Plant Sciences Masters Theses

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Browsing Plant Sciences Masters Theses by browse.metadata.department "Plant Pathology"

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    Assessment of Bacterial Blight Pathogens Prevalent on Dry Bean and Identification of Sources of Resistance to Rhizoctonia Root Rot in North Dakota
    (North Dakota State University, 2011) Yen-Wei, Chang
    Bacterial blights and root rots are two major diseases affecting dry edible bean (Phaseolus vulgaris L.) production in North Dakota and Minnesota (Venette and Lamey 1998). Bacterial blights of dry bean are commonly caused by three bacterial pathogens, namely Pseudomonas syringae pv. phaseolicola (Psp), Pseudomonas syringae pv. syringae (Pss) and Xanthomonas axonopodis pv. phaseoli (Xap), which can appear either together or independently under natural conditions. The bacterial portion of this study involved ascertaining the extent of incidence of bacterial blight in the major dry bean production areas of ND through surveys, determining the prevalence of Psp and Pss and screening a collection of commercial varieties from different market classes for resistance to these two bacterial pathogens. In this study, more than 50% of the fields surveyed in all the major dry bean producing counties, including Grand Forks, Pembina, Traill and Walsh from year 2008 to 2010, were found to have been affected by bacterial blight. Among the bacterial diseases, bacterial brown spot (caused by Pss) appeared to be the most prevalent. Representative isolates for both Psp and Pss randomly selected from the survey were used for pathogenicity tests and confirmed to be pathogenic. Race typing of the Psp isolates confirmed the presence of the races 6 and 8 in the field samples with race 6 being the most common. Susceptibility of the 11 varieties used in this study was also variable. Difference in aggressiveness was observed among the Psp isolates.
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    Exploring Cover Crops for Managing Plant-Parasitic Nematodes Heterodera Glycines and Pratylenchus Penetrans
    (North Dakota State University, 2022) Neupane, Kamal
    Three studies were conducted to assess the effects of cover crops on plant-parasitic nematodes (PPNs) of potato and soybean. The first study investigated the hosting and population reduction abilities of 25 cover crops to Pratylenchus penetrans and found alfalfa (Bullseye) to reduce the initial population densities consistently. The second study tested the population reduction abilities of ten cover crops to two soybean cyst nematode (SCN; Heterodera glycines) populations in the microplot. Sunnhemp (cultivar not specified) was the most effective to reduce both SCN populations. The third study evaluated ten cover crops in a growth chamber for their impacts on hatching and root penetration of SCN and their potential as trap crops. Faba bean (Petite) showed the greatest potential to act as a trap crop for SCN, based on its effect on hatching and root penetration by SCN. These results help select suitable cover crops to manage PPNs in infested fields.