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• Field observation embodying that Litchi chinensis Sonn. cv. 'Huaizhi' as rootstock did show a wide compatibility. • Nutrients contents, mineral nutrition (N and P) levels, and antioxidant enzyme activities, might be related to the wide compatibility of Huaizhi as rootstock. • Microscopic observation showed a compatible healing dynamics. • DEGs related to phenylpropanoid biosynthesis, plant hormone biosynthesis and signal transduction, sucrose and starch metabolism, MAPK signaling pathway might be involved in the wide compatibility of 'Huaizhi' as rootstock. Litchi chinensis Sonn. cv. 'Huaizhi' (HZ) is an ancient cultivar of litchi. It has been used as widely compatible rootstock for litchi grafting for a long time. However, the mechanism of HZ as widely compatible rootstock is still unclear. In the present study, physiology, morphological anatomy, as well as transcriptomics were conducted to reveal the reasons for HZ with wide compatibility in litchi grafting. Field observation were conducted on the grafting combinations of HZ/HZ (homografting as the control), FZX/HZ and MGL/HZ (the scion with good grafting compatibility in production), SYH/HZ, HHDHL/HZ and WHL/HZ (the scion with weak grafting compatibility in production), embodying that HZ as rootstock did show a wide compatibility. The physiological and biochemical indicators of scion new shoot leaves and scion mother tree indicated that nutrients contents (dry matter weight, total soluble sugar, and starch), mineral nutrition (N and P) levels, and antioxidant enzyme (superoxide dismutase and peroxidase) activities, might be related to the wide compatibility of HZ as rootstock. Microscopic observation of the paraffin sections of healing sites at different stages showed that the necrotic layer of three representative litchi grafting combinations of HZ/HZ, WHL/HZ and MGL/HZ basically disappeared from 14 d to 21 d after grafting, and the callus differentiated into a large number of protoxylem cells, indicating a compatible healing dynamics. Subsequently, a total of 14,384 differentially expressed genes (DEGs) were identified by RNA-seq, of which 2,831 DEGs exhibited the same expression trend within three grafting combinations, enriching into phenylpropanoid biosynthesis, plant hormone biosynthesis and signal transduction, sucrose and starch metabolism, MAPK signaling pathway, peroxisome and other metabolic pathways. These results provide a theoretical basis for the adjustment of cultivar structure in litchi production. [ABSTRACT FROM AUTHOR]

Understanding of the shoot growth pattern and precise determination of flush maturation time is the key to targeted management of flush cycle, which is important for productivity of litchi. In this study, the shoot growth rhythm and changes in leaf greenness and functionality in developing leaves were studied for two consecutive years in litchi (Litchi chinensis Sonn.), a typical tree species with delayed greening leaves. Two cultivars 'Baili' and 'Heiye' with significant difference in leaf greenness were compared. The study showed that the shoot growth was cyclic but the stem expansion continued until winter. Leaf greenness, indicated by SPAD value, increased with leaf maturation following a modified logistic model. The asymptotic deceleration point (PDA) was assumed as the full maturity point of the new leaves, when their SPAD value had increased to 90% of its maximum (Vmax). The average SPAD values at PDA were 45 and 31 in 'Heiye' and 'Baili', respectively. At this point, maximal net CO2 assimilation (A) and photochemical efficiency of photosystem II (PSII) (Fv/Fm) were attained. The average growing degree days (GDD) for flush growth from bud break till SPAD value reached PDA across seasons were similar in 'Baili' and 'Heiye' (587.4°D vs 546.7°D). It was concluded that the apical meristem of litchi alternates between resting and active states, while the vascular cambium maintains active state throughout the growth season. SPAD meter provides a rapid and non-destructive technique to indicate the flush maturity of litchi with delayed greening leaves. Thermal time for flush growth was not significantly different between the two cultivars despite their great difference in leaf greenness. [ABSTRACT FROM AUTHOR]

Abstract: Calcium in different forms was compared in the pericarp of cracked and healthy fruit in the cracking-susceptible litchi (Litchi chinensis Sonn.) cultivar ‘Nuomici’. Incorporation of 45Ca into the cell walls of the pericarp and effects of sprays of calcium chloride (0.2% or 0.5%) on endogenous calcium and cracking incidence were examined. The results showed that calcium concentration in cracked fruit was significantly lower than in healthy fruit. Structural calcium as part of cell wall components contributed to the majority of the difference in calcium concentration between cracked fruit and healthy fruit. Surface spray of calcium chloride, either once or three times at different stages of fruit development exhibited no significant effect on fruit cracking and hardly increased calcium, especially structural calcium in the pericarp. X-ray microanalysis revealed that the applied calcium remained on pericarp surface. Radioisotope test showed that less than 0.1% of 45Ca applied on fruit surface was incorporated into the cell walls. It is suggested that spraying calcium on fruit surface is not an effective way to prevent litchi fruit cracking due to the difficulty in uptake of the calcium sprayed on fruit surface. [Copyright &y& Elsevier]

Abstract: Gas exchange of 3-year-old potted ‘73-S-20’ litchi (Litchi chinensis Sonn.) plants were measured under controlled conditions. At 28.8±0.3°C, dark respiration (R d) was estimated at 0.6 CO2 μmolm−2 s−1, quantum yield (Φ) was 0.024mol CO2 mol−1, and light compensation point (PPFDcomp) was 24μmolm−2 s−1 photosynthetic photo flux density (PPFD). Maximum net CO2 assimilation () (6.5–8μmolm−2 s−1), stomatal conductance (g s) (0.07–0.09molm−2 s−1) and transpiration (E) (0.7mmolm−2 s−1) were recorded at PPFD >800μmolm−2 s−1, leaf temperature (T L) between 27 and 32°C, and vapor pressure deficit (VPD) <0.7kPa. When VPD and T L simultaneously increased maximum was obtained between 25 and 28°C. CO2 compensation point (Ccomp) was recorded between 90 and 100ppm. saturated at external CO2 concentration >800ppm. responses to light, and VPD were mainly regulated by stomata. On the other hand, response to internal CO2 was mainly through leaf photochemistry. At T L <28°C leaf photochemistry dominated responses, while at T L >28°C stomatal regulated responses. Effects of leaf age and location as well as cropping on gas exchange were also studied on 9-year-old in the field trees. Leaf , g s and E on the well-exposed, younger flushes and adjacent to fruit were greater than those on shaded older flushes and woods or those on de-fruiting shoots. Our findings indicated that potential depression of leaf photosynthetic efficiency in litchi might occur due to low temperature in bloom season and early fruit set, as well as due to hot and dry mid-day in early summer. [Copyright &y& Elsevier]

Abstract: Litchi and longan are famous southern subtropical fruits in China. Besides closely related to each other taxonomically, litchi and longan share many similarities in origin, cultivation history and environmental requirements; furthermore, the developments of research on litchi and longan germplasm resources are somewhat similar and comparable. This paper reviews the literature on origin and distribution, collection and conservation, classification and identification, selection and breeding of litchi and longan germplasm resources in China. The classification of litchi and longan can be divided into three stages: classification based on morphological traits, classification by isozyme analysis and DNA markers. The expression of morphological traits is often affected by environmental conditions; the number of loci that isozyme analysis can examine is small, cultivars, which are closely related often have identical isozyme patterns. The limitations of classification based on morphological traits and isozyme analysis are then overcome by the utilization of molecular markers. At present, most new litchi and longan cultivars are selected from superior seedlings obtained after open-pollination or sport; germplasm with desirable characteristics such as aborted seeds, rather big-fruit and rather late-bearing have not been fully exploited. In order to achieve the goal of improving fruit quality and agronomic characteristics, it is suggested that additional studies of genetic diversity on litchi and longan germplasm should be carried out with more powerful markers such as SSR and ISSR; marker assisted selection (MAS) should be employed to improve litchi and longan''s cross breeding efficiency. [Copyright &y& Elsevier]

The effects of autumnal water stress on the levels of zeatine-riboside and dihydrozeatin-riboside in the shoot xylem-sap and on the intensity of flowering in the following year were studied in commercial lychee (Litchi chinensis Sonn.) during the 1995/1996 season. Four irrigation treatments were initiated at the beginning of October coinciding with the end of the second vegetative flush after harvest as follows: 0.5, 0.25, 0.125 and 0 Class A pan evaporation coefficient, designated as 100, 50, 25 and 0%, respectively, were applied. Soil and midday stem water potentials were determined several times during October, after the beginning of treatment. Xylem-sap concentrations of trans-zeatin-riboside (t-ZR) and dihydrozeatin-riboside (DHZR) were determined 20 days after the start of the irrigation treatments. Both soil and midday stem water potentials decreased with the decrease in the irrigation levels. Flowering intensities in the following spring were higher after the reduced irrigation treatments than in the control (100%). DHZR and t-ZR concentrations in the xylem-sap increased with decreasing irrigation level, down to the 25% irrigation level. Cessation of irrigation (0%) resulted in a steep decrease in the t-ZR concentration and a further increase of DHZR. The relationships between plant and soil water status, cytokinin xylem-sap content and flower bud differentiation reported herein suggest that moderate water stress is sufficient to induce fruit bud differentiation without any visible damage to the trees. [Copyright &y& Elsevier]

Abstract: In order to increase the fruit weight of a shriveled-seed cultivar, trees of ‘Yu Her Pau’ litchi (Litchi chinensis Sonn.) growing in Taiwan were sprayed with Gibberellic acid (GA3) (ProGibb®, 20% of GA3) at 5 and 10mg/l 14 days after full bloom (AFB) over 2 years. Both concentrations of GA3 significantly increased fruit longitudinal and transversal diameter, and fruit, aril and pericarp weight (40–41 and 37–38mm, and 27.3–28.4, 21.7–22.7 and 5.0–5.3g, respectively) compared with control (35–36 and 33–34mm, and 22.3–22.4, 17.8–17.9 and 3.9–4.0g), but had no significant effects on seed weight, percentage of aril weight of total fruit weight or total soluble solids (0.5–0.7g, 78.9–80.3% and 18.1–19.0°Brix, respectively). Fruit characteristics within the two concentrations of GA3 showed no significant difference. The results indicated that sprays of GA3 should be evaluated in ‘Yu Her Pau’ commercial orchards, and in other elite cultivars. [Copyright &y& Elsevier]