Naslov
Recurrent selection for nitrogen use efficiency in maize

Autori
Bukan, Miroslav

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Agronomski fakultet

Mjesto
Zagreb

Datum
28.09

Godina
2011

Stranica
104

Mentor
Kozumplik, Vinko

Ključne riječi
maize; nitrogen use efficiency; recurrent selection; allele frequency; SSR

Sažetak
Nitrogen use efficiency (NUE) has become an important trait for sustainable agriculture. Traits present in maize (Zea mays L.) landraces that contribute to adaptation in nitrogen-limited environments are not easily implemented directly into modern maize breeding programs. Thus, the landraces might be improved by recurrent selection and afterwards used as source of certain traits for elite breeding material. The Maksimir 3 Synthetic (M3S) maize population was created from landraces traditionally grown under low levels of soil fertility. The synthetic was subjected to recurrent selection for yield and stalk rot resistance during three cycles and for improved NUE in the fourth cycle. In order to determine the effect of four cycles of recurrent selection, performance of populations per se (S0), population testcrosses, and populations per se selfed (S1) were evaluated in field trials under high and low nitrogen input conditions at four locations during 2010. Thirty two plants from each of the C0, C3, C4N0 and C4N150 population were genotyped by 40 SSR loci, equally spread across the maize genome, in order to estimate the changes of allele frequency after four cycles of recurrent selection. Generally, relative population yield improvement was more evident in the later cycles of selection at 0 than at 150 kg N ha-1, with C4N0 exhibiting the greatest improvement at the low N rate and C4N150 at high N rate. Yield results for populations per se might indicate a tendency for specific adaptation of C4N0 to low and C4N150 to high N input conditions. Similar yield pattern of the two populations from the fourth cycle of selection was not the same in the testcross populations, but the general combining ability of the improved population was preserved. Traits which might be related to improvement of yield were ear length, ear diameter, 1000 kernel weight, and also increased plant and ear height. Drought might have offset the expression of the NUE in the fourth cycle selection trials in 2007, leading to selection of primarily drought resistant S1 progenies. Significantly shorter anthesis-silking interval (ASI) observed in the two fourth cycle populations (C4N0 and C4N150) could lead to a similar conclusion. The high number of loci with significant changes in allele frequency (38% from C0 to C3, 21% from C3 to C4N0, and 39% from C3 to C4N150) suggests that selection was a significant factor affecting allelic frequencies. Majority of loci involved in significant linkage disequilibrium were selectively nonneutral according to Waples’ neutrality tests, indicating that selection was important factor in generating linkage disequilibrium in the M3S maize population.

Izvorni jezik
Engleski

Znanstvena područja
Poljoprivreda (agronomija)

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