Microsporogenesis associated with seed yield in Urochloa sexual polyploid hybrids

Abstract

High seed yield is a fundamental characteristic of apomictic and sexual hybrids of the genus Urochloa P. Beauv. (syn. Brachiaria (Trin.) Griseb.). It has been suggested that there is an association between polyploidy, the presence of meiotic irregularities, and low seed formation in this genus. The present study aimed to correlate these characteristics in Urochloa polyploid sexual interspecific hybrids in relation to the production of pure seeds. Segregational and non-segregational abnormalities were shown to led to cause the formation of tetrads with micronuclei, microcytes, polyads, and anomalous end products. The correlation between the percentage of meiotic abnormalities and the total production of pure seeds was negative and significant. To our knowledge, this is the first research with sexual polyploid hybrids from Urochloa and is relevant to identify hybrids with less frequent meiotic abnormalities and higher seed yield, with promising female parents for the breeding program.

Association between seed production traits in Urochloa spp.

“…If the goal is to improve the GP, it is possible to do this through selection cycles since most of the variation can be inherited. Considering Urochloa , the mean number of filled seeds per individual (%) for eight different hybrids was 4.6% (Ragalzi et al., 2021). For bahiagrass ( Paspalum notatum Flüggé) genotypes, GP ranged from 5.1% to 39.3% (Rios et al., 2020).…”

“…The lack of technical knowledge for the production of forage seeds, combined with adverse weather conditions, has caused a drop in production; consequently, there was an increase in the price of seeds (Catuchi et al., 2019). It is important to have a high seed production in Urochloa because it ensures sexual progenies in crosses and the cost of establishing pastures with apomictic hybrids is low (Ragalzi et al., 2021). Therefore, improving seed yield in both sexual and apomictic genotypes is essential to increase the efficiency of the breeding programs and decrease the cost of seeds.…”

Chaotic spindles causes abnormal chromosome behavior in an interspecific sexual hybrid of Urochloa

“…Although the sexual hybrid S44 was selected due to its good agronomic characteristics, such as eld vigor and resistance to pasture spittlebugs, severely abnormal meiotic behavior may compromise the formation of viable pollen and consequent formation of viable seeds. Studies conducted by Ragalzi et al (2021) in interspeci c sexual polyploid hybrids of Urochloa showed a negative and signi cant correlation between meiotic abnormalities and pure seed production. For this reason, it is suggested that this hybrid be discarded from the breeding program of Urochloa carried out by Embrapa Beef Cattle.…”

Advances in genomic characterization ofUrochloa humidicola: exploring polyploid inheritance and apomixis

“…However, the extent to which such abnormalities influence seed yield is less well known. Improving seed yield, one of the major challenges faced by U. humidicola breeding programs, is an important goal that allows the establishment of cost-effective pastures, ensures the production of abundant progenies through intraspecific crosses and has economic implications for seed producers (Filho 1983; Ragalzi et al 2021).…”

“…Previous studies evaluated seed production in hybrids of U. humidicola , all of which were generated from a cross between the sexual genotype H031 and pollen donor apomictic accessions from the EMBRAPA germplasm collection. The sexual hybrids were evaluated according to their meiotic abnormalities, and the authors observed a significant negative correlation between the percentage of meiotic abnormalities and the total production of pure seeds (Ragalzi et al 2021). Similarly, the apomictic hybrids did not maintain the seed yield potential of their male parent (de Assis et al 2016).…”