Creation of Hexaploid and Octaploid Zoysiagrass Using Colchicine and Breeding

Zoysiagrasses (Zoysia Willd.) are a slow-growing, tetraploid (2n = 4x = 40) turfgrass that can be successfully managed with less input than many other warm-season grasses. Despite extensive genetic and morphological variation, genotypes with the ability to recuperate quickly from damage are rare. Therefore, a long-term effort to increase vegetative growth rates was initiated during 2009 by first studying the effectiveness of six colchicine seed treatments and breeding for manipulating the ploidy level of 'Zenith' zoysiagrass. Colchicine-treated seedlings were screened using flow cytometry for genome size changes. Four putative octaploids and one cytochimera were identified. Average stomata length of the four colchicine-induced putative octaploids were 28% larger than that of Zenith, but the cytochimera's stomata length was not altered. Pollen diameter of the four putative octaploids was larger than that of Zenith and the cytochimera. Pollen stainability was relatively unchanged by the colchicine treatments. Further self-and cross-pollination of 09-TZ-103 (putative M₀ octaploid) led to the development and verification of M₁ octaploid and M₁ hexaploid genotypes. These results support that DNA content of the L-I (epidermis), L-II (germ line), and L-III (adventitious roots) histogenic layers of Zoysia can be manipulated with colchicine and breeding. Future evaluation of the turfgrass performance of these polyploids is the next step in determining the value of this breeding procedure for improvement of zoysiagrass.Keywords: Flow cytometry, Chromosome numbers, Establishment rates, Stolon growth, Annual ryegrass, Cultivars, Registration, Nuclear DNA content, Genetic control, Ploidy leve

Pearl millet genome sequence provides a resource to improve agronomic traits in arid environments

Pearl millet [Pennisetum glaucum (L.) R. Br., syn. Cenchrus americanus (L.) Morrone], is a staple food for over 90 million poor farmers in arid and semi-arid regions of sub-Saharan Africa and South Asia. We report the ~1.79 Gb genome sequence of reference genotype Tift 23D2B1-P1-P5, which contains an estimated 38,579 genes. Resequencing analysis of 994 (963 inbreds of the highly cross-pollinated cultigen, and 31 wild accessions) provides insights into population structure, genetic diversity, evolution and domestication history. In addition we demonstrated the use of re-sequence data for establishing marker trait associations, genomic selection and prediction of hybrid performance and defining heterotic pools. The genome wide variations and abiotic stress proteome data are useful resources for pearl millet improvement through deploying modern breeding tools for accelerating genetic gains in pearl millet.publishersversionPeer reviewe

Melanaphis sorghi (Hemiptera: Aphididae) Clonal Diversity in the United States and Brazil

Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Americas. Previous studies have found that a super-clone that belongs to multilocus lineage (MLL)-F predominated in the U.S. from 2013 to 2018 and uses multiple hosts besides sorghum. In contrast, previous studies found that aphids in South America belong to MLL-C, but these studies only examined aphids collected from sugarcane. In this study we sought to determine if the superclone persisted in the U.S. in 2019–2020 and to determine the MLL of aphids found on sorghum in the largest country in South America, Brazil. Melanaphis spp. samples (121) were collected from the U.S. in 2019–2020 and Brazil in 2020 and were genotyped with 8–9 Melanaphis spp. microsatellite markers. Genotyping results showed that all samples from the U.S. in 2019 and Brazil in 2020 had alleles identical to the predominant superclone. Of the 52 samples collected in the U.S. in 2020, 50 samples were identical to the predominant super-clone (multilocus lineage-F; M. sorghi), while two samples from Texas differed from the super-clone by a single allele. The results demonstrated that the super-clone remains in the U.S. on sorghum, Johnsongrass, and giant miscanthus and is also present on sorghum within Brazil

Identification of Cultured and Diazotrophic Bacterial Endophytes in Warm-Season Grasses

Endophytes can have positive effects on plant health and growth, but endophytes of warm-season grasses are largely understudied, and inocula are rarely applied to cultivated grasses. To identify endophytes in warm-season grasses, 35 endophytic bacterial isolates were cultured from the roots, rhizomes, and shoots of bermudagrass (Cynodon dactylon), energy cane (Saccharum spp.), Johnsongrass (Sorghum halepense), napiergrass (Cenchrus purpureus), perennial sorghum (Sorghum bicolor × S. halepense), sorghum (Sorghum bicolor), sorghum × sudangrass (Sorghum × drummondii), and peanut (outgroup). Sequencing of the 16S rRNA fragment from the endophytes revealed that the bacterial sequences were similar to Bacillus spp. (19 isolates), Burkholderia spp. (4), Pantoea spp. (4), Pseudomonas spp. (3), Enterobacter spp. (2), Kosakonia spp. (2), and Sphingomonas sp. (1). To identify diazotrophic endophytes, DNA isolated from surface-disinfected tissue from warm-season grasses was used to amplify nifH. Bacteria containing nifH were similar to 13 genera, and sequences similar to Pseudolabrys sp. were present in the greatest number of warm-season grasses. Bacteria similar to Bradyrhizobium frederickii strain CNPSo 3447 were identified frequently from the leaves and roots of sorghum × sudangrass (and peanut roots). Using similarity to known nifH fragments, six genera were identified that had not been previously identified in grasses. Thus, a large number of endophytes were found in warm-season grasses and could enhance plant growth or grass nitrogen levels by using nitrogen fixation. [Graphic: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023

Electrochemical Evaluation of Sweet Sorghum Fermentable Sugar Bioenergy Feedstock

Although sweet sorghum is a promising feedstock for bioenergy and biobased products, sweet sorghum-based biorefineries in the U.S. are still in the planning or pilot-scale stages. Accurate, rapid, and inexpensive metrology is known to streamline (bio)­refining operations and drive the return on investment. In this study, new cyclic voltammetry (CV)-based methods were developed to rapidly classify sweet sorghum fermentable sugar feedstocks for electroactive functionalities. In addition to providing industrial QA/QC protocols, developed methods could be used to screen for the pest-resistant cultivars containing redox-active antifeedants (e.g., flavonoids, alkaloids, and aconitic acid), enabling germplasm development for a sustainable feedstock supply chain. Developed CV methods were tested on five male (Atlas, Chinese, Dale, Isidomba, and N98) and three female (N109B, N110B, and N111B) inbred lines and their hybrids (23 cultivars total) planted in April, May, and June of 2015 in Georgia, and harvested at the hard-dough stage. The peak anodic potential (<i>E</i>_pa in volts) of derivative CV (pH 5, 0.1 M KCl) overlapped with quercetin and tannic acid model reductants. Fluorescent porphyrin/chlorophyll-like condensed and recalcitrant aromatic structure is likely to be the primary electron-enriched (highest CV peak areas) secondary product, and showed significant (<i>p</i> < 0.05) cultivar and planting date dependencies

Genetic and phenotypic diversity of Fusarium oxysporum f. sp. niveum populations from watermelon in the southeastern United States.

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (FON), occurs worldwide and is responsible for substantial yield losses in watermelon-producing areas of the southeastern United States. Management of this disease largely relies on the use of integrated pest management (i.e., fungicides, resistant cultivars, crop rotation, etc.). Knowledge about race structure and genetic diversity of FON in the southeastern US is limited. To determine genetic diversity of the pathogen, FON isolates were collected from symptomatic watermelon plants in commercial fields in Georgia and Florida, USA, and identified based on morphological characteristics and PCR analysis using FON-specific primers. Discriminant analysis of principal components (DAPC) of 99 isolates genotyped with 15 simple sequence repeat (SSR) markers grouped the isolates in eight distinct clusters with two prominent clusters (clusters 1 and 8). Cluster 1 consisted of a total of 14 isolates, out of which 85.7% of the isolates were collected in Florida. However, most of the isolates (92.4%) in cluster 8 were collected in Georgia. Both DAPC and pairwise population differentiation analysis (ФPT) revealed that the genetic groups were closely associated with geographical locations of pathogen collection. Three races of FON (races 0, 2 and 3) were identified in the phenotypic analysis; with race 3 identified for the first time in Georgia. Overall, 5.1%, 38.9% and 55.9% of the isolates were identified as race 0, race 2 and race 3, respectively. The majority of the isolates in cluster 1 and cluster 8 belonged to either race 2 (35.6%) or race 3 (45.8%). Additionally, no relationship between genetic cluster assignment and races of the isolates was observed. The information obtained on genotypic and phenotypic diversity of FON in the southeastern US will help in development of effective disease management programs to combat Fusarium wilt

Insect Feeding on Sorghum bicolor Pollen and Hymenoptera Attraction to Aphid-Produced Honeydew

Pollinators are declining globally, potentially reducing both human food supply and plant diversity. To support pollinator populations, planting of nectar-rich plants with different flowering seasons is encouraged while promoting wind-pollinated plants, including grasses, is rarely recommended. However, many bees and other pollinators collect pollen from grasses which is used as a protein source. In addition to pollen, Hymenoptera may also collect honeydew from plants infested with aphids. In this study, insects consuming or collecting pollen from sweet sorghum, Sorghum bicolor, were recorded while pan traps and yellow sticky card surveys were placed in grain sorghum fields and in areas with Johnsongrass, Sorghum halepense to assess the Hymenoptera response to honeydew excreted by the sorghum aphid (SA), Melanaphis sorghi. Five genera of insects, including bees, hoverflies, and earwigs, were observed feeding on pollen in sweet sorghum, with differences observed by date, but not plant height or panicle length. Nearly 2000 Hymenoptera belonging to 29 families were collected from grain sorghum with 84% associated with aphid infestations. About 4 times as many Hymenoptera were collected in SA infested sorghum with significantly more ants, halictid bees, scelionid, sphecid, encyrtid, mymarid, diapriid and braconid wasps were found in infested sorghum plots. In Johnsongrass plots, 20 times more Hymenoptera were collected from infested plots. Together, the data suggest that sorghum is serving as a pollen food source for hoverflies, earwigs, and bees and sorghum susceptible to SA could provide energy from honeydew. Future research should examine whether planting strips of susceptible sorghum at crop field edges would benefit Hymenoptera and pollinators