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1.
We report the effects of the root hemiparasite Striga hermonthica (Del.) Benth. on the growth and photosynthesis of two cultivars of sorghum: CSH-1, a susceptible variety, and Ochuti, which shows some tolerance to S. hermonthica in the field. Within 4 d of parasite attachment to the host roots, infected plants of both cultivars were significantly shorter than uninfected controls. At 55 d, infected plants of both cultivars had significantly less shoot and root biomass, and significantly smaller leaf areas than uninfected controls. The dry weight of S. hermonthica attached to host roots was insufficient at this stage to explain the decreased growth in terms of a competing sink for carbon and nitrogen. Leaf chlorophyll and nitrogen per unit area were greater in infected plants of both cultivars compared with control plants. However, whereas photosynthesis and transpiration in young leaves of infected CSH-1 plants declined with time when compared with controls, the rates in infected Ochuti plants were similar to those in uninfected controls throughout the time course of observation. In both cultivars, a strong correlation was observed between the rate of photosynthesis and stomatal conductance during photosynthetic induction, but infection resulted in a much slower induction than in controls. In CSH-1 plants, both steady-state photosynthesis and stomatal conductance were lower than in controls, whereas in leaves of Ochuti steady-state photosynthesis and stomatal conductance eventually reached the same values as in the control leaves. Results from AlCi analysis and also from determination of 13C isotope discrimination were consistent with a stomatal limitation to photosynthesis in the leaves of Striga-infected plants. The concentration of the plant growth regulator abscisic acid (ABA) was measured in the xylem sap of infected CSH-1 plants only, and was found to be twice that of uninfected plants. A possible role of ABA in determining host response to infection by S. hermonthica is discussed.  相似文献   
2.
Sweet sorghum (Sorghum bicolor L.) is a type of cultivated sorghums and has been recognized widely as potential alternative source of bio-fuel because of its high fermentable sugar content in the stalk. A substantial variation of sugar content and related traits is known to exist in US sweet sorghum. The objectives of the study were to assess the genetic diversity and relationship among the US sweet sorghum cultivars and lines using SSR markers and to examine the genetic variability within sweet sorghum accessions for sugar content. Sixty-eight sweet sorghum and four grain sorghum cultivars and lines were genotyped with 41 SSR markers that generated 132 alleles with an average of 3.22 alleles per locus. Polymorphism information content (PIC) value, a measure of gene diversity, was 0.40 with a range of 0.03–0.87. The genetic similarity co-efficient was estimated based on the segregation of the 132 SSR alleles. Clustering analysis based on the genetic similarity (GS) grouped the 72 sorghum accessions into 10 distinct clusters. Grouping based on clustering analysis was in good agreement with available pedigree and genetic background information. The study has revealed the genetic relationship of cultivars with unknown parentage to those with known parentage. A number of diverse pairs of sweet sorghum accessions were identified which were polymorphic at many SSR loci and significantly different for sugar content as well. Information generated from this study can be used to select parents for hybrid development to maximize the sugar content and total biomass, and development of segregating populations to map genes controlling sugar content in sweet sorghum.  相似文献   
3.
Bacteria causing mottled stripe disease in sugar cane, known asPseudomonas rubrisubalbicans, were shown to be able to fix molecular N2 and to grow on it. The root associated diazotroph known asHerbaspirillum seropedicae, after artificial inoculation caused mottled stripe disease symptoms on sorghum and Napier grass but not on sugar cane. Both bacteria could be reisolated from leaves even 60 days after. Sugar cane leaves contained large numbers of these bacteria even in the uninoculated controls. Additional physiological characteristics of six strains ofP. rubrisubalbicans were compared with those of twoH. seropedicae strains and were shown to be very similar.  相似文献   
4.
QTL for stem sugar-related and other agronomic traits were identified in a converted sweet (R9188) × grain (R9403463-2-1) sorghum population. QTL analyses were conducted using phenotypic data for 11 traits measured in two field experiments and a genetic map comprising 228 SSR and AFLP markers grouped into 16 linkage groups, of which 11 could be assigned to the 10 sorghum chromosomes (SBI-01 to SBI-10). QTL were identified for all traits and were generally co-located to five locations (SBI-01, SBI-03, SBI-05, SBI-06 and SBI-10). QTL alleles from R9188 were detected for increased sucrose content and sugar content on SBI-01, SBI-05 and SBI-06. R9188 also contributed QTL alleles for increased Brix on SBI-05 and SBI-06, and increased sugar content on SBI-03. QTL alleles from R9403463-2-1 were found for increased sucrose content and sucrose yield on SBI-10, and increased glucose content on SBI-07. QTL alleles for increased height, later flowering and greater total dry matter yield were located on SBI-01 of R9403463-2-1, and SBI-06 of R9188. QTL alleles for increased grain yield from both R9403463-2-1 and R9188 were found on SBI-03. As an increase in stem sugars is an important objective in sweet sorghum breeding, the QTL identified in this study could be further investigated for use in marker-assisted selection of sweet sorghum.  相似文献   
5.
为评价新入侵害虫草地贪夜蛾对我国不同品种玉米的为害潜能,本文采用组建实验种群生命表的方法研究了草地贪夜蛾对3种甜质型玉米(穗甜1号、正甜68和华金甜1号)以及3种糯质型玉米(京科糯2000、广黑甜糯和广糯1号)的生存适合度,分析了草地贪夜蛾生物学指标与玉米叶片主要营养物质及粗纤维含量间的相关性。结果表明: 取食甜质型玉米的草地贪夜蛾的幼虫存活率、蛹重、雌成虫产卵量均显著高于取食糯质型玉米;取食甜质型玉米草地贪夜蛾的内禀增长率介于0.1566~0.1843,净生殖力介于187.97~353.35,也均高于取食糯质型玉米(内禀增长率介于0.0998~0.1465,净生殖力介于25.89~95.34),表明取食甜质型玉米的草地贪夜蛾具有更高的种群增长能力。甜质型玉米叶片中主要营养物质维生素C、淀粉、可溶性糖、蛋白质、脂肪、总氨基酸及粗纤维的含量普遍高于糯质型玉米,草地贪夜蛾的净生殖力与维生素C、淀粉、可溶性糖、蛋白质及粗纤维的含量均存在显著正相关关系。草地贪夜蛾在甜质型玉米上具有更高的生存适合度。  相似文献   
6.
Soil and crop management practices may influence biomass growth and yields of cotton (Gossypium hirsutum L.) and sorghum (Sorghum bicolorL.) and sequester significant amount of atmospheric CO2in plant biomass and underlying soil, thereby helping to mitigate the undesirable effects of global warming. This study examined the effects of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops [legume (hairy vetch) (Vicia villosa roth), nonlegume (rye) (Secale cerealeL), hairy vetch/rye mixture, and winter weeds orno covercrop], and three N fertilization rates (0, 60–65, and 120–130 kg N ha –1) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain, their stalks (stems + leaves) and roots, and underlying soil from 2000 to 2002 in central Georgia, USA. A field experiment was conducted on a Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults). In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha –1 but in stalks, it was greater in ST with 60 and 120 kg N ha –1 than in CT with 0 kg N ha –1. In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha –1 than in NT with or without N rate. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha –1 and in sorghum ranged from 3.4 to 7.2 Mg ha –1. Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. In NT, soil organic C at 0–10 cm depth was greater in vetch with 0 kg N ha –1 or in vetch/rye with 120–130 kg N ha –1 than in weeds with 0 and 60 kg N ha –1 but at 10–30 cm, it was greater in rye with 120–130 kg N ha –1 than in weeds with or without rate. In ST, soil organic C at 0–10 cm was greater in rye with 120–130 kg N ha –1 than in rye, vetch, vetch/rye and weeds with 0 and 60 kg N ha –1. Soil organic C at 0–10 and 10–30 cm was also greater in NT and ST than in CT. Since 5 to 24% of C accumulation in lint and grain were harvested, C sequestered in cotton and sorghum stalks and roots can be significant in the terrestrial ecosystem and can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Conservation tillage, such as ST, with hairy vetch/rye mixture cover crops and 60–65 kg N ha –1 can sustain C accumulation in cotton lint and sorghum grain and increase C storage in the surface soil due to increased C input from crop residues and their reduced incorporation into the soil compared with conventional tillage, such as CT, with no cover crop and N fertilization, thereby maintaining crop yields, improving soil quality, and reducing erosion.  相似文献   
7.
Developmental changes and effects of various abiotic stresses on peptidyl prolyl cis-trans isomerase (PPIase) activity were studied in the seedlings of sorghum [Sorghum bicolor (L.) Moench cv. CSH-6]. The PPIase activity of sorghum seedlings markedly decreased after two days of germination. Up to 90 % of the PPIase activity was inhibited by cyclosporin-A. Maximal increase in specific PPIase activity in the 3-d-old seedlings was observed in response to osmotic stress and it was transient in nature. The stress-induced enhancement in PPIase activity, depending upon tissue and stress treatment, was due to induction of cyclophilins as well as other PPIases. Osmotic stress-induced enhancement in PPIase activity in the drought susceptible cv. SPRU-94008B was maximal in roots, as compared to shoots in the drought tolerant cv. ICSV-272. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
8.
Successful modification of plant cell-wall composition without compromising plant integrity is dependent on being able to modify the expression of specific genes, but this can be very challenging when the target genes are members of multigene families. 4-coumarate:CoA ligase (4CL) catalyzes the formation of 4-coumaroyl CoA, a precursor of both flavonoids and monolignols, and is an attractive target for transgenic down-regulation aimed at improving agro-industrial properties. Inconsistent phenotypes of transgenic plants have been attributed to variable levels of down-regulation of multiple 4CL genes. Phylogenetic analysis of the sorghum genome revealed 24 4CL(-like) proteins, five of which cluster with bona fide 4CLs from other species. Using a map-based cloning approach and analysis of two independent mutant alleles, the sorghum brown midrib2 (bmr2) locus was shown to encode 4CL. In vitro enzyme assays indicated that its preferred substrate is 4-coumarate. Missense mutations in the two bmr2 alleles result in loss of 4CL activity, probably as a result of improper folding as indicated by molecular modeling. Bmr2 is the most highly expressed 4CL in sorghum stems, leaves and roots, both at the seedling stage and in pre-flowering plants, but the products of several paralogs also display 4CL activity and compensate for some of the lost activity. The contribution of the paralogs varies between developmental stages and tissues. Gene expression assays indicated that Bmr2 is under auto-regulatory control, as reduced 4CL activity results in over-expression of the defective gene. Several 4CL paralogs are also up-regulated in response to the mutation.  相似文献   
9.
Abstract

Experiments were carried out from 2002 to 2003 to determine the most suitable form of fungal delivery for possible use by farmers in biological control of Striga hermonthica. Six mycoherbicides were developed, based on Fusarium oxysporum isolated from wilted S. hermonthica. In mycoherbicide formulation, rock phosphate powder, sorghum bran and gum arabic powder were used as carriers. Besides its role as a carrier, gum arabic powder was used as a sticker. There were three carriers with two formulations each, making six treatments altogether. Living propagule studies were based on colony, mycelium and conidium number of F. oxysporum. In greenhouse evaluation of mycoherbicides, each kg sorghum seed was coated with 10 g mycoherbicide before sowing. Carrier rock phosphate powder with gum arabic powder as a sticking agent was the most suitable form of its delivery for use by peasant farmers.  相似文献   
10.
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