Distribution of downy mildew (Bremia lactucaeRegel) resistances in a genebank collection of lettuce and its wild relatives

Genebanks serve as a rich source of diversity that can be exploited for crop improvement. However, large numbers of accessions usually have to be evaluated to find material with the characters of interest, and therefore, enhanced trait information can facilitate the more efficient selection of accessions by users. In this study, we report on the distribution of resistances to 28 races of downy mildew among 1223 genebank accessions of cultivated lettuce (Lactuca sativaL.) and 14 related wild species. Due to modern plant breeding, the overall level of resistance of cultivars released after 1950 appears to have increased two- to three-fold compared with varieties from earlier periods. Although fully resistant reactions could be observed among the accessions of cultivated lettuce for each of the 28 investigated races, the resistance probability was more than two-fold higher on average for accessions from the wild gene pool. In general, species of the primary gene pool appeared less resistant than those of the secondary or tertiary gene pool. Probabilities for examinedLactucaspecies ranged from 0.29 forL. serriolato 1.00 forL. perenniscompared with 0.19 for cultivated lettuce, with lower overall resistance probabilities observed only forL. altaica,L. dregeanaandL. tenerrima. ForL. serriola, the closest relative of cultivated lettuce and the wild species with the highest number of examined accessions, resistance probabilities to each of the investigated downy mildew races were relatively high for populations originating from Eastern Europe and Northern Asia.

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ValSten: a new wild species derived allotetraploid for increasing genetic diversity of the peanut crop (Arachis hypogaea L.)

Genetic Resources and Crop Evolution ◽

10.1007/s10722-020-01076-2 ◽

2021 ◽

Author(s):

Dongying Gao ◽

Ana C. G. Araujo ◽

Eliza F. M. B. Nascimento ◽

M. Carolina Chavarro ◽

Han Xia ◽

...

Keyword(s):

High Resistance ◽

Wild Species ◽

Chromosome Doubling ◽

Crop Improvement ◽

Snp Array ◽

Great Majority ◽

Morphological Variations ◽

Peanut Crop ◽

Cultivated Peanut ◽

Wild Peanut

AbstractIntrogression of desirable traits from wild relatives plays an important role in crop improvement, as wild species have important characters such as high resistance to pests and pathogens. However, use of wild peanut relatives is challenging because almost all wild species are diploid and sexually incompatible with cultivated peanut, which is tetraploid (AABB genome type; 2n = 4x = 40). To overcome the ploidy barrier, we used 2 wild species to make a tetraploid with the same allotetraploid genome composition as cultivated peanut. Crosses were made between 2 diploid wild species, Arachis valida Krapov. and W.C. Greg. (BB genome; 2n = 2x = 20) and Arachis stenosperma Krapov. and W.C. Greg. (AA genome; 2n = 2x = 20). Cuttings from the diploid F1 AB hybrid were treated with colchicine to induce chromosome doubling thus generating an induced allotetraploid. Chromosome counts confirmed polyploidy (AABB genome; 2n = 4x = 40). We named the new allotetraploid ValSten. Plants had well-developed fertile pollen, produced abundant seed and were sexually compatible with cultivated peanut. ValSten exhibits the same high resistance to early and late leaf spot and rust as its diploid parents. Notably, we observed morphological variations, including flower width and branch angles in the earliest generation (S0) of allotetraploids. A SNP array was used to genotype 47 S0 allotetraploids. The great majority of markers showed the additive allelic state from both parents (AABB). However, some loci were AAAA or BBBB, indicating homeologous recombination. ValSten provides a new, vigorous, highly fertile, disease resistant germplasm for peanut research and improvement.

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Peronospora destructor. [Descriptions of Fungi and Bacteria].

IMI Descriptions of Fungi and Bacteria ◽

10.1079/dfb/20056400456 ◽

1975 ◽

Author(s):

K. G. Mukerji

Keyword(s):

South Africa ◽

New Zealand ◽

East Asia ◽

Downy Mildew ◽

Geographical Distribution ◽

Wild Species ◽

Peronospora Destructor ◽

North East

Abstract A description is provided for Peronospora destructor. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Affects species of Allium; common on A. cepa, rarer on A. ascalonicum, A. fistulosum, A. porrum, A. sativum, A. schoenoprasum, and a few wild species. DISEASE: Downy mildew (mildiou, falscher Mehitau) of onion. GEOGRAPHICAL DISTRIBUTION: On onion in all parts of Europe and America; north, east and south Africa, west, south and east Asia, Australia, New Zealand; and Tasmania. On other Allium crops in a few countries in Europe and on other continents (CMI Map 76. ed. 3, 1969).

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