Cross pollination of different peony cultivars with ‘Feng dan’

ABSTRACT: Paeonia ostii ‘Feng dan’ is recommended as a new promising oil crop because of the nutrient elements in its seed; however, the development of this new oil crop is now limited due to its low seed setting rate. This study identified ways to improve the cross pollination of Feng dan as the maternal parent, which has been proved to be a suitable oil crop, so as to improve the seed setting rate of ‘Feng dan’, and to predict the functional relationship between pollen vigor and seed setting rate. improving the efficiency of cross pollination. Three major steps were conducted, first, to screen the appropriate method of measuring pollen vigor of the paternal parent, which could have a strong relationship with seed setting rate. Second, to obtain the corresponding seed setting rate by cross pollination. Third, the functional relationship between two indexes was founded which could be used in cross pollination practice. Results indicated that the best paternal parents of ‘Feng dan’ were ‘Feng dan’ cultivars from other different cultivation populations; The most suitable medium concentration for pollen germination was 100~150 g/L sucrose, 0.06~0.08 g/L boric acid, and 50~200 g/L PEG-6000. Both the seed setting rate and the number of seed grains were positively correlated with the pollen activity, and the seed setting rate was negatively correlated with the local precipitation.

The HD-ZIP IV transcription factor GL2-LIKE regulates male flowering time and fertility in cucumber

Cucumber is dioecious by nature, having both male and female flowers, and is a model system for unisexual flower development. Knowledge related to male flowering is limited, but it is reported to be regulated by transcription factors and hormone signals. Here, we report functional characterization of the cucumber (Cucumis sativus) GL2-LIKE gene, which encodes a homeodomain leucine zipper (HD-ZIP) IV transcription factor that plays an important role in regulating male flower development. Spatial–temporal expression analyses revealed high-level expression of CsGL2-LIKE in the male flower buds and anthers. CsGL2-LIKE is closely related to AtGL2, which is known to play a key role in trichome development. However, ectopic expression of CsGL2-LIKE in Arabidopsis gl2-8 mutant was unable to rescue the gl2-8 phenotype. Interestingly, the silencing of CsGL2-LIKE delayed male flowering by inhibiting the expression of the florigen gene FT and reduced pollen vigor and seed viability. Protein–protein interaction assays showed that CsGL2-LIKE interacts with the jasmonate ZIM domain protein CsJAZ1 to form a HD-ZIP IV–CsJAZ1 complex. Collectively, our study indicates that CsGL2-LIKE regulates male flowering in cucumber, and reveals a novel function of a HD-ZIP IV transcription factor in regulating male flower development of cucumber.

Pollen number and vigor contribute to effective ovule numbers among contrasting nitrogen utilization efficiency oilseed rapes genotypes before heart stage

Background: While no significant differences in initial ovule number were found among oilseed rape genotypes, there was a large variation in effective ovule number (EON), which determines the final seeds per silique (SPS), a critical component of yield. Up to date, on study has been focused on unraveling the pre-flowering main factors to restrict EON and identifying the critical period of EON formation among contrasting nitrogen utilization efficiency (NUtE) oilseed rape genotypes.Results: In this study, we selected 18 oilseed rape genotypes with different NUtE to identify the main factors that contribute to EON, and determine if genotypes differed in the critical period of EON formation under both field and pot experiments from 2016-2018. Our results showed the high NUtE genotypes also showed 14.3% higher NUtE, accompanied with 29.4% higher yield per plant and 21.1% higher SPS. The greater productivity of the high NUtE oilseed rape genotypes was associated with 44.1% greater pollen number, 23.5% higher pollen vigor, and 39.3% lower ovule abortion rate, compared to the low NUtE genotypes. In addition, at the heart stage, the high NUtE genotypes displayed higher silique net photosynthetic rate, surface area, biomass, and RNA expression levels, compared to the low NUtE ones. Taken together, this study indicated the pollen number, pollen vigor and ovule abortion rate contributed to the final EON of diverse oilseed rape genotypes; the critical period of determining EON among contrasting NUtE genotypes was at the heart stage.Conclusion: Increasing pollen number and vigor, and decreasing ovule abortion rate before the heart stage should be the prerequisite for breeders to improve yield and NUtE of oilseed rape genotypes.

POLLEN VIABILITY AND VIGOR IN TOMATO PLANTS UNDER HIGH TEMPERATURES

High temperatures during flowering have been implicated in reducing seed set and fruit set in tomatoes (Lycopersicon esculentum). Pollen viability and vigor were studied by measuring in vitro germination and pollen tube development in pollinated pistils of four processing tomato cultivars under normal (25° C day/15° C night) and high (32° C day/23° C night) temperatures. Preliminary studies were carried out to determine the length of pollen tubes in styles collected in times ranging from 3 to 48 hours after pollination. Under normal temperatures the pollen tubes reach the end of the style between 12 and 18 hours. At high temperatures there are fewer pollen tubes moving through the style and the time to reach the end of the style is longer. In pollen vigor studies, crosses were made between pollen and pistils of plants grown under different temperature treatments, then pollinated pistils were collected at 4, 8 and 12 hours after pollination. There were differences in in vitro pollen germination percentage and pollen tube length in the pollinated pistils, suggesting that high temperatures act to slow down pollen activity.