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Buffalograss resistance to mealybugs: Germplasm evaluation, mechanisms, and inheritance
Abstract
Buffalograss, Buchloe dactyloides (Nutt) Engelm, is receiving attention as an alternative turfgrass species because of its drought tolerance and low maintenance requirements. The University of Nebraska is conducting research on the breeding, management, and potential pests of buffalograss. Two insects known to cause injury are the mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. This project investigated the potential of developing buffalograss cultivars with improved resistance to mealybugs. Dramatic differences in resistance to mealybugs were found among buffalograss selections in greenhouse and field screening trials. Cultivars 'Prairie' and '609', and several experimental selections showed excellent resistance to mealybugs; most selections were moderately susceptible; and a few selections, such as 85-97, were highly susceptible. Initial observations of highly resistant selections revealed glabrous leaves. Therefore, selections were evaluated for pubescence and significant positive correlations were found between pubescence and mealybug susceptibility. Pubescence ratings correlated with trichome counts, which ranged from 0-11 trichomes per mm$\sp2.$ Scanning electron microscopy studies suggested that pubescence may provide a framework for the waxy ovisac and a foothold for mobile early-instar nymphs. In preliminary choice trials, mealybugs did not exhibit a preference for susceptible 85-97 over resistant '609'. To study inheritance of resistance and pubescence, progeny of 20 genotypes were evaluated and significant differences were found among half-sib families. Relatively high heritabilities were estimated for mealybug resistance using maternal half-sib analysis (${\rm h\sp2\sb{m} = 0.87})$ and offspring-parent regression (${\rm h\sp2\sb{op} = 0.56}).$ Heritability estimates for leaf pubescence were ${\rm h\sp2\sb{m} = 0.59}$ and ${\rm h\sp2\sb{op} = 0.28}.$ Less than 1% of progeny had glabrous leaves, suggesting a simply inherited recessive trait. A non-significant correlation (${\rm r\sp2 = 0.06})$ was found between pubescence and mealybug susceptibility of progeny. Since numerous pubescent plants were resistant, additional factors are likely involved in resistance to mealybugs. The 119 plants which showed no signs of mealybug infestation (10% of total evaluated) were grown in an isolated crossing block and seed was harvested. Progeny from 16 of these plants were evaluated and 359 (43% of total) were free of mealybugs. This high percentage of mealybug-resistant progeny was consistent with the high heritabilities previously estimated. Highly resistant families are suggested for use in the development of a seeded mealybug-resistant buffalograss cultivar.
Subject Area
Agronomy|Entomology|Plant propagation
Recommended Citation
Johnson-Cicalese, Jennifer Mildred, "Buffalograss resistance to mealybugs: Germplasm evaluation, mechanisms, and inheritance" (1995). ETD collection for University of Nebraska-Lincoln. AAI9538636.
https://digitalcommons.unl.edu/dissertations/AAI9538636