【Objective】 To explore the molecular mechanism of graft healing in pecan, we cloned the CiMYB46 gene and analyzed its expression pattern and cis-elements. 【Method】 We extracted RNA from graft unions of pecan plants at different developmental stages and designed primers, based on our previous transcriptome results, to clone the desired gene by RT-PCR. In addition, genomic DNA was used as a template for PCR amplification and cloning of the promoter area of the desired gene.【Result】 The amplified fragment obtained by RT-PCR was cloned and sequenced. It contained an open reading frame of 969 bp that started with the initiation codon, ATG and ended with the termination codon, TAA, encoding a polypeptide of 322 amino acids. The deduced amino acid sequence of the cloned gene contained a MYB domain and was closely clustered withArabidopsis AtMYB46. Thus, we designated our sequence as CiMYB46. Real-time PCR analyses demonstrated that CiMYB46 was highly expressed during the vascular formation stage of graft union development in pecan and had a similar expression profile to that of some functional genes involved in secondary cell wall synthesis. A 1 070 bp promoter region upstream of the initiation codon of CiMYB46 was obtained through PCR and cloning, using genomic DNA as a template. PlantCARE analysis revealed that the promoter region of CiMYB46 contained two basic cis-acting elements, a CAAT box and a TATA-box, drought responsive elements, and hormone responsive elements, including ABA, Me-JA, GA, and SA. 【Conclusion】 CiMYB46 might be associated with vascular bundle formation during the graft healing process of pecan. It may be induced by GA.
【Objective】 The objective of the present study was to explore the effects of slow-release fertilizer dosage on the growth and nutrient contents of pecan (Carya illinoensis) container seedlings and to determine a reasonable slow-release fertilizer dosage for cultivating these seedlings. 【Method】 A single-factor, completely randomized block design was used to set up the treatments T0, T1, T2 and T3 (0, 3, 6 and 9 kg/m3, respectively) with different slow-release fertilizer dosages, and the growth of seedlings and nutrient content [nitrogen (N), phosphorus (P) and potassium (K)] were determined and compared. 【Result】 Compared with the control treatment (T0), the different slow-release fertilizer treatments significantly promoted seedling height, root collar diameter, biomass per plant, total root length, total root surface area, total root volume, root diameter, and N, P, and K levels in all organ. The nutrient content improved the root-to-shoot ratio, and the treatment effect was found to be optimum with T1. As the fertilizer concentration increased, the promoting effect decreased. Dynamic measurement showed that the slow-release fertilizer treatment maintained rapid increase in seedling height and root collar diameter during the treatment period; the root collar diameter lasted longer than other factors, and the growth stage (after mid-August) and seedling height were non-synchronous. 【Conclusion】 An appropriate slow-release fertilizer dosage can promote growth, biomass accumulation, and root development in pecan container seedlings. The promoting effect was related to increased nutrient content, and the optimum fertilizer dosage was 3 kg/m3.
【Objective】 The effects of nitrogen (N), phosphorus (P) and potassium (K) treatments on the nutrient content and physiological characteristics of young grafted pecan seedlings were studied to determine the optimum fertilization scheme. 【Method】 Two-year-old seedlings from native Chinese ‘Shaoxing’ pecan seeds were collected as rootstock and the U.S.-released pecan cultivar ‘Mahan’ as scion. After one year of growth, the young grafted seedlings were transplanted into pots for use as experimental materials. Based on the L 9(34) orthogonal experimental design, fertilization experiments were conducted with three factors, i.e., N, P and K, and three treatments, i.e., N: 4,6,8 g/plant; P: 2,3,4 g/plant; K: 1,3,5 g/plant. The effects of different treatments on the nutrient content (total N, total P and total K) of different tissues (roots, shoots and leaves) and the whole plant as well as the chlorophyll content and photosynthesis-related indicators [net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr)] of pecan leaves were tested and analyzed. 【Result】 Proportional fertilization significantly increased the total N, total P and total K contents of the whole plant and all tissues of young grafted pecan seedlings. Among the different tissues, the total N and total P contents were the highest in leaves, followed by the roots and then shoots. Further, the total K content was the highest in the roots, followed by the shoots and then leaves. Chlorophyll a and b contents peaked in mid-July. Proportional fertilization significantly affected the photosynthesis-related indicators of seedlings, exceptTr; the other indicators were present as N>K>P. 【Conclusion】 Proportional fertilization of pecan seedlings significantly increased the nutrient content of the whole plant and different tissues, chlorophyll content in leaves, and photosynthetic capacity. It was preliminarily concluded that the optimum fertilization ratio for pecan seedlings was that used in the last treatment, i.e., N: 6 g/plant, P: 2 g/plant, and K: 5 g/plant.
