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Although it is well-known and established that light plays important roles in plant development, up to now, there is no substantial improvements in how to deal with the light factor of spring phenology under natural condition. By monitoring the local meteorologic data and mature dates of two types (male and female) of flower from four pecan cultivars during 9 years, it was found that the complementary pattern of growing degree day and sunshine duration helped to maintain a threshold of driving force related to the maturity of pecan flower during 9 years. A novel photothermal time model based on the linear combination of growing degree day and sunshine duration was then proposed and validated to interpret the variance of mature dates of pecan cultivars. Comparative analysis showed that the new model had made extremely significant improvements to the traditional thermal time model. In addition, this model introduced the conversion coefficient K, which quantified the effect of light on the flowering drive, and revealed the differences of base temperature among cultivars. This was the first time that sunshine duration instead of photoperiod was adopted to develop into a verified model on spring phenological event of tree species. It will help to model the spring phenologies of other tree species more reasonably. [ABSTRACT FROM AUTHOR]

Pecan is one of the most important horticultural nut crops in the world. Germination tests are vital to the safe application of artificial pollination and cross breeding of pecan. Although many in vitro germination methods have been proposed, the realization of robust and reproducible methods to induce morphologically normal growth pollen tubes in vitro for detailed dynamic observation has often proved challenging in pecan. We employed a mixing and spreading method to realize the uniform distribution and germination on agarose medium, which resulted in the unprecedented level of germinational repeatability and observability. With this method, we investigated the influence of environmental variance on the in vitro germination of pecan pollen. The data from germination rate, burst rate, pollen tube length and germination speed indicated the pecan pollen had an optimal germination temperature at 25 °C but optimal rehydration temperature at 16 °C which was lower than minimum germination temperature. And this optimal rehydration temperature was harmful to pollen germination if pollen was ready to germinate after rehydration. It helped researchers understand the mechanism of probable promotion of high day/low night temperatures to pollen germination in nature. Results further revealed that pecan pollen didn’t lose their viability rapidly in first several days at ambient conditions but changed to a different rehydration and germination condition. In addition, we proposed here a new germination speed parameter GT50 to indicate the early change of pollen viability. [ABSTRACT FROM AUTHOR]

A fungus with biocontrol potential was isolated from the roots of hickory trees. The strain named sj18 was classified as a member of the genus Hypoxylon (Hypoxylaceae) after multigene phylogenetic analysis (beta-tubulin gene, internal transcribed spacer, 28S large subunit ribosomal RNA gene, and RNA polymerase II subunit gene). The strain grew well on a PDA with an optimum temperature range between 32 and 34 °C. The fungus had obvious inhibitory effects on Botryosphaeria dothidea , Colletotrichum gloeosporioides, and Gibberella moniliformis in fumigation experiments on solid agar plates. In an inoculation experiment of Chinese cabbage, the fungus was also found to have an obvious repellent effect on cabbage caterpillars. In vitro experiments on Petri dishes showed that the fermentation broth of the sj18 strain could kill 100% of Bursaphelenchus xylophilus within 8 h even if the fermentation broth was diluted 8 times. The inoculation test of Arabidopsis thaliana showed that the fungus could promote the lateral root formation of plants and significantly increase their aboveground biomass. Through the analysis of solid phase microextraction (SPME), it was found that the main volatile components of the fermentation products were azulene 65.39% (61.77% + 3.62%), caryophyllene 7.41%, and eucalyptol 6.83% according to the peak area ratio. Therefore, sj18 can be used as a candidate for the further research and development of biocontrol agents. • A fungus Hypoxylon spp. Sj18 had obvious inhibitory effects on pathogens in fumigation experiments. • Sj18 have an obvious repellent effect on cabbage caterpillar and promote the lateral root formation of plants. • The fermentation broth of sj18 strain diluted 8 times could kill Bursaphelenchus xylophilus 100% within 8 h. • Sj18 can be used as a candidate for further research and development of biocontrol agent. [ABSTRACT FROM AUTHOR]