Suppression of Rice Blast by Preinoculation with Avirulent Pyricularia oryzae and the Nonrice Pathogen Bipolaris sorokiniana

ABSTRACT Avirulent isolates of Pyricularia oryzae and isolates of Bipolaris sorokiniana, a nonrice pathogen, were used to suppress rice blast caused by P. oryzae. In greenhouse experiments, both fungi substantially reduced leaf blast when applied 24 h or more before the pathogen. B. sorokiniana, but not avirulent isolates of P. oryzae, systemically reduced disease in leaf 5 when applied to whole plants at the four-leaf stage. In field experiments, both fungi were able to reduce neck blast significantly. No increase in grain yield was obtained by using avirulent isolates of P. oryzae, whereas five sprays with B. sorokiniana from seedling to heading stages increased the grain yield in two of three experiments conducted at two locations in Nepal. The significant increase in yield was observed under high inoculum pressure of P. oryzae. Induced resistance is suggested to be involved in the suppression of disease.     

The study of introgressive lines of Triticum aestivum × Aegilops speltoides by in situ and SSR analyses

Fluorescence in situ hybridization (FISH) with a genome‐specific repeat, Spelt1, and wheat simple sequence repeat (SSR) markers were used to analyse the chromosome constitution of two Triticum aestivum×Aegilops speltoides introgressive lines. The lines 170/98i and 178/98i carried one and two subtelomeric regions of Ae. speltoides (per haploid genome), respectively, marked by Spelt1 repeats according to FISH data. SSR analysis detected homoeologous substitution of wheat chromosome 7D with Ae. speltoides chromosome 7S in the lines 178/98i and 170/98i as well as the assumed terminal translocation in the short arm of chromosome 3A in the line 178/98i. Anthocyanin pigmentation of the coleoptiles was found in the lines 170/98i and 178/98i and resulted from the 7S (7D) substitution. It was demonstrated that Spelt1 could be effectively used for the rapid identification (without DNA isolation) of terminal translocations of T. aestivum×Ae. speltoides introgressive lines as well as for further analysis of the stability of the hybrid plants.     

DUBA: a deubiquitinase that regulates type I interferon production

Production of type I interferon (IFN-I) is a critical host defense triggered by pattern-recognition receptors (PRRs) of the innate immune system. Deubiquitinating enzyme A (DUBA), an ovarian tumor domain-containing deubiquitinating enzyme, was discovered in a small interfering RNA-based screen as a regulator of IFN-I production. Reduction of DUBA augmented the PRR-induced IFN-I response, whereas ectopic expression of DUBA had the converse effect. DUBA bound tumor necrosis factor receptor-associated factor 3 (TRAF3), an adaptor protein essential for the IFN-I response. TRAF3 is an E3 ubiquitin ligase that preferentially assembled lysine-63-linked polyubiquitin chains. DUBA selectively cleaved the lysine-63-linked polyubiquitin chains on TRAF3, resulting in its dissociation from the downstream signaling complex containing TANK-binding kinase 1. A discrete ubiquitin interaction motif within DUBA was required for efficient deubiquitination of TRAF3 and optimal suppression of IFN-I. Our data identify DUBA as a negative regulator of innate immune responses.     

Occurrence of Fusarium species and mycotoxins in nepalese maize and wheat and the effect of traditional processing methods on mycotoxin levels

Maize (Zea mays) and wheat (Triticum aestivum) collected in the foothills of the Nepal Himalaya Mountains were analyzed for Fusarium species and mycotoxins: fumonisins, nivalenol (NIV), and deoxynivalenol (DON). Predominant species were Gibberella fujikuroi mating population A (F. moniliforme) in maize and F. graminearum in maize and wheat; G. fujikuroi mating population D (F. proliferatum), F. acuminatum, F. avenaceum, F. chlamydosporum, F. equiseti, F. oxysporum, F. semitectum, and F. torulosum were also present. Strains of G. fujikuroi mating population A produced fumonisins, and strains of F. graminearum produced NIV or DON. By immunoassay or high-performance liquid chromatography, fumonisins were >1000 ng/g in 22% of 74 maize samples. By immunoassay or fluorometry, NIV and DON were >1000 ng/g in 16% of maize samples but were not detected in wheat. Fumonisins and DON were not eliminated by traditional fermentation for producing maize beer, but Nepalese rural and urban women were able to detoxify contaminated maize by hand-sorting visibly diseased kernels.     

Gibberella ear rot of maize (Zea mays) in Nepal: distribution of the mycotoxins nivalenol and deoxynivalenol in naturally and experimentally infected maize

The fungus Fusarium graminearum (sexual stage Gibberella zeae) causes ear rot of maize (Zea mays) and contamination with the 8-ketotrichothecenes nivalenol (1) or 4-deoxynivalenol (2), depending on diversity of the fungal population for the 4-oxygenase gene (TRI13). To determine the importance of 1 and 2 in maize ear rot, a survey of naturally contaminated maize in Nepal was combined with experiments in the field and in a plant growth room. In the survey, 1 contamination was 4-fold more frequent than 2 contamination and 1-producers (TRI13) were isolated more than twice as frequently as 2-producers (Psi TRI13). In maize ear rot experiments, genetically diverse 1-producers and 2-producers caused ear rot and trichothecene contamination. Among strains with the same genetic background, however, 1-producers caused less ear rot and trichothecene contamination than did 2-producers. The high frequency of 1 contamination and the high virulence of many 1-producers are of concern because maize is a staple food of rural populations in Nepal and because 1 has proven to be more toxic than 2 to animals.     

Identification of a new family of tandem repeats in Triticeae genomes

A new family of cereal tandem repeats was isolated, characterised and designated as spelt-1. The family of repeats comprises about 2% of the Aegilops speltoides genome; however, its content differs considerably in the genomes of various Triticeae species. Copy number of the constituent sequence, relative to Ae. speltoides, proved to be 40-60 times reduced in the genomes of tetraploid wheats, 400-fold reduced in the genome of Triticum monococcum, and 1200-2400 times in the genomes of the other 19 Triticeae species studied. Drastic difference in the copy number and homology extent of the spelt-1 family sequences between Ae. speltoides and other diploid species allows the utilisation of these sequences as species-specific telomeric markers for Ae. speltoides, provided stringent hybridisation conditions apply. RFLP (restriction fragment length polymorphisms) analysis of spelt-1 reveals polymorphism between the above species. This study of spelt-1 organisation in different Triticum species provided further substantiation of the polyphyletic origin of the B genome of polyploid wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Isolation of Microdochium oryzae and Pinatubo oryzae from Rice Seeds and their Survival on Stored Seeds

The aim of these studies was to develop a semi-selective medium to differentiate Microdochium oryzae and Pinatubo oryzae, determine the frequency of seed infection of M. oryzae, study survival of the pathogen in stored seeds, and determine the frequency of infection of seed components. To simulate epidemics of differing intensities, panicles of rice cultivars that are susceptible (IR36) and resistant (IR42 and IR46) to M. oryzae were either non-inoculated, inoculated once, twice, or three times with a conidial suspension of M. oryzae. Both M. oryzae and P. oryzae colonies were recovered from seeds and were similar in culture. A semi-selective medium developed to detect M. oryzae seed infection rates aided in differentiating M. oryzae and P. oryzae by stimulating aerial conidiogenesis of P. oryzae. The conclusions taken from these results were: (a) seeds of IR36 had higher infection of M. oryzae than of IR42 and IR46 from plants grown in the dry season, but had lower infection of M. oryzae than of IR42 and IR46 from plants grown in the wet season; (b) M. oryzae infected seeds increased with an increase in the epidemic intensity with the highest occurring after three inoculations, the least occurring with non-inoculation, and intermediate with one, or two inoculations; (c) survival of M. oryzae decreased over time in seed lots stored at 10°C and 40% relative humidity and (d) all components of the rice seeds of IR36, IR42 and IR46 lots were infected with M. oryzae with the highest frequency in the endosperm and lemma, intermediate in the basal glumes and palea, and the least in the embryo.     

Increase of forest carbon biomass due to community forestry management in Nepal

Community forest management helps in mitigating deforestation and forest degradation by addressing the negative aspects of rural livelihoods such as poverty and social exclusion. It is important in regulating global climate by encouraging sequestration of carbon in shoots, roots and soils. We studied the status of community forest management, forest resource harvest and carbon stocks in two community forests of the mid hill region of central and western Nepal. The study was based on primary and secondary data collected through carbon stock measurement from field visits and allometric equations, household surveys, focus group discussions, key informant interviews, and review of past studies. Socioeconomic variables such as gender, age group, livestock and landholding status were related to resource utilization, conservation, and management of community forest. Forest resources such as timber, firewood, fodder and leaf litter were harvested in sustainable ways. People were involved in forest thinning, co-management meetings, guarding and planting trees for forest conservation and management. Density and carbon stock of trees increased gradually in comparison to a previous study. We recommend further research on other community forests for more accurate and better results.     

Breeding apple varieties for orchards producing raw materials

Data of long-term investigations of the suitability of widespread apple varieties for producing high-quality juice are given. A purposeful breeding program made it possible to create forms with a high juice yield and quality for orchards producing raw materials.