Genetic difference analysis of BC₁F₂ materials of sugarcane and Erianthus fulvus hybrids based on karyotypes and phenotypic traits

【Objective】This study aimed to analyze the genetic differences in karyotypes and phenotypic traits of BC₁F₂ materials of sugarcane and Erianthus fulvus hybrids and elucidate the association between phenotypic traits and chromosome numbers， providing theoretical basis for innovation and utilization of sugarcane germplasms.【Method】The BC₁F₁ materials 16-12 （2n=104） produced by backcrossing of sugarcane Dianzhe 01-58 （2n=100） and Erianthus fulvus （2n=20） were used for selfing to obtain 21 BC₁F₂ materials. The chromosome number counting， karyotype analysis， and phenotypic trait determination were performed to conduct correlation analysis， principal component analysis， and cluster analysis for elucidating the association between chromosome number and phenotypic traits.【Result】The chromosome numbers of the 21 BC₁F₂ materials fell into six types， namely 2n=98， 100， 102， 104， 106， and 108. Among the 21 BC₁F₂ materials， except for 20-129 whose karyotype was 3B， the karyotypes of the other 20 BC₁F₂ materials were 2B， showing a relatively symmetrical karyotype. The majority of chromosomes had metacentric centromeres （m）， while a minority possessed submetacentric centromeres （sm）， with the proportion of metacentric chromosomes ranging from 57.00% to 87.25%. The coefficients of variation of phenotypic traits of BC₁F₂ materials and the parent 16-12， as well as Erianthus fulvus ranged from 9.32% to 42.59%， with an average coefficient of variation of 20.71%. Different degrees of correlations were found between seven phenotypic traits and chromosome number， and extremely significant positive correlations were found between plant height and single-stalk weight， between stalk diameter and leaf width， single-stalk weight， chromosome number， between leaf width and single-stalk weight， chromosome number， and between single-stalk weight and chromosome number （P<0.01，the same below）. Extremely significant negative correlations were observed between brix and plant height， single-stalk weight， between plant height and leaf length， and between internode length and chromosome number. Significant positive correlation was found between plant height and internode length. Significant negative correlations were observed between brix and internode length， between stem diameter and internode length， and between leaf length and single-talk weight. Principal component analysis results showed that the first three principal components exhibited cumulative contribution rate of 77.92%， with the first principal component （PC1） showing an eigenvalue of 3.11 and a contribution rate of 38.91%， and chromosome number， single-talk weight， leaf width， and stalk diame-ter were principal determination factors. Cluster analysis showed that the BC₁F₂ materials and the parents （16-12 and Erian-thus fulvus） were divided into five groups. Group I consisted of eight materials， characterized mainly by long leaves； Group II consisted of six materials， characterized mainly by wide leaves； Group III contained only one material， characterized mainly by high brix； Group IV contained seven materials， characterized mainly by greater plant height and high single-stalk weight； Group V contained only one material， Erianthus fulvus， characterized mainly by long internodes， lower stalk diameter， and low brix.【Conclusion】Correlations of varying degrees are found between phenotypic traits and chromosome number of BC₁F₂ materials， demonstrating that obvious genetic differences in phenotypic traits are due to different chromosome numbers of BC₁F₂ materials. These hybrid progeny materials with Erianthus fulvus genetic background can be used for subsequent sugarcane breeding.