Zefa Liu

Low-light stress is known to have a significant impact on pumpkin yield in greenhouse conditions, it is crucial to understand the characteristics of low-light tolerance and identify resistant germplasm resources. In this study, four pumpkins (Cucurbita moschata) varieties were used, including three inbred lines (10–32, NY-1, and JB-1) and one hybrid line (NY-1×JB-1). Various low-light treatments (T0, no shade; T40, 40% shading; T80, 80% shading) were set, to explore their effects on morphology, photosynthetic characteristics, osmotic regulation substance content, and antioxidant enzyme activity in pumpkin seedling leaves. In the results, seedlings of inbred lines 10–32 and JB-1, as well as hybrid NY-1×JB-1, exhibited low-light resistance with shading rate increases. The maximum photochemical quantum yield of photosystem II (Fv/Fm) of all varieties decreased under low-light stress. Catalase (CAT) activity initially increased and then decreased, while superoxide dismutase (SOD) activity showed the opposite trend. Peroxidase (POD) activity gradually increased in 10–32, JB-1, and NY-1×JB-1, with JB-1 showing a significant increase at T80, and NY-1 displaying an initial decrease followed by an increase. Noteablely, the soluble proline (Pro) content decreased in 10–32, NY-1, and NY-1×JB-1. Significant differences in malondialdehyde (MDA) content were observed among the seedlings of four varieties. The MDA contents increased in 10–32 and JB-1 under T0 and T40, while showed no significant change in NY-1. The MDA content at T80 significantly decreased in NY-1, and first decreased and then significantly increased in NY-1×B-1. The soluble sugar content in 10–32 remained unchanged between T0 and T40, but significantly increased at T80. While in JB-1 and NY-1, it initially increased then decreased with increasing shading rate. The trend in NY-1×JB-1 was opposite to that of JB-1 and NY-1, with initially decreased followed by a significant increase. In conclusion, morphological characteristics associated with low-light tolerance can serve as reference indices for breeding low-light tolerance pumpkins. These parameters can be used as reference indices to assess pumpkin resistance to low-light stress.

Cucurbita maxima Duch is a widely cultivated and consumed vegetable with high economic and nutritional value. The complete mitochondrial (mt) genome of C. maxima was characterized by Illumina paired-end sequencing and is reported here. The size of the complete mt genome was 640,814 bp, and its GC content was 43.37%. Sequence analyses showed that the mt genome encoded 68 genes, consisting of 38 mRNA, 27 tRNA, and 3 rRNA genes. Phylogenetic analysis indicated that C. maxima was most closely related to Cucurbita pepo (NC-014050.1). This study provides useful genetic information for further studies on the genetic structure and evolutionary patterns of C. maxima for species identifications. The genome can be accessed on GenBank with the accession number (OL350846.1).

Hybrid incompatibility and F₁ hybrid dysgenesis in the interspecific hybridization between pumpkin (Cucurbita moschata Duch.) and winter squash (Cucurbita maxima Duch.) have been previously noted. For this reason, it is difficult to obtain F₂ generations due to F₁ sterility. However, back-crossing and add-crossing can be utilized to overcome these incompatibility barriers in interspecific hybridization. To date, few studies have focused on parental selection, the back-crossing process, and offspring characteristics related to interspecific hybridization. Hence, we explored the F₁ seed acquisition rate, plant characteristics, and F₂ generation fertility after interspecific back-crossing and add-crossing hybridization of C. moschata and C. maxima. Moreover, as a female parent, X-1 (C. moschata) yielded F₁ seeds when crossed with winter squash (C. maxima) 10-04-3, 10-37, or 10-05-2. BC₁F₁ seeds and plants could be obtained with winter squash (C. maxima) as the recurrent parent. Some healthy F₂ seeds and plants were obtained from the interspecific hybrids, including ZJ-13, ZJ-8, and ZJ-11. Further fruit nutrition quality analysis showed that the starch, polysaccharide, cellulose, and dry material contents of ZJ-7 and ZJ-8 were significantly higher than those of the parent pumpkin and winter squash lines. The bioflavonoid content of ZJ-8 was lower than that of its parents, and its soluble protein was at the median value. Meanwhile, the bioflavonoid content of ZJ-1 was lower than that of its parents, but its soluble protein was significantly higher. These results suggest that back-crossing and multi-crossing can overcome the barriers to interspecific crossing of C. moschata × C. maxima. Some interspecific hybrid fruits had nutritional contents much higher than those of their parent lines. Additionally, X-1 (C. maxima) was found to act as a bridge species in interspecific hybridization. Collectively, in this study, the barriers to interspecific hybridization of C. moschata × C. maxima were addressed through crossing methods and choice of parents, and the obtained results are expected to provide novel support for interspecific hybrid breeding between C. moschata and C. maxima.

In this paper, we propose a low-jitter reference-less clock and data recovery (CDR) circuit with a speed range of 9.8–12.5[ ]Gb/s. The proposed CDR uses a multi-stage half-rate bang-bang phase detector (ML-HR-BBPD) to maximize the quantization of the phase difference. In addition, a unit interval adjuster (UIA) is added to the CDR circuit. So that the circuit can minimize the phase detector’s phase error before the output clock frequency is locked. Finally, the loop filter (LF) is improved to realize the coarse and fine adjustment of the phase error over a wide range of phase differences. The CDR circuit’s total power consumption is reduced by using a half-rate phase detector. The CDR circuit was fabricated in TSMC 40[ ]nm CMOS process. The measured results are obtained in the proposed CDR circuit at a data rate of 12.5[ ]Gb/s. With a pseudo-random bit sequence (PRBS) of [ ], the measured result shows that the bit error rate (BER) is [ ], and the root mean square jitter recovered in the output is 0.302 [ ]. The circuit’s jitter tolerance (JTOL) is 0.46 UI_pp, and its total power consumption is 74.8[ ]mW with a 5.98[ ]pJ/bit energy efficiency.