Land‐use changes influence the sporulation and survival of Phytophthora agathidicida,a lethal pathogen of New Zealand kauri (Agathis australis)

Phytophthora agathidicida is the accepted causal agent of dieback in remnant stands of long‐lived indigenous New Zealand kauri (Agathis australis) and poses a significant threat to the long‐term survival of this species. Little is known about the effect of key soil physicochemical characteristics on the growth of P. agathidicida. In this study, we investigated the growth of P. agathidicida in soils collected from adjacent areas under original kauri forest, short rotation pine (Pinus radiata) plantation forest and grazed pastures. A growth response assay was used to quantify asexual (sporangia) and sexual (oospore) spore counts over 8 days in soils sampled from each land‐use. Significantly higher numbers of sporangia (p < 0.001) and oospores (p < 0.01) were found in pasture and pine forest soil within 2 days of the growth assay trials, suggesting these soils may favour asexual/sexual reproduction in the early stages of P. agathidicida establishment compared to kauri forest soils. Additionally, oospore production significantly increased over 8 days in pine forest soil, suggesting that with an increase in inoculum loads, these soils potentially act as pathogen reservoirs. The soil physicochemical properties (e.g., pH, C and N, phosphorus content and electrical conductivity) investigated in this study did not significantly correspond to spore count data between land‐uses, suggesting that differences in growth response are driven by other edaphic factors not explored in the present study.     

Pathogenicity of Malaysian Phytophthora palmivora on cocoa,durian, rubber and oil palm determines the threat of bud rot disease

The epidemic of bud rot disease affecting oil palm in Colombia is primarily caused by Phytophthora palmivora. The pathogen has a cosmopolitan presence that includes Southeast Asia, but to date, bud rot has not been reported in this region. This study provides an overview of the potential risk of Malaysian P. palmivora isolates cross‐infecting other host species, including cocoa, durian, rubber and Malaysian oil palm planting materials (Dura × Pisifera, D × P). On cocoa pods, the durian isolate PP7 caused dark brown necrotic lesions. Detached leaf bioassays showed that P. palmivora isolates PP3 and PP7 infected different hosts, except rubber foliage without wounding. Inoculation tests on cocoa, durian and rubber seedlings caused brown necrotic lesions when stems were wounded, with 10% mortality in cocoa and durian at 17 days post‐inoculation (dpi). However, no further infection was observed, and lesions closed within 14–28 dpi on the non‐wounded seedlings. Pathogenicity tests of oil palm seedlings inoculated with isolates PP3 and PP7 indicated that Malaysian P. palmivora isolates were not pathogenic to oil palms based on localized infection observed only through wounding. Overall, the work demonstrated that Malaysian P. palmivora isolates were able to cross‐infect multiple hosts but did not show severe infections on oil palms.     

砧木及嫁接方法和时间对张氏红山茶嫁接成活率的影响

采用L16(43)正交试验设计方法,对影响张氏红山茶嫁接成活率的砧木种类、嫁接方法和嫁接时间等因子进行研究。结果表明:砧木种类和嫁接方法是影响张氏红山茶嫁接成活率的主要因子;3个因子不同水平对嫁接成活率的影响各有差异;以油茶大砧或红露珍做为砧木,采用皮接法嫁接张氏红山茶,全年均可嫁接,且其嫁接成活率均较高。     

嫁接方法、时间及捆绑材料对黄连木育苗成活率及生长的影响

为解决黄连木嫁接育苗成活率偏低和苗木生长不良的问题,2013—2015年研究分析了不同嫁接方法、时间、捆绑材料对黄连木育苗成活率及生长的影响,结果表明:4月10日的劈接、切接和腹接,接后用黑色地膜捆绑,成活率最高的是切接,高达95.8%,平均苗高161cm,平均地径1.40cm;与4月10日用白色地膜作捆绑材料的劈接、切接、腹接中成活率最高的切接相比,成活率提高14.7%、平均苗高提高19.3%、平均地径提高27.3%,为进一步提高黄连木嫁接育苗成活率和苗木生长量提供理论依据和技术参考。