QUANTITATIVE AND MORPHOLOGICAL CHARACTERISTICS OF NP9BR RANDOM-MATING POPULATION OF SORGHUM AFTER NINE CYCLES OF SELECTION (MALE-STERILITY, DROUGHT, HERITABILITY, ARIZONA).
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PublisherThe University of Arizona.
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AbstractThis study sought to determine the effects of reselection on the adaptation of a grain sorghum (Sorghum bicolor (L.) Moench) population to heat and drought. A random-mating population, NP9BR, was subjected to selection under heat and moisture stress for nine generations to improve its resistance to drought. One hundred single plants selected from the original (C₀) and the reselected (C₉) population were grouped by maturity and evaluated for drought resistance by measuring morphological and agronomic characters under wet (normal irrigation) and dry (restricted irrigation) conditions at the University of Arizona, Marana Agricultural Center, Arizona. Eighty of the selections were grown under a sprinkler irrigation gradient system at Yuma Mesa Agricultural Center, Arizona. Selection under drought conditions reduced plant height, head exsertion, leaf width and length, and seed weight of the population. Blooming was evened out from predominantly early in C₀ to early, medium and late maturing in C₉. Moisture stress reduced grain yield by an overall 16%. The medium maturing selections suffered less yield reduction than the early and late. Although C₉ progenies showed a greater reduction in grain yield, several of them produced equal yields in wet and dry treatments. Leaf width and length were significantly correlated (p = .1%) with yield under dry conditions in all maturity groups. Most selections with very short narrow leaves had small heads and low yields. Some with medium leaf width and length out-yielded broad-leaved ones especially under dry conditions. Forty percent of the selections from C₉ had good head production characteristics under the irrigation gradient system, compared to only 20% from C₀. There were four times as many selections in C₀ unable to produce heads under the system as there were in C₉. The majority of genotypes with good head production in both populations came from the early maturing group. The highest grain yields came from C₀ selections but some C₉ selections with comparable yields were observed. This study indicates that phenotypic selection may still have potential for isolating high-yield genotypes from random-mating populations but may be inadequate for separating differences in drought tolerance among genotypes.
Degree ProgramPlant Sciences