基于四个遗传群体的西瓜整合图谱构建及重要经济性状QTL定位

目的与意义:人们长期对于现代栽培西瓜优良性状的选育使得西瓜遗传基础变得狭隘.野生亚种是西瓜育种中优异基因的重要来源,但将野生亚种中的优良性状基因转入到现代栽培西瓜中的成功率很低.由于缺乏高质量的遗传图谱致使分子标记辅助选择(MAS)在西瓜中的应用尚未实现,难以在图谱之间进行整合和比较分析.本研究的目的是整合现有的利用单核苷酸多态性(SNP)和简单重复序列(SSR)标记构建西瓜整合遗传图谱.

Effect of Various Soil Media on Disease Severity of <i>Fusarium</i>Wilt in Watermelon

Fusarium wilt is a major disease of watermelon (Citrullus lanatus) caused by Fusarium oxysporum f. sp. niveum (Fon). Use of host resistance is the most effective management strategy for the disease, and a major objective for breeding programs. Screening assays rely on the ability to discriminate resistant and susceptible genotypes in segregating populations. However, complex interactions between Fon and the soil environment can influence symptom development and disease severity rating. In the current study, severity of Fusarium wilt (race 1) in sand-peat (1:1 v/v), sand-perlite (1:1), sand-peat-vermiculite (4:1:1), peat-perlite (1:1) and Fafard 3B potting media was compared among five watermelon cultivars: Calhoun Gray (resistant), SunSugar (resistant), Allsweet (moderately resistant), Sugar Baby (susceptible) and Charleston Gray (susceptible). Plant biomass (average dry weight/plant) was lowest in peat-perlite (1.67 g) and sand-peat (2.16 g), and was significantly different (α = 0.05) from that of sand-perlite (3.48 g), sand-peat-vermiculite (4.94 g) and Fafard 3B (6.90 g). Conversely, disease severity [area under disease progress curve (AUDPC)] across cultivars was significantly higher in peat-perlite (AUDPC = 62.96) and sand-peat (AUDPC = 40.87), than in sand-perlite (AUDPC = 11.55), sand-peat-vermiculite (AUDPC = 10.67) and Fafard 3B (AUDPC = 9.29). Consistent discrimination (α = 0.05) of resistant and susceptible cultivars was realized in sand-peat-vermiculite and Fafard 3B, but was not possible in peat-perlite, sand-peat and sand-perlite. Collectively, these findings support suitability of sand-peat-vermiculite and Fafard 3B for routine screening of Fusarium wilt resistance in watermelon.

The disease reactions of heirloom bell pepper “California Wonder” to <i>Phytophthora capsici</i>

Greenhouse studies were performed to determine the reactions of 10 “California Wonder” (Capsicum annuum) accessions to the three forms of Phytophthora blight (root rot, stem blight and foliar blight) caused by Phytophthora capsici. Differences in root rot, stem blight and foliar blight severities among accessions were significant. The accessions consistently differentiated into two groups across the three disease syndromes. Simple sequence repeat (SSR) markers showed variability both within and between accessions of California Wonder. The variability in the responses to the three forms of Phytophthora blight does not warrant its usefulness as a standard susceptible control in studies involving the Capsicum-P. capsici patho-system.