Chapter 5 Genetic Analysis of Apomixis - cimmyt

10M.. Be,th.dcategories n + nand 2n + n appeared at signifi- presented in Table 2.5. According to the table,cant rates. Stebbins and Kodani (1944) showed it appears that within one species, but ina frequency of occurrence of 2n+n progeny of various populations, the rate of 2n + n5.6%, ranging from 0.14% to 49%. Thus, progeny is variable and significant, beingapomixis in Parthenillm is largely facultative. quite high in the case of population #39 "LaToma." Experiments are in progress toIn Tripsawm we found an average 2.7% (n +analyze the effect of the environment11) progeny, 8.1% (2/1 + 11), and 89.2% (2n + 0)(flowering and pollination) on the stability ofprogeny (Table 2.4). From seeds collected inthese parameters.wild populations, we analyzed the occurrenceof 2n + n progeny (it is difficult to test for n + n For Dichanthium and Bothriochloa (Poaceae),progeny in this situation because clones are Harlan et al. (1964) reported rates of 211+11distributed in small niches of land and progeny from crosses between tetraploidinterpollination occurs from identical species. These combinations, however, aregenotypes, making detection of new isozyme interspecific and therefore are difficult topatterns difficult). The frequencies for three compare with the former examples. Bashawwild populations of TripsaCllm we observed are et al. (1992) showed that in crosses betweenTable 2.4 Estimation of apomixis rate and categories of progeny from chromosome counts and isozymeanalyses of Tripsacum populations (Berthoud et 01., unpublished data)Species 2n= %Pop ID Plant ID tested Size 72 90 108 n+n 2n+n n+n 2n+n 2n+024 143 DHBV 10 10 0 0 0 a a a 10028 163,164 MZ 20 18 a 2 a 2 a 10 9029 183 MZ 12 10 a 2 a 2 a 16.7 83.337 282, 283, 772 OM 46 43 a 3 1 3 2.1 6.5 91.443 358,361 OM 14 14 a a a a a a 10047 414 BV 12 12 a a 3 a 25 a 7548 421,423 OM 39 38 a 1 a a a 5 9552 497 OM 10 5 a 5 a 5 a 50 5053 545 II 19 17 a 2 2 2 10.5 10.5 7954 588 OH 15 13 a 2 a 2 a 13.3 86. 755 608 OH 18 12 2 4 a 6 a 33.3 66. 759 641 OM 7 7 a a a a a a 10060 654, 655 OM 23 21 a 2 a 2 a 8.7 91.362 675 OH 14 12 a 2 a 2 a 14.3 85.763 689 OH 12 11 a 1 a 1 a 8.3 91.767 734 OH 11 11 a a a a a a 10071 853 BV 14 13 a 1 a 1 a 7.1 92.872 879 OM 19 18 a 1 a 1 a 5.3 94.774 898 OM 21 20 a 1 5 1 23.8 4.8 71.4B3 960 OM 8 8 a a a a a a 10087 990 OM 5 5 a a a a a a lOa96 1076 Jl 35 31 a 4 1 4 2.85 11.4 85.798 1093 OHII 23 23 a a a a a a 100100 11,201,121 IT 40 38 a 2 a 2 a 5 95Total 446 12 36 2.7 8.1 89.2Abbreviations used: TBV=T. bravum Gray, TDH=T.dactylaides var. hispidum (Hitchc.) De Wet et Harlan, TDM=T.dactylaides var. mex;canum De WeI etHarlan, TIT=T. in/ermedium De Wet et Harlan, IJl=T. jalapense De Wet et Brink, TlC=T.lancealalum Ruprecht ex Fournier, TlT=T.lalifalium Hilchc.,TMZ= T. maizar Hernandez el Randolph.