Strains of Fusarium moniliforme (Gibberella fujikuroi mating population A) that differ in fu-monisin production in vitro were previously identified in a Kansas field population. One strain that produced high levels of fumonisins and two strains that produced very low levels of fu-monisins were applied to maize kernels at planting at the Rocky Ford Farm near Manhattan, Kansas. The distribution of fumonisins in symptomatic and symptomless kernels from individual harvested ears was determined by high performance liquid chromatography, and the distribution of the three applied strains in the kernels was determined by vegetative compatibility group analysis. Both symptomatic and symptomless kernels were extensively colonized with F. moniliforme, but the highest levels of fumonisins were in the symptomatic kernels. All three applied strains were recovered from kernels in 1993, and two of them were recovered from kernels in 1994. However, a high frequency of ear and kernel infection with a strain that produced little fumonisin in vitro did not consistently decrease the level of fumonisins. The frequency of infection with fumonisin low-producing strains may have been too low for competitive exclusion of naturally occurring fumonisin high-producing strains. Also, strains that are low-fumonisin producers under laboratory conditions may be high producers in the field.
To transform grain sorghum (Sorghum bicolor (L.) Moench) with a visual reporter gene (gfp) and a target gene (tlp), three genotypes (two inbreds, Tx 430 and C401, and a commercial hybrid, Pioneer 8505) were used. We obtained a total of 1011 fertile transgenic plants from 61 independent callus lines, which were produced from 2463 zygotic immature embryos via Agrobacterium-mediated transformation. The reporter gene, gfp, encoding green fluorescent protein (GFP), was used as a visual screening marker, and the target gene, tlp, encoding thaumatin-like protein (TLP), was chosen for enhancing resistance to fungal diseases and drought. Both genes were under the control of the maize ubi 1 promoter in the binary vector pPZP201. A total of 320 plants showing GFP expression, derived from 45 calli, were selected and analyzed by Southern blot analysis. There was a 100% correlation between the GFP expression and the presence of the target gene, tlp, in these plants. Transgenic plants showing strong TLP expression were confirmed by Western blotting with antiserum specific for TLP. The transgene segregated in various ratios among progeny, which was confirmed by examining seedlings showing GFP fluorescence. The progeny also showed different copy numbers of transgenics. This report describes the successful use of GFP screening for efficient production of stably transformed sorghum plants without using antibiotics or herbicides as selection agents.
Forty‐five drought tolerant sorghum [Sorghum bicolor (L.) Moench] genotypes were screened for stalk rot resistance by artificial inoculation with Fusarium proliferatum in field trials near Manhattan, KS, in 2000. Four lines, SC134, SC1154, SC1039, and SC564, were identified with lesions that were smaller than the standard resistant check, SC599. These lines and four other checks were intercrossed in a Design II mating scheme with ‘AWheatland’ and ‘ARedlan’ to produce hybrids for further testing. The inbred parent lines and corresponding hybrids were evaluated for resistance to four major stalk rot pathogens, F. proliferatum, F. thapsinum, F. andiyazi, and Macrophomina phaseolina, using randomized complete block designs in field trials near Manhattan and Hesston, KS, in 2001. Significant differences in lesion length were detected among the inbred parent lines and their corresponding hybrids. Comparisons among entries indicated that crosses of SC701 and SC564 were susceptible and produced very large lesions following inoculation with each of the stalk rot pathogens evaluated in this study. Only small lesions were produced in SC599 and its hybrids following inoculation with either Fusarium species or M. phaseolina SC134 also exhibited high levels of resistance to Fusarium species and SC35 to M. phaseolina Comparisons among pathogens showed that inoculations with M. phaseolina produced larger lesions than the Fusarium species in most sorghum genotypes. The most resistant accessions in these studies were all from East Africa; therefore, an analysis of genetic diversity was conducted to evaluate the pattern of genetic relationships among the full set of drought tolerant lines. DNA fingerprinting followed by cluster analyses grouped the entries into five distinct clusters, mainly according to geographical origin. Three of the resistant lines grouped together in a cluster that contained mostly Ethiopian landraces while SC599 grouped in another cluster.
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