Host Plant Resistance to Pathogens in MAR Cotton Germplasm
Feb 6, 2019
Cotton growers face intense economic pressures as cotton prices hold steady while cost of production increases. Pathogens that cause: seed-seedling diseases, bacterial blight, Fusarium and Verticillium wilts, Phymatotrichum root rot, nematodes and leaf spots reduce yield and fiber quality. Host-plant resistance offers durable, economic control of pathogens. The multi-adversity resistance (MAR) genetic improvement program pioneered the development of cultivars resistant to several pathogens. The system utilizes specific seed, seedling, and plant screening and selection techniques in the laboratory, greenhouse and field for the simultaneous genetic improvement of resistance to pathogens, insects and abiotic stresses in addition to yield, earliness, seed and fiber quality. Since the 1970's the MAR program has developed eight MAR gene pools from which cotton cultivars and germplasm with progressive genetic improvement in resistance to pathogens, have been selected and released. Field tests are conducted each year at 10 naturally infested locations in Texas to determine the levels of resistance to pathogens. Levels of resistance to seed deterioration and seedling disease have progressed from susceptible in the MAR-1 to resistant in the MAR-8. High resistance to USA races of the bacterial blight pathogen has been maintained through the MAR gene pools. Progressive improvements in levels of resistance to root pathogens and nematodes have been made, even though no direct selection was practiced. Current MAR-8 germplasm combines higher levels of resistance to eight pathogens.