Non-vernalization requirement in Chinese kale caused by loss of BoFLC and low expressions of its paralogs

Key message We identified the loss ofBoFLC gene as the cause of non-vernalization requirement inB. oleracea. Our developed codominant marker ofBoFLCgene can be used for breeding program ofB. oleraceacrops. Abstract Many species of the Brassicaceae family, including some Brassica crops, require vernalization to avoid pre-winter flowering. Vernalization is an unfavorable trait for Chinese kale (Brassica oleracea var. chinensis Lei), a stem vegetable, and therefore it has been lost during its domestication/breeding process. To reveal the genetics of vernalization variation, we constructed an F2 population through crossing a Chinese kale (a non-vernalization crop) with a kale (a vernalization crop). Using bulked segregant analysis (BSA) and RNA-seq, we identified one major quantitative trait locus (QTL) controlling vernalization and fine-mapped it to a region spanning 80 kb. Synteny analysis and PCR-based sequencing results revealed that compared to that of the kale parent, the candidate region of the Chinese kale parent lost a 9,325-bp fragment containing FLC homolog (BoFLC). In addition to the BoFLC gene, there are four other FLC homologs in the genome of B. oleracea, including Bo3g005470, Bo3g024250, Bo9g173370, and Bo9g173400. The qPCR analysis showed that the BoFLC had the highest expression among the five members of the FLC family. Considering the low expression levels of the four paralogs of BoFLC, we speculate that its paralogs cannot compensate the function of the lost BoFLC, therefore the presence/absence (PA) polymorphism of BoFLC determines the vernalization variation. Based on the PA polymorphism of BoFLC, we designed a codominant marker for the vernalization trait, which can be used for breeding programs of B. oleracea crops.

Identification of Quantitative Trait Loci Controlling the Development of Prickles in Eggplant by Genome Re-sequencing Analysis

Eggplant (Solanum melongena L.) is the third most important crop in the family of Solanaceae. Prickles are considered as the undesirable traits during the plantation of eggplant and the transportation of fruits. In this study, we constructed a high-quality genetic linkage Bin map derived from the re-sequencing analysis on a cross of a prickly wild landrace, 17C01, and a cultivated variety, 17C02. The major quantitative trait locus (QTL) controlling the development of prickles on the calyx (explained 30.42% of the phenotypic variation), named as qPC.12, was identified on a ~7 kb region on chromosome 12. A gene within qPC.12, which encodes a WUSCHEL-related homeobox-like protein, with higher expression levels in 17C01 calyx and 22-bp deletion in 17C02 was probably the functional gene for prickle formation. Results from this study would ultimately facilitate uncovering the molecular regulatory mechanisms underlying the development of a prickle in eggplant.

Fine Mapping of Qph9, A Major Quantitative Trait Locus, Responsible for Plant Height In Foxtail Millet [Setaria Italica (L.) P. Beauv.]

Plant height is vital for crop yield by influencing plant architecture and resistance to lodging. Although lots of quantitative trait loci (QTLs) controlling plant height had been mapped in foxtail millet, their contributions to phenotypic variation were generally small and mapping regions were relatively large, indicating the difficult application in molecular breeding using marker-assisted selection. In the present paper, a total of 23 QTLs involving in 15 traits were identified via a high-density Bin map containing 3024 Bin markers with an average distance of 0.48 cM from an F2 population. Among them, qPH9 with a large phenotypic variation explained (51.6%) related to plant height, was one of the major QTLs. Furthermore, qPH9 was repeatedly detected in multi-environments under field conditions using two new F2 population from the same F1 plant, and was narrowed down to a smaller interval of 281 kb using 1024 recessive individuals of F2 population. Finally, we found that there was an extremely significant correlation between marker MRI1016 and plant height, and speculated that Seita.9G088900 and Seita.9G089700 could be key candidates of qPH9. This study laid an important foundation for the cloning of qPH9 and molecular breeding of dwarf varieties via marker-assisted selection.

Maize Head Smut: Pathogenesis, Epidemiology, and Management Options

Maize (Zea mays) head smut caused by Sphacelotheca reiliana, a basidiomycete with worldwide distribution, can cause devastating crop losses that pose a food security threat. While Kenya has experienced high incidences of the disease in the recent years, the seed certification regulation has a zero tolerance on S. reiliana. The spores of S. reiliana remain viable in soil for many years and serve as the main inoculum source as they germinate when the conditions are favourable and infect the host in the early stages of growth after germination. After penetration, the fungus grows systemically as the plant matures eventually transforming part or all of the inflorescence (ears and tassels) tissues into smut galls. The symptoms develop because the inflorescences have increased levels of reactive oxygen species, auxin, and misregulation of floral regulatory transcription factors. The most practical control strategy for maize head smut encompasses the use of resistant/tolerant cultivars, fungicide treatment (of seed or drenching of rows immediately after seeding), and field hygiene/ sanitation. Crop rotation may help when host crops are not planted for between 2-3 years or even more. Resistance genes, including ZmWAK, found in the major quantitative trait locus qHSR1/qHS2.09 regulate resistance of maize to head smut. The objective of this review paper is to provide an understanding of the head smut disease pathogenesis, epidemiology, and effective management options. Key words: Sphacelotheca reiliana, basidiomycete, seed certification, smut galls, resistance gene