Ambika Chandra

Susceptibility of Genera and Cultivars of Turfgrass to Southern Chinch Bug Blissus Insularis (Hemiptera: Blissidae)

ABSTRACT The southern chinch bug (Blissus insularis Barber) is the most damaging insect pest of St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze), across the southern U.S.A. Susceptibility to the southern chinch bug and reproductive potential of the bugs on 24 cultivars from 7 genera in 8 turfgrasses were evaluated under greenhouse conditions. Stenotaphrum secundatum (‘Raleigh’, ‘Texas Common’, and ‘Captiva’) cultivars were the most susceptible among all the turfgrass genera and each produced populations ≥97.5 bugs per 15-cm diameter plant within the 11-week test period from Jul to Sep 2008. Substantial populations also developed on zoysiagrass (Zoysia spp.) (‘Emerald’, ‘Empire’, ‘Palisades’, and ‘Zorro’) cultivars and on ‘609’ buffalograss (Buchloë dactyloides (Nutt.) Engelm.). Low population development was recorded on cultivars of bermudagrass (Cynodon spp.), centipedegrass (Eremochloa ophiuroides (Munro) Hack.), seashore paspalum (Paspalum vaginatum Swartz), bahiagrass (Paspalum notatum Flugge), and tall fescue (Festuca arundinacea Schreb.).

A Fungal Parasite Regulates a Putative Female-Suppressor Gene Homologous to Maize Tasselseed2 and Causes Induced Hermaphroditism in Male Buffalograss

Parasitically induced hermaphroditism is a fascinating illustration of floral sex organ modification; however, knowledge of how parasites induce hermaphroditism in plants is limited. Here, we show the fungal parasite pistil smut induces development of female sex organs (pistils) in flowers of male buffalograss, potentially by downregulating a putative female-suppressor gene, BdTs2, homologous to maize Tasselseed2 (ZmTs2). Full-length BdTs2, isolated using rapid amplification of cDNA ends, exhibits 89% nucleotide sequence similarity with ZmTs2 and 85% amino acid sequence homology with ZmTs2 protein. Scanning electron micrographs demonstrate that unisexual buffalograss flowers develop through a process of selective abortion of opposite sex organs within hermaphroditic floral primordia. Quantitative real-time polymerase chain reaction showed that high expression levels of BdTs2 within male inflorescences correlate with the selective abortion of gynoecium, leading to the development of unisexual male flowers. RNA in situ hybridization confirmed the expression of BdTs2 precisely within vestigial gynoeciums of male flowers and not in other floral organs of the inflorescence. Furthermore, we show that BdTs2 expression is downregulated by pistil smut infection, which corresponds to the presence of pistils in flowers otherwise destined to become unisexual male. This study provides a potential molecular basis for pistil smut-induced hermaphroditism in male buffalograss.

Genetic Variability in Populations of the Southern Chinch Bug, Blissus insularis, Assessed using AFLP Analysis

Abstract Southern chinch bug, Blissus insularis Barber (Heteroptera: Blissidae), is the most destructive insect pest of St. Augustine grass, Stenotaphrum secundatum Waltz (Kuntze), in the southern United States. The present study is focused on assessing genetic variability in five populations of B. insularis collected from Texas and Florida where St. Augustine grass is widely grown. The amplified fragment length polymorphism technique was used to DNA fingerprint individuals from each population (a total of 46 individuals) using five primer combinations (EcoRI/MSeI). Analysis of molecular variance results show no evidence to support significant genetic variability among Texas and Florida populations of B. insularis. Nearly all genetic variation was found to reside within populations (95%), with only approximately 3% residing among populations between regions. Low GST values obtained from POPGENE and low FST values obtained from the analysis of molecular variance both support the conclusion for high levels of gene flow resulting from interbreeding and/or migratory events among the populations. A Mantel test of Euclidean squared distances showed no correlation between the genetic distance and geographic distance matrices of tested populations of B. insularis. The results of the present study suggests that gene flow is occurring among populations of B. insularis and, therefore, breeders need to be aware that this resistance will most likely not remain localized, and it has the potential to spread as a result of migratory events.

Recovery growth of Meyer and experimental zoysiagrass progeny after sod harvest.

Information is limited on the recovery growth of zoysiagrass (Zoysia spp. Willd.) after sod harvest. ‘Meyer’ and DALZ 0102 (both Z. japonica Steud.) and eighteen zoysiagrass progeny originating from crosses between a Z. matrella (L.) Merr. × Z. japonica or ‘Emerald’ (Z. matrella × Z. pacifica Goudsw.) × Z. japonica were evaluated for sod recovery growth after harvest in Manhattan in 2008 and 2009, and in Olathe, KS, in 2009 and 2010. Sod pieces (51 cm wide × 102 cm long × 5 cm thick) were harvested on 9 July 2008 at Manhattan and on 8 July 2009 at Olathe using a mechanical sod cutter. Sod recovery growth in areas of harvested strips was determined by taking an overhead digital image of a 40- by 35-cm area to determine percentage green coverage. At 60 days after harvest in Manhattan, coverage ranged from 17% to 97%; a progeny from Z. matrella × Meyer (97% coverage) demonstrated superior recovery growth to Meyer (38% coverage). Recovery growth was slower in Olathe where irrigation was applied less frequently, and all progeny were similar to Meyer until 15 July of the summer following harvest, when individual progeny from ‘Cavalier’ × Chinese Common and Emerald × Meyer were superior to Meyer. The potential for faster recovery after harvest compared to Meyer may be attractive to sod producers seeking to maximize the number of harvests from a zoysiagrass sward.

Pistil Smut Infection Increases Ovary Production, Seed Yield Components, and Pseudosexual Reproductive Allocation in Buffalograss

Sex expression of dioecious buffalograss [Bouteloua dactyloides Columbus (syn. Buchloë dactyloides (Nutt.) Engelm.)] is known to be environmentally stable with approximate 1:1, male to female, sex ratios. Here we show that infection by the pistil smut fungus [Salmacisia buchloëana Huff & Chandra (syn. Tilletia buchloëana Kellerman and Swingle)] shifts sex ratios of buffalograss to be nearly 100% phenotypically hermaphroditic. In addition, pistil smut infection decreased vegetative reproductive allocation, increased most seed yield components, and increased pseudosexual reproductive allocation in both sex forms compared to uninfected clones. In female sex forms, pistil smut infection resulted in a 26 fold increase in ovary production and a 35 fold increase in potential harvest index. In male sex forms, pistil smut infection resulted in 2.37 fold increase in floret number and over 95% of these florets contained a well-developed pistil. Although all ovaries of infected plants are filled with fungal teliospores and hence reproductively sterile, an average male-female pair of infected plants exhibited an 87 fold increase in potential harvest index compared to their uninfected clones. Acquiring an ability to mimic the effects of pistil smut infection would enhance our understanding of the flowering process in grasses and our efforts to increase seed yield of buffalograss and perhaps other grasses.

Release of KSUZ 0802 Zoysiagrass

A new zoysiagrass cultivar, under the experimental designation KSUZ 0802, was released jointly by the Kansas Agricultural Experiment Station and Texas A&M AgriLife Research in 2015.