Host Susceptibility of Citrus Cultivars to Queensland Fruit Fly (Diptera: Tephritidae)

Citrus crops are considered to be relatively poor hosts for Queensland fruit fly, Bactrocera tryoni (Froggatt), as for other tephritid species. Australian citrus growers and crop consultants have reported observable differences in susceptibility of different citrus cultivars under commercial growing conditions. In this study we conducted laboratory tests and field surveys to determine susceptibility to B. tryoni of six citrus cultivars [(Eureka lemon (Citrus limon (L.) Osbeck); Navel and Valencia oranges (C. sinensis (L.) Osbeck); and Imperial, Ellendale, and Murcott mandarins (C. reticulata Blanco)]. The host susceptibility of these citrus cultivars was quantified by a Host Susceptibility Index, which is defined as the number of adult flies produced per gram of fruit infested at a calculated rate of one egg per gram of fruit. The HSI was ranked as Murcott (0.083) > Imperial (0.052) ≥ Navel (0.026) ≥ Ellendale (0.020) > Valencia (0.008) ≥ Eureka (yellow) (0.002) > Eureka (green) (0). Results of the laboratory study were in agreement with the level of field infestation in the four citrus cultivars (Eureka lemon, Imperial, Ellendale, and Murcott mandarins) that were surveyed from commercial orchards under baiting treatments against fruit flies in the Central Burnett district of Queensland. Field surveys of citrus hosts from the habitats not subject to fruit fly management showed that the numbers of fruit flies produced per gram of fruit were much lower, compared with the more susceptible noncitrus hosts, such as guava (Psidium guajava L.), cherry guava (P. littorale Raddi), mulberry (Morus nigra L.), loquat (Eriobotrya japonica (Thunb.) Lindl.), and pear (Pyrus communis L.). Therefore, the major citrus crops commercially cultivated in Australia have a relatively low susceptibility to B. tryoni, with Eureka lemons being a particularly poor host for this tephritid fruit fly.

采后果实衰老和冷害的机理及调控研究

衰老和冷害是果实采后极易发生的两种重要的生理性失调，严重影响了果实的商品质量和市场价值。本论文选用在采后贮藏期间容易衰老和出现冷害的枇杷、杧果和桃果实作为研究材料，比较深入系统地研究了这些果实采后衰老或冷害的机理和调控。主要的研究内容包括：（1）枇杷果实在不同贮藏条件下（低温、气调）的生理代谢、品质变化、衰老进程和贮藏性;（2）杧果果实采后生理特性及外源草酸和水杨酸处理对杧果冷害、品质和活性氧代谢的影响;（3）桃果实在低温贮藏下冷害发生特征，并从氧化还原平衡和蛋白质组表达方面探讨了桃果实采后冷害的发生机理。 试验结果表明：（1）与自发气调包装（MAP）相比，气调（CA, 10% O2＋1%CO2）能更有效的抑制枇杷果实的腐烂、延缓衰老、保持品质，以及控制多聚半乳糖醛酸酶（PG）和多酚氧化酶（PPO）的活性。枇杷果实在1 ºC气调下贮藏50天，腐烂指数低于7%，并保持固有的风味品质。短时间的高氧处理对果实腐烂和品质影响不大，促进了贮藏后期果实内乙醇的积累;（2）外源草酸和水杨酸处理显著减轻了杧果果实在贮藏期间的冷害程度，但对果实的硬度、可溶性固型物和可滴定酸含量影响不大。外源草酸和水杨酸提高了果实内抗坏血酸和谷胱甘肽的还原状态、提高了H2O2含量、降低了O2-含量和脂氧合酶活性，并提高了超氧化物岐化酶、过氧化氢酶、过氧化物酶、抗坏血酸氧化酶和谷胱甘肽还原酶的活性;（3）与非冷害桃果实相比，冷害桃果实呈现较低的H2O2含量、较高的膜透性、较高的酚类物质含量以及较高的抗坏血酸和谷胱甘肽还原状态。水杨酸对果实内H2O2含量、膜透性、酚类物质含量有显著的影响。冷害桃果实与非冷害桃果实的蛋白质表达也有明显的区别，32个差异表达蛋白依其功能分为8类，分别为能量产生、代谢、次生代谢、抗性、蛋白质的分布、基因转录、细胞结构和细胞生长。水杨酸对其中20个蛋白质的表达有显著影响。烯醇化酶、脂质运载蛋白、脱水蛋白、分支酸变位酶以及桂醇脱氢酶等与桃冷害发生有密切关系。 通过对上述结果的分析，得出如下结论：（1）与MAP相比，CA（10% O2 + 1% CO2）可显著延缓枇杷果实的衰老、腐烂和品质下降，CA延缓枇杷衰老的作用机理可能与其减轻果实内氧胁迫、降低PG和PPO活性有关;（2）用外源草酸或水杨酸处理杧果，可减轻贮藏期间果实的冷害程度，其调控机制可能与提高果实抗坏血酸和谷胱甘肽的还原状态、抑制O2－含量和提高H2O2含量有关;（3）在低温贮藏下，桃冷害发生与果实内较低的H2O2含量、生物膜完整性的破坏以及酚类物质含量增加密切相关，果实生物膜完整性的破坏与烯醇化酶、脂质运载蛋白、过敏蛋白以及脱水蛋白的下调表达有关，而酚类物质含量的增加与分支酸变位酶、桂醇脱氢酶的上调表达有关。

Capacidade de enraizamento de variedades de nespereira submetidas à poda de renovação

O presente trabalho avaliou a capacidade de enraizamento de cinco variedades de nespereira (Eriobotrya japonica Lindl.), sendo Champagne, Precoce de Itaquera, Mizuho, Mogui e Tanaka, obtidas pela poda de renovação. Estacas tenras apicais, contendo um par de folhas e cerca de 15 cm, foram tratadas por cinco segundos com ácido indolbutírico (IBA) (0; 1.000; 3.000; 5.000 e 7.000 mg.L-1). O experimento foi conduzido em câmara de nebulização intermitente pertencente à UNESP/FCAV (21º15'22 S e 48º18'58 W). O delineamento experimental foi inteiramente casualizado, em esquema fatorial 5x5 (5 variedades e 5 concentrações de IBA), com 4 repetições e 10 estacas por parcela. As avaliações foram feitas após 90 dias. Os resultados indicaram um incremento de enraizamento e número de raízes crescente com a concentração de IBA utilizada, com exceção da variedade Mogui, que apresentou melhores resultados apenas quanto ao comprimento de raízes. Posterior ao transplantio, a sobrevivência das mudas foi alta (90%), apresentando condições de serem plantadas no campo, aos seis meses, ou de serem enxertadas aos oito meses, decorrido desde o estaqueamento.

Enraizamento de estacas herbáceas de nespereira (Eriobotrya japonica Lindl)

O cultivo da nespereira (Eriobotrya japonica Lindl) tem despertado interesse no Brasil, devido ao bom rendimento que proporciona aos produtores e à facilidade de comercialização. Com isso, cada vez mais se buscam métodos de propagação que preservem as características genéticas de interesse, induzam precocidade na formação da muda e no início de produção, além de baixo custo. O método de estaquia se adequa a estas características; sendo assim, o objetivo deste experimento é avaliar o efeito do tipo de estaca herbácea na produção de mudas de nespereira, num experimento conduzido na Faculdade de Ciências Agrárias e Veterinárias - FCAV/UNESP, Câmpus de Jaboticabal (SP), utilizando plantas matrizes de nespereiras, plantadas em 1977, da variedade Mizuho, pertencentes à coleção de plantas frutíferas da Universidade. Utilizaram-se estacas apicais herbáceas com e sem meristema apical, com 2 ou 4 folhas inteiras ou cortadas pela metade, num total de 6 tratamentos, 4 repetições e 12 estacas por parcela, em delineamento inteiramente casualizado. Após 120 dias do plantio das estacas em bandejas com vermiculita e mantidas sob câmara de nebulização, concluiu-se que a porcentagem de estacas vivas e a presença de calos foram significativamente maiores nas estacas apicais sem meristema e com quatro folhas inteiras, e não há efeito do tipo de estaca herbácea sobre o número de estacas enraizadas, número e comprimento médio de raízes. A presença de calos na base das estacas indica a possibilidade de estímulo natural de enraizamento que pode ser potencializada com a utilização de fitorreguladores.

Doses e modos de aplicação de boro na produção de mudas de nespereira

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Factors supporting the non-persistence of fruit fly populations in South Australia

For purposes of interstate and international fruit trade, it is necessary to demonstrate that in areas in which fruit fly species have not previously established permanent populations, but which are subject to introductions of fruit flies from outside the area, the introduced population once detected, has not become established. In this paper, we apply methodology suggested mainly by Carey (1991, 1995) to introductions of Mediterranean fruit fly (Medfly), Ceratitis capitata Weid., and Queensland fruit fly (QFF) Bactrocera tryoni Froggatt (Diptera: Tephritidae) to South Australia, a state in which these species do not occur naturally and in which introductions, once detected, are actively treated. By analysing historical data associated with fruit fly outbreaks in South Australia, we demonstrate that: (i) fruit flies occur seasonally, as would occur in established populations, except there is no evidence of the critical spring generation of either species; (ii) there is no evidence of increasing frequency of outbreaks, trapped flies or larval occurrences over 29 years; (iii) there is no evidence of decreasing time between catches of adult flies as the years progress; (iv) there is no decrease in the mean number of years between outbreaks in the same locations; (v) there is no statistically significant recurrence of outbreaks in the same locations in successive years; (vi) there is no evidence of spread of outbreaks outwards from a central location; (vii) the likelihood of outbreaks in a city or town is related to the size of the human population; (viii) introduction pathways by road from Western Australia (for Medfly) and eastern Australia (for QFF) are shown to exist and to illegally or accidentally carry considerable amounts of fruit into South Australia; and (ix) there was no association between the numbers of either Queensland fruit fly or Medfly and the spatial pattern of either loquat or cumquat trees as sources of larval food in spring. This analysis supports the hypothesis that most fruit fly outbreaks in South Australia have been the result of separate introductions of infested fruit by vehicular traffic and that most of the resultant fly outbreaks were detected and died out within a few weeks of the application of eradication procedures. An alternative hypothesis, that populations of fruit flies are established in South Australia at below detectable levels, is impossible to disprove with conventional technology, but the likelihood of it being true is minimised by our analysis. Both hypotheses could be tested soon with newly developed genetic techniques.