Identification And Control Of Major Fungal Diseases From Shengzhou Nane(Prunus Salicina Var.taoxingli) Fruit

The main fungi caused the Shenzhou nane fruit rot was identified by using morphological and molecular methods.The antifungal effects and the mechanisms of sodium bicarbonate（SBC）,boric acid（BA）,and natamycin（NT）against the diseases were investigated.The main results are as follows:1.Brown rot was the most serious disease caused Shengzhou nane fruit decay before and during harvest.The pathogen causing brown rot disease is Streptococcus suis of the American Australian type（Monilinia fructicola）.The optimal growth temperature for M.fructicola was22.5℃and p H was 6.0.Glucose and beef paste was the best carbon and nitrogen sources,respectively.2.5 g?L^-1sodium bicarbonate（SBC）,2.5 g?L^-1boric acid（BA）and 25 mg?L^-1natamycin（NT）could completely inhibit the growth of M.fructicola in PDA culture medium.Moreover,10.0 g?L^-1SBC,5.0 g?L^-1BA and 400 mg?L^-1NT could effectively inhibit the occurrence of Shenzhou nane brown rot disease caused by M.fructicola in vivo.2.Aspergillus niger was another major fungus causing Shenzhou nane fruit decay.The optimal growth conditions for A.niger were temperature 30°C,p H 5.0-6.0,and fructose,peptone was the most optimal carbon and nitrogen sources.Treatment with 4.0 g?L^-1SBC+5.0 mg?L^-1NT inhibited mycelial growth and spore germination as completely as 12.0 g?L^-1SBC or 25.0 mg?L^-1NT.Moreover,experimental results in vivo showed that the rot lesion diameter and decay rate of Shengzhou nane fruit treated with SBC and NT were significantly reduced compared with the control.The results suggested that the combination treatment of SBC and NT could be an alternative to synthetic fungicides for controlling postharvest Shengzhou nane decay caused by A.niger.3.SBC,BA and NT treatments disrupted the structural integrity of cell and mitochondria membranes and decreased enzyme activities involved in TCA cycle,mitochondrial membrane potential（MMP）,ATP production in mitochondria,and ergosterol content in the plasma membrane,thus leading to the inhibition of fungi growth.The results of scanning electron microscope observations revealed that SBC,BA,and NT could cause distortion,contraction,and breakage of the M.fructicola mycelium.4.Compared with the control,B1-1（Bacillus velezensis）could effectively inhibit the growth of M.fructicola and A.niger both in vitro and in vivo.Gene expression results showed that B1-1could inhibit pathogen growth by increasing the synthesis of Bacillaene S（BAES）,Fengycin B（FENB）,Iturins D（ITUD）,Bacilysin D（BACD）,Macrolides-NI（MLNI）,Bacilysin A（BACA）,Surfactin AD（SRFAD）,Iturins A（ITUA）,Mycosubtilin-B（MYCB）,Surfactin AA（SRFAA）.