Heat tolerance in groundnut

Tolerance to high soil and air temperature during the reproductive phase is an important component of adaptation to and and semi-arid cropping environments in groundnut. Between 10 and 22 genotypes were screened for tolerance to high air and soil temperature in controlled environments. To assess tolerance to high soil temperature, 10 genotypes were grown from start of podding to harvest at ambient (28 degrees) and high (38 degreesC) soil temperatures, and crop growth rate (CGR), pod growth rate (PGR) and partitioning (ratio PGR:CGR) measured. To assess tolerance to high air temperature during two key stages-microsporogenesis (3-6 days before flowering, DBF) and flowering, fruit-set was measured in two experiments. In the first experiment, 12 genotypes were exposed to short (3-6 days) episodes of high (38 degreesC) day air temperature at 6 DBF and at flowering. In the second experiment, 22 genotypes were exposed to 40 degreesC day air temperature for I day at 6 DBF, 3 DBF or at flowering. Cellular membrane thermostability (relative injury, RI) was also measured in these 22 genotypes. There was considerable variation among genotypes in response to high temperature, whether assessed by growth rates, fruit-set or RI. Pod weight at high soil temperature was associated with variation in CGR rather than partitioning. Flowering was more sensitive to high air temperature than microsporogenesis. Genotypes tolerant to high air temperature at microsporogenesis were not necessarily tolerant at flowering, and nor was tolerance correlated with RI. Six genotypes (796, 55-437, ICG 1236, ICGV 86021, lCGV 87281 and ICGV 92121) were identified as heat tolerant based on their performance in all tests. These experiments have shown that groundnut genotypes can be easily screened for reproductive tolerance to high air and soil temperature and that several sources of heat tolerance are available in groundnut germplasm. (C) 2003 Elsevier Science B.V. All rights reserved.

Saturated salt solutions for humidity control and the survival of dry powder and oil formulations of Beauveria bassiana conidia

Oil-based formulated conidia sprayed on steel plates and conidia powder (control) of Beauveria bassiana isolate IMI 386243 were stored at temperatures from 10 to 40 degrees C in desiccators over saturated salt solutions providing relative humidities from 32 to 88%, or in hermetic storage at 40 degrees C, and moisture contents in equilibrium with 33 or 77% relative humidity. The negative semi-logarithmic relation (P < 0.005) between conidia longevity (at 40 degrees C) and equilibrium relative humidity did not differ (P > 0.25) between formulated conidia and conidia powder. Despite this, certain saturated salts provided consistently greater longevity (NaCl) and others consistently shorter longevity (KCl) for formulated conidia compared to conidia powder. These results, analysis of previous data, and comparison with hermetic storage, indicate that storage of conidia over saturated salt solutions provides inconsistent responses to environment and so may be problematic for bio-pesticide research. In hermetic storage, oil formulation was not deleterious to longevity and in the more moist environment enhanced survival periods. (c) 2005 Elsevier Inc. All rights reserved.

Phenotyping parents of mapping populations of rice for heat tolerance during anthesis

Seed set of rice (Oryza sativa L.) is highly sensitive to short episodes of high temperature at anthesis events that are likely to be more frequent in future climates. Breeding for tolerance is therefore an essential component of adaptation to climate variability and change. Experiments were conducted in 2003 and 2004 at optimum (30 degrees C daytime) and high (35 and 38 degrees C) air temperature using parents of some prominent mapping populations (i) to determine whether there were differences in the daily flowering pattern and hence a potential heat avoidance mechanism, and (ii) to identify rice genotypes having true heat tolerance during anthesis, that is, high seed set in spikelets exposed to high temperature. Rice cultivar CG14 (O. glaberrima) reached peak anthesis earlier in the morning (1.5 h after dawn) under both control (30 degrees C) and high (38 degrees C) temperature conditions than O. sativa genotypes (>= 3 h after dawn). Exposure to high temperature (centered on the time of peak anthesis) for 6 h reduced spikelet fertility more than exposure for 2 h, and fertility was lower at 38 degrees C than at 35 degrees C. Genotypic ranking for spikelet fertility at 35 and 38 degrees C was highly correlated in both 2003 and 2004. Fertility was also highly correlated across years, suggesting a consistent and reproducible response of spikelet fertility to temperature. The check cultivar N22 was the most heat tolerant genotype (64-86% fertility at 38 degrees C) and cultivars Azucena and Moroberekan the most susceptible (<8%).

Drying method influences the development of germinability, dessication tolerance and subsequent longevity of immature seeds of sumauma (Ceiba pentandra (L.) Gaertn. [Bombacaceae])

The ability to germinate, tolerate desiccation and survive in air-dry storage was investigated during early seed development in planta and subsequent ex planta maturation of sumauma (Ceiba pentandra). Immature fruits were collected on three different dates (i.e. from about 5 days before until 7 days after mass maturity). Immature fresh seeds were not able to germinate. Fruits or seeds were subjected immediately after each collection to three different drying treatments with progressively slower rates of dessication: (i) seeds were extracted from the fruits and dried immediately; (ii) fruits were dried in a thin layer; (iii) fruits were dried in a tied polyethylene bag (with 10 holes of 1cm diameter). Drying was in a room maintained at 25 degrees C +/- 3 degrees C and 65%+/- 5% r.h. For treatment (i) the seeds were dried for 6 days in order to reduce moisture content to around 13% ( +/- 2%) moisture content. For treatments (ii) and (iii) the fruits were subjected to different periods of drying depending upon collection date. The results of these post-collection treatments showed generally that the more immature the seeds the slower the rate of drying that is required to improve ability to germinate, ability to tolerate desiccation and potential longevity, but at the third harvest, 7 days after mass maturity, the intermediate drying rate treatment was the most beneficial. Thus post fruit collection treatments can be modified depending upon the stage of seed development in order to provide good to high quality seeds of sumauma when collection has to be made at a site with difficult access at less than ideal times. The results are relevant to seed collection practices for both forestry and ex situ plant biodiversity conservation.

Onset of germinability, desiccation tolerance and hardseededness in developing seeds of Peltophorum pterocarpum (DC) K. Heyne (Caesalpinioideae)

In the hot and dry conditions in which seeds of the tree legume Peltophorum pterocarpum develop and mature in Vietnam, seed moisture content declined rapidly on the mother plant from 87% at 42 d after flowering (DAF) to 15% at 70 DAF. Dry weight of the pods attained a maximum value at about 42 DAF, but seed mass maturity (i.e. the end of the seed-filling phase) occurred at about 62 DAF, at which time seed moisture content was about 45-48%. The onset of the ability of freshly collected seeds to germinate (in 63-d tests at 28-34degreesC) occurred at 42 DAF, i.e. about 20 d before mass maturity. Full germination (98%) was attained at 70 DAF, i.e. at about 8 d after mass maturity. Thereafter, germination of fresh seeds declined, due to the imposition of a hard seed coat. Tolerance of desiccation to 10% moisture content was first detected at 56 DAF and was complete within the seed population by 84 DAF, i.e. about 22 d after mass maturity. Hardseededness began to be induced when seeds were dried to about 15% moisture content and below, with a negative logarithmic relation between hardseededness and moisture content below this value.

The influence of commercial film-forming polymers on reducing salt spray injury in evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.)

A field trial was undertaken to determine the influence of four commercially available film-forming polymers (Bond [alkyl phenyl hydroxyl polyoxyethylene], Newman Crop Spray 11E™ [paraffinic oil], Nu-Film P [poly-1-p menthene], and Spray Gard [di-1-p menthene]) on reducing salt spray injury on two woody species, evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.). Irrespective of species, the film-forming polymers Nu-Film-P and Spay Gard did not provide any significant degree of protection against salt spray damage irrespective of concentration (1% or 2%) applied as measured by leaf chlorophyll concentrations, photosynthetic efficiency, visual leaf necrosis, foliar sodium and chloride content, and growth (height, leaf area). The film-forming polymer Newman Crop Spray 11E™ provided only 1-week protection against salt spray injury. The film-forming polymer Bond provided a significant (P < 0.05) degree of protection against salt spray injury 3 months after application as manifest by higher leaf chlorophyll content, photosynthetic efficiency, height and leaf area, and lower visual leaf necrosis and foliar Na and Cl content compared with nontreated controls. In conclusion, results indicate that application of a suitable film-forming polymer can provide a significant degree of protection of up to 3 months against salt spray injury in evergreen oak and laurel. Results also indicate that when applied at 1% or 2% solutions, no problems associated with phytotoxicity and rapid degradation on the leaf surface exist.

Tolerance traits and the stability of mutualism

Identifying factors which allow the evolution and persistence of cooperative interactions between species is a fundamental issue in evolutionary ecology. Various hypotheses have been suggested which generally focus on mechanisms that allow cooperative genotypes in different species to maintain interactions over space and time. Here, we emphasise the fact that even within mutualisms (interactions with net positive fitness effects for both partners), there may still be inherent costs, such as the occasional predation by ants upon aphids. Individuals engaged in mutualisms benefit from minimising these costs as long as it is not at the expense of breaking the interspecific interaction, which offers a net positive benefit. The most common and obvious defence traits to minimise interspecific interaction costs are resistance traits, which act to reduce encounter rate between two organisms. Tolerance traits, in contrast, minimise fitness costs to the actor, but without reducing encounter rate. Given that, by definition, it is beneficial to remain in mutualistic interactions, the only viable traits to minimise costs are tolerance-based 'defence' strategies. Thus, we propose that tolerance traits are an important factor promoting stability in mutualisms. Furthermore, because resistance traits tend to propagate coevolutionary arms races between antagonists, whilst tolerance traits do not, we also suggest that tolerance-based defence strategies may be important in facilitating the transition from antagonistic interactions into mutualisms. For example, the mutualism between ants and aphids has been suggested to have evolved from parasitism. We describe how phenotypic plasticity in honeydew production may be a tolerance trait that has prevented escalation into an antagonistic arms race and instead led to mutualistic coevolution.

Triazole induced drought tolerance in horse chestnut (Aesculus hippocastanum)

We determined the influence of the triazole derivatives paclobutrazol, penconazole, epixiconazole, propiconazole and myclobutanil on the drought tolerance and post drought recovery of container-grown horse chestnut (Aesculus hippocastanum L.) saplings. Myclobutanil neither conferred drought resistance, as assessed by its effects on a number of physiological and biochemical parameters, nor affected growth parameters measured after recovery from drought. Chlorophyll fluorescence (F,IF,,), photosynthetic rates, total foliar chlorophyll and carotenoid concentrations, foliar proline concentration and superoxide dismutase and catalase activities were consistently higher and leaf necrosis and cellular electrolyte leakage was lower at the end of a 3-week drought in trees treated with paclobutrazol, penconazole, epixiconazole or propiconazole than in control trees. Twelve weeks after drought treatment, leaf area and shoot, root and total plant dry masses were greater in triazole-treated trees than in control trees with the exception of those treated with myclobutanil. In a separate Study, trees were subjected to a 2-week drought and then sprayed with paclobutrazol, penconazole, epixiconazole, propiconazole or myclobutanil. Chlorophyll fluorescence, photosynthetic rate, foliar chlorophyll concentration and catalase activity over the following 12 weeks were 20 to 50% hi-her in triazole-treated trees than in control trees. At the end of the 12-week recovery period, leaf area and shoot, root and total plant dry masses were higher in triazole-treated trees than in control trees, with the exception of trees treated with myclobutanil. Application of triazole derivatives, with the exception of myclobutanil, enhanced tolerance to prolonged drought and, when applied after a 2-week drought, hastened recovery from drought. The magnitude of treatment effects was in the order epixiconazole approximate to propiconazole > penconazole > paclobutrazol > myclobutanil.

Diversity, phylogeny and distribution of bean rhizobia in salt-affected soils of North-West Morocco

Different molecular methods: BOX-PCR fingerprinting, R-FLP-PCR and sequencing of the 16S rDNA as well as the symbiotic genes nodC and nifH, were used to study the genetic diversity within a collection of nodulating bean rhizobia isolated from five soils of North-West Morocco. BOX fingerprints analysis of 241 isolates revealed 19 different BOX profiles. According to the PFLP-PCR and sequencing of 16S rDNA carried out on 45 representative isolates, 5 genotypes were obtained corresponding to the species Rhizobium etli, R. tropici, R. gallicum, R. leguminosarum and Sinorhizobium meliloti. The most abundant species were R. etli and R. tropici (61% and 24%, respectively). A high intraspecific diversity was observed among the R. etli isolates, while the R. tropici group was homogeneous. Most of the rhizobia studied belong to species known to nodulate common bean, while 2 species were unconventional microsymbionts: R. leguminosarum biovar viciae and S. meliloti. Our results, especially the nodulation promiscuity of common bean and the relation between the predominance of some species of rhizobia in particular soils and the salt content of these soils, indicate that there is a real need for a better understanding of the distribution of common bean rhizobia species in the soils of Morocco before any inoculation attempt.

The chromosomal assessment of salt tolerant substituted tritipyrum using genomic fluorescent in situ hybridiization (FISH)

Wheat, although moderately tolerant to salt, can not be cultivated in many areas. However, in the triticeae tribe, some of the wild wheat relatives are highly tolerant, e.g. Thinopyrum bessarabicum, which grows on the sea shore. Eight primary hexaploid tritipyrum lines, amphiploids between Triticum durum and Thinopyrum bessarabicum have been produced which can set seed in at least 250 mM NaCl. These tritipyrums (2n=6x=42, AABBEbEb) due to reasons such as brittle rachis, continuous production of tillers, late maturity, tall stature and meiotic instability will not fulfill the requirements of a successful commercial salt tolerant crop. To overcome such problems the substituted tritipyrum, in which selected Eb chromosomes are replaced by D genome chromosomes of 6x wheat, was produced from 6x tritipyrum x 6x wheat hybrids (F1: 2n=6x=42, AABBDEb) followed by selfing and backcrossing with 6x tritipyrum. The fertile plants among the above progenies were screened by the genomic fluorescent in situ hybridization technique to identify their Eb and D chromosome constitution. This study showed that producing tritiprum with variable numbers of Eb and D genome chromosomes is feasible and that FISH is a useful technique for determining the number of Eb chromosomes present.

Carbohydrate preference, acid tolerance and bile tolerance in five strains of Bifidobacterium

Aims: To assess the suitability of bifidobacteria for inclusion in synbiotic products on the basis of carbohydrate preference, acid and bile tolerance. Methods and Results: Five strains of Bifidobacterium were analysed for their carbohydrate preference from 12 substrates. Maximum growth rates were used to compare substrate preferences. Galacto-oligosaccharides and isomalto-oligosaccharides were well utilized by all the test species. Most bacteria tested could also utilize at least one type of fructan molecule. To determine transit tolerance of potentially probiotic bifidobacteria, acid and bile resistance was tested. A wide range acid resistance was found. Bile tolerance also varied. Conclusions: GOS and IMO were generally well utilized by the tested species. Other substrates were used to different degrees by the different species. Most bifidobacteria are poorly resistant to strongly acidic conditions with the exception of Bifidobacterium lactis Bb12. Bile tolerances were widely variable and it was shown that caution should be exercised when using colorimetric methods to assess bile tolerance. Significance and Impact of Study: The study allows the comparison of the properties of bifidobacteria, allowing a cost effective screen for the best species for use in synbiotic products to allow better survival and efficacy.