Adventitious root formation (ARF) at the soil surface is one of the most important adaptations to soil flooding or waterlogging. Quantitative trait loci (QTL) controlling ARF under flooding condition were identified in a 94 F 2 individual population by crossing maize (Zea mays L., B64) × teosinte (Z. mays ssp. huehuetenangensis). A base-map was constructed using 66 SSR and 42 AFLP markers, covering 1,378 cM throughout all ten maize chromosomes. The ARF capacity for seedlings was determined by evaluating the degree of root formation at the soil surface following flooding for 2 weeks. ARF showed continuous variation in the F 2 population. Interval mapping and composite interval mapping analyses revealed that the QTL for ARF was located on chromosome 8 (bin 8.05). Utilising a selective genotyping strategy with an additional 186 F 2 population derived from the same cross combination and 32 AFLP primer combinations, regions on chromosomes 4 (bin 4.07) and 8 (bin 8.03) were found to be associated with ARF. Z. mays ssp. huehuetenangensis contributed all of the QTL detected in this study. Results of the study suggest a potential for transferring waterlogging tolerance to maize from Z. mays ssp. huehuetenangensis.
Morphological and anatomical factors such as aerenchyma formation in roots and the development of adventitious roots are considered to be amongst the most important developmental characteristics affecting flooding tolerance. In this study we investigated the lengths of adventitious roots and their capacity to form aerenchyma in three-and four-week-old seedlings of two maize (Zea mays ssp. mays, Linn.) inbred accessions, B64 and Na4, and one teosinte, Z. nicaraguensis Iltis & Benz (Poaceae), with and without a flooding treatment. Three weeks after sowing and following a seven day flooding treatment, both maize and teosinte seedlings formed aerenchyma in the cortex of the adventitious roots of the first three nodes. The degree of aerenchyma formation in the three genotypes increased with a second week of flooding treatment. In drained soil, the two maize accessions failed to form aerenchyma. In Z. nicaraguensis, aerenchyma developed in roots located at the first two nodes three weeks after sowing. In the fourth week, aerenchyma developed in roots of the third node, with a subsequent increase in aerenchyma in the second node roots. In a second experiment, we investigated the capacity of aerenchyma to develop in drained soil. An additional three teosinte species and 15 maize inbred lines, among them a set of flooding-tolerant maize lines, were evaluated. Evaluations indicate that accessions of Z. luxurians (Durieu & Asch. Bird) and two maize inbreds, B55 and Mo20W, form aerenchyma when not flooded. These materials may be useful genetic resources for the development of flooding-tolerant maize accessions.
Measurements of nonstructural carbohydrates (NSC) in plant tissues are important to estimate plant organ resources available for plant growth and stress tolerance or for feed value to grazing animals. A popular commercially available assay kit used to detect glucose with a light‐sensitive dye reaction was recently discontinued and replaced by a test‐tube‐scale glucose kit (GAHK‐20) that assays glucose through enzymatic coupled reactions and the formation of reduced nicotinamide adenine dinucleotide. The objective of this study was to develop a microplate assay method that uses the GAHK‐20 to quantify forage NSC composition. A laboratory microplate enzymatic method was developed for the new glucose kit and evaluated for rapidly assaying NSC components, including glucose, fructose, sucrose, fructan, and starch in 11 species of cool‐season perennial grasses. By standard addition, dilution, and temporal tests of enzyme reactions, we found that this microplate enzymatic assay is a rapid and reliable method to quantify NSC composition in grass forage samples. The microplate method allows analysis of many samples per day and considerably improved time and reagent use efficiencies, especially for a large number of samples. In addition to forage, this method should be suitable for measuring NSC concentrations in fresh or dry tissues of a variety of other plant samples.
As the bioenergy industry expands, producers choosing to shift current forage crop production to dedicated biomass crops can benefit from growing lower risk multipurpose crops that maximize management options. Hybrid forage sorghums (HFS) and sorghum-sudangrass hybrids (SSG) are capable of impressive biomass yields and tolerance to environmental stress. Multiple vegetative harvests (ratoon harvests) of sorghum are possible and there are photoperiod-sensitive sorghums that remain vegetative. However, the response of newer HFS and SSG cultivars to harvest management practices designed for forage or cellulosic feedstock production has not been fully investigated in all environments. The objectives of this study were to: (i) determine biomass production and quality characteristics of a genetically diverse range of HFS, SSG and sudangrass cultivars and evaluate their interaction with harvest system; and (ii) provide data to aid selection of sorghum cultivars for both forage and biofuel uses. Mean yield across all entries and years for a single late season harvest was 27.1 Mg ha -1 of dry matter per year. Mean total yield for a first harvest plus a ratoon crop was 25.5 Mg ha -1 of dry matter per year. However, entries varied for yield and interacted with harvest system. Mean caloric value was 16.5 Gj Mg -1 and modest differences were observed among cultivars evaluated. The best performing entry (cv. Tentaka) yielded 40.3 Mg ha -1 of dry matter for a single late season harvest, demonstrating the biomass potential of existing sorghum cultivars, specifically those possessing photoperiod-and/or thermosensitive genotypes.Sorghum as forage and biomass feedstock B.
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