F. M. Santana

Sources of resistance in Lycopersicon spp. to a bipartite whitefly-transmitted geminivirus from Brazil

Accessions of Lycopersicon chilense, L. peruvianum, L.hirsutum and sixteen L. esculentum genotypes were evaluated undergreenhouse conditions for resistance to a whitefly-transmitted geminivirusisolate from Brasilia-DF (DF1). Artificial cage inoculation oftomato plants at the two true-leaf stage, using 20 viruliferous whiteflies perplant in individual insect-proof cages, ensured 100% infection ofsusceptible tomato plants. Virus infection was confirmed by symptomdevelopment and dot-blot or squash-blot hybridization. In advanced testing,accessions of L. chilense (LA 1967), L. peruvianum (CNPH784) and L. hirsutum (PI-127827) and three selected inbred lines(TY 197, TY 198 and Tx 468-1) showed no symptoms and viral DNAwas barely detectable four weeks after inoculation, indicating good sourcesof resistance to the virus.Accessions of Lycopersicon chilense, L. peruvianum, L.hirsutum and sixteen L. esculentum genotypes were evaluated undergreenhouse conditions for resistance to a whitefly-transmitted geminivirusisolate from Brasília-DF (DF1). Artificial cage inoculation oftomato plants at the two true-leaf stage, using 20 viruliferous whiteflies perplant in individual insect-proof cages, ensured 100% infection ofsusceptible tomato plants. Virus infection was confirmed by symptomdevelopment and dot-blot or squash-blot hybridization. In advanced testing,accessions of L. chilense (LA 1967), L. peruvianum (CNPH784) and L. hirsutum (PI-127827) and three selected inbred lines(TY 197, TY 198 and Tx 468-1) showed no symptoms and viral DNAwas barely detectable four weeks after inoculation, indicating good sourcesof resistance to the virus.

Inheritance of resistance to the bipartite Tomato chlorotic mottle begomovirus derived from Lycopersicon esculentum cv. ‘Tyking’

Severe outbreaks of bipartite begomoviruses (family Geminiviridae) have been observed on tomatoes after the introduction of the whitefly Bemisia tabaci (biotype B) in Brazil. The Lycopersiconesculentum line ‘TX 468-RG’ was identified as one of the best sources of broad-spectrum resistance to species comprising the tomato-infecting Begomovirus complex in Brazil. The genetic basis of resistance to one Begomovirus isolate was investigated using populations from the cross between ‘TX 468-RG’ (P1) and the susceptible line ‘Ohio 8245’ (P2). Parental lines, F1, backcross (BC) to P1 and BC to P2 and F2 generations were inoculated at the two true-leaf stage using 20 viruliferous whiteflies per plant. Assessment was done two weeks after inoculation based upon visual analysis of symptom expression. The ratio of resistant to susceptible plants closely fit to a single recessive gene (locus) model. The sequence analysis indicated that the Begomovirus isolate used in this assay was closely related to the bipartite Tomato chlorotic mottle virus. Therefore, this gene/locus, was tentatively named tcm-1 (tomato chlorotic mottle virus resistance-1). This locus has been transferred to distinct tomato cultivars and levels of resistance similar to that of ‘TX 468-RG’ were observed in advanced (F8 and F9) generations. In addition, breeding lines carrying the tcm-1 locus were also resistant to other Brazilian bipartite tomato-infecting Begomovirus species.

Quantitative Review of the Effects of Triazole and Benzimidazole Fungicides on Fusarium Head Blight and Wheat Yield in Brazil

Triazole and benzimidazole fungicides have been used for controlling Fusarium head blight (FHB) in wheat for over two decades. In Brazil, it was only during the last five years that uniform fungicide trials for FHB control have been established yearly, thus contributing to a new large body of fungicide efficacy data for this country. A systematic review of both peer- and non-peer-reviewed studies on chemical control conducted since 2000 in Brazil was performed. Fungicides of interest were the triazoles tebuconazole (TEBU1x and TEBU2x) and propiconazole (PROP2x), and the benzimidazole carbendazim (CARB2x). Most fungicides were applied twice, the first at early to mid-flowering and the second 7 to 10 days later. Only TEBU was tested as one or two applications, and thus four treatments were evaluated. For these fungicides, there were 35 trials reporting FHB index and 48 reporting mean yield. Network meta-analytic models were fitted to the data of the log of the means of FHB index for each fungicide and for the nontreated check. The meta-analytic estimates were used to obtain control efficacy ( C¯ ), or percent disease reduction relative to the nontreated check. The absolute mean difference ( D¯ ) in yield (kg/ha) between the fungicide-treated and the nontreated check plots was also estimated. Yield response relative to the nontreated check ( Y¯ ) was also calculated based on the difference in the logs of the means of yield between fungicide-treated and nontreated check. The TEBU1x, TEBU2x, and CARB2x treatments performed similarly with regards to control efficacy (= 59%, 53% and 55%, respectively), and although better than PROP2x (47%), the difference was marginally significant. Yield response ( D¯ ) was highest for TEBU2x, ( D¯ = 558 kg/ha, Y¯ = 19.2%) followed by PROP2x (497 kg/ha, 16.0%), TEBU1x (457 kg/ha, 17.3%), and CARB2x (456 kg/ha, 12.8%). For an average 2016 scenario of fungicide plus application costs (FC =

BRS 374 - wheat cultivar

18 U.S./ha) and average wheat price (WP =

Characterization of Phytophthora infestans populations of southern Brazil in 2004 and 2005

215 U.S./MT), the probability of breaking even on the financial investment in the four treatments ranged from 59 to 63%. For 140 scenarios (four fungicides) created based on the combination of five WP (

Época de semeadura reduz a incidência da brusone do trigo

133 to 266 U.S./MT) and seven FC (

Resultados agronômicos e qualitativos da nova cultivar de trigo 'BRS Marcante'

5 to 35 U.S./ha), the probability of breaking even was >50% for all but two scenarios. The information may serve as a guide for planning future trials and provides a baseline and first step toward optimizing FHB management in Brazil.

Multi-environment assessment of fungicide performance for managing wheat head blast (WHB) in Brazil and Bolivia

BRS 374 is a wheat cultivar developed by Embrapa. It resulted from a cross between the F1 generation of PF 88618/Coker80.33 and Frontana/Karl. BRS 374 belongs to the soft wheat class, has a low plant height, a high potential grain yield, and white flour.

BRS Pastoreio: extensão de indicação de cultivo para a RHA 2 do RS.

The populations of Phytophthora infestans (Pi) in southern Brazil in 2004 and 2005 are characterized herein. The isolates were collected from potato and tomato plants in the states of Paraná (PR), Santa Catarina (SC), and Rio Grande do Sul (RS). The mating type of 131 potato and 32 tomato isolates was determined. Forty-nine isolates from potatoes and 11 from tomatoes were analyzed for their Gpi phenotype. A subset of 35 isolates was evaluated for mitochondrial (mtDNA) polymorphisms. A sample of 146 isolates was tested for sensitivity to the fungicide metalaxyl, and most isolates (64%) were moderately sensitive. Fifty-nine isolates were classified as A1 mating type and 103 as A2. One isolate behaved as both A1 and A2 mating type. All tomato isolates were A1 mating type and presented the 86/100 pattern for the enzyme GPI and mtDNA Ib, indicating that these isolates belong to the US-1 clonal lineage. Of the 131 potato isolates, 103 were A2, 27 were A1 and one was A1/A2 mating type. Among the potato isolates 27 exhibited the Gpi phenotype 100/100, the same as BR-1, and 20 were 86/100, the same as US-1. Potato isolates presented the mitochondrial haplotypes Ia (74%) and IIa (26%). The data suggest the presence of only the BR-1 clonal lineage on potatoes in the states of PR and SC. However, in the state of RS, more than one clonal lineage was observed infecting potatoes, and there may be sexual reproduction between the lineages.