新月弯孢菌Curvularia lunata营养体亲和性的进一步研究

来自全国39个地区的70株新月弯孢菌Curvularialunata在WAC培养基上诱导培养后,随机挑取10197个抗KClO3突变体,经CDA鉴定获得2207株nit突变体,nit突变体频率为21.64%。在这些nit突变体中,1397个为nit1,占63.30%;734个为NitM,占33.26%;76个为nit3,占3.44%。70个菌株全部获得了稳定的nit突变体,其中52个菌株获得了NitM突变体。结果表明WAC比先前报道的KPS更适合用于C.lunatanit突变体的筛选。通过不同菌株间互补nit突变体配对测试,将其中的65个C.lunata菌株划分为22个营养体亲和群(VCGS),而另外5个菌株因未获得NitM突变体暂时无法确定其VCG。划分出的22个VCGs中,有11个VCGs是由多菌株组成的,VCG3为优势类群,含18个菌株,其地理来源最复杂,主要为致病性中等以上的菌株;其余11个VCGs内均仅有1个自身亲和的菌株。以上结果初步表明,在C.lunata群体内存在丰富的VCG多样性,VCG3可能是与致病性相关的优势VCG,但营养体亲和性与菌株地理来源没有明显的直接关系。

Further study on vegetative compatibility groups of Curvularia lunata isolated from corn in China

Vegetative compatibility groups (VCGs) of 70 strains of Curvularia lunata isolated from infected corn leaves collected from different regions in China were assessed through complementation tests of nitrate-nonutilizing (nit) mutants. Strains cultured on water agar chlorate medium (WAC) (containing 2.5% KClO3) were tested for their ability to produce chlorate-resistant sectors. Among 10,197 chlorate-resistant mutants, 2,207 nit mutants (21.64% of all tested chlorate-resistant mutants) were screened onto Czapek-Dox agar medium (CDA). These nit mutants were divided into three phenotypes by their growth response to nitrate, nitrite, and hypoxanthine as the nitrogen sources. Among the nit mutants, 63.30% were characterized as nit1, 33.26% as NitM, and 3.44% as nit3. At least two nit mutants were recovered from each of the 70 tested strains, and 52 strains obtained NitM mutants. The results showed WAC medium was more suitable than KPS medium (previously published) for the generation of nit mutants in C. lunata. All strains recovered both NitM and nit1 or nit3 demonstrated self-compatibility. Based on positive complementary reaction between NitM and nit1 or nit3 mutants derived from the different strains (between nit mutants) onto CDA, 65 strains were assigned to 22 VCGs and exhibited rich VCG diversity. The remains (7.14% of all tested isolates) could not be assigned to any VCG because of the absence of their NitM mutants. Of 22 VCGs, 11 were multimember and VCG3 was the dominant group containing 18 strains collected from different geographic regions. Each of the remained 11 VCGs only contained one self-compatibility strain. These results preliminarily showed that there was significant VCG diversity in C. lunata population. The results suggested that VCG3 may be correlated with pathogenicity. However, no close correlation was found between VCG diversity and geographic origin.