CONSTANS Polymorphism Modulates Flowering Time and Maturity in Soybean.

CONSTANS (CO) plays a critical role in the photoperiodic flowering pathway. However, the function of soybean CO orthologs and the molecular mechanisms in regulating flowering remain largely unknown. This study characterized the natural variations in CO family genes and their association with flowering time and maturity in soybeans. A total of 21 soybean CO family genes (GmCOLs) were cloned and sequenced in 128 varieties covering 14 known maturity groups (MG 0000-MG X from earliest to latest maturity). Regarding the whole genomic region involving these genes, GmCOL1, GmCOL3, GmCOL8, GmCOL9, GmCOL10, and GmCOL13 were conserved, and the remaining 15 genes showed genetic variation that was brought about by mutation, namely, all single-nucleotide polymorphisms (SNPs) and insertions-deletions (InDels). In addition, a few genes showed some strong linkage disequilibrium. Point mutations were found in 15 GmCOL genes, which can lead to changes in the potential protein structure. Early flowering and maturation were related to eight genes (GmCOL1/3/4/8/13/15/16/19). For flowering and maturation, 11 genes (GmCOL2/5/6/14/20/22/23/24/25/26/28) expressed divergent physiognomy. Haplotype analysis indicated that the haplotypes of GmCOL5-Hap2, GmCOL13-Hap2/3, and GmCOL28-Hap2 were associated with flowering dates and soybean maturity. This study helps address the role of GmCOL family genes in adapting to diverse environments, particularly when it is necessary to regulate soybean flowering dates and maturity.

Development of a New Molecular Marker for the Resistance to Tomato Yellow Leaf Curl Virus.

Tomato yellow leaf curl virus (TYLCV) responsible for tomato yellow leaf curl disease (TYLCD) causes a substantial decrease in tomato (Solanum lycopersicum L.) yield worldwide. The use of resistant variety as a sustainable management strategy has been advocated. Tremendous progress has been made in genetically characterizing the resistance genes (R gene) in tomato. Breeding tomato for TYLCV resistance has been based mostly on Ty-3 as a race-specific resistance gene by introgression originating from wild tomato species relatives. Improvement or development of a cultivar is achievable through the use of marker-assisted selection (MAS). Therefore, precise and easy use of gene-targeted markers would be of significant importance for selection in breeding programs. The present study was undertaken to develop a new marker based on Ty-3 gene sequence that can be used for MAS in TYLCV resistant tomato breeding program. The new developed marker was named ACY. The reliability and accuracy of ACY were evaluated against those of Ty-3 linked marker P6-25 through screening of commercial resistant and susceptible tomato hybrids, and genetic segregation using F2 population derived from a commercial resistant hybrid AG208. With the use of bioinformatics and DNA sequencing analysis tools, deletion of 10 nucleotides was observed in Ty-3 gene sequence for susceptible tomato variety. ACY is a co-dominant indel-based marker that produced clear and strong polymorphic band patterns for resistant plant distinguishing it from its susceptible counterpart. The obtained result correlates with 3:1 segregation ratio of single resistant dominant gene inheritance, which depicted ACY as gene-tag functional marker. This marker is currently in use for screening 968 hybrids varieties and one thousand breeding lines of tomato varieties stocked in Jiangsu Green Port Modern Agriculture Development Company (Green Port). So far, ACY has been used to identify 56 hybrids and 51 breeding lines. These newly detected breeding lines were regarded as potential source of resistance for tomato breeding. This work exploited the sequence of Ty-3 and subsequently contributed to the development of molecular marker ACY to aid phenotypic selection. We thus recommend this marker to breeders, which is suitable for marker-assisted selection in tomato.

Identification of salt tolerant rice cultivars via phenotypic and marker-assisted procedures.

Eleven genotypes, including the salt tolerant cultivar Pokkali as check, were used to evaluate salinity tolerance phenotypically and genotypically. Three selected SSR primers viz., RM7075, RM336 and RM253 were used to evaluate rice genotypes for salt tolerance. Two setups were maintained for this study viz., the seedling and reproductive stages. Phenotyping at the seedling stage was done in hydroponic system using salinized (EC 12 dS m(-1)) nutrient solution and at the reproductive stage using salinized tap water (EC 6 dS m(-1)). IRRI standard protocol was followed to evaluate salinity tolerance in rice. The genotypes having similar banding pattern with Pokkali were considered as tolerant. Phenotypically, three genotypes Pokkali, THDB and TNDB-100 and five genotypes RD-2586, TNDB-100, Dhol Kochuri, PNR-519 and Pokkali were identified as salt tolerant at the seedling and reproductive stages, respectively. These genotypes were also identified as salt tolerant genotypically (with markers). Through phenotypic and genotypic study, five genotypes viz., Pokkali, Dhol Kochuri, RD-2586, TNDB-100 and PNR-519 were identified as salt tolerant. Therefore, these microsatellite markers used in this study could be efficiently used for identification of salt tolerant rice varieties in marker-assisted breeding and quantitative trait loci analysis.