Genomic characterization of drought tolerance-related traits in spring wheat

Drought tolerance was investigated in ‘C306’, one of the most drought tolerant wheat cultivars bred in India in the 1960’s. An intervarietal mapping population of recombinant inbred lines of the cross ‘C306’ × ‘HUW206’ was evaluated for drought tolerance components, namely potential quantum efficiency of photosystem (PS) II (F_v/F_m), chlorophyll content (Chl), flag leaf temperature (Lt), and grain yield per plant (Gyp) under stress. Three independent experiments were conducted under well-watered and water-stressed conditions in greenhouses and growth chambers at Kansas State University (USA). Five hundred and sixty microsatellite markers covering the entire genome were screened for polymorphism between the parents. A QTL (QLt.ksu-1D) for Lt (low flag leaf temperature under stress) on the short arm of chromosome 1D between markers Xbarc271 and Xgwm337 at LOD 3.5 explained 37% of the phenotypic variation. A QTL for F_v/F_m (QF _v /F _m .ksu-3B) and Chl (QChl.ksu-3B) controlling quantum efficiency of PS II and chlorophyll content under stress were co-localized on chromosome 3B in the marker interval Xbarc68–Xbarc101 and explained 35–40% of the phenotypic variation for each trait. A QTL (QGyp.ksu-4A) for Gyp on chromosome 4A at a LOD value of 3.2 explained 16.3% of the phenotypic variation. Inconsistent QTLs were observed for F_v/F_m on chromosomes 3A, 6A, 2B, 4B, and 4D; for Chl on 3A, 6A, 2B and 4B; and for Lt on 1A, 3A 6A, 3B and 5B. The identified QTLs give a first glimpse of the genetics of drought tolerance in C306 and need to be validated in field experiments using the marker-phenotype linkages reported here.     

Development and evaluation of a loop-mediated isothermal amplification assay for detection of Erwinia amylovora based on chromosomal DNA

A reliable and rapid pathogen detection protocol that utilizes loop-mediated isothermal amplification (LAMP) was developed for detection of Erwinia amylovora, the casual agent of fire blight. The six LAMP primers applied were derived from the highly conserved fragment of the chromosomally amsH gene. Despite the proposed LAMP as well as nested PCR presenting equal values of sensitivity (2?×?10¹?CFU/ml or more) for pure cultures, as compared with conventional PCR (2?×?10³?CFU/ml), both methods were together superior. The specificity assay also showed that the LAMP protocol is species-specific for detection of E. amylovora even in inter-species analysis. Meanwhile, when all 208 naturally infected samples were examined, the specificity value of LAMP was 84%, while conventional and nested PCR could detect only 59% and 73% of the whole collection. Significantly, an independent behaviour versus host plant as well as each strain origin was also observed regarding the current LAMP method as well as other two PCR-based methods. All the results, overall, indicated that the LAMP offers an interesting novel and convenient assay format for the quick and specific chromosomal detection and diagnostic tool of recognition of E. amylovora and therefore presents an alternative to PCR-based assays.     

Mapping of quantitative trait loci for carotenoid pigmentation in flower tepals of Asiatic hybrid lily

Flower pigmentation is one of the most important traits for ornamental plants. To clarify the genetic basis for carotenoid pigmentation in flower tepals of Asiatic hybrid lily (Lilium sp.), we evaluated the segregation of a tepal-carotenoid content among F₁ plants derived from a cross between ‘Montreux’ (having a small amount of carotenoids) and ‘Connecticut King’ (having a large amount of carotenoids), and mapped genetic loci for the carotenoid pigmentation onto the molecular linkage maps of ‘Montreux’ and ‘Connecticut King’ that we constructed previously. The tepal-carotenoid content among the F₁ plants showed continuous segregation, indicating that several genes are associated with this trait. Quantitative trait loci (QTL) analysis identified one QTL, qCARmon6, on the sixth linkage group of the ‘Montreux’ map. qCARmon6 explained 58.2% of the total phenotypic variation, that is, this locus had a large effect on the carotenoid accumulation. The result that qCARmon6 was mapped on the linkage group of ‘Montreux’ which has a small amount of carotenoid pigments in tepals indicates that this locus has a dominant negative effect on carotenoid pigmentation.     

Effect of plant growth promoting rhizobacteria on young apple tree growth and fruit yield under orchard conditions

The effects of rootstocks (M9 and MM 106), cultivars (Granny Smith and Stark Spur Golden) and growth promoting rhizobacteria (OSU-142, OSU-7, BA-8 and M-3) on the tree growth and yield at apple (Malus domestica Borkh) trees were studied in a clay loam soil in the eastern Anatolia region of Turkey in 2002–2004. Plant growth promoting rhizobacteria (PGPR) were capable of producing indole acetic acid (IAA) and cytokinin, but three of them (OSU-7, BA-8 and M-3) were also able to dissolve phosphate. Maximum shoot number of apple trees was found after inoculation with BA-8 followed by OSU-7 and M-3. All the inoculated PGPR strains contributed to the increase in fruit yield of apple when compared to control but it was strongly depended on rootstocks, cultivars and treatments. Plant growth responses were variable and dependent on bacterial strains, rootstock and cultivar and growth parameters evaluated of young apple trees. Newly planted apple trees inoculated with OSU-142, OSU-7, BA-8 and M-3 PGPR increased average shoot length by 59.2, 18.3, 7.0 and 14.3% relative to the control and fruit yield by 116.4, 88.2, 137.5 and 73.7%, respectively. Bacterial inoculation increased shoot diameter from 7.0 to 16.3% when compared to control. The production of plant growth hormones has been suggested as one of the mechanisms by which PGPRs stimulate young apple sapling growth. The growth-promoting effect appears to be direct, with possible involvement of the plant growth regulators indole-3-acetic acid and cytokinin. In view of environmental pollution due to excessive use of fertilizers and high costs of the production of fertilizers, PGPR strains tested in our study have potential to be used for the sustainable and environmentally benign horticultural production.     

Estimation of direct and maternal (co)variance components for pre-weaning growth traits in Muzaffarnagari sheep

Genetic parameters and (co)variance components were estimated for weight at birth and at 15, 30, 45, 60 and 75 days of age for a flock of Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura over a period of 27 years (1976–2002). Records on 5201 lambs descended from 1568 ewes and 170 rams were included in the analysis. Analyses were carried out by REML fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits, and the best model was chosen after testing improvements in log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. Direct heritability estimates were 0.08 ± 0.02 for birth weight and 0.02 ± 0.02, 0.02 ± 0.02, 0.27 ± 0.08, 0.09 ± 0.04, and 0.29 ± 0.08 for weights at 15, 30, 45, 60, and 75 days, respectively. Maternal genetic effects contributed only 4 to 8% of the total phenotypic variance from birth to 30 days of age, and this effect diminished further with increasing age. Maternal heritability was low for pre-weaning growth traits and should have only a small effect on selection response. Estimates of the fraction of variance due to maternal permanent environmental effects were 0.09 ± 0.02, 0.15 ± 0.04, 0.12 ± 0.03, 0.11 ± 0.04, 0.14 ± 0.02, and 0.08 ± 0.04 for body weights at birth and at 15, 30, 45, 60, and 75 days, respectively. These results indicate that selecting for improved maternal and/or direct effects in Muzaffarnagari sheep would generate only slow genetic progress in early growth traits.     

Spatial distribution of nutsedge (Cyperus spp. L.) seed bank in rice growth cycle using geostatistics

A field experiment was conducted to investigate the spatial distribution of nutsedge (Cyperus spp L.) seed bank in rice growth cycle using geostatistics in 2010–11. The sampling from seed banks were performed prior to rice farm preparation and after rice harvest; also weeds density was determined in three different dates during the growing season. The results showed that the highest amount of weed population was belonging to nutsedge (Cyperus spp. L.) including Cyperus difformis, C. rotundus and C. esculentus species. Nugget/sill ratios for all variogram models ranged from 15.2 to 46.9%, indicated that there was strong and moderate spatial correlation as spherical and exponential variograms models between weed and seedling nutsedge at all stages of sampling. Visual assessments of the weed growth in these field indicated that the weed exist in patches, but mapping results showed that the size and morphology of these patches varied within field. In the present study, seed bank patchy pattern was roughly in accordance with seedling germination pattern. Generally the provided seed bank maps can be used not only as information database of seedling germination, but also for predicting of seed bank dynamics and weed management programs.     

Efficacy and timing of application of fungicides for plum rust control in Turkey

Little information is available regarding the efficacy and timing of modern fungicides for the control of plum rust. In this study, modern fungicides, including triazoles, strobilurins, and benzimidazoles, and a classic fungicide (chlorothalonil) were tested under both greenhouse and field experiments. Excellent disease control was obtained by the pre-inoculation application of all fungicides in the greenhouse experiments. However, only triazoles (tebuconazole, difenoconazole, flusilazole and hexaconazole) were effective when applied up to 6 or 7 days after inoculation. Unexpectedly, strobilurins (azoxystrobin and trifloxystrobin) and benzimidazoles (thiophanate-methyl and carbendazim) were not effective when applied at any time after inoculation. In field experiments, early-season fungicide applications effectively inhibited primary infections; however, these applications provided no apparent benefit in preventing secondary infections and premature leaf fall later in the season. All fungicides provided better control over the season and significantly reduced premature leaf fall when applied immediately after rust pustules (uredinia) were first observed. It is suggested that all fungicides tested in this study can be used for plum rust control. Disease monitoring data indicated that disease severity remained low throughout May but dramatically increased in early June. Mid-May is evidently the best time to initiate fungicide sprays against rust on plums; the spray should be applied before or when rust pustules are first observed and when rust is present at low severity.     

Cotton yield and fiber quality affected by row spacing and shading at different growth stages

Carbohydrate production and reproductive structure development in cotton (Gossypium hirsutum) depends on light availability, a determinant of cotton yield. Light availability is decreased by cloud cover or self-shading when cotton plants are grown in dense populations. The objective of this study was to evaluate the effects of shading during cotton growth and its interactions with plant row spacings on yield and fiber quality. Three independent experiments were conducted as follows: in Paranapanema (23°39′S; 48°58′W), cotton was planted in November in row spacings of 0.45, 0.75 and 0.96 m; in Primavera do Leste (15°33′S; 54°11′W), planting was in January with at row spacings of 0.45 and 0.76 m; and in Chapadão do Céu (18°38′S; 52°40′W), cotton was planted in February in rows spaced at 0.45 and 0.90 m. Plants were exposed to shading during the phenological stages B1 (floral bud), F1 (early flowering), PF (peak flowering) and 3OB (fruit maturity). In addition, there was one treatment without shade. There were no interactions of crop spacing with shading. Increasing plant population and shading both decreased net photosynthetic rate. The number of bolls m⁻² increased with higher plant populations only when planting was delayed, and were not affected by shading. When cotton was planted in November and January, higher yields were obtained at 0.75/0.76 m, but when planting was delayed to February, 0.45 m resulted in higher yields with no effect on fiber quality. Shading for eight or ten days decreases boll weight and yields, but do not affect fiber quality. Cotton yield is the most decreased when shading occurs during flowering. These results may be used to build management strategies to minimize shading effects by adjusting cotton sowing time and plant density, by selecting cultivars with increased shade tolerance and by choosing an adequate irrigation period to improve yield.