Assessment of Five Chilling Tolerance Traits and GWAS Mapping in Rice Using the USDA Mini-Core Collection

Rice (Oryza sativa L.) is often exposed to cool temperatures during spring planting in temperate climates. A better understanding of genetic pathways regulating chilling tolerance will enable breeders to develop varieties with improved tolerance during germination and young seedling stages. To dissect chilling tolerance, five assays were developed; one assay for the germination stage, one assay for the germination and seedling stage, and three for the seedling stage. Based on these assays, five chilling tolerance indices were calculated and assessed using 202 O. sativa accessions from the Rice Mini-Core (RMC) collection. Significant differences between RMC accessions made the five indices suitable for genome-wide association study (GWAS) based quantitative trait loci (QTL) mapping. For young seedling stage indices, japonica and indica subspecies clustered into chilling tolerant and chilling sensitive accessions, respectively, while both subspecies had similar low temperature germinability distributions. Indica subspecies were shown to have chilling acclimation potential. GWAS mapping uncovered 48 QTL at 39 chromosome regions distributed across all 12 rice chromosomes. Interestingly, there was no overlap between the germination and seedling stage QTL. Also, 18 QTL and 32 QTL were in regions discovered in previously reported bi-parental and GWAS based QTL mapping studies, respectively. Two novel low temperature seedling survivability (LTSS)–QTL, qLTSS3-4 and qLTSS4-1, were not in a previously reported QTL region. QTL with strong effect alleles identified in this study will be useful for marker assisted breeding efforts to improve chilling tolerance in rice cultivars and enhance gene discovery for chilling tolerance

Seed factors involved in early seedling establishment of Festuca arundinacea (tall fescue) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology and Biotechnology at Massey University, New Zealand

New Zealand pastures are commonly based on vigorously growing Lolium (ryegrass) species. In many situations, however, it is often advantageous to combine the vigorous qualities of Lolium species with the versatility of other species such as Festuca arundinacea (tall fescue) to result in a pasture which is high in quality all year. F. arundinacea, however, has poor seedling vigour which places it at a competitive disadvantage when sown with Lolium. During seedling establishment, the seedling is dependent upon the food reserves present in the seed. The nature and amount of these reserves and the ability of the seed to mobilise them are therefore likely to have an affect on seedling perfonnance. While much knowledge exists about the processes involved in seed reserve mobilisation in some cereals, little information is available for pasture grasses. An in depth investigation of the behaviour of one seed lot of F. arundinacea was undertaken in order to gain a more detailed understanding of germination, reserve mobilisation and establishment processes in pasture grasses and how they relate to the processes of seedling growth. Comparisons between this species and Lolium multiflorum (Italian ryegrass) were undertaken throughout the study. Germination and seedling growth of the F. arundinacea seed lot was found to be heterogenous and slower than in L. multiflorum due to later radicle emergence. Mobilisation of reserves and the onset of α-amylase activity correlated well with the utilisation of reserves in L. multiflorum. In both prechilled and non prechilled F. arundinacea seeds, however, anomalies were identified in the process which indicated that reserve mobilisation was less tightly coupled to seedling growth in F. arundinacea. Reciprocal plot analyses indicated that the beneficial effects of prechilling in most seeds of the F. arundinacea seed lot were not related to residual dormancy but were a thermal time benefit. It appears prechilling was allowing rate limiting steps in embryo growth to be advanced before visible germination. Apart from this, no real differences were detected in the way the two species mobilised reserves. Differences in the appearance of α-amylase isoenzymes of F. arundinacea at different times during germination indicated that gene expression may be under some complex differential control mechanisms during germination and reserve mobilisation. Prechilling was not found to change the spectrum of isoenzymes, but merely to advance the time-course in which different isoenzymes appeared. There were also distinct differences in α-amylase isoenzyme patterns between F. arundinacea and L. multiflorum, and also wheat. Preliminary studies indicated that exogenous gibberellic acid was more effective in promoting α-amylase production in L. multiflorum than in F. arundinacea. However, α-amylase production in F. arundinacea was more susceptible to promotion by prechilling. This study has identified a wide range of variables impacting on germination and seedling establishment in F. arundinacea. This, together with the lack of previous detailed studies on grass seed germination and seedling growth and the lack of literature on F. arundinacea germination in particular, highlights the enormity of the task ahead of extending key areas of this study to different seed lots and species

Effect of Growing Season on Growth and Relation of Height and Above Ground Biomass of Avicennia Marina

Relation of height of seedling stands and above ground biomass is an important indicator of successful stand establishment and effectivity of carbon cycle which requires further study. This research aimed to study the growth level of Avicennia marina seedling planted in dry season and rainy season and to analyze the relation of mangrove stand height to above ground biomass of seedling for each season. This research was conducted through field experiment involving grouped random design including group of seedling plantation in dry season and rainy season with 40 replication for each group and 6 months of experiment period. Data collection including stand height above ground biomass, followed by data analysis on the relation of seedling height and above ground biomass. The result showed that the growth of mangrove stand planted in rainy season was better than those planted on dry season. Average height of mangrove Avicennia marina stand planted in dry season was 30,5 ± 7,3 cm while stand height of mangrove planted in rainy season was 42,7 ± 11,4 cm. Above ground biomass data showed the average of 4,1 ± 1,8 gr in the dry season treatment group and 6,6 ± 2,5 gr in the rainy season treatment group. Regression analysis on the relation of stand height and above ground biomass of Avicennia marina seedling showed that the above ground biomass was significantly affected by stand height both for dry season and rainy season treatments. But, there was a difference on the determination index and the coefficient of the effect on each treatment groups. The relation of stand height and above ground biomass was Y = 0.1871 X0.8832 with R2 = 0.2802 for the dry season group and Y = 0.0506 X1.2892 with R2 = 0.743 for the rainy season group.

Differences between spring wheat cultivars for emergence and early development after seed infection with Fusarium culmorum

Infection of wheat seeds with Fusarium spp. causes seedling blight. As a result of this disease, fields sown with infected seeds show a reduced plant density. This is especially a problem in organic agriculture, for which currently no practical seed disinfection methods are available. In the present project we investigated whether spring wheat cultivars differ in sensitivity to seedling blight, whether the possible differences could be linked to cultivar differences in early growth rates, and what size the delay in canopy closure resulting from the plant reductions was. Six spring wheat cultivars (Melon, Lavett, SW Kungsjet, Epos, Pasteur, Thasos), containing three infection levels (averages 5, 15 and 27%) of Fusarium culmorum were obtained and were sown in a field experiment in 2006 in 4 repetitions. Measurements included percentage of emergence, light interception and above ground dry matter to calculate relative growth rates. Infection of seeds with F. culmorum resulted in lower plant densities and a delay in time to 10% light interception of up to 5 days. First preliminary results also show that cultivars differ for sensitivity to seedling blight, and that cultivars with higher early growth rates appeared to be less sensitive to seedling blight, with the exception of cultivar Thasos. If future experiments confirm this relation, it could be used to select cultivars which are more resistant to seedling blight

Impact of forest management regimes on ligneous regeneration in the Sudanian savanna of Burkina Faso

Annual early fire, selective tree cutting and grazing exclusion are currently used to manage the State forests of the Sudanian savanna of Burkina Faso, West Africa. Such prescriptions, however, are not based on experimental evidence. The long-term effects of such management on seedlings and saplings and the germination of selected tree species are discussed. Seedling quality attributes are also assessed. Studies over a 10-year period examined the effects of the three management regimes on species richness and population density. Burkea africana Kook, f., Detarium microcarpum Guill. et Perr., Entada africana Guill. et Perr., and Pterocarpus erinaceus Poir. seed germination was tested for different temperatures, light conditions, dry heat treatments and scarification methods. The quality of Acacia macrostachya Reichenb.ex DC. and P. erinaceus planting stock was evaluated in relation to nursery production period; field performance was assessed with and without watering. Fire, grazing, and selective tree cutting acted independently on sapling and seedling population dynamics. Early fire reduced sapling recruitment; moderate grazing had no significant effect. Although the overall seedling population density was not affected by any of the treatments, fire and grazing had strong effects on single-stemmed seedling density. Ordination using Principal Component Analysis of the seedling population data revealed species-specific responses to treatments, in particular an increase of lianas compared to other species. D. microcarpum and E. africana seeds did not exhibit dormancy. Exposing B. africana seeds to 95-97% sulphuric acid for 15–20 minutes broke their physical dormancy. All seeds tested were neutrally photoblastic, with an optimal germination temperature of 25–35 oC. E. africana, however, germinated over a wider temperature range. P. erinaceus seeds did not tolerate heat shock; while D. microcarpum and E. africana seeds responded positively at low intensity. Eighteen months after outplanting, survival and growth of Acacia macrostachya and Pterocarpus erinaceus seedlings were not affected by their initial size. Drought and non-drought factors affected seedling survival. Performance of P. erinaceus seedlings could be predicted from initial root collar diameter; more data will be required to build a reliable model. This thesis recommends the use of annual early fire as a forest management tool to be continued if timing, weather conditions and other factors affecting fire intensity are given due consideration. Moderate level of grazing does not affect seedling and sapling recruitment. The current prohibition on grazing State forests may need revision to allow multiple-use management. The low seedling density of socio-economically valuable species indicates that natural regeneration could be supplemented by planting high quality seedlings

Postgerminative growth and lipid catabolism in oilseeds lacking the glyoxylate cycle

The glyoxylate cycle is regarded as essential for postgerminative growth and seedling establishment in oilseed plants. We have identified two allelic Arabidopsis mutants, icl-1 and icl-2, which lack the glyoxylate cycle because of the absence of the key enzyme isocitrate lyase. These mutants demonstrate that the glyoxylate cycle is not essential for germination. Furthermore, photosynthesis can compensate for the absence of the glyoxylate cycle during postgerminative growth, and only when light intensity or day length is decreased does seedling establishment become compromised. The provision of exogenous sugars can overcome this growth deficiency. The icl mutants also demonstrate that the glyoxylate cycle is important for seedling survival and recovery after prolonged dark conditions that approximate growth in nature. Surprisingly, despite their inability to catalyze the net conversion of acetate to carbohydrate, mutant seedlings are able to break down storage lipids. Results suggest that lipids can be used as a source of carbon for respiration in germinating oilseeds and that products of fatty acid catabolism can pass from the peroxisome to the mitochondrion independently of the glyoxylate cycle. However, an additional anaplerotic source of carbon is required for lipid breakdown and seedling establishment. This source can be provided by the glyoxylate cycle or, in its absence, by exogenous sucrose or photosynthesis

The effect of temperature, soil nitrogen and gastropods on _Thuja plicata_ growth and reproduction

Humans are changing the environment. For example, nitrogen deposition, rising temperatures, and non-native species are influencing plant communities. These changes have and will continue to affect trees, thus, understanding the response of species to global change will help conservationists plan for the future. Urban areas already experience higher temperatures, elevated CO~2~, greater nitrogen levels, and more non-native species compared to rural areas. The response of trees to urban parks and park edges can therefore be used as a proxy for the net effects of global change on trees. We investigate the growth and reproduction of _Thuja plicata_, a native Pacific Northwest conifer, in both urban and rural forest fragments to understand global change impacts. Data collected from sites include hourly temperature, soil NO~3~^-^, seedling counts, and an increment core. After observing extremely low conifer germination rates across sites, we concluded that factors such as herbivory might be important. Gastropods have been shown to impact communities through consumption of plants at the seedling stage, and to limit seedling survival of a European conifer. The effects of soil moisture, soil nitrogen, and gastropod herbivory on _Thuja plicata_ seedlings was analyzed experimentally to determine the relative effect each might be having on the observed germination rate. Our results suggest that urban forest edges resemble future global change conditions of higher temperature and nitrogen. These global change factors appear to be positively influencing tree growth, suggesting that _Thuja plicata_ will benefit from future conditions. However, low seedling recruitment may be a concern, because it appears that urban and rural forests are currently failing to regenerate on their own. Introduced gastropods could play a role, as they have the ability to reduce seedling biomass significantly. The relative impacts of invasive slug herbivory and other global change factors on native conifer recruitment should be prioritized in future study

Seedling salt tolerance in tomato

Soils with higher concentrations of salt are becoming more and more a constraint for many crops to obtain high yields. Wild tomato species, adapted to adverse environments, are a potential reservoir for genes underlying quantitative trait loci (QTL) related to salt tolerance in tomato. In this study two introgression line (IL) libraries derived from two different wild species, Solanum pennellii LA716 and Solanum lycopersicoides LA2951, were used to identify QTLs for salt tolerance in the seedling stage. In the S. pennellii IL library, four major QTLs were identified on chromosomes 6, 7 and 11. In the S. lycopersicoides IL library, six major QTLs were discovered which are located on chromosomes 4, 6, 9 and 12. Co-localization of QTLs on chromosome 6 in the two IL libraries and previously reports hinted that this locus might be conserved in the tomato crop. Three S. pennellii ILs (IL6-2, IL7-1 and IL7-5) harboring QTLs on chromosome 6 and 7 were crossed. Semi-dominance and dominance were shown for these three QTLs, and non-additive and epistatic interactions between them were observe

Effects of Stock Type and Planter Experience on the Time Required to Plant Loblolly Pine Seddlings

Inexperienced workers planted container-grown and bare-root seedlings of loblolly (Pinus taeda L.) on a rocky, upland site near Batesville, AR in a comparison of planting speed and survivability. Planting speed depended on the type of seedling planted and the amount of planting experience. Significantly less time was required to plant an acre with container-grown than bare-root seedlings. Experience increased the consistency and speed of planting for both seedling types

Fertirrigação e regulador de crescimento na produção de mudas de café em tubete

The use of quality seedlings is important in establishing a productive coffee crop. However, the most widely used method to produce coffee seedlings is time consuming (6-12 months) and lacks new production technologies. This study aimed to assess the use of fertigation and a growth regulator in the production of coffee seedlings, in order to develop a system faster than the conventional method. For that, Topázio coffee cultivar seeds were pre-germinated and planted in tubes flled with substrate (composted pine bark), in a protected nursery. A randomized block design was used, in a 4 x 2 (fertigation levels x the use or not of growth regulator) factorial scheme, with four replications. Daily fertigation positively influenced all the growth variables evaluated. The foliar spraying of the growth regulator had little effect on seedling growth. When compared to the conventional system described in the literature, the coffee seedling production system described here reduced, by around 60 days, the production time and enables a largescale productionA utilização de mudas de boa qualidade é importante para a formação de uma lavoura produtiva de café. Entretanto, o método mais utilizado atualmente para a produção de mudas de cafeeiro é demorado (6-12 meses) e carece de novas tecnologias de produção. Objetivou-se avaliar a utilização de fertirrigação e regulador de crescimento na produção de mudas de cafeeiro, com vistas ao desenvolvimento de um sistema mais rápido que o sistema convencional de produção. Para isso, sementes da cultivar Topázio foram pré-germinadas e plantadas em tubetes com substrato (casca de pinus compostada), em viveiro coberto. Adotou-se o delineamento de blocos ao acaso, em esquema fatorial 4 x 2 (níveis de fertirrigação x utilização ou não de regulador de crescimento), com quatro repetições. A fertirrigação diária influenciou positivamente em todas as variáveis de crescimento analisadas. A pulverização foliar do regulador de crescimento apresentou pouco efeito sobre o crescimento das mudas. Quando comparado ao sistema convencional descrito na literatura, o sistema de produção de mudas de cafeeiro descrito neste trabalho reduziu, em cerca de 60 dias, o tempo de produção e permite a produção em larga escala.info:eu-repo/semantics/publishedVersio