CORRELATIONS AMONG AGRONOMIC TRAITS IN FAOSYNFR1B MAIZE POPULATION

Poznavanje korelacija između različitih svojstava kod kukuruza može biti od velike pomoći oplemenjivaču u izboru najučinkovitijeg selekcijskog postupka. Cilj ovog rada bio je istražiti korelaciju između različitih agronomskih svojstava tijekom drugog ciklusa rekurentne selekcije u FAOSYNFR1B populaciji kukuruza. U 1995. godini provedeni su selekcijski pokusi koji su uključivali 167 S1 potomstava, kao i 167 njima pripadajućih test-križanaca s inbred linijom BcA632N. Pokusi su postavljeni prema shemi 13x13 nepotpunog bloka na tri lokacije. Ukupno gledano pronađeno je više signifikantnih korelacija između proučavanih svojstava u pokusima sa S1 potomstvima nego u pokusima s test-križancima. Većina korelacija kretala se u rasponu od vrlo slabe (r= 0.15*) do osrednje (r= 0.49**). Jedine dvije korelacije koje su u svim pokusima bile jake do potpune bile su korelacija između metličanja i svilanja (r= 0.85** do r= 0.96**), te korelacija između visine biljke i visine do klipa (r= 0.72** do r= 0.81**). Korelacija za trulež stabljike između S1 potomstava i test-križanaca kretala se u rasponu od slabe (r= 0.34**) do osrednje (r= 0.40**). Za prinos zrna niti na jednoj lokaciji nije pronađena signifikantna korelacija između S1 potomstava i test-križanaca. Ukupno je pronađen manji broj signifikantnih korelacija između različitih lokacija za isto svojstvo kod test-križanaca nego kod S1 potomstava. Stoga se može zaključiti da su rezultati S1 potomstava manje varirali s okolinom u usporedbi s test-križancima, što je omogućilo bolju procjenu vrijednosti kod S1 potomstava nego kod test-križanaca za svojstva na koja se vršila selekcija.Information on correlations among different traits in maize could help plant breeders to choose the most suitable selection procedure. The aim of this study was to estimate the correlation among different agronomic traits during the second cycle of recurrent selection in FAOSYNFR1B maize population. In 1995 the selection trials with 167 S1 progenies as well as with their 167 corresponding testcrosses with inbred line BcA632N were set up as 13x13 incomplete block design at three locations. On average, more significant correlations among studied traits were found in the trials including S1 progenies than in those including testcrosses. Most correlations ranged from very weak (r= 0.15*) to intermediate (r= 0.49**). The highest correlations at all locations for both S1 progenies and testcrosses were between pollen shed and silking (r= 0.85** to r= 0.96**), and between ear and plant height (r= 0.72** to r= 0.81**). The correlation for stalk rot between S1 progenies and testcrosses ranged from weak (r= 0.34**) to intermediate (r= 0.40**). The correlations between S1 progenies and testcrosses for grain yield were not significant at all locations. Generally, less significant correlations among different locations for the same trait were found in testcrosses than in S1 progenies. Thus it can be concluded that the traits in S1 progenies varied to the lower extent with the environment compared to the testcrosses. This allowed a better estimate of S1 progeny performances than testcross performances for traits under selection

Population genomics provide insights into the global genetic structure of Colletotrichum graminicola, the causal agent of maize anthracnose

Understanding the genetic diversity and mechanisms underlying genetic variation in pathogen populations is crucial to the development of effective control strategies. We investigated the genetic diversity and reproductive biology of Colletotrichum graminicola isolates which infect maize by sequencing the genomes of 108 isolates collected from 14 countries using restriction site-associated DNA sequencing (RAD-seq) and whole-genome sequencing (WGS). Clustering analyses based on single-nucleotide polymorphisms revealed three genetic groups delimited by continental origin, compatible with short-dispersal of the pathogen and geographic subdivision. Intra- and intercontinental migration was observed between Europe and South America, likely associated with the movement of contaminated germplasm. Low clonality, evidence of genetic recombination, and high phenotypic diversity were detected. We show evidence that, although it is rare (possibly due to losses of sexual reproduction- and meiosis-associated genes) C. graminicola can undergo sexual recombination. Our results support the hypotheses that intra- and intercontinental pathogen migration and genetic recombination have great impacts on the C. graminicola population structure