Hollow heart of pea (Pisum sativum)

Book reviewed in this article: The Way Ahead in Plant Breeding. Proceedings of the Sixth Congress of Eucarpia. Edited by F. G. H. Lupton , G. Jenkins and R. Johnson . Basic Electron Microscope Techniques. By M. A. Hayat . The Logit Transformation (with special reference to its uses in bioassay). By W. D. Ashton . Families of Frequency Distributions. By J. K. Ord .     

Verticillium wilt of pea (Pisum sativum)

A wilt disease of garden pea (Pisum sativum) caused by Verticillium dahliae is described and the range of pathogenicity of the isolate investigated. It is pathogenic to potato, sweet pea, antirrhinum and broad bean and isolates of V. dahliae from potato, lucerne and sweet pea and V. albo-atrum from lucerne are pathogenic to pea. Since the most common disease symptoms, acropetal progression of chlorosis and necrosis of the leaves followed by premature defoliation are indistinguishable from natural senescence, it is probable that disease and senescence symptoms are confused in the field. The premature defoliation results in marked reduction in green leaf area, leaf dry weight and pod yield.     

Embryogenesis of the pea (Pisum sativum)

Summary The most striking internal feature of the suspensor cells inPisum is the abundant occurrence of a plastid containing spherical bodies consisting of intertwined bundles of tubules. These tubular complexes are not typical prolamellar bodies and they are not converted into grana. Cytochemical reactions indicate that they are proteinaneous. The participation of this plastid in the possible nutritional function of the suspensor is discussed but it is pointed out that critical experimental evidence is needed before the role of the suspensor and its contents in embryogenesis can be understood.Supported by a grant from the Australian Research Grants Committee.     

Genetic diversity among varieties and wild species accessions of pea (Pisum sativum L.) based on molecular markers, and morphological and physiological characters.

Random amplified polymorphic DNA, simple sequence repeat, and inter-simple sequence repeat markers were used to estimate the genetic relations among 65 pea varieties (Pisum sativum L.) and 21 accessions from wild Pisum subspecies (subsp.) abyssinicum, asiaticum, elatius, transcaucasicum, and var. arvense. Fifty-one of these varieties are currently available for growers in western Canada. Nei and Li's genetic similarity (GS) estimates calculated using the marker data showed that pair-wise comparison values among the 65 varieties ranged from 0.34 to 1.00. GS analysis on varieties grouped according to their originating breeding programs demonstrated that different levels of diversity were maintained at different breeding programs. Unweighted pair-group method arithmetic average cluster analysis and principal coordinate analysis on the marker-based GS grouped the cultivated varieties separately from the wild accessions. The majority of the food and feed varieties were grouped separately from the silage and specialty varieties, regardless of the originating breeding programs. The analysis also revealed some genetically distinct varieties such as Croma, CDC Handel, 1096M-8, and CDC Acer. The relations among the cultivated varieties, as revealed by molecular-marker-based GS, were not significantly correlated with those based on the agronomic characters, suggesting that the 2 systems give different estimates of genetic relations among the varieties. However, on a smaller scale, a consistent subcluster of genotypes was identified on the basis of agronomic characters and their marker-based GS. Furthermore, a number of variety-specific markers were identified in the current study, which could be useful for variety identification. Breeding strategies to maintain or enhance the genetic diversity of future varieties are proposed.     

Boron alleviates aluminum toxicity in pea (Pisum sativum)

One important target of boron (B) deficiency and aluminum (Al) toxicity is cell wall. Thus we studied the hypothesis that B is capable of alleviating Al toxicity in pea (Pisum sativum). Short-term and prolonged Al exposure to pea roots at different B levels was carried out on uniform seedlings pre-cultured at a low B level. When seedlings with a low B level were supplied with or without B for 1 and 2 days before 24 h Al exposure, roots were longer while root diameter was thinner after B addition especially for 2 days even with exposure to Al; root elongation was inhibited while root diameter was enlarged by Al exposure. Callose induction by Al toxicity was higher with B added, but this was reversed after the removal of the cotyledons. Hematoxylin staining was lighter in the root tips given B, and Al content in the root tips and cell walls dropped after exposure to B. This indicates that B alleviated Al toxicity in the root tips during short-term Al exposure by decreasing Al binding in root cell walls. An increase in chlorophyll and biomass and reduced chlorosis were found at the higher level of B during prolonged Al treatment, which was coincided with the decreased Al contents, indicating that B alleviated Al toxicity to shoots. B supplementation alleviates some of the consequences of Al toxicity by limiting some Al binding in cell walls, resulting in less injury to the roots as well as less injury to the shoots.     

The protective effect of desferrioxamine on paraquat-treated pea (Pisum sativum)

Paraquat, a widely used herbicide, is photoreduced by photosystem I to the monovalent cation radical, which in turn, can react quickly and efficiently with molecular oxygen to produce superoxide anion radicals. In the presence of redox-active iron (or copper) superoxide radicals can serve as a source for the more active species such as hydroxyl radicals. The present sludv investigated the possible mediatory role of iron in paraquat to xicity. The results demonstrate that desferrioxamme (0–150μM) a highiy specific iron chelator, reduces the loss of proteins (by 34–69%) and lipid peroxidation (by 31–96%) in paraquat treated leaf cuts. Dcsferrioxamine also protects malate dehydrogenase (61–70%) hydroxvpyruvate reductase (54–100%), and Ca²⁺-dependent ATPase (25–34%) against the paraquat-induced loss of their activity. It also induces an increase in glutathione reductase activity (by 188%). These results, together with those from other experiments concerning the effect of desferrioxamine on paraquat uptake by the leaf cuts, suggest that the protection by desferrioxamine arises from its specific iron chelanon properties, and lead to the conclusion that nan-protein-bound and redoxactive forms of iron pluy a role in the manifestation of paraquat toxicity in plants.     

Optimum plant densities for three semi-leafless combining pea (Pisum sativum) cultivars under contrasting field conditions

Yield and yield components of three semi-leafless pea (Pisum sativum) cultivars, of contrasting seed type/growth habit, were assessed at target planting densities of 40–140 plants/m² on nine sites over three years. Flat-topped parabolic/asymptotic yield/density relationships were obtained. The plant density required to maximise (p max) and optimise (p opt) yield differed between cultivars: Helka, small blue, p max 126 plants/m², p opt 101 plants/m²; Solara, large blue, p max 124 plants/m², p opt 94 plants/m²; and Countess, white-seeded, p max 104 plants/m², p opt 71 plants/m². Near-maximum yields were maintained between 70 and 140 plants/m² due to the ability of the pea crop to make compensatory increases in the number of pods per plant as density declined. Yield/density responses were influenced by site (e.g. soil type) more than by seasonal factors. The risk of yield reductions occurring at densities below 70 plants/m² was greater on a mineral soil than on a fertile organic soil. On the basis of agronomic and economic considerations, there was no evidence that target plant densities required to optimise yield should necessarily be higher for semi-leafless cultivars studied than for conventional leafed peas.     

Protochlorophyllide forms in non-greening epicotyls of dark-grown pea (Pisum sativum)

Low-temperature fluorescence emission spectra of 6.5-day-old dark-grown epicotyls of pea ( Pisum sativum ) revealed the presence of protochlorophyll(ide). The upper part of the epicotyl contained 30% of the protochlorophyll(ide) content per fresh weight found in pea leaves, whereas the lower part contained 3%. Three discrete spectral forms of protochlorophyll(ide) were clearly distinguished after Gaussian deconvolution of fluorescence excitation and emission spectra. Adding the satellite bands of the Qy_(0-0) transitions (the emission vibrational (Emv) bands with correlated amplitudes, gave the following delineation: Ex439–Em629–Emv684, Ex447–Em636–Emv700 and Ex456–Em650–Emv728. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunodetection of whole tissue extracts of the epicotyl indicated the presence of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33). Electron micrographs showed prolamellar bodies in at most 11 % of the plastid profiles of the epicotyl cells. These prolamellar bodies were smaller, and many of them showed less regular structure than those of the leaves. Taken together, the results indicate that the protochlorophyll(ide) in epicotyls is arranged in a different way than in leaves.     

A rapid method to increase the number of F(1) plants in pea (Pisum sativum) breeding programs

In breeding programs, a large number of F(2) individuals are required to perform the selection process properly, but often few such plants are available. In order to obtain more F(2) seeds, it is necessary to multiply the F(1) plants. We developed a rapid, efficient and reproducible protocol for in vitro shoot regeneration and rooting of seeds using 6-benzylaminopurine. To optimize shoot regeneration, basic medium contained Murashige and Skoog (MS) salts with or without B5 Gamborg vitamins and different concentrations of 6-benzylaminopurine (25, 50 and 75 μM) using five genotypes. We found that modified MS (B5 vitamins + 25 μM 6-benzylaminopurine) is suitable for in vitro shoot regeneration of pea. Thirty-eight hybrid combinations were transferred onto selected medium to produce shoots that were used for root induction on MS medium supplemented with α-naphthalene-acetic acid. Elongated shoots were developed from all hybrid genotypes. This procedure can be used in pea breeding programs and will allow working with a large number of plants even when the F(1) plants produce few seeds.     

Regeneration of shoots from pea (Pisum sativum) hypocotyl explants

A sequential indole-3-acetic acid (IAA)-zeatin treatment was applied to Pisum sativum hypocotyl explants, resulting in shoot formation from 50% of the explants. Shoots were easily rooted and transplantable plants could be obtained in 3 months. The method has been applicable to the 5 cultivars tested. Histological examination of explants suggests the shoots to be of de novo origin, which would make the system suitable for transformation experiments.     

Seasonal radiation interception, dry matter production and yield determination for a semi-leafless pea (Pisum sativum) breeding selection under contrasting field conditions

Radiation interception, dry matter accumulation, flower and pod production and yield were measured for a semi-leafless pea (Pisum sativum) breeding selection (BS3) on three contrasting sites. Differences in soil moisture availability were largely responsible for a three-fold difference in yield between sites. Radiation interception was related to dry matter production by calculating photosynthetic efficiencies. In the absence of lodging, crop canopies converted intercepted radiation into dry matter with constant efficiency (?) throughout the season; under conditions of moisture stress ? was reduced. Serious lodging during the post-flowering period on one site resulted in a mean seasonal photosynthetic efficiency (?) 17% lower than ?. The ability of the pea crop canopy to intercept radiation was related also to yield components.     

Physiology of acclimation to salinity stress in pea (Pisum sativum)

Pea (Pisum sativum L.) seedlings were grown in half strength Hoagland solution and exposed to 0, 10, 25 mM NaCl and 2.5% PEG 6000 for 1 week (pre-treatment). Thereafter plants were exposed to 0 and 80 mM NaCl for 2 weeks (main treatment). The control plants were maintained in half strength Hoagland solution without NaCl. Various physiological parameters were recorded from control, pretreated and non-pretreated plants. There was no negative effect of the pre-treatments on growth (total fresh and dry matter production), and plants pre-treated with 10 mM NaCl had biomass accumulation equal to control plants. The beneficial effect of salt acclimation was also evident in the prevention of K⁺ leakage and Na⁺ accumulation, primary in roots, suggesting that here the physiological processes play the major role. 2.5% PEG 6000 was not as efficient as salt in enhancing salt tolerance and acclimation appears to be more related to ion-specific rather than osmotic component of stress. We also recorded an increase of the xylem K/Na in the salt acclimated plants. Therefore, the present study reveals that short-term exposure of the glycophyte P. sativum species activates a set of physiological adjustments enabling the plants to withstand severe saline conditions, and while acclimation takes place primary in the root tissues, control of xylem ion loading and efficient Na⁺ sequestration in mesophyll cells are also important components of this process.     

Transient protein expression in three Pisum sativum (green pea) varieties

The expression of proteins in plants both transiently and via permanently transformed lines has been demonstrated by a number of groups. Transient plant expression systems, due to high expression levels and speed of production, show greater promise for the manufacturing of biopharmaceuticals when compared to permanent transformants. Expression vectors based on a tobacco mosaic virus (TMV) are the most commonly utilized and the primary plant used, Nicotiana benthamiana, has demonstrated the ability to express a wide range of proteins at levels amenable to purification. N. benthamiana has two limitations for its use; one is its relatively slow growth, and the other is its low biomass. To address these limitations we screened a number of legumes for transient protein expression. Using the alfalfa mosaic virus (AMV) and the cucumber mosaic virus (CMV) vectors, delivered via Agrobacterium, we were able to identify three Pisum sativum varieties that demonstrated protein expression transiently. Expression levels of 420 ( 26.24 mg GFP/kgFW in the green pea variety speckled pea were achieved. We were also able to express three therapeutic proteins indicating promise for this system in the production of biopharmaceuticals.     

Danish Rhizobium leguminosarum strains nodulating 'Afghanistan' pea (Pisum sativum)

A wild pea ( Pisum sativum L.) native to Afghanistan normally known to be resistant to nodulation with European strains of Rhizobium leguminosarum was nodulated early and effectively in field soil in Denmark. Isolates from nodules formed effective nodules abundantly on 'Afghanistan' on reinfection under aseptic conditions. Five types differing in isoenzyme composition pattern were found among 15 isolates from 'Afghanistan' nodules. None were identical with the 'Tom' strain from Turkey, which also forms effective nodules with 'Afghanistan'. The five types were also different with respect to isoenzyme pattern from Rhizobium leguminosarum strains isolated from a modern pea variety cultivated in the same field.