The Interspecific Hybridization Among Domesticated Species In Capsicum And The Cytogenetic Characterization Of The Interspecific Hybrids

Capsicum chinense, C. frutescens, C. baccatum and C. pubescens have manyexcellent characters which C.annuum doesn't have, such as the resistance to TMV, CMVand the tolerance to cold. In order to improve C.annuum by using the above characters,the karyotype analysis and interspecific hybridization among the five domesticatedspecies were performed for the first time in China. The results suggest the relationship andthe crossability among them. Two combinations of interspecific hybrid were obtained andwere also identified by morphology, isozyme electrophoresis and cytogeneticsobservations. The derivatives of two interspecific hybrid were also partly obtained bybackcross and self-cross.The detailed results as following:1. Karyotype Analysis of Domesticated Species of White-flowered Group in CapsicumThe karyotypes of the four domesticated species of white-flowered group inCapsicum were reported. The karyotype formulae were as follows: Sujiao 5th (C. annuum)2n=2x=24=22m+2st,PI439487 (C. chinense) 2n=2x=24=22m+2st,YN01 (C. frutescens)2n=2x=24=2sm(SAT)+22m,PI241679 (C. baccatum ) 2n=2x=24=20m+2st+2t. Thekaryotypes of the four species were uniform and belong to Stebbins's 2A type. Thekaryotype of YN01 (C. frutescens), which came from Yunnan Province China, wasreported for the first time. According to the karyotype analysis data, the relationship amongthem was primarily discussed. And we found that the karyotype of YN01 (C. frutescens)was more original than those of the other three genotypes. It can be inferred thatXishuangbanna Yunnan China may be another origin of Capsicum.2. Interspecific Hybridization and Identification of the F₁ Hybrids in CapsicumThree hybrid plants from the combination of C. baccatum×C. chinense (H_bc) andseven hybrid plants of C. annuum×C. chinense (H_ac) were obtained through reciprocalinterspecific hybridizations among the five cultivated species C. annuum, C. chinense, C. frutescens, C. baccatum, and C. pubescens. Except for the H_ac-7 which exhibited virus-likesymptoms, all the other hybrid plants grew normally. The pollen stainability percentagesof H_ac and H_bc were 13.9ï¼…and 23.8ï¼…respectively, and were significantly lower thanthose of their corresponding parents. The pollen stainability percentage, morphologicalcharacters and band patterns of isozyme in the hybrid plants were identical within eachcombination. The nature of hybrid was confirmed by morphological characteristics andisozyme (peroxidase and esterase) analysis.3. Cytological Observations on Interspecific Hybrids F₁ from Capsicum annuum×C.chinense, C. baccatum×C. chinenseThe meiosis of pollen mother cells (PMC) of Capsicum annuum×C, chinense (H_ac)and C. baccatum×C. chinense (H_bc) were ananlysed. The congfiguration formulae of H_acand H_bc at diakinesis and metaphaseâ… were 0.82â… +3.92ringâ…¡+3.75 rodâ…¡+0.32â…¢+1.08â…£+0.12â…¤+0.22â…¥and 3.59â… +1.37 ringâ…¡+2.63 rodâ…¡+1.27â…¢+0.80â…£+0.45â…¤+0.10â…¥+0.14â…¦+0.10â…§, respectively. Chromosome bridges, chromosome laggings,microspores and polyads were also observed in the PMCs of both interspecific hybrids. Allthese abnormal meiotic behaviors led to the formation of sterile gametes, and also indicatethe hybrids nature from the cytogenetics. Additonally, the fertility of F₁ suggests thepossibility of the alien useful genes can be transferred to gone pool of C. annuum by usingbackcross of interspecific hybrids to broaden the genetic bases of C. annuum.