in improving Sclerotinia blight prediction models for recommending protective fungicide applications.

Histological analysis of somatic embryogenesis and organogenesis induced from mature zygotic embryo-derived leaflets of peanut ( Arachis hypogaea L.)

The initiation and development of somatic embryos and organogenic buds in peanut ( Arachis hypogaea L.) obtained from mature zygotic embryo-derived leaflets (MZELs) was studied histologically. The MZELs were cultured on Murashige and Skoog (MS) basal medium supplemented with 20 mg l −1 2,4-dichlorophenoxyacetic acid (2,4-D) for embryogenic mass induction. Somatic embryos developed from these masses following transfer to a medium containing 3 mg l −1 2,4-D and were germinated on hormone-free medium. A combination of 4 mg l −1 α-naphthaleneacetic acid (NAA) and 5 mg l −1 6-benzylamino purine (BAP) was optimum to induce organogenic buds which developed into shoots once placed on a medium containing 0.5 mg l −1 BAP and 0.5 mg l −1 kinetin. Histological studies of explants at various developmental stages of somatic embryogenesis and organogenesis revealed that both somatic embryos and organogenic buds developed directly from the mesophyll layers of MZELs, and both were of multicellular origin. Initially, MZELs underwent periclinal division when cultured on MS medium containing 20 mg l −1 2,4-D giving rise to somatic embryos. Interestingly, MZELs underwent anticlinal division when cultured on MS medium containing 4 mg l −1 NAA and 5 mg l −1 BAP that resulted in organogenesis. Initial failure of somatic embryos to convert into plantlets was due to malformation of the shoot meristem. However, transfer to medium containing 2 mg l −1 BAP and 3 mg l −1 kinetin, or 5 mg l −1 thidiazuron (TDZ) resulted in the appearance of broad shoot apices which could be induced to produce plantlets.

Electroporation of intact embryonic leaflets of peanut: Gene transfer and stimulation of regeneration capacity

Direct gene transfer into peanut intact embryonic leaflets was performed through electroporation. In transient β-glucuronidase expression assays, maximal expression was obtained by using pulses of 625 V cm−1 in EPRm (modified electroporation) buffer supplemented with 75 μM NaCl. Kanamycin-resistant plants were obtained, and the presence of the nptII gene was demonstrated by PCR analysis. The positive effect of electroporation on the efficiency of in vitro regeneration was demonstrated. Explants submitted to field strengths between 500 and 625 V cm−1 displayed a significantly increased number of shoots and originated faster growing calluses relative to control explants. Whereas in control explants callus formation occurred only at the petiolule, electroporated leaflets developed additional organogenic calluses on the foliar lamina.

Genotypic control of peanut somatic embryogenesis.

The protocol for obtaining a high frequency of plant development via somatic embryogenesis from mature zygotic embryo-derived leaflets of peanut (Arachis hypogaea L.) involves multiple stages; these include the induction of embryogenic masses, development of embryos, radicle emergence/conversion of embryos and the development of plants from rooted abnormal embryos. Sixteen genotypes were subjected to this protocol by exposing mature zygotic embryo-derived leaflets to the common media sequence and comparing responses. Although the protocol was effective for all the genotypes, variation in frequency of response at each stage of development indicated that, with the exception of root meristem differentiation and subsequent radicle emergence, the whole process of somatic embryogenesis depended on the genotypic constitution of the original plant. The failure of somatic embryos to undergo conversion to plantlets could be a genotype-dependent characteristic.

High Efficiency Peanut Regeneration Using a Nonimbibed Immature Leaflet Culture Method

Abstract Efficient plant regeneration is an essential part of gene transfer systems using recombinant DNA technology. Efficiency of regeneration from immature leaflets of peanut (Arachis hypogaea L.) was compared among several explant treatments in an effort to maximize recovery of plants from culture. In one experiment, explants were derived from leaflets of cv. NC 7 from dry mature seeds or from mature seeds which had been imbibed for 1 or 4 d. To avoid confounding treatment effects with variation among individual seeds, both nonimbibed and imbibed leaflets originated from a single seed. For each seed, four nonimbibed leaflets from a single leaf were excised, sterilized, rinsed, and plated on MS-based medium amended with 4 mg L-1 benzylaminopurine and 2 mg L-1 naphthaleneacetic acid. The embryonic axis with the other leaf (four remaining leaflets) and one cotyledon attached was then imbibed in water for 1 or 4 d. After 4 wk in culture, 53% of nonimbibed leaflets, 37% of leaflets imbibed for 1 d, and 6% of leaflets imbibed for 4 d produced shoots. Subsequently, regeneration efficiency was compared among immature leaflet cultures from nonimbibed seeds of four cultivars representing three botanical varieties from two subspecies. Shoot frequency after 4 wk in culture averaged 9% for Peruvian introduction A2 (NC Ac 17090) representing subsp. fastigiata var. peruviana versus 53% for cv. NC 7 and Bolivian introduction B2 (PI 274191), both representing subsp. hypogaea var. hypogaea. At 6 wk after plating, these frequencies increased to 28 and 61%, respectively. The response of Argentine introduction C2 (PI 262000) representing subsp. fastigiata var. vulgaris was intermediate to vars. hypogaea and fastigiata. Shoot proliferation in var. hypogaea was significantly greater than in the other varieties, whereas it was significantly lower in var. peruviana. Regenerated plants developed normal flowers and pods in the greenhouse. The study indicated that A. hypogaea can be cultured efficiently from nonimbibed leaflets.

Plant Regeneration and Microprojectile-Mediated Gene Transfer in Embryonic Leaflets of Peanut (Arachis hypogaea L.)

Excised leaflets from mature embryos of peanut cultivars Robut, Gajah, McCubbin and NC-7 produced multiple shoot primordia via organogenesis on Murashige and Skoog medium supplemented with 3 mg L-1 BAP and 1 mg L-1 NAA. Plants were regenerated by elongation of shoot primordia on transfer to MS medium supplemented with 5 mg L-1 BAP. The regeneration frequency of five plants per embryonic leaflet was 10-40-fold higher than previously reported from seedling leaflets. Microprojectile bombardment parameters were optimised for high transient expression rates of the β-glucuronidase (uidA or gus) reporter gene in peanut embryos (> 2000 cells per bombardment) and in excised embryonic leaflets (> 1200 cells per bombardment). The firefly luciferase reporter gene (luc) allowed repeated non-toxic assays, revealing the transition from hundreds of transiently expressing cells soon after bombardment, to a few stably expressing regions in callus grown without selection for 8 weeks after bombardment of embryonic leaflets.

Somatic embryogenesis from mature embryo-derived leaflets of peanut (Arachis Hypogaea L.)

Embryogenic masses were obtained from immature leaves of peanut (Arachis hypogaea L.) cultured on a medium containing 20 mg/l 2,4-D. Somatic embryos developed from these masses following transfer to a medium containing 3 mg/l 2,4-D. The embryo morphology was quite variable. Following transfer to hormone-free medium, these embryos germinated. Shoot elongation was obtained in 25% of the embryos following transfer to a medium supplemented with 0.5 mg/l each of BAP and Kn. The plants grown in vitro by this method survived in sand:soil mixture and were grown to maturity.

Intrinsic Rate of Increase of Frankliniella fusca (Thysanoptera: Thripidae) on Peanuts

Frankliniella fusca (Hinds) is a thrips species of economic importance that produces direct injury to leaves and is a vector of the tomato spotted wilt virus. The intrinsic growth rate of increase and the effect of two initial densities of immature F. fusca on immature survivorship and adult emergence was determined by enclosing adult or immature thrips on peanut leaflets. The number of emerging immature thrips was 14.5 per female. Immature emergence began in 7 d with a peak of emergence (67%) between 8 and 9 d. No males emerged. Females reached maturity 11.7 d after emergence. The gross value of the intrinsic growth rate of increase was 0.500 and the value determined by iteration was 0.405. Total emergence of cohorts with smaller initial numbers of immatures (32 larvae per bag) was significantly higher than of larger cohorts (117 larvae per bag). Under high population densities, reduced survivorship may assure that enough resources are available for successful reproduction of some adults. Our studies reveal that F. fusca has the potential for high population increases in peanut which may favor persistence and spread of tomato spotted wilt virus disease.

Leaflet and Canopy Photosynthesis of Peanut Affected by Late Leaf Spot

AbstractLate leaf spot, induced by Cercosporidium personatum (Berk. & Curt.) Deighton, is the most important foliar disease affecting peanut (Arachis hypogaea L.) in Florida and neighboring states. The disease first occurs as necrotic lesions on peanut leaflets and subsequently induces leaflet abscission. Field experiments were conducted to study the effects of late leaf spot on leaflet and canopy photosynthesis. Fully expanded leaflets at the tip of the main stem were tagged and leaflet photosynthesis was measured during the subsequent weeks with a portable photosynthesis system. Leaflet photosynthesis was reduced linearly with the increase in the percentage of necrotic leaf area. Reduction in light utilization due only to necrotic leaf area did not explain completely the reduction in leaflet photosynthesis. Regression analysis suggested that 15% necrotic leaf area contributed to a 65% reduction in the photosynthesis of infected leaflets. It appears that there was an effect on leaflet photosynthesis due to host cells invaded or affected by the pathogen. A chamber made of aluminum frame covered with mylar film was used to estimate canopy photosynthesis over a land area of 0.56 m2. At the canopy level, the effect of reduction in leaflet photosynthesis was negligible compared to the effect of disease‐induced defoliation. The decrease in leaf area index was the major component involved in the reduction of canopy photosynthesis because of the effect of late leaf spot. Canopy photosynthesis was inversely proportional to total disease severity, which is an expression of both defoliation and necrotic area.

Somatic embryogenesis and plant regeneration from leaflets of peanut, Arachis hypogaea

Somatic embryos were induced on peanut (Arachis hypogaea) leaflets from aseptically germinated embryo axes. Leaflet size influenced percent somatic embryogenesis; 5-8 mm long cut leaflets were superior to 2-3 mm long uncut leaflets. Maximum embryogenesis of 14.6% was obtained after a 15 d incubation on induction medium (modified MS with B5 vitamins, 30 g/l sucrose, 4 g/l Gel-Gro, 40 mg/l 2,4-D +0.2 mg/l kinetin) followed by transfer to a secondary medium with 5 mg/l 2,4-D+0.2 mg/l kinetin. Primary somatic embryos were fused along the axes with no distinct cotyledons, but secondary embryos had single axes with two cotyledons. Other treatments had lower percent embryogenesis, no secondary embryogenesis, and embryos with single axes with two cotyledons. Some somatic embryos converted into normal plants capable of greenhouse survival.

The effect of temperature on colonization of Cercosporidium personatum leafspot of peanuts by the hyperparasite Dicyma pulvinata

Colonization of lesions of Cercosporidium personatum on detached peanut leaflets by the hyperparasite Dicyma pulvinata followed a logistic growth curve. The initial colonization rate and the asymptotic level of colonization were estimated by plotting the calculated relative rate of colonization against the percentage colonization. These two parameters and a subjective estimate of the time-lag in colonization were used to compare colonization of lesions, in the dark, by the hyperparasite at constant and cycling temperature regimes. No colonization was observed at constant temperatures ⩾31.5°C. The time-lag in colonization increased and the asymptotic level declined markedly at constant temperatures >28°C. At cycling temperature regimes, the initial colonization rate and the asymptotic level of colonization were directly related to the difference between maximum and minimum temperatures, especially at maximum temperatures >28°C.

Peanut Web Blotch: I. Cultural Characteristics and Identity of Causal Fungus1

Abstract A foliar disease of peanuts, previously unreported in the USA, was found in Texas in 1972. The pathogen was identified as a species of Ascochyta. Further cultural studies have revealed this fungus to be Phoma arachidicola Marasas, Pauer, and Boerema. Pycnidia form profusely at 20 C and 25 C. Pycnidiospores are borne on short pycnidiosphores and are predominantly one-celled in culture. Spores produced in pycnidia on infected leaflets become 1 septate. Large 1-septate spores, as well as an occasional 2-septate spore, may form in culture. Optimum temperature for mycelial growth in 20 C; little or no growth occurs at 5 C or above 30 C. The teleomorphic state develops in the field on fallen leaflets and can be induced to form in the laboratory on sterilized peanut leaflets between 15 and 20 C. Cultures derived from single ascospores form pseudothecia. Pycnidiospores, ascospores, and chlamydospores are all infective units. Because this fungus produces hyaline ascospores and pseudoparaphyses, it has been transferred to the genus Didymella as Didymella arachidicola (Choch.) comb. nov. Comparisons with 15 isolates causing web blotch of peanut in the USA, Argentina, and South Africa indicate that web blotch symptoms are produced by the same fungal species.

Effect of Cyhexatin (Plictran) on Growth, Conidial Germination And Sporulation of Cercospora arachidicola1

Abstract Growth of Cercospora arachidicola Hori, the causal agent of early leaf spot disease on peanuts, was completely inhibited on Czapek-Dox broth medium amended with the acaricide cyhexatin (Plictran) at ≤ 73.5 μg/ml; however, at 14.7 μg/ml traces of growth occurred after 6 weeks of incubation at 27±2C and continuous fluorescent light (800 lux). Aqueous preparations of cyhexation at ≤ 147.0 μg/ml completely inhibited the germination of conidia of C. arachidicola. At a concentration of cyhexatin ≤ 73.5 and 14.7 μg/ml, less than two percent of the conidia germinated as compared with more than 95 percent germination in distilled water. Misting of aqueous preparations of cyhexatin at ≤ 147.0 μg/ml on the adaxial or both surfaces of peanut leaflets with mature leafspot lesions was very effective in reducing the sporulating potential of C. arachidicola.