Pathogen Isolation and Identification of a Serious Leaf Disease of Red Sandalwood (Pterocarpus santalinus) Seedlings

In the introduction and propagation of red sandalwood （Pterocarpus santalinus）, a serious leaf disease of its seedlings in winter and spring seasons was found, but the name of the disease and its pathogen species have not been reported. The pathogen isolated from infected leaves of 18-month-old seedlings was identi- fied as Colletotrichum gloeosporioides by morphological characteristics of colony and conidium, and analysis results of rDNA-intemal transcribed spacer sequence （ITS） of the strain. Pathogenicity test results further confirmed that C. gloeosporioides was the pathogen responsible for the infected leaves symptoms of red sandal- wood. However, the disease belongs to an atypical anthraenose. Control of the leaf diseases of red sandalwood seedlings was discussed.

Grafting Propagation Techniques of Red Sandalwood(Pterocarpus santalinus),a Precious Hongmu Tree Species

[Objectives] This article aimed to study the grafting propagation techniques of red sandalwood ( Pterocarpus santalinus ), so as to provide technical support for the effective propagation of seedlings of this precious Hongmu species.[Methods] Based on the analysis and comparison of the growth performance of the Hongmu tree species introduced to China, taking 1 to 2-year-old Pterocarpus indicus seedlings as rootstocks and single-bud stems of P. santalinus as scions, grafting was carried out from January to April using three grafting propagation methods, cut grafting propagation, skin grafting propagation and oblique grafting propagation.[Results] The results of several years of experiments show that in early spring, P. santalinus could be propagated well using the grafting propagation methods of skin grafting propagation and oblique grafting propagation, with survival rate over 80%. For rootstocks with young age or thin stems, the joint unions of the oblique grafting propagation healed well, without apparent protrusions, unlike those of skin grafting propagation. The survival rate of oblique grafting propagation that is fast and reliable was higher than that of cut grafting propagation.[Conclusions] It is feasible to use the grafting propagation methods to propagate P. santalinus seedlings. This is a traditional and innovative technology path in the propagation of high-quality seedlings of precious Hongmu trees, and can be promoted and applied in industrial practice.

Growth response of Pterocarpus santalinus seedlings to native microbial symbionts(arbuscular mycorrhizal fungi and Rhizobium aegyptiacum)under nursery conditions

The objective of this research was to improve the growth and biomass of Pterocarpus santalinus L.f.(an endangered leguminous tree)using native microbial symbionts such as arbuscular mycorrhizal fungi and Rhizobium associated with native populations of P.santalinus.The native arbuscular mycorrhizal fungi isolated from P.santalinus soils were identifi ed as(1)Glomus fasciculatum;(2)Glomus geosporum;and Glomus aggregatum.A nitrogenfi xing microbial symbiont was isolated from the root nodules of P.santalinus and identifi ed as Rhizobium aegyptiacum by 16s rRNA gene sequencing.These microbial symbionts were inoculated individually and in combination into P.santalinus seedling roots.After 90 days,growth and biomass had improved compared with uninoculated controls.Shoot and root lengths,number of leaves,stem circumference,number of root nodules,biomass,nutrient uptake and seedling quality index were signifi cantly increased by a combined inoculation of arbuscular mycorrhizal fungi+Rhizobium aegyptiacum.It was concluded that native microbial symbionts positively infl uenced P.santalinus seedling growth which will be helpful for successful fi eld establishment.

Tissue Culture of Red Sandalwood (Pterocarpus santalinus)

[Objectives] This study was conducted to develop a rapid propagation method for red sandalwood ( Pterocarpus santalinus ) by tissue culture.[Methods] The well-grown red sandalwood seed embryos were inoculated into three kinds of culture media after aseptic treatment,and the aseptic explants were obtained and inoculated into six kinds of media for light culture.[Results] In the best disinfection schemes of red sandalwood,disinfecting with HgCl 2 for 8 min achieved the highest germination and survival rates;when the medium for inducing red sandalwood explants was MS+0.2 mg/L IBA,the induction rate reached a maximum value;and when the culture medium for inducing stem segments of aseptic red sandalwood plantlets was MS+3.0 mg/L 6-BA+0.3 mg/L IBA,the growth of the stem segments achieved the best effect.The optimal medium for inducing red sandalwood explants was MS+IBA 0.2 mg/L,and the optimal medium for inducing stem segments of red sandalwood was MS+3.0 mg/L 6-BA+0.3 mg/L IBA.[Conclusions] The results of this study have a large reproductive coefficient,simple process and low cost,which have outstanding value for promoting the breeding and promotion of red sandalwood seedlings.

Experimental Study on Heartwood Formation and Development of Red Sandalwood by Grafting

Red sandalwood(Pterocarpus santalinus)is the most precious species of Pterocarpus,and the long maturity period of its heartwood is an important factor limiting its development.The 1-year-old plants of P.macarocarpus were chosen as the rootstocks to graft red sandalwood with single-bud scions of 1-year-old shoots in spring.The 5-month survival rate reached over 80%,and the grafted plants grew well.Moreover,the grafting significantly promoted the formation and development of the heartwood of red sandlawood.At 18^(th)month after grafting,compared with the seedling plants,the diameter of heartwood was increased by 82.8%and 29.6%,respectively,and the ratio of heartwood increased by 64.8%and 29.6%,respectively.The propagation technology had outstanding practical value and scientific significance,which has not been reported at home and abroad.