Assessment of the protein quality of 15 new northern adapted cultivars of quality protein maize using amino acid analysis.

Amino acid determinations were carried out on 15 new northern adapted cultivars of quality protein maize (QPM) containing opaque-2 modifier genes to ascertain whether their amino acid scoring patterns could be used to select high-lysine QPM genotypes and to assess their protein quality. Total protein in these cultivars ranged from 8.0 to 10.2% compared to two commercial maize varieties, Dekalb DK435 (7.9%) and Pioneer 3925 (10.3%). Four of these QPM genotypes, QPM-C26, QPM-C21, QPM-C79, and QPM-C59, contained high levels of lysine (4.43-4.58 g of lysine/100 g of protein), whereas the remaining varied from 3.43 to 4.21 g of lysine/100 g of protein, compared to Dekalb DK435 and Pioneer 3925, which contained 2.9 and 3. 1 g of lysine/100 g of protein, respectively. Although lysine is the first limiting amino acid in QPM inbreds, the high-lysine QPM genotypes may supply approximately 70.2-72.6% of human protein requirements, compared to 46.2% for Dekalb DK435 and 50.1% for Pioneer 3925, 55-63% for oats, and 59-60.3% for barley. Northern adapted QPM genotypes may have the potential to increase their lysine content even further, either by an increase in specific high-lysine-containing nonzein proteins, such as the synthesis of factor EF-1a, or by a further reduction in the 19 and 22 kDa alpha-zein in the endosperm or both. This knowledge could assist maize breeders in the selection of new high-performance QPM genotypes with improved protein quality and quantity.

Improved diagnosis of cowpea aphid-borne mosaic virus in Africa: significance for cowpea seed-indexing, breeding programs and potyvirus taxonomy.

Large-scale surveys in Africa for blackeye cowpea mosaic (B1CMV) and cowpea aphid-borne mosaic (CABMV) showed that several CABMV isolates from Southern Africa were either not or poorly recognized by monoclonal antibodies prepared to isolates collected in West Africa. Selection of three new monoclonal antibodies prepared against the Maputo (Mozambique) isolate of CABMV, and their incorporation into a revised panel of monoclonal antibodies, resulted in the assignment of four of these new CABMV isolates to existing serotypes (II, IV, and V) and three others to a new serotype (VI). The South African isolate of passiflora mosaic virus was shown to be related to CABMV isolates in serotype IV. It is proposed that CABMV isolates be assembled into a distinct species in the legume-infecting, aphid-transmissible potyviruses.

Leaf profile of maize resistance factors to European corn borer,Ostrinia nubilalis.

The feeding preference of European corn borer larvae for immature whorl tissue of maize was examined by conducting leaf bioassays and quantifying resistance factors along the length of mid-whorl leaves from the maize synthetic BS9(C4) developed by recurrent selection for resistance. Potential resistance factors that were quantified included percent foliar nitrogen, gravimetric determination of soluble metabolites and fiber, soluble phenolics and hydroxamic acids, cell-wall-bound phenolics, leaf toughness, and UV absorbance of the epidermal cell wall determined by microspectrophotometry. Larvae consumed immature tissue at a higher rate than more mature tissue outside of the whorl, despite higher levels of DIMBOA in immature tissue. Consumption rate was highly negatively correlated with epidermal cell wall absorbance and leaf toughness. Fiber content and phenolic fortification of cell walls are proposed as the major resistance components that influence European corn borer feeding preference within the resistant synthetic BS9(C4).

Capsid protein properties of cowpea aphid-borne mosaic virus and blackeye cowpea mosaic virus confirm the existence of two major subgroups of aphid-transmitted, legume-infecting potyviruses.

A study of the capsid proteins of different legume-infecting potyviruses using specific monoclonal antibodies on immunoblots of crude extracts from infected plants revealed that cowpea aphid-borne mosaic virus (CAMV) and blackeye cowpea mosaic virus (BICMV) have coat protein M(r) values of 32K and 35K, respectively. Immunoblot comparisons of BICMV, peanut stripe mosaic virus (PStV), bean common mosaic virus (BCMV) and azuki bean mosaic virus (AzMV) revealed equal reactivity of their 35K coat proteins. Similar comparisons between CAMV and the necrotic strain of BCMV (isolate NL3) showed a serological relationship between their 32K coat proteins, results providing the first evidence of a possible similarity between CAMV and BCMV NL3. Peptides from trypsin digests of the coat proteins of several of these legume-infecting potyviruses were analysed by HPLC. Comparison of the peptide profiles confirmed the serological results in distinguishing the two subgroups. Peptide profiles of coat protein from BICMV, PStV, AzMV and BCMV were almost identical, results suggesting that they could be considered as strains of one virus. In contrast, peptide profiles of various CAMV serotypes and BCMV NL3 were distinct from the first group and exhibited limited similarities to each other.

Involvement of the cucumber necrosis virus coat protein in the specificity of fungus transmission by Olpidium bornovanus.

Cucumber necrosis (CNV) and the cherry strain of tomato bushy stunt (TBSV-Ch) are tombusviruses which differ in transmissibility by the fungus Olpidium bornovanus (Sahtiyanci) Karling (= O. radicale Schwartz and Cook). Zoospores acquire and transmit CNV, but not TBSV-Ch, in the in vitro manner. To assess the role of the coat protein in the specificity of fungus transmission, reciprocal exchanges were made between the coat protein genes of these two viruses in full-length infectious cDNA clones. Virions containing a modified TBSV-Ch genome with the CNV coat protein gene were efficiently transmitted, but those containing a modified CNV genome with the TBSV-Ch coat protein gene were not. This is the first direct demonstration for the role of a viral coat protein in the specificity of transmission by a fungus.

Failure of long-distance movement of southern bean mosaic virus in a resistant host is correlated with lack of normal virion formation.

Sunn-hemp mosaic tobamovirus (SHMV) facilitated the spread of the cowpea strain of southern bean sobemovirus (SBMV-C) only in inoculated leaves of common bean (Phaseolus vulgaris L. cv. Bountiful), a resistant host for SBMV-C. Tissue prints of bean primary leaves doubly inoculated with SHMV and SBMV-C, developed by Western blotting, showed the presence of the SBMV-C capsid antigen in the mesophyll and epidermis, but no antigen was detected in the conducting bundles. Typical SBMV-C virions were not seen in electron micrographs of immunogold-labelled mesophyll cells; instead, specifically labelled, amorphous protein clumps were found in the vacuole. Particles of smaller diameter than that of typical SBMV-C virions were specifically trapped by SBMV antibodies following immunosorbent electron microscopy of extracts from doubly infected leaves. SBMV-C coat protein from infected Vigna unguiculata L. (cowpea) and bean plants showed no difference in its mobility following electrophoresis in denaturing SDS-polyacrylamide gels. Lack of efficient assembly of SBMV-C virions does not impede cell-to-cell movement of the virus in doubly infected leaves of bean, yet it is probably an important factor in determining the inability of SBMV-C to move into and/or through the vascular system of this host.

Symptomatology and movement of a cucumber necrosis virus mutant lacking the coat protein protruding domain.

A cucumber necrosis virus (CNV) mutant which lacks the coding sequence for the coat protein protruding domain, PD(-), was constructed by site-directed mutagenesis of an infectious CNV cDNA clone, pK2/M5 (wild-type, 4701 nt). Transcripts of PD(-) were infectious on Nicotiana clevelandii; however, local lesions produced were significantly smaller than those on the corresponding leaves of plants inoculated with wild-type transcript. In addition, systemic symptoms took 8 to 12 days longer to develop than in wild-type-inoculated plants. The distinctive PD(-) phenotype was lost when N. clevelandii was inoculated with sap from systemically infected leaves of PD(-) transcript-inoculated plants and was replaced by symptoms that were the same as those with wild-type infections. High-molecular-weight RNA from mutant- and wild-type-infected plants was extracted and analyzed by Northern blotting. Full-length PD(-) RNA could be detected only rarely in RNA preparations from transcript-inoculated leaves; a further deleted, stable RNA species of approximately 3800 nucleotides was found in preparations from systemically infected leaves of PD(-) transcript- and sap-inoculated plants. CNV coat protein could not be detected by ELISA or ISEM in PD(-)-infected leaf material. The ca. 3.8-kb RNA, when cloned and sequenced, was found to have lost all but 74 of the 1140 nucleotides of the CNV coat protein open reading frame. Transcripts from this coat proteinless CNV cDNA clone produced wild-type symptoms on N. clevelandii. It would appear that CNV is able to replicate and move systemically, in both transcript-inoculated and sap-inoculated N. clevelandii, in the absence of a functional coat protein. Additionally, mechanical transmission of this virus occurs in the absence of the coat protein; however, such transmission is less efficient when compared with wild-type infections.

Evidence that cowpea aphid-borne mosaic and blackeye cowpea mosaic viruses are two different potyviruses.

The immunoreactivity of a panel of polyclonal antibodies and monoclonal antibodies (MAbs) raised against African isolates of potyviruses from cowpea and African yam bean was examined in ELISAs. A serological study including reference isolates followed by further characterization in differential hosts resulted in separation of the potyviruses into two distinct serogroups, one containing blackeye cowpea mosaic virus (BlCMV) and the other containing cowpea aphid-borne mosaic virus (CAMV). Using biotin-labelled MAbs, the BlCMV isolates were further subdivided into two serotypes and the CAMV isolates into five serotypes. Because both BlCMV and CAMV induce a very similar mosaic disease in cowpea, different ELISA procedures using mixed MAbs were evaluated and a single protocol was developed which allowed reliable diagnosis of both viruses.

Properties of the Mentha strain of lychnis ringspot virus.

A hordeivirus isolated from horsemint (Mentha longifolia Huds.) was designated as the mentha strain of lychnis ringspot virus (LRSV-M) on the basis of serological relationship with the type strain (LRSV-T) and similarities in nucleotide sequence and properties of genomic and replicative RNAs of the two strains. Four ssRNAs in addition to the three genomic RNAs were encapsidated by LRSV-M coat protein. No genomic sequence similarity was detected between LRSV-M and either barley stripe mosaic or poa semilatent viruses under high stringency conditions, confirming that the hordeiviruses are a group of morphologically similar, but genomically distinct viruses.

A potexvirus isolated from Silene pratensis.

A potexvirus, silene virus X (SVX), was isolated from the weed Silene pratensis. Infectious preparations contained nucleoprotein rods predominantly 546 nm in length, consisting of a 6.9-kb polyadenylated single-stranded RNA and a 29-kd capsid protein. Double-stranded RNAs of 17.1, 7.0, 5.7, and 4.6 kbp were isolated from SVX-infected plants. In vitro translation products of SVX single-stranded or denatured double-stranded RNAs reacted with SVX antiserum. Hybridization studies with SVX cDNAs showed no nucleotide homology with seven other potexviruses. The virus is more closely related serologically to narcissus mosaic virus than to nine other potexviruses.

Cellular double-stranded RNA in Phaseolus vulgaris.

High molecular weight double-stranded (ds) RNAs have been detected in apparently virus-free French (common) bean Phaseolus vulgaris cv. Black Turtle Soup (BTS). Several other bean cultivars were free of detectable high molecular weight dsRNAs. The dsRNAs have been partially characterized and have homology to the BTS genome as well as to the genomes of other bean cultivars. The T m of hybrids formed between BTS DNA and denatured dsRNA have been estimated.

Purification and some properties of a double-stranded DNA containing virus-like particle from Uronema gigas, a filamentous eucaryotic green alga.

A scheme has been developed for the recovery and purification of about 50% of the 390-nm-diameter virus-like particles (VLPs) present in filtered medium in which Uronema gigas was grown for 6 to 10 weeks. Purification was assayed by electron microscopy of negatively stained samples. Yield of VLPs was low, for example 150 mug from 8 liters of medium. The purified VLP had the following properties:A260/A280 = 1.14 to 1.21;s(20,w) = 6340 +/- 300 S; buoyant density in sucrose, 1.30 g/ml. One major polypeptide (MW = 45,000) and up to nine minor polypeptides (MW = 26,000 to 64,000) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The nucleic acid associated with the VLP was double-stranded DNA with a buoyant density of 1.719 g/ml in cesium chloride and 1.436 g/ml in cesium sulfate. Molecules of the DNA were linear with a length of 4 to 36 mum (MW = 8 to 72 x 10(6)). No modal length was observed. These properties distinguish this VLP from other groups of viruses with dsDNA genomes.