= Solution
Write $Y_{gj}$ for the yield in replicate $j$ of genotype $g\in\{aa,Aa,AA\}$. Model 1 is the one-way cell-means model
$$
Y_{gj}=\mu_g+\varepsilon_{gj},
\qquad
\varepsilon_{gj}\mathrel{\overset{\mathrm{iid}}\sim}N(0,\sigma^2).
$$
Thus its three coefficients estimate the three genotype means directly.
Put $D_i=\mathbf1\{\text{count}_i\geq1\}$. Model 2 is
$$
Y_i=\beta_0+\beta_1D_i+\varepsilon_i,
\qquad
\varepsilon_i\mathrel{\overset{\mathrm{iid}}\sim}N(0,\sigma^2).
$$
It imposes $\mu_{Aa}=\mu_{AA}=\beta_0+\beta_1$ and $\mu_{aa}=\beta_0$. The reported finite-sample p-values assume independent normal errors, a common unknown variance in every genotype, fixed full-rank design <matrices>, and correctness of the relevant mean model. Random assignment of genotypes supports interpreting the fitted differences as treatment effects.
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