Pathogenicity of Aphelenchoides pseudogoodeyi on the ornamental plants Asplenium nidus and Lilium speciosum in Brazil

SummaryAphelenchoides pseudogoodeyi has recently been reported in association with seeds of forage grasses and rice in Brazil and senescent strawberry plants, in the United States. This nematode is likely a mycophagous species; however, so far, its pathogenicity potential to plants is unclear. This study aimed to verify the pathogenicity of A. pseudogoodeyi to two species of ornamental plants. The experiments were conducted by inoculating A. pseudogoodeyi onto Bird’s-Nest Fern (Asplenium nidus) and Oriental Lily (Lilium speciosum) leaves, using two inoculation methods (with and without injury). After 40 days of inoculation (DAI) in Bird’s-Nest Fern and 5, 10, 20 and 40 DAI in Oriental Lily, the pathogenicity and the host efficiency were evaluated by symptoms observation and by severity, final nematode population and reproductive factor (RF), respectively. Additionally, a histopathological study was performed by inoculating A. pseudogoodeyi onto Bird’s-Nest Fern for observing anatomical alterations. A. pseudogoodeyi was able to cause local necrotic lesions on both Bird’s-Nest Fern and Oriental Lily leaves. However, the presence of injury was essential to enable A. pseudogoodeyi to penetrate and cause those symptoms in both plant species. Also, the total population of A. pseudogoodeyi decreased drastically over time and RF was <1, which characterized these species as poor-host or resistant plants. A. pseudogoodeyi penetrated into the foliar tissue and induced a total destruction of the mesophyll and collapse of the cells, with the formation of large intercellular spaces. It is concluded that A. pseudogoodeyi is an opportunistic pathogen as injury was required to induce symptoms in Bird’s-Nest Fern and Oriental Lily.

The R2R3-type LoMYB20s gene regulates programmed cell death and secondary wall biosynthesis, and affects anther development and dehiscence in Lily

Background Lilies are the widely cultivated cut flowers worldwide, while lily anthers carry a large amount of colored pollen dispersed easily to stain petals that makes serious problems for commerical sales. Improving pollen pollution in lily is one of the major goals of lily breeding. Results In this study, we identified a putative R2R3 MYB transcription factor LoMYB20s from oriental lily ( Lilium spp. ‘Siberia’). LoMYB20s mainly expressed in anther wall during the late stages of lily anther development. Suppression of LoMYB20s by virus-induced gene silencing (VIGS) in lily led to a failure of the anthers to dehisce. Induction of LoMYB20s in DEX::LoMYB20s transgenic Arabidopsis caused the rosette leaves turning yellow and the inflorescences becoming procumbent and infertile. And the downstream genes of LoMYB20s were involved in multiple metabolic processes including jasmonate (JA) biosynthetic, gibberellin (GA)-deactivating, programmed cell death (PCD), and secondary wall biosynthesis (SWB). These results suggested that LoMYB20s participated in anther development and dehiscence possibly through regulating the PCD and SWB processes in a JA/GA-associated manner. Conclusions Our results demonstrated the indispensable role of LoMYB20s in lily anther development and dehiscence, and provide a possibility of using LoMYB20s silencing to produce anther-indehicent lilies.

The Suppression of a R2R3-type LoMYB gene damaged the anther dehiscence in lily

Background Lilies are the widely cultivated cut flowers worldwide, while lily anthers carry a large amount of colored pollen dispersed easily to stain petals that makes serious problems for commerical sales. Improving pollen pollution in lily is one of the major goals of lily breeding.Results In this study, we identified a putative R2R3 MYB transcription factor LoMYB from oriental lily ( Lilium sp. ‘Siberia’). LoMYB mainly expressed in anther wall during the late stages of lily anther development. Suppression of LoMYB by virus-induced gene silencing (VIGS) in lily led to a failure of the anthers to dehisce. Induction of LoMYB in DEX:: LoMYB transgenic Arabidopsis by spraying dexamethasone (DEX), caused the rosette leaves turning yellow and the inflorescences becoming procumbent and infertile. And the induced genes in Arabidopsis include developmental programmed cell death (PCD) and secondary wall biosynthesis (SWB) related genes. These results suggested that MYB regulated anther dehisce possibly through promoting the PCD and SWB processes in cells.Conclusions Our results demonstrated the indispensable role of LoMYB in lily anther dehisce, discovered LoMYB participated in PCD and SWB regulatory processes, and provide a possibility of using LoMYB silencing to produce anther-indehicent lilies.

Morphological development of lily (Lilium ‘Siberia’) floral organs

Effects of flower buds of oriental lily “Siberia”, Asian Lily “Desert Storm” and “Shuttle Red” on the growth and development during different developmental stages of plants were investigated. The results showed that the plant height of different lily was not different in different periods, and the growth increased rapidly during seeding stage to squaring period while slowly in the squaring period to full-bloom stage. The size of flower organs was different, the "Siberia" was significantly larger than "desert storm" and "shuttle red", and the development of ovary and anther was earlier. The intraepidermal of epidermal cells of lily petals were smaller than those of outer epidermal cells. The number of intraepidermal cells is much more higher than the number of outer epithelial cells. The infiltration degree of lily petals was related to the growth of intraepidermal and outer epidermal cells of petals. The growth rate of intraepidermal cells in "Siberia" was significantly higher than that in outer epidermal. The growth rate of intraepidermal cells in "desert storm" and "shuttle red" was slightly higher than that of outer epidermal, which proved that the uneven growth of petals of intraepidermal and outer epidermal cells leads to lily petals’ bent, thereby results in the formation of different flower types.

Comparison of Defensive Enzyme Activities in the Leaves of Seven Oriental Lily Hybrids after Inoculation with Botrytis elliptica

Plant resistance characteristics are closely related to changes in the activities of self-defense enzymes after infection. Despite significant differences in the resistance of different lily (Lilium sp.) cultivars to leaf blight (Botrytis elliptica), few studies of their resistance physiology exist. This study explored changes in the resistance-related enzyme activity of several lily cultivars after leaf blight inoculation. Seven oriental lily cultivars (Lilium hybrids) with obvious differences in resistance were used as experimental materials. After inoculation with B. elliptica, the activities of four defense enzymes, superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), and peroxidase (POD), were determined according to the light absorption values at different wavelengths after their reactions. The results showed that the activities of SOD and CAT differed between the highly resistant and highly susceptible hybrids. Before inoculation, SOD activity was relatively low in all cultivars. However, after inoculation, the SOD activity increased sharply in the resistant cultivars. In the moderately resistant cultivars, the SOD activity did not change drastically. In the susceptible cultivars, the SOD activity initially showed slight increases or decreases and then increased. CAT activity showed reactions similar to those of SOD. Some changes in PAL and POD activity occurred after inoculation, but no significant correlations were present between these trends and resistance characteristics. In addition, no significant changes in enzyme activities were found in the control plants of the seven cultivars during the testing period. Overall, the resistance of Lilium oriental hybrids to B. elliptica is related to SOD and CAT activity but does not show much of a relationship with PAL and POD activity. Studying the physiological metabolic pathways of SOD and CAT appears to be an important direction in research to elucidate resistance to B. elliptica in Lilium oriental hybrids.