S1 families as a source of beneficial alleles for breeding drought tolerant maize genotypes

Abstract

As water resources for agronomic use become more limiting development of drought tolerant genotypes become increasingly more important. In maize, under drought stress conditions, an increase in the length of anthesis- silking interval and a decrease of grain yield is observed. Different strategies have been proposed to overcome negative effects of drought on maize. Breeders at Maize Research Institute (MRI) have created and used adapted drought tolerant population - DTP-A (DTP79xDTP12xDwarf), that was shown to be a good source of drought tolerance for locally adapted germplasm. In this research s1 families from DTP-A x B84 were scored for anthesis-silking interval and genotyped with SSR markers using BSA approach, with the aim to create a new gene pool for breeding drought tolerant hybrids. SSR analysis was performed in order to identify putative genomic segments and allele pattern differences responsible for expression of ASI, thus providing an insight into the genetic structure of s1 families. Four SSR loci, different in allelic structure between short and long ASI families, were identified. The main characteristic of these differences was the presence or absence of DTP79/DTP12 alleles. It seems that combination of several different genes and alleles influence ASI expression, with DTP79 alleles being beneficial and DTP12 alleles detrimental. Two chromosome regions identified in this work were congruent with qASI regions reported in Maize Genetics and Genomics Database. Clustering revealed that all sASI families grouped with DTP79, but one of the long ASI grouped with these genotypes too. This could indicate that, although total participation of DTP79 genome was similar in all the analyzed families, only a small portion of its genome influence anthesis-silking interval.

U uslovima stresa suše kod kukuruza dolazi do povećanja dužine intervala između svilanja i metličanja (ASI) i do smanjnja prinosa zrna. U oplemenjivanju se primenjuju različite strategije da bi se prevazišli negativni efekti suše. U Institutu za kukuruz stvorena je DTP-A (DTP79xDTP12xDwarf) populacija, koja se pokazala kao dobar izvor tolerantnosti na sušu za germplazmu adaptiranu na uslove umerenog klimatskog pojasa. U ovim istraživanjima s1 familije DTP-AxB84 su ocenjene za ASI i analizirane SSR markerima primenom analize grupnih uzoraka, radi stvaranja novog genetičkog pula za dobijanje hibrida tolerantnih na sušu. SSR analiza je omogućila identifikaciju potencijalnih genomskih segmanata i identifikaciju razlika u alelnoj strukturi, odgovornih za ekspresiju ASI. Identifikovana su četiri SSR lokusa, koja se razlikuju u alelnoj strukturi familija sa kratkim i dugačkim ASI. Glavna karakteristika ovih razlika je u prisustvu/odsustvu DTP79/DTP12 alela. Najverovatnije da kombinacija nekoliko različitih gena i alela utiče na ekspresiju ASI, pri čemu DTP79 aleli pokazuju pozitivan, a DTP12 negativan efekat. Dva hromozomska regiona koja su identifikovana u ovom radu su prijavljena za ASI i u Maize Genetics and Genomics Database. Rezultati dobijeni klaster analizom su pokazali da sve familije sa kratkim ASI grupišu sa DTP79, mada se i jedna dugačka ASI familija grupiše sa navedenim genotipovima. Ovo može ukazivati da, iako je ukupno učešće DTP79 genoma slično kod svih analiziranih familija, samo mali deo njegovog genoma utiče na ekspresiju ASI.