ABSTRACT The sugarcane spittlebug, Mahanarva fimbriolata (Walker) (Hemiptera: Cercopidae) is an economically important pest of sugarcane in Brazil. The purpose of this study was to develop and validate a greenhouse methodology to screen large sugarcane populations for resistance to spittlebug Mahanarva fimbriolata. A resistant and a susceptible genotype (H. Kawandang and SP81-3250) were first used to determine adequate days after infestation and levels of infestation (number of nymphs per plant) for comparing the resistance of genotypes. Then, 74 sugarcane genotypes including three susceptible and three resistant controls were screened for resistance. The screening method consists in infesting single-tiller plants supported in a small plant growth unit and assessing the damage by using a 1-5 visual damage score. Our data suggest screening with four to six nymphs per plant and the damage score assessment at least 21 days after infestation. The screening technique was proved reliable as susceptible and resistant controls were placed in their respective resistance category. Three genotypes were classified as resistant while the majority of genotypes were classified as susceptible to spittlebug, indicating the need of breeding for resistance.

O objetivo deste trabalho foi avaliar alguns aspectos da biologia floral e do sistema reprodutivo de Jatropha curcas, em Janaúba, MG. Foram registrados: o número de flores femininas e masculinas; o intervalo de abertura das flores femininas; e a formação de frutos por apomixia, autofecundação, geitonogamia e xenogamia. A proporção de flores masculinas para femininas foi de 20:1. O intervalo de abertura das flores femininas variou de um a sete dias, conforme o número delas na inflorescência. No teste de apomixia, houve formação de frutos em apenas 5% das flores avaliadas. A percentagem de frutificação variou de 79 a 88% na autofecundação manual, na geitonogamia e na xenogamia. Na autofecundação sem a polinização manual a frutificação foi de 20%, e os frutos formados foram significativamente menores, com número inferior de sementes por fruto e menor índice de velocidade de emergência. As sementes foram semelhantes às formadas por polinização natural. é possível a realização de cruzamentos controlados em pinhão-manso, e não há autoincompatibilidade nesta espécie.

The aim of this work was to evaluate some aspects of the floral biology and of the reproductive system of Jatropha curcas, in Janaúba county, MG, Brazil. The number of female and male flowers, the interval between the opening of female flowers, and the formation of fruits by apomixis, self-pollination, geitonogamy and by xenogamy were registered. The ratio of male to female flowers was 20:1. The interval of opening of female flowers was of one to seven days, depending on the number of female flowers in the inflorescence. On the apomixy test, the formation of fruits occurred in only 5% of the evaluated flowers. The fruit set was between 79 and 88% through the manual self-pollination, and through the geitonogamy, and the xenogamy. In the self-pollination treatment, without the hand-pollination, the fruit set was of 20%, and the fruits formed were significantly smaller, with a lesser number of seeds per fruit and lower rate of emergence. The seeds were similar to the ones formed by natural pollination. Artificial cross-pollination is possible on physic nuts, and there is no self-incompatibility within this species.

O objetivo deste trabalho foi avaliar a base genética da resistência de Lycopersicon hirsutum ao potyvírus Pepper yellow mosaic virus (PepYMV). Foram avaliadas 540 plantas, inclusive os parentais 'Santa Clara' (suscetível) e 'BGH 6902' (resistente), e as gerações F1, F2, RC1:1 e RC1:2, derivadas do cruzamento desses parentais. As plantas receberam inoculações mecanicamente, e a concentração viral de PepYMV em cada planta foi determinada por ELISA indireto. Foram realizadas as análises quantitativa e qualitativa. A primeira, baseada na concentração viral de cada planta, indicou herança oligogênica com herdabilidade de 99%. Os mesmos dados, quando analisados de forma qualitativa, indicaram herança governada por dois genes, com interação epistática dominante e recessiva. Entretanto, quando foi analisada a geração F2:3, oriunda da autofecundação de plantas F2 resistentes, a hipótese de dois genes foi descartada e a de um gene, com dominância completa entre os alelos, foi a que melhor se ajustou aos dados. A análise qualitativa, pela sintomatologia observada, demonstrou que a herança da resistência ao PepYMV é determinada por um gene recessivo, com ausência de dominância entre os seus alelos.

The aim of this work was to evaluate the genetic basis of resistance of Lycopersicon hirsutum to the potyvirus Pepper yellow mosaic virus (PepYMV). Five hundred and forty plants, including the parentals 'Santa Clara' (susceptible) and 'BGH 6902' (resistant) were evaluated, as well as the generations F1, F2, RC1:1 and RC1:2, from the crossing of the above parentals. PepYMV was mechanically inoculated, and the virus concentration in each plant was determined by indirect ELISA. The quantitative and qualitative analyses were carried out. The first one, based on the virus concentration of each plant, suggest oligogenic inheritance with heritability of 99%. The same data, when analyzed under the qualitative form, indicated an inheritance governed by two genes, with dominant and recessive epistatic interaction. However, when F2:3 generation, arising from self-fertilization of resistant F2 plants, was analyzed, the hypothesis of two genes was rejected, while the best fitted to data was that of one gene with complete dominance among the alleles. The qualitative analysis, considering sintomatology observed, showed that the inheritance of resistance to PepYMV is determined by a recessive gene, with the absence of dominance among their alleles.

O tomateiro é uma olerícola de grande importância econômica, porém suscetível a um grande número de patógenos, dentre os quais os vírus, cuja forma de controle mais eficiente é a resistência genética. A doença causada pelo Pepper yellow mosaic virus (PepYMV) tem se tornado um problema recente. Por isso, o presente estudo teve por objetivo avaliar 376 acessos de Lycopersicon sp. visando identificar fontes de resistência ao PepYMV. Dos 355 acessos de L. esculentum inoculados com o PepYMV, 52 não apresentaram sintomas. No entanto, não foram considerados fonte segura de resistência por conterem alta concentração viral quando avaliados pelo teste de ELISA indireto. Dentre os 21 acessos de espécies silvestres do gênero, foi detectado um acesso de L. hirsutum resistente por ser assintomático. Baixa concentração do vírus foi detectada pelo teste de ELISA indireto. Este acesso pode ser indicado para programas de melhoramento visando incorporar resistência a este vírus em cultivares comerciais de tomate.

The tomato is a crop of great economical importance, however it is susceptible to a large number of pests and diseases, including viral disease for which the best control strategy is genetic resistance. The disease, caused by Pepper yellow mosaic virus (PepYMV) has become a recent problem. Consequently, the idea of this work was to screen 376 accessions of Lycopersicon sp. to find possible sources of resistance to PepYMV. Out of 355 accessions of L. esculentum inoculated with PepYMV, 52 did not express symptoms. However, the virus reached high concentration in the tissues as measured by indirect ELISA, and therefore they were not considered as safe sources of resistance. Among 21 accessions of wild Lycopersicon species, one of L. hirsutum was shown to be resistant, with no observed symptoms. A low concentration of the virus was detected as measured by indirect ELISA. This accession seems to be suitable for breeding programs aiming at incorporating resistance for this disease into commercial tomato cultivars.