A pinboard by
Joseph Kalasa

Lecturer, University of Livingstonia





Genetic Analysis of Resistance to Soybean Mosaic Virus in PI 438307 Soybean Accession

Abstract: Soybean mosaic virus (SMV) is the most prevalent viral pathogen and economic threat to soybean production worldwide. Three independent genes harboring SMV resistance have been identified: Rsv1, Rsv3, and Rsv4. Although the resistance genes (R-genes) have been found in some germplasm, usually they provide protection to some, but not all, viral strains. The objective of this research was to identify a new source of SMV resistance in Korean soybean accession PI 438307. The soybean genotype PI 438307 was crossed with susceptible parent ‘Essex’ (rsv), and differential parents PI 96983 (Rsv1), L29 (Rsv3), and V94-5152 (Rsv4). F2 plants and F2:3 lines derived from all four cross combinations were screened with SMV-G7 strain. Additionally, F2 plants obtainSed from PI 438307 (R) × Essex (S) were genotyped with two simple sequence repeat (SSR) markers on chromosome 2 (MLG D1b). Inheritance and allelic studies revealed that resistance to SMV in PI 438307 is controlled by a single dominant gene allelic to the Rsv4 locus. PI 438307 exhibited unique symptomology when compared to reported Rsv4 alleles in V94-5152, PI 88788 and Beeson. PI 438307 was resistant to SMV-G1 through G6 and resistant at seedling stages to SMV-G7. Therefore, it was proposed that the new allele Rsv4-v might be assigned to the SMV resistance in this soybean accession. Soybean sources carrying Rsv4 alleles are rare among the soybean germplasm and confer resistance to all or most SMV strains; therefore, this allele may be a good choice for breeding programs in the future.

Pub.: 01 Nov '16, Pinned: 04 Aug '17

Genesis and Identification of Octoploids Generated from Tetraploid Prairie Cordgrass

Abstract: Prairie cordgrass (Spartina pectinata Link) is a warm season (C4) perennial grass that could be a potential candidate for studying polyploidization and its effects on environmental adaptability. Polyploidy plays an important role in prairie cordgrass’s adaptation and distribution on different ecoregions in the North American Prairie. However, the genetic backgrounds of polyploidy prairie cordgrass distributed in the different edaphic regions are different. Thus, to extend our knowledge of the effect of polyploidy on environmental adaptation, it is necessary to have diverse ploidy levels of plants with a similar genetic background. Tetraploid prairie cordgrass, IL-102 (2n = 4x = 40), was used as explant material to generate octoploids. Germinated seeds were treated with 0.00, 0.03, 0.06, 0.1, and 1% colchicine or 0.000, 0.002, 0.003, 0.005, and 0.007% oryzalin solution with 0.5% dimethyl sulfoxide (DMSO) for 6, 12, or 24 h. Ploidy levels of treated seedlings were determined by flow cytometric analysis and their putative ploidy were confirmed by the chromosome count. Our results show that stable octoploid plants (2n = 8x = 80) were obtained directly by treating with antimitotic agents or by propagating cytochimeric plants. Induced octoploid plants showed increased genome size and stomata size compared with tetraploid plants. By obtaining different cytotypes in the same genetic background, sole effects of ploidy variations on agronomic traits can be determined.

Pub.: 01 Nov '16, Pinned: 04 Aug '17

Water and Nitrogen Use of Winter Wheat under Different Supplemental Irrigation Regimes

Abstract: Winter wheat (Triticum aestivum L.) production in the Huang-Huai-Hai plain of China has been threatened by drought. This study was conducted to determine the water and N use of wheat under quantifying irrigation (W1, 60 mm of irrigation each at jointing and anthesis) and supplemental irrigation, determined by measuring the water content in the 0- to 20-cm (W2), 0- to 40-cm (W3), and 0- to 60-cm (W4) soil layers. The highest grain yields of 9177 kg ha−1 in 2012 to 2013 and 9460 kg ha−1 in 2013 to 2014 were obtained in W3, which exhibited greater soil water consumption in the 60- to 140-cm soil layers. Soil nitrate N uptake in the 40- to 160-cm soil layers was higher than in W1, W2, and W4 treatments. Compared with the W1, W2, and W4, the total N uptake in W3 was higher by 9.4, 27.1, and 7.7%, respectively, and the grain N content was higher by 13.3, 33.0, and 11.2%. The water use efficiency, partial factor productivity of applied fertilizer and N harvest index were the highest in W3, which also showed high N utilization efficiency. Quadratic relationships of the amount of irrigation with soil water consumption, grain yield, water use efficiency, total N uptake, N translocation amount, N uptake for grain postanthesis, partial factor productivity of applied fertilizer, and N harvest index were also observed. Optimizing the supplemental irrigation regime improved uptake water and N uptake from the soil and increased the grain yield and water and N use.

Pub.: 01 Nov '16, Pinned: 04 Aug '17